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EVALUATION OF PROPRIOCEPTION IN PATIENTS WITH ANTERIOR SHOULDER DISLOCATION

BY OANA S. SCAFESI

A thesis submitted in conformity with the requirements for the degree ofMaster of Science

Graduate Department of Rehabilitation Science University of Toronto

O Oana S. Scafesi, 1998

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ABSTRACT

EVALUATION OF PROPRIOCEPTION ]IN PATIENTS WITH ANTERIOR

SHOULDER DISLOCATION Oana Sanda Scafesi, M.Sc (1998), Graduate

Department of Rehabilitation Science.

The shoulder complex has a high degree of mobility in 3-D space. The stability of the

gienohumeral joint (GHJ) relies on static and dynamic constraints, as well as peripheral

feedback from sensory receptors. The aim of the present study was to investigate

shoulder position sense (proprioception) in the normal and affected side of patients with

Anterior Shoulder Dislocation (ASD) using a functional active movement. Ten subjects

with ASD performed external shoulder rotation movements bilaterally to different targets.

The present study has demonstrated that proprioception is more accurate in the non-

affected versus the previously dislocated shoulder. This difference was statistically

significant using a Mann Whitney U-test with Bonfemoni correction @ s 0.004). This

finding confirms and extends the results of previous studies (passive movement: Smith &

Brunolli, 1989; Lephart et al. 1994; and active/passive movement: Alvematm et al- 1996).

Decreased proprioception performance in subjects who had dislocation of the shoulder

may be related to alteration in peripheral sensory receptors, and has implications for the

treatment approach of shoulder complex disorders.

I would like to thank the foUowing people for their support during the count of my studies:

To my supervisor, Professor Mow Verrier, who stood by my side from the beginning in solving such an interesting and difficult subject. Professor Molly Verrier guided my previous knowledge in orthopaedics in a new way, that of research in rehabilitation. She encouraged and successfully guided me whenever new questions and diflkulties arose. I owe Professor Molly Vemer the orientation of my training at the University of Toronto and her generous support in fmishing the task that I am presenting in this paper.

I also feel grateful to Professor Jonathan Dostrovsky, who helped me to improve and to complete my knowledge in necroscience, a field in which my training was somehow reduced. His lectures offered me a new vision of the complicated mechanisms of the nervous system and, he helped me to approach my research target.

I wish to express my thanks to Dr Paul Marks who guided me in the clinical evaluation of the patients who had anterior shoulder dislocation. I highly appreciate his efforts to encourage the patients to take part in the research work to the benefit of all present and future people in pain.

To Dr Paul Corey for his help in the statistical field.

I am grateful to Mrs. Lee Marks and Mrs. Jackie Markstrom for their kindness and their help in referring the patients without whom this study would not have been finished.

To Chanh Diep, for his technical and mathematical expertise and also for his assistance in all experiments perCormed in the lab.

I want also to express my gratitude to the University of Toronto that offered me a chance to use my background, in the field of research in rehabilitation in the beoefit of so many patients expecting solutions for their pain.

TABLE OF CONTENTS

. * ABSTRACT., .................................................. ,. .................... ,,. ....................................... u *.* ACKNOWLEDGEMENTSSSSS..SSSSS.S.SS..~~ ..........................SS............................................. lu

............................................................................................... TABLE OF CONTENTS .iv ....................................................................................................... LIST OF TABLES.. .vi

.* .................................................................................................... LIST OF FIGURES.. .vu -.. ..................................................................................... LIST OF ABBREVIATIONS.. -w ...................................................................................................... LIST OF SYMBOLS .x

............................................................... ....................... LIST OF APPENDICES,. ,.,,. .xi

CHAPTER 1: INTRODUCTION, PROPIUOCEPTION, SHOULDER DISLOCATION, REVIEW OF LITERA=

1.2 PROPRIOCEPTION.. ............................................................................................. -3

1.2.1 Definition .................................................................................................. 3

1.2.2 Peripheral receptors: anatomy and physiology.. .......................................... 3

a) cutaneous receptors.. ............................................................. -4 . . b) jo~nt receptors ........................................................................ 5 c) muscle receptors ........... .... ........................................-......- 7

1.2.3 Central pathways anatomy and physiology ...................... .. ................... -9

.............................................. 1 -2.4 Central representation of proprioception.. -1 1

......................................................................... 1 -2.5 Psychophysical studies.. .14

..................................... 1-3 ANATOMY AND PATHOLOGY OF THE SHOULDER 21

................................ 1.3.1 Anatomy and stability of the glenohumerd joint.. .2 1

............................................................. 1 -3 -2 Anterior Shoulder Dislocation.. .26

................................... 1 -3 -3 Epidemiology of Anterior Shoulder Dislocation.. .27

1.3.4 Pathophysiology of Anterior Shoulder Didocation. ................................ -28

1.3.5 Previous studies of proprioception in the non-affected shoulder and in

Anterior Shoulder Dislocation ............................................................... -30

............................................................................... 1 .3.6 Research questions -34

CHAPTER 2: METHODS ......................................................................................... -35

2.1. Subjects ................................................... 35

2.2. Experimental procedure ......................................................................... -36

.......................... 2.3 Data collection ., .. - ..-.. 37

...................................................................................... 2.4 Data analysis -39

CHAPTER 3: RESULTS.. ................................................... ,. .................................... -41

3.1 Characteristics of study sample: clinical evaluation and pathology ......... -41

3.2 Comparison of target error in two conditions in the

....................................................................... non-afF'ed shoulder 43

3 -3 Comparison of proprioception in the dislocated shoulder versus the

non-affected shoulder ........................................................................... 46

.......... 3.4 Stability of end point in both shoulders related to both conditions -49

CHAPTER IV= DISCUSSION. ................................................................................... 52

................................................. CEAPTER V= SUMMARY A N D CONCLUSIONS 60

................................................ ..................... ...................*.. REFERENCES .... .... -62 ........................................................................................................... APPENDIX A -70

................................................................................... APPENDIX B ...................... ,, 73 ............................................................................................................. APPENDIX C 77

.................................................................................... APPENDIX D .................. ., 79 ............................................................................................................. APPENDIX E 83 ...................................................................................... APPENDIX F 87

LIST OF TABLES

TABLE 1.1:

TABLE 2.1 :

TABLE 3.1-1:

TABLE 3.1-2:

TABLE 3.2-1:

TABLE 3 -2-2:

TABLE 3.3-1:

TABLE 3.3-2:

Anatomy, morphology and physiology ofjoint receptors ..........-... .6

Demographic data for subjects with Anterior Shoulder Dislocation .36

Clinical and pathological evaluation of the dislocated shoulder ..... -4 1

Mardmum range of movement in non-affected and dislocated .............................................. shoulder, and target angles .42

Mean target error for all subjects in the non-afFected shoulder ..... -43

Mean target error for all subj-s with and without visual feedback in the non-affected shoulder ............................................... -45

Mean target error in the dislocated shoulder with and without ........................................................... visual feedback .46

Mean target error in the dislocated shoulder for aN subjects in both ................................................................. conditions -48

LIST OF FIGURES

FIGURE 1.3.1-a

FIGURE 1.3.1-b

FIGURE 2.3-1

FIGURE 2.3-2

FIGURE 3.2-1

FIGURE 3.2-2

FIGURE 3.3-1

FIGURE 3.3 -3

FIGURE 3 - 4 1

FIGURE 3 -4-2

The capsuloligamentous structure of the shoulder joint ............... -25

The anatomy of the shoulder joint ....................................... -25

Diagnun of coordinates of planar angular movement .................. 38

............................. Shoulder angular movement to target (93O) 39

Mean target error for each subject with and without visual feedback in the non-affected shoulder ............................................ -44

Median target error for all subjects in the non-affected shoulder ... -46

Mean target error in the dislocated shoulder with and without visual ................................................................. feedkack -47

Median target error in the dislocated shoulder for all subjects in both ................................................................ conditions -48

Median target error for all subjects in the dislocated shoulder and non-affected shoulder without visual fdback ..................... -49

End point variability for each subject in the non-affected shoulder: ................................... target XI, III, IV in both conditions -50

End point variability for each subject in the dislocated shoulder: target II, III, N in both conditions ................................... 51

vii

ACJ

AR

ASD

cm

CNS

COS

DC

DS

DIP

rnL

EMG

ER

ERR

Hz

IGHL

IR

LAN

LED

m

mm

ms

LIST OF ABBREVIATIONS

acromioclavicular joint

angular reproduction

anterior shoulder dislocation

centimeter

central nervous system

cosimls

dorsal coturns

dislocated shoulder

distal interphalangeal

extensor digitorurn Longus

electromyography

external rotation

end range reproduction

Hertz

inferior glenohumeral ligament

internal rotation

lateral articular nerve

Light emitting diodes

meter

millimeter

millisecond

MCP

MGHL

MTE

N

N-AS

ov

NR

PAN

PIP

RA

ROM

RPP

s

SA

SCh

SD

SGHL

T

TA

TSM

v

metacarpophalangeal

middle glenohumeral ligament

mean target error

Newton

non-affected shoulder

without vision

neutral rotation

posterior articular nerve

proximal interphalangeal

rapidly adapting

range of motion

reproduction of passive position

second

slowly adapting

succinylcholine

standard deviation

superior glenohumeral ligament

target

tibidis anterior

threshold sensation of movement

vision

VS. versus

LIST OF SYMBOLS

e 0 degree

YO percentage

LIST OF APPENDICES

...................................................................................... APPEMXX A 70

APPENDIX B ............................................... - 3 3

APPENDIX C ...............-................................................*..~..~......*....... -77

APPENDIX D ........................-...............................*........................*... -79

APPENDIX E ...................................................................................... 83

APPENDIX F ..................................................................................... 37

1.1 INTRODUCTION

Neumphysiological and psychophysical studies have revealed that peripheral

sensory receptors evoke sensations related to proprioception Q3urgess & Clark, 1969;

Clark & Burgess, 1975; Burgess et al. 1982; Hall & McCloskey, 1983; Clark et al. 1989;

Macefield et ale 1990). In addition, Gandevia and McCloskey (1976) and Gandevia et aL

(1983) have emphasized the role of muscle spindle receptors in the proprioception of

active movement. Proprioceptive performance has been reported to be better when all

receptors are functional, compared to when intramuscular receptors could not contribute

or when only muscle spindIes could participate in the task of joint movement. Based on

previous studies Gandevia et al. (1 992) suggested that proprioception should be assessed

during active movements that activate all peripheral receptors and particularly the muscle

spindle endings.

In recent years investigators have studied proprioception of the shoulder joint

during movement. Shoulder movement is a complex motion that is dependent on four

joints: glenohumeral, scapulothoracic, stemoclavicular, and acromioclavicular (Lucas,

1973; Bechtol, 1980). The glenohumeral joint (GHJ) sacrifices stability for mobility

(Donatelli, 1994) and therefore is prone to dislocation. Cave et al. (1974) reported the

incidence of Anterior Shoulder Dislocation (ASD) to be 84 percent (%) f?om 394

dislocations. Recurrent dislocation is the most common complication of ASD and is

estimated to be 80% in young active people (Sirnonet & Cofield, 1983). Factors

contributing to the stability of the GHJ during movement are static (articular components,

glenoid labrum, negative-intraarticular pressure, capsule, and ligaments) and dynamic

(rotator cuff, biceps tendon) constraints. Perhaps proprioceptive feedback f?om sensory

receptors located in the joint and muscle complex contributes to stability of the GHJ.

According to Lephart et al. (1994) the perception of joint position sense and joint

movement (proprioception) of the shoulder has been reported to be essential for upper

limb hnction and stability.

Smith and Bmnolli (1989), and Lephart et al. (1994) assessed proprioception of

the shoulder by measuring reproduction of passive movements. The authors reported

decreased proprioception in the dislocated shoulder and related it to an alteration of

peripheral rrcepton caused by the traumatic dislocation.

The aim of the present study was to measure proprioception of the shoulder joint

in the normal and affected side of patients with previous ASD while subjects performed

an active angular movement. The current experiment had the advantage of being able to

assess the contribution of all types of sensory receptors including muscle spindles. The

movement of the arm resembled the physiological task of external rotation in preparation

for throwing. The arm measured was externally rotated to different t;rrgets with and

without visual feedback, and a Selspot II kinematics system detected the angular

movement.

Subsequent to the initiation of the present study, Forwell and Camahan (1996)

reported a deficit in proprioception in the dislocated shoulder using an active manual

reaching task and emphasized the importance of muscle spindle activity for accurate

movement. They also suggested that &re studies should be performed with the arm in

abduction and external rotation to create more stress on the joint. Furthermore Alvemalm

et aL (1996) using an active and passive test of reproduction of angular position to study

proprioception supported the findings of previous studies that proprioception is affected

by prior shoulder dislocation. They emphasized the role of active movement in

pro prioception because they found a statistically signi f i a t difference between active

and passive movements in both normal and surgically repaired dislocated groups.

The present study demonstrated a decrease in proprioception (accuracy of end

angular movement) of subjects who had had a dislocated shoulder and thus confirms the

finding of the previous studies. This finding suggests that peripheral sensory receptors

could be altered due to trauma of the shoulder joint during dislocation. The finding may

have implications for the therapeutic approach to ASD. Decrease of proprioception

associated with multiple dislocations supports the recommendation of Wirth and

Rockwood (1993) that young athletes should undergo an early repair t o avoid recurrent

dislocation and reduction of fbnction of the shoulder. The present study also provides a

better understanding of proprioception during active movement of the upper limb. The

understanding of the deficit of proprioception in the GKV resulting fiom ASD may be

important in improving proprioceptive neuromuscular fkcilitation rehabilitation

approaches.

1.2.1 Definition

As early as 1835 Sir Charles Bell defied ''the sixth sense" as a sense of positions

and actions of the limbs. Later Sherrington (1906) introduced the term "proprioceptive

system". This system was responsible for "functional unity" and relied on vestibular

sensations, inputs fiom muscles, joints and the "central organ", the cerebellum that was

described by Sherrington as the head - ganglion of the proprioceptive system. Later

Paillard and Brouchon (1974) defined proprioception as the conscious experience

informing us about the position and motion of our limbs, permitting us to reproduce

positions and movements. Recently Lephart et al. (1994) regarded proprioception as a

specialized variation of the sensory modality of touch which encompasses the sensations

of joint position (joint position sense), and joint motion (kinesthesia).

Measurement of proprioception requires an integrated approach where learning of

position sense or movement is evaluated by a comparative reference often using the

visual system or alternatively using a contralateral movement (matching paradigm).

1.2.2 Peripheral receptors: anatomy and physiology

The sensory system provides exteroceptive information arriving fiom the external

world and also proprioceptive and interoceptive information arising from our bodies.

The sensory system receives information related to modality, intensity, duration and

location of the stimulus. The initial neural structure that captures the sensory information

is called a sensory receptor. Sensory receptors transform different types of energy

(mechanical, thermal, chemical, or electromagnetic) into nerve impulses that reach the

central nervous system (CNS). This transformation is called "stimulus transduction".

Thus the stimulus information is represented in a series of action potentials in a process

termed "neural encoding". The action potentials follow the hierarchical organization and

parallel afferent pathways of the nervous system The afferent$ fibers are classified as

large myelinated 0, small myelinated (n), smaller myelinated 0, and unmyelinated

- An alternative classification also relates to the sizes of axons is Aa, 4, A6, and C fibers. The afEerents reach the cerebral cortex where the information is decoded and

results in conscious sensation. It is known that sensory receptors have a specific

morphology related to their physiological characteristics. Cutaneous joint and muscle

receptors mediate the sensation of limb position and movement (for details see Martin,

199 1).

a) Cutaneous Receptors

The skin is a complex structure, of which the main elements are the epidermis, the

dermis, and the subcutaneous tissue. Throughout the skin there are sensory receptors that

are sensitive to different stimuli. Mechanoreceptors, thennoreceptors, and nocicepton

are functional classes of cutaneous receptors. Mechanoreceptors mediate tactile

sensation and they can also be involved in proprioception Mechanoreceptors are

sensitive to pressure on or stretch of the skin, or to movement of the hairs.

Thennoreceptors respond to warm or cold while nociceptors are sensitive to stimuli that

can damage the skin.

Mechanoreceptors can be separated in two major groups: the slowly adapting

(SA) mechanoreceptors which respond continuously to the stimulus, and rapidly adapting

@A) or fast adapting (FA) receptors which respond only at the onset of a stimulus

(Martin & Jessell, 1991). Rapidly adapting mechanoreceptors are present in hairy and

glabrous skin and they are represented by Pacinian corpuscles, Meissner corpuscles, and

hair follicle afferents. Pachian corpuscles are small gray and pearl-shaped with an onion

like lamellar structure. The afferent fiber is myelinated. Because of their anatomical

structure they are sensitive to high frequencies of vibrations: 200400 Hertz (Hz). The

Meissner corpuscle is an encapsulated receptor that lies in the dermis. It is sensitive to

velocity of movement of the skin, and responds to vibration at a lower frequency than

Pacinian corpuscles (1 0-1 00 Hz). Slowly adapting mechanoreceptors are Merkel cells

and Ruffmi endings. The Merkel cells are located near the surfsce of the skin and they

are disc shaped and have a myelinated sensory axon. The Ruffini endings are

encapsulated receptors situated in the dermis and glabrous skin- They provide

information about the intensity of steady pressure or tension within the skin. Potential

but not well studied important classes of mechanoreceptors are unmyelinated (C-fiber)

axons, which are located in all skin areas. These C-fibers respond to slow rates of

deformation, and to stimuli moving slowly over skin surface. Presently it is not known if

they contribute to proprioception. Nocicepton could be either unmyelinated (C or group

related to "slow pain" (burning sensation) or myelinated (A6) fibers associated to

"fast pain" (sharp pain), (Martin & Jessell 1991). Cold sensation is mediated by A6 and

C fibres whereas warmth is mediated by C fibres.

In summary, cutaneous sensory receptors (mechanoreceptors, nociceptors, and

thermoreceptors) can be SA and RA. Slowly adapting mechanoreceptors include

receptors that respond with dynamic and then irregular static discharge ( S A I ) and others

that respond with dynamic and regular static discharge (SAI I ) , and can function as

position detectors. Another classification is related to the information that they can

encode: cutaneous displacement, velocity detectors and cutaneous transient detectors.

Cutaneous nociceptors comprise A6 nociceptors that are activated by noxious mechanical

stimuli, and C-polymodal nociceptors that respond to noxious mechanical, thermal and

chemical stimuli. Cutaneous thermoreceptors include cold and warm receptors and

cooling or wanning stimuli respectively excite them.

b) Joint receptors

The joints are innervated by sensory receptors that respond to mechanical andlor

nociceptive stimuli. Some articular receptors signal mechanical changes in the capsule

and ligaments, however they are related to joint movement. Afferents from joint

receptors include SA and RA mechanoreceptors. Studies using optical and electron

microscopy have described the morphology of articular receptors

human joints. Newton (1982) reviewed the neuroanatomy and

receptors based on previous studies of Freeman and Wyke (1967).

Walata (1977). These studies described

around joints (Table 1.1).

Table 1.1 Anatomy, morphoIogy, and

in both animal

6

and

physiology o f joint

Polacek (1966), and

four types of joint recepton located within and

physiology of joint receptors

The physiologic function of type I Rufini-like receptors is related to speed and

direction of movement. Type II Pacinian-like recepton can detect small movements as

well as accelerating movements. Type III GoIgi-like receptors can detect position and

direction of movement.

Burgess and Clark (1969) recording fiorn single joint afferent fibers from

posterior articular nerve in cat showed that activation of joint receptors is associated with

joint movement. The authors divided joint receptors into SA and RA types. The authors

found that the conduction velocities of the 278 posterior nerve fibers in dorsal root

filaments ranged between 10-110 meter/second (ds). One hundred forty fibers

responded at marked flexion and marked extension (47 at flexion and 12 were active

during extension). The majority of these fibers were SA and responded to marked

flexion and marked extension Other fibers were sensitive to flexion, extension or to both

and were also excited by pressure on the back of the knee and, they were related with

Ruffini endings. The rapidly adapting receptors (Pacinian corpuscles) responded

primarily to joint movement. Burgess and Clark (1969) noticed that the discharge

activity was related to the pressure applied on the side of the joint. The authors suggested

that the Pacinian receptors lie in the capsule and provide information regarding joint

movement. Four fibers were activated at intermediate joint position and they responded

to succinylcholine (SCh). The authors suggested that they originated from muscle

spindles. Succinycholine is an analogue of acetylcholine and excites muscle spindle

afEerents @utia, 1995). Pressing about the capsule and sides of the knee did not change

the response of these receptors.

Therefore joint receptors appear to respond primarily to extreme extension and

flexion of the joint and they are SA and RA receptors. Joint nociceptors have group IlI

and N afferent fibers and they are sensitive to extreme movement of the joint and when

the joint is inflamed.

c) Muscle Receptors

Charles Bell (1835) first suggested that skeletal muscle had not only a motor role,

but also a sensory function. He proposed that skeletal muscle contained sensory

receptors, although he was not able to describe these receptors. Presently it is well

documented that the most important muscle receptors are the muscle spindles and Golgi

tendon organs (GTO). Clark and Burgess (1975) suggested that muscle spindle receptors

are sensitive to stretch of the muscle and they could provide proprioceptive information

related to mid-range of joint motion.

Muscle spindles

Muscle spindle receptors are an encapsulated group of fine specialized intr&sal

muscle fibers ( M h & Jessell, 1991). The muscle spindles are 4-7 millimeter (mm)

long and 80-200 microns wide. Their locations are in deep muscle tissue, and they are

m g e d in parallel with the muscle fibers. The location and attachment of the muscle

spindles make them sensitive to changes in the length of the muscle. There are two types

of intrafbsal muscle fibers: nuclear bag and nuclear chain. The nuclear bag fibers are

longer and thicker and they have multiple nuclei arranged centrally. The nuclear chain

fibers are shorter and thinner and they have fewer nuclei. Usually spindle receptors have

two nuclear bag fibers and four or five nuclear chain fibers. The nuclear bag fibers are

involved in slow contraction, and the chain fibers in fast contraction. The intrafusal

fibers receive innervation fiom gamma motor neurons. The afferent terminals consist of

primary (group Za) and secondary endings (group 11). The two types differ not only in

their morphology, but also in their responses to stretch of the muscle. The primary

endings are sensitive both to the length of the muscle and to the rate of stretch of the

spindle (dynamic phase) while the secondary endings are mainly sensitive to the length of

the muscle (Willis & Coggeshall, 1991).

In recent years electrophysiological studies of muscle receptors have emphasized

the role of muscle spindles in detection of intermediate joint position sense. Clark and

Burgess (1975) recorded the afferent activity in the lateral (LAN), and posterior articular

nerves (PAN) in the cat knee joint. The activity was recorded while the joint was held at

intermediate positions. Because spindle receptors have been reported to be sensitive to

SCh, the authors used SCh to differentiate joint fiom muscle receptors at the intermediate

range of movement. Only 4 of 18 midrange receptors did not respond to SCh. The

discharge activity of fibers in the PAN was increased when the leg was abducted and the

foot twisted outward. This activity was explained as arising due to muscle spindle

activation £iom popliteal muscle stretch. In the same experiment they observed that when

the leg was held at intermediate positions and the popljteal muscle was stretched, the

afferent activity in the PAN was increased. From these results the authors emphasized

the role of muscle spindle receptors signaling the midrange position of the joint. The

LAN fibers were less important because they showed leu activity at intermediate

positions. The study supported the idea that muscle spindle receptors are important in

sending information related to midrange position where the joint receptors are less active.

Gold Tendon Organ (GTO)

The GTO is a slender capsule approximately 1 mm long and 0.1 mm in diameter

located in tendons and aponeuroses. The GTO is arranged in series with 15-20 extrafUsal

skeletal muscle fibers. Tendon organs are sensitive to muscle stretch and contraction and

are innervated by group Ib axons (large myelinated fibers), (Willis & Coggeshall, 1991).

Matthews (1981) reported an increase in discharge activity of both receptors when the

muscle was stretched which implies that muscle spindle and GTO activity are strongly

related. The author recorded fiom the afferent axon of muscle spindles or tendon organs.

If the muscle contracted actively while it was stretched, the spindle discharge decreased

or ceased and the tendon organ activity was increased.

Other aEerents

The muscle is also innervated by group III and group IV. Group III muscle afferent

fibers can be activated by mechanical stimulation of the muscle. Group III muscle

afferent fibers have different types of receptors. Some respond to the pressure applied at

the junction between the muscle and the tendon; others are activated when the pressure is

on the belly of the muscle; some are activated to muscle stretch, and others respond to

manipulation of the space between muscles. Group IV afferents have a role in muscle

pain during ischemia because they respond to noxious chemical stimulation (Willis &

Coggeshall, 1991).

1.2.3. Central pathways anatomy and physiology

AfEerent fibers arising &om peripheral sensory receptors enter the spinal cord

through the dorsal roots. From the spinal cord somatosensory information follows

different parallel pathways to the CNS.

Based on neuroanatomical and physiological studies that have been performed on

monkeys and cats somatic sensory information ascends in the spinal cord done in two

major pathways: the anterolateral and the dorsal column medial lemniscal system The

anterolateral system is related to pain, temperature sense, and crude-touch and its

projection is via the contralateral side of the spinal cord. The axons of the antedated

system terminate in the reticular formation of the pons and medulla, the midbrain, and the

thalamus. The dorsal column pathway is related to information about tactile sensation

and proprioception. The dorsal column is subdivided into fssciculus p c i l i s and

fasciculus cuneatus. The fasciculus gracilis includes the ascending branches of afferents

fmm midthoracic region and caudal parts of the body. The fasciculus cuneatus consists

of fierents from midthoracic to upper cen6cal level. The fasciculus gracilis and

cuneatus terminate in nucleus gracilis and cuneatus located in the medulla From the

dorsal column nuclei the axons project to the ventral posterior lateral nucleus of the

contralateral thalamus (see for more details Martin & Jessell, 1991; and Willis &

Coggeshal~ 1991).

Other afEerents leave fasciculus gracilis and synapse on the cells of Clarke's

column. From cells of Clarke's column the information follows the dorsai

spinocerebellar tract to the cerebellum, or to nucleus Z (situated in the medulla) and from

there to the thalamus w d g r e n & Silfienius, 1971; Grant et al. 1973). Merents &om

joint and muscle receptors in forelimbs leave the cuneate nucleus to the external cuneate

nucleus, and reach the cerebellum (Rosen, 1969).

Somatosensory information follows parallel ascending pathways and projects to

more than one cortical area &andel& Jeuell, 1991). The primary somatosensory cortex

(SI) is located in the postcentral gyms and in the depths of the central sulcus, which

corresponds to Brodmann's areas 1, 2, 3a and 3b. Projections to ST fiom thalamus are

related to the contralateral side of the body. The secondary somatic sensory cortex (SII)

is located in the lateral sulcus- The SII receives information fiom SI. The third cortical

region that receives somatic inputs is represented by posterior parietal cortex (area 5 and

7). This region of posterior parietal cortex is tenned as the somatosensory association

area because it connects different sensory inputs and motor commands %om motor

cortex. In the cortex sensory submodalities are arranged in columns. Each of the four

subregions represents information rzlated to a specific sensory input.

1.2.4 Central representation of proprioception

The perception of information arriving fkom peripheral sensory receptors has been

studied in detail in recent years. Gardner (1988) examined somatosensory cortical

mechanisms involved in tactile and kinesthetic discrimination. Neuron activity was

recorded fiom areas 1, 2, 3b and 3a and was related to tactile and proprioceptive

information. In areas 3a and 2, most of the neurons were related to movement of one of

the joints (shoulder or elbow joint). The neurons that represented the hand movement

were more sensitive to multiple joint movements. The author found RA neurons which

responded only to joint movement and SA neurons that were sensitive to joint position

and movement. Another important finding was that the firing patterns of multiple joint

neurons appeared to provide information about the coordinated position of adjacent

joints.

Kalaska (1988) emphasized the role of transcortical projections in kinesthetic

sense and focused his studies on the neural representation of arm movements by cells in

the postcentral gyms, including primary somatosensory cortex, area 5, the superior

parietal cortex, and area 7. The anatomical evidence shows that areas 3a and 3b project

to area 1, and 2, area 1 to areas 2 and 5, and area 2 to 5. Area 5 had a large arm

representation. Movement of each joint activated many cells separately and also

simultaneous movement of combinations of joints excited them. The author emphasized

the idea that perception of joint position and movement should be seen in a context of

spatial orientation of whole body segments. The author was more concerned in his study

with area 5 that appeared to be the "integration site", where somatosensory and motor

information converged. Area 5 had some cells that were excited by movement direction

and other neurons that were activated before the onset of movement indicating that area 5

has a role in proprioception and represents the connection between peripheral sensory

receptors and the motor cortex.

This suggestion was based on his previous work (Kalaska et al. 1983) which

recorded the discharge of 321 neurons in motor cortex and area 5. The discharge

frequencies of most neurons were associated with movement in more than one direction.

The neuron's activity in area 5 was similar to the one in motor cortex. This finding

suggested that area 5 had a sensory input and motor coordination fiom motor cortex. The

sensory input participation in area 5 and motor cortex was demonstrated by the discharge

activity related to changes in electmrnyography (EMG) of muscles around shoulder and

proximal arm. The study emphasized that the role of neurons in parietal cortex was

related to specific direction of movements. The discharge activity of central neurons

showed that movements performed in directions W e r away from the preferred direction

had less activity. However, the neurons' activity related to preferred directions were

different in area 5 than motor cortex. In motor cortex the preferred direction was at 4S0

compared to area 5 where the vector direction was at 90°. The direction of movement

was the same in area 5 and motor cortex. The authors could not explain the difference in

the neurod activity in the two areas, but they named the motor cortical discharge as an

intended direction and the activity in area 5 as an actual direction of movement. The

experiment could not differentiate the neurons' activity related to passive or active

movement. In summary Kalaska et al. (1 983) suggested that area 5 is an important nodal

point between the sensory and motor cortex in control of movement in space.

Furthermore Gandevia and Burke (1995) suggested that the neuronal activity in motor

cortex exist prior to voluntary movement. Contraction of the muscles could be generated

using two signals. One is central and is prior to neural activity in motoneurons and the

other is peripheral and is based on afferent activity (McCloskey et al. 1983).

The input to SI from peripheral proprioceptors related to active and passive

movement of the arm in different directions was studied by Prud'Hornme and Kalaska

(1994). The discharge activity was compared when the arm moved f?om a central to a

peripheral point and fiom the periphery to a central point and also between active and

passive movements. Differences were related to muscle spindle activity. In addition they

tested the SI neuron's activity while the arm worked against external loads. The ST

neurons showed an increase in activity as a fbnction of the load direction applied. The

discharge activity of neurons in SI was related direction of movement and also was

similar to those in motor and parietal cortex. For shoulder movement tasks flexion-

extension produced more activity than abduction-adduction, and internal-external

rotations. The authors postulated that SI represented an intrinsic coordinate fiarnework

while the parietal and motor cortex represented the extrinsic parameters. Prud'Homrne

and Kalaska (1994) emphasized the influence that gravity during limb movement might

have on position sense since the pattern of discharge was different when the arm was in

different spatial locations requiring the muscles to compensate for changes in load. The

activity of neurons in SI appeared to be related not only to the joint angle and the muscle

length, but also to the orientation of the arm within the gravity field.

Furthermore, somatosensory evoked potentials were recorded following

controlled mechanical stimulation of the peripheral sensory receptors in the shoulder joint

in human subjects (Tibone et al. 1997). The authors compared three groups of subjects

with varying pathology. They reported no statistically significant difference between

groups comparing the amplitude and latency of the waves of somatosensory evoked

potentials. The authors suggested that anterior shoulder instability could be related to

decrease in receptors or decrease in sensitivity of receptors. However the study could not

provide information related to somatosensory evoked potentials associated with

peripheral sensory receptors during shoulder movement because the experiment was

performed in a relaxed position.

Another important structure of the CNS involved in sensorimotor integration is

the cerebellum. Lesions of the cerebellum decrease the ability to specify precise

trajectories of movement (dysmetrias). Merent iinformation fiom proprioceptive, visual,

and vestibular inputs reach the cerebellum and are used to modulate the motor control

loop. On the other hand, cerebellar outputs influence the activity of motoneurons and

therefore the movement of the limb (MacKay & Murphy, 1979). Joint position and

movement has been observed to be related to dentate activity (Strick 1978 and Thach,

1978a). Brooks (1972) observed that peak accelerations and velocities of elbow rotation

in monkeys were slower than in normal conditions when reversibIe cooling of dentate

neurons was used. Presently it is not known whether altered proprioception has an

influence on, or is influenced by cerebellum.

In summary, recording the activity from sornatosensory, motor cortex, and

cerebellum is vita1 to describe the neural representation of arm posture and movement in

space related to proprioception. Gardner (1988) noticed that the neuronal activity in SI

was related to shoulder movement to different directions and also to the elbow's posture.

The author concluded that the fbnction of one joint should be seen related to adjacent

joints. Based on central recordings Kalaska (1988) added the involvement of cutaneous,

joint, and muscle receptors in proprioceptioa In the same study and a previous one

(Kalaska et. al; 1983) the authors emphasized the role of area 5. Area 5 represents an

important relay between sensory and motor cortex. Brooks (1986) implied that the

sensory along with motor system corrects the errors in executed movements. In

conclusion, peripheral sensory receptors project to the various structures of the CNS,

information related to joint position and movement (passivdactive and direction) in

relation to other joints and also in relation to the body postures and to the external

environment. Altered inputs could have impact on motor planning which could be

incorporated into the assessment of proprioception during active movement paradigms.

1.2.5 Psychophysical studies

Psychophysics is a study of the correlation between physical stimuli and sense

perception. Psychophysics is based on sensory physiology. Psychophysics relies on

physical characteristics of a stimulus that create a sensory experience. In contrast sensory

physiology studies the transformation of sensory information and its integration in the

CNS. It has been suggested that the CNS selects specific and certain information fiom

peripheral receptors. Our perceptions are created by an internal and an external

representation of sensory experience (Martin, 1991).

Psychophysics can assist in differentiating the role of cutaneous joint and muscle

receptors in proprioception. Joint sense, muscle sense and their contribution in position

sense, were studied by Gandevia and McCloskey (1976). They used human subjects for

studying joint movement with and without engagement of the muscles at the joint.

Proprioceptive acuity was measured fiom the distal interphalangeal PIP) joint of the

middle finger. When the position sense of the joint was tested with muscles disengaged

the detection of imposed movements relied on sensory information fkom joint and skin

receptors. The performance was improved at higher angular velocities, suggesting that

joint receptors are sensitive to velocity. When the muscles were engaged, the

performance of proprioception was markedly improved. Another explanation could be

that muscle contraction increases capsular tension and therefore joint afferent discharge.

They suggested that the difference in perception shown by various subjects was related to

the variability of &sirnotor activity. In the last part of the test the skin was anaesthetized

by digital nerve block During the period of anesthesia of the finger joint all subjects

reported that the movement was more difficult to detect. Their performance improved

during and after recovery from anesthesia. Gandevia and McCloskey (1976) concluded

that performance of proprioception in detection of joint movement was increased when

all receptors were involved in the task. Later Gandevia et. al; in 1983 extended the

findings of the previous paper by assessing performance of proprioception of the middle

finger under four conditions: when joint and skin receptors were involved and muscles

disengaged, only flexor muscles were engaged, flexor and extensor muscles were

activated and when the joint and skin receptors were anesthetized. Proprioception

performance was significantly reduced when only joint and cutaneous receptors were

involved. The authors observed that proprioception was related to angular velocity. At

the slowest angular velocity (1.2S01s) the subjects did not report any sensation and it was

concluded that the value must exceed 20°/s to detect the joint movement. When only the

intramuscular receptors of the deep flexors were available the acuity of position sense

was variable and often poor. The authors found that proprioceptive performance was

improved when both groups of muscles were engaged in movement, even if joint and

skin receptors were eliminated. The best score was obtained when skin, joint, and muscle

receptors were involved in perception ofthe movement. Gandevia et al. (1983) suggested

that all types of sensory receptors are important in proprioception. On the other hand

they suggested that muscle spindles had a more important contribution in proprioception

than skin and joint receptors. Hall and McCloskey (1983) who measured the

proprioceptive performance of the shoulder, the elbow and the terminal joint of the

middle finger in human subjects confirmed the above studies. It was noticed that in terms

of angular displacement and angular velocities the proprioception performance was

superior at the shoulder and elbow compared to the finger joint, perhaps because there are

more muscles around the shoulder compared to muscles around the finger joint. Another

observation was related to angular velocity of displacement. The authon noted that for

slower movement the subjects were uncertain about the direction of the movement,

compared to faster movement when the subjects had no doubt. This finding emphasized

that the detection of movement had a lower threshold than the detection of the direction

of movement. Hall and McCloskey (1983) investigated proprioception performance in

all three joints when the subjects were asked to point (self-paced movement) with the

middle finger at the different targets. The authors found that the subjects used different

velocities to make an accurate pointing movement at different joints. The experiment

was important because the authors did comparative studies of proprioception

performance in finger, elbow, and shoulder joint in terms of angular displacement and

angular velocity, and in terms of linear displacement. The authors suggested that the

difference in proprioception between joints might be related to different peripheral

representation in the CNS. The difference in proprioception performance between joints

was related to different inputs fiom muscle receptors that are different fiom joint to joint

and may be less represented in fingers than in larger joints. Another finding was

associated with proportional changes in the lengths of muscles and the increase of the

tension in capsules when the range of the movement in elbow and finger joint reached

90°.

Muscle receptors not only provide proprioceptive sensations of movement but

they also provide perceived signals related to position of the joint and intramuscular

tension (Clark et d. 1985). To distinguish a position sense from a movement sense, the

authors tested the subject's ability to detect equal amplitude displacements of joint,

varying the velocity of rotation. Subjects detected slow displacements and at Wer

speeds they had clear and accurate sensations of movement. When the muscle nerves

were blocked, the subjects' ability to sense displacements of the ankle and

metacarpophalangeal (MCP) joints was abolished at slow speed, but not at fast speed.

These findings indicated that there was a loss of normal position sense but preservation of

the movement sense. The threshold of position sense was related to the velocity and

amplitude of the movement. Another finding was superior performance of the MCP joint

in comparison to the ankle joint during nerve block. The authors related the finding to the

greater representation of the fingers in the cerebral cortex On the other hand the

existence of extraneous cues (traction of the skin) helped the subjects to have better

scores. When the ulnar and the common peroneal nerve were blocked and muscle

involvement was eliminated the performance of position sense and movements were

decreased despite an increased displacement. In the same experiment three additional

subjects received a local anesthetic into the MCP joint. The ability to detect either slow

or f a t movements was not affected implying that joint receptors, at least for the MCP

joint, had little effect on proprioception Clark et aL (1986) extended the above studies to

the proximal interphalangeal joint (PIP) using the same paradigm. They found a lack of

static-position sense with PIP and a clear evidence of position-sense at the MCP. The

authors explained the difference through the relationship between muscle spindle

receptors and the lengths of the muscles. Muscles that work at a single joint give accurate

information Muscles that cross two or more joints send the information to CNS related

to multijoint movement. This finding may be important when the proprioception is

assessed using an active movement. In contrast, Taylor and McCloskey (1990)

demonstrated the existence of position sense in MCP, PIP and DIP with no differences

between them. They found no improvement when the muscles were contracted without

moving the joint. This may suggest that not only the muscle spindles but also the joint

receptors are sensitive to the movement of the joint. At slow speed the accuracy of

position sense was similar at all joints. The authors suggested that the contradiction

could be related to a dierent description of movement that was more confusing in the

study of Clark et af. (1 986).

Other psychophysical studies (vibration, cooling, or loading the muscle)

emphasized the importance of muscle receptors in proprioception. The involvement of

muscle receptors in proprioception was demonstrated by vibration of a tendon of a

muscle while the joint was moved passively or actively. Vibration produced an illusion

of sense of movement, change in joint position and an increase in error of reaching the

target (Paillard & Brouchon, 1974). Vibrating the muscle influences the discharge of

group Ia afferent fibers and it alters the transitory signals necessary for accurate

movement. Active movement was more auwate than passive because muscle spindles

activity is increased in active movement. Another observation was related to the speed of

the movement. The accuracy of the reaching point was greater with faster (9.5 mk) than

slower speed (0.3 m/s - 5 d s ) movements. Other psychophysical experiments by

Colebatch and McCloskey (1987) investigated the ability of normal subjects to maintain

either constant position of the limb, or to exert a constant force against an elastic load

applied to the wrist without visual feedback. When perturbations were small like 0.92

Newton (N) and undetected, subjects were able to keep the position of the limb or the

force constant. When the perturbations were larger (9.8 N) and detected, subjects

adjusted contractions of muscles that implies that muscle spindles are implicated in

control the limb position.

Using microneurography Roll and Vedel (1982) recorded the muscle afferent

activity from tibialis anterior and extensor digitorurn longus when vibration was applied

on the tendon and during active and passive movement of elbow and ankle joint.

During active movement discharge frequency of the primary endings was constant and

related to the velocity of the movement. In the same condition the discharge fkquency of

the secondary endings was associated with joint position and the increasing of the

movement velocity. The findings suggested that muscle spindles are implicated in

proprioception. Gregory et al. (1988) extended the above findings on the role of muscle

spindles in limb position in experiments with both human subjects and in anesthetized

cats. Merent activity recorded in the dorsal roots in the anesthetized cat while the soleus

muscle was contracted at different lengths showed that the resting discharge of muscle

spindles contributed to the sense of limb position in humans. In the same study Gregory

et al- (1988) measured the error in elbow position in blindfolded subjects in an arm

matching task. Contraction and vibration were applied to biceps and triceps after the

elbow was held at an intermediate position. The matching errors were attributed to the

changes in resting discharges of muscle receptors. Furthermore even vibration of an

antagonist muscle (hglis & Frank, 1990) while subjects performed an active matching

position test of the elbow joint demonstrated that muscle spindle receptors fiorn the

antagonist muscles produced an illusion of movement.

The microneurographic technique a1 so allows the assessment of the responses of

different types of mechanoreceptors. Vallbo et al. (1984) subdivided skin receptors in

FAI, F A q SAI and SAII types. Using this technique Burke et al. (1988) recorded fiom

the joint, muscle, and cutaneous afFerents fiom the digital joint in humans during passive

movements. Of 120 single fierents sampled fkom the median and ulnar nerves at the

wrist, 15% were classified as joint afferents, 72.5% cutaneous and 12.5% muscle spindles

and GTOs. Muscle spindle affierents were not subclassified, or differentiated from GTOs.

The response of muscle spindle afferents was related to the length of the muscle and to

the movement of all joints on which the muscles operated. The muscle receptors

responded to angular displacements in the direction that caused stretch of the "parent"

muscle within the physiological range of rotation. Burke et aL (1988) suggested that the

muscle receptors could be sensitive to angular movement of the joint whereas joint

Berents started to be active near the limit of passive joint rotation. They concluded that

human joint receptors play little role in proprioception because most of them were active

only near the end range of movement. All cutaneous receptors were excited only by

extreme angular positions. Later Edin and Vallbo (1990) identified and classified muscle

stretch receptor afferents and differentiated them fiom GTO. Macefield et d. (1990)

used the microneurography technique and microstimulation of single afferent axons

within cutaneous and motor fascicles7 of the median and ulnar nerves at the wrist. They

c o h e d the above study and concluded that muscle spindle afferents were involved in

proprioception because they responded to unidirectional movement of the joint within the

physiological range of displacement. Furthermore Macefield et al- (1990) postulated that

the CNS gets the information on muscle length related to joint position fkom multiple

muscle spindles.

In recent years the importance of proprioception in accurate movement and

position has been emphasized in studies performed in deaerented patients. Sainburg g

al. (1995) examined the role of proprioception during a motor performance task without - vision in n o d subjects and in two patients with large fiber sensory neuropathy with

normal muscle strength and EMG. In control subjects outward and inward paths were

straight and overlapped. The patients showed an increase in errors at reversal of

movement. The error of movement was related to the lack of movement concordance of

the two joints (elbow and shoulder) indicating that the two patients used a co-contraction

of muscles to compensate the lack in proprioception input. Ghez and Sainburg (1995)

used the same task with visual feedback. 'Vision of the limb prior and during the

movement improved the accuracy of the performance of patients with sensory

neuropathy. The study involved a complex movement that required a three-dimensional

movement of the hand and multijoint coordination. The time and movement pattern was

uncoordinated and prolonged in the patients compared to nonnal subjects suggesting that

the coordination of the movement relies on proprioceptive information. Gordon et al.

(1995) investigated the trajectory and the end point emrs in reaching movements. In the

controls the movement was terminated abruptly, and the trajectories and the paths were

relatively straight. In the patient group movement paths were highly d. The end

point was larger than normal and it became greater with increasing the magnitude of the

movement indicating that the patients could not compensate for inertial variations

perhaps because of lack of proprioception. Ghez et al. (1995) demonstrated how visual

feedback prior and during the task influenced the subject's performance. Vision

influenced the duration, the paths and directional errors of the movement. When visual

feedback was used before the task the accuracy of the movement was improved and when

the visual feedback was eliminated the performance of the movement was decreased. On

the other hand these scientists have suggested that planning reaching movements require

continuous proprioceptive information which relies on peripheral sensory receptors. The

authors considered that vision before the movement gives information associated with the

relationship of the limb to the body.

In summary, in recent years the idea of participation of all peripheral receptors in

proprioception has been widely extended. The main role of skin and joint receptors has

been under question, and the role of muscle receptors has gained importance in this

complex process of joint position and sense of movement. Cutaneous receptors are

activated at extreme angular positions of the joint (Burke et al. 1988).

Microneurographic and neural stimulation (Vallbo et al. 1984; Macefield et al. 1990)

could differentiate the cutaneuos receptors related to movement of the joint. However

some studies (Rymer & D' Almeida, 1980; Clark et al. 1989) suggested that anesthesia of

the finger did not impair the ability of detection of joint movement. Joint receptors that

were first thought to be related to proprioception appear to respond only to the extremes

of movement and have bidirectional sensitivity (Burgess & Clark, 1969; Hall &

McClosey, 1983; Macefield et al. 1990; Gandevia et al. 1983). However the role of joint

receptors in proprioception is controversial as proprioception testing showed a normal

position test after complete removal of the joint and the capsule (Cross & McCloskey,

1973). Perhaps their influence is joint specific. In recent years Clark and Burgess (1975)

and Gregory et al. (1988) have suggested an important role of intramuscular receptors in

proprioception of the joints, particularly muscle spindle endings because they are active

in the physiological range of joint movement. Furthermore it has been suggested that

muscle spindle receptors are more sensitive to active movement and that proprioception

is increased when the task is performed during active rather than passive movement

(Paillard & Brouchon, 1974; Kalaska, 1988; Gandevia et al. 19923. Proprioception is

important in coordinated movement of joints, and patients who have sensory neuropathy

demonstrate a dBicu1ty in movement concordance of two joints (Ghez & Sainburg,

1995; Gordon et al. 1995, Ghez et al. 1995).

In conclusion the CNS is able to use proproceptive information £?om cutaneous,

joint and muscle receptors to achieve coordination of discrete movement sequences, and

to differentiate static and dynamic position of the joints. In addition the CNS is

influenced by the state of the organism, fatiguey and dmgs that may change the perception

level, even if the afferent input is the same @ickinson, 1974).

1.3 ANATOMY AND PATHOLOGY OF THE S H O W E R

1.3.1. Anatomy and stability of the glenohumeral joint

The shoulder joint is a multiarticular system that requires a complex coordination

of static and dynamic restraints. The shoulder joint in normal subjects is able to move in

over 16000 positions that are different by lo (Perry, 1976). This wide range of mobility

sacrifices the stability of the shoulder joint. The stability of the GHJ is dependent on the

static and active stabilizers. Bony structures7 the glenoid cavity and soft tissue (labrum,

glenohumeral ligaments and capsular attachment) represent static stabilizers. Celli et al.

(1990) classified active stabilizers as: ~ntinuous, complementary, and occasional

muscles.

The GHJ is composed of the humeral head and the glenoid d a c e . The humeral

head is directed medially upward and posteriorly. In the transverse plane the humeral

head is retroverted 20" (Sarrafian, 1988). The glenoid cavity is shallow, oriented outward

and it matches to the retroverted orientation of the humeral head. Because of this

anatomical position only 1/4 of the humeral head is covered by the glenoid cavity (Saha,

1971). Using a stereophotognunmetry technique that allows a three dimensional study of

the GHJ, Soslowski (1989, 1991) confirmed the above finding. The glenoid labrum is a

fibrocartilaginous tissue that is formed by three surfaces. One surface is attached to the

glenoid cavity, the second one is around the neck of the scapula and it serves as the

insertion to the capsule. The third d a c e is free Howell and Galiant (1989) suggested

that the glenoid labrum has an important role in stability of the GHJ. Because of the

anatomical structure the labrum increases the depth of the glenoid cavity and allows the

humeral head to be compressed into the glenoid fossa even when ligaments are cut

(Vanderhooft et d- 1992). In addition, the labrum is attached to the tendon of the long

head of the biceps superiorly and to the tendon of the triceps inferiorly (Sarrafian, 1988).

The capsule represents another passive restraint of the GHI. The role of the

capsule in the stability of the joint depends on the ligaments and tendons of the rotator

cuff (Frankel & Nordin, 1980). The capsule is a continuation of the external surface of

the labrum and the posterior side has its insertion on the anatomical neck of the humerus.

Inferiorly the capsule attaches to the surgical neck of the humerus. The superior part the

capsule is tightened by the superior glenohumeral ligament. Anteriorly the capsule has

the attachment of the anterior glenohumeral ligaments and the insertion of the

subscapularis tendon, posteriorly the attachment of the teres minor and infraspinatus

tendons (Ovesen & Nielsen, 1986). The inferior part is thin and when the arm is elevated

becomes tensed (Peat & Culham, 1994).

The ligaments are coracohumeral and glenohumeral. The anatomical aspect of

the glenohumeral ligaments can be observed in the deep h c e of the capsule. The

coracohumeral ligament is located on the superior aspect of the glenohumeral joint

between the attachment of the supraspinatus and subscapularis tendons. The

coracohumeral ligament originates on the coracoid and it has the insertion on the greater

and the lesser tuberosity of the humerus blending with the adjacent capsule. It has been

suggested that the coracohumeral ligament is involved in abduction of the arm against

gravity along with the superior capsule and the inferior glenohumeral ligament

(Turkel et al. 198 1; Ferrari, 1990).

The glenohumerai ligaments are very important reinforcements of the capsule.

The glenohumeral ligaments maintain stability of the GW. Peat and Culham (1994)

described these ligaments as thick structures that lie on the anterior and inferior aspect of

the joint. The glenohumeral ligaments (Figure 1.3.1-a) are composed of three bundles:

superior, middle and inferior (Caspari & Geissler, 1993). The superior glenohumeral

ligament (SGHL) arises near the origin of the long head of the biceps and has the

insertion superior to the lesser tuberosity of the humerus. Turkel et al. (1981) suggested

that the SGHL has a role in prevention of anterior dislocation, and is tensed when the arm

is in abduction and external rotation. The middle glenohumeral ligament (MGHL) arises

fiom the glenoid labrum inferior to the origin of SGHL, or f?om the adiacent neck of the

glenoid. The MGHL stabilizes the GHJ when the shoulder is abducted to 45" (Roland

Matthews, 1995). The MGHL has two morphologic aspects: sheet like and cord like

(Warner, 1993). Anterior stability of the shoulder is suggested to be related to the cord

aspect of the MGHL (Rames et al. 1991; and Warner et al. 1992). The inferior

glenohumeral ligament (IGHL) is a complex structure that arises from the anterior-

inferior margin of the labrum and inserts on the inferior aspect of the surgical neck of the

humerus (Ruland & Mattews, 1995).

The IGHL reinforces the inferior capsule between subscapularis and teres minor

(Sarrafian, 1988). Turkel et al. (1981) separated the IGHL into three bundles: anterior,

posterior, and axillary pouch. The axillary pouch is the confluence of the anterior and

posterior inferior glenohumeral ligaments. O'Brian et al. (1990) described the knction

of the IGHL as a hammock supporting the humeral head in the glenoid during abduction

and rotation of the shoulder joint. In abduction and external rotation the anterior bundle

becomes lax and the posterior one becomes cord-like. In abduction and internal rotation

the two bundles change functions conversely. The morphological aspect of the IGHL is

related to the stability of the GHJ mainly during throwing motion and during overhead

activity (Peat & Culham, 1994).

The rotator cuff muscles represent the dynamic stability: supraspinatus,

subscapularis, teres minor and infi-aspinatus (Figure 1.3.1 -b). Their attachments to the

capsule are different: supraspinatus superiorly, subscapularis anteriorly, teres minor and

infraspinatus posteriorly. The rotator cuff muscles have been considered for a long time

to provide the most active support of the joint (Inman et al. 1944). The long head of the

biceps is another important fador in stability of the joint during elbow flexion and

forearm supination opposing upward translation of the head of the humerus (Kumar et al.

1989). In the view of Celli et al. (1990) the supraspinatus is a continuous stabilizer that is

capable of moving the ann in all directions. The infiaspinatus and subscapularis are

considered as complementary stabilizers. The inikpinatus and subscapularis hold the

humerd head into the glena, forwards or backwards in abduction and intra and

extrarotation. Celli et d- (1990) suggested that the hfkspinatus and subscapularis

compensate for the supraspinatus muscle when it is affected by trauma. When the

supraspinatus is damaged the subjects loose their ability to actively abduct their arm &om

30° to 90°, but passive abduction below 90° is preserved. Occasional stabilizer muscles

are the deltoid and the long head of the biceps. They are active when the shoulder is

abducted and when the arm works against resistance. In abduction of the arm the deltoid

and the long head of the biceps assists the rotator cuff muscles by centering the humeral

head in the glenoid cavity. The muscles of the GHJ have to work at rest, against gravity

during sport activity, and they play an important role in the movement of the joint in all

directions (Celli et al. 1990). However, De Luca et al. (1973) have a different view

regarding the action of the rotator &and the deltoid muscles. They have suggested that

the deltoid and the supraspinatus are prime movers in the abduction of the GHJ.

The innervation of the shoulder joint is by four nerves: the axillary, supra~capu1a.r~

subscapular and musculocutaneous. In recent years descriptive and qualitative studies of

the shoulder joint (Jerosch et aI. 1993; and Vangsness et al. 1995) identified two

morphological types of mechanoreceptors and free nerve endings in human shoulder.

Slowly adapting Ruffini end organs and RA Pacinian corpuscles were found in

glenohumeral ligaments. The fiee nerve endings were seen in coracoclavicuiar,

cora~oacromiaf~ and in glenoid labrum Vangsness et al. (1995) concluded that the

existence of these receptors if damaged, could be related to the decrease of

proprioception that is starting to be reported.

Figure 13.1 -a The eopsuloligamentoru structure o f the shoulder joint

Modified fiom O'Brien (1990)

Figure 1.3.1 -b The anatomy of the shoulder joint

B - tendon biceps

SGHL - superior glenohumeral Ligament

MGHL - middle glenobumeral ligament

IGHL - inferior glenohmera1 ligament

Modified fkom Turkel et al. (1981)

1.3.2 Anterior Shoulder Dislocation

The shoulder is the most mobile joint of the body because it wmbines the action

of four joints (Paet & CuUm, 1994). The three dimensional range of motion allows the

shoulder to perform gross and skilled fbndions. The overall activity of the upper

extremity is wntroled by static and dynamic restraints along with neurosensory feedback.

When bony, articular, muscular and newoperipherd receptors are affected by trauma or

other factors, the shoulder becomes unstable. Shoulder dislocation is a well known injury

described as early as 3000 on Egyptian wall paintings (Rowe, 1988) and Hippocrates

in the 4th century described the anatomy of the shoulder, the types of dislocations and the

surgical repair. Because of the high frequency of shoulder dislocation, over the years

many studies have provided information related to the anatomy, pathophysiology, and the

treatment of shoulder instability.

Rowe (1 98 8) classified the glenohumeral instability as traumatic and atraumatic.

Traumatic gleno humeral instability is classified in degree, chronology, and direction of

instability. There are two categories of instability: dislocation and subluxation. The

glenohumaral joint dislocation represents a complete separation of the articular surfaces,

whereas the glenohumeral subluxation is a symptomatic translation of the humeral head

on the glenoid.

Wirth and Rockwood (1993) suggested that instability of the joint could be acute,

chronic, and recurrent.

Related to the direction of instability there are four types: anterior, posterior,

inferior and superior. Traumatic ASD is generated by an acute injury to the shoulder

produced by a direct impact on the elbow, or shoulder, or by an indirect forcell

movement of the shoulder joint in abduction, external rotation and extension. Wirth and

Rockwood (1993) noticed that the most common type of ASD is subcoracoid when the

humeral head is moved anteriorly to the glenoid and the humeral head is inferior to the

corachoid process. The other types (subglenoid, subclavicular, and intrat horacic) are

very rare and they are associated with serious trauma

1.33 Epidemiology of Anterior Shoulder Dislocation

Traumatic instability of the shoulder is the most frequent cause of dislocation:

fmm 500 dislocations of the glenohumerai joint 96% were traumatic and 4% atraumatic

(Rowe, 1956). Cave et al. (1974) analyzed 1600 shoulder injuries, 394 were dislocations;

of these 84% were anterior, 12% acromioclavicular, 2.5% were stemoclavicular, and 1%-

5% were posterior dislocations that means that ASD occurs more often than other types

of dislocation.

Anterior shoulder dislocation, most of the time is related to recurrent dislocation,

which represents the most common complication following trauma of the shoulder.

McLaughlin and McLellan (1 967) reported £?om 18 1 primary traumatic

dislocations in teenagers a 95% recurrence. Henry and Genung (1982) noticed the same

high incidence of recurrence: 85% to 90% redislocations in young patients and Rowe

(1988) found a 94% recurrence in ages between 20-40. Simonet and Cofield (1983)

observed 80% recurrent dislocations in athletes younger than 20 years. Because the

incidence in the above studies is based on a selected group of patients seen in hospital,

Hovelius (1982) studies the frequency of shoulder dislocation in a general population.

Two thousand and ninety-two people between 18-70 years old were randomly selected

and interviewed at the Swedish Institute for Public Opinion Research. He founO that 35

subjects (1.7%) had shoulder dislocation, 2 of them had bilateral dislocation, and 4

subjects had recurrent dislocation. The difference between Hovelius (1982) and the

above studies was related to the sample group. Hovelius (1987) followed 257 of the

patients with ASD, (254 were between 12 to 40 years old), 55% had two or more

recurrences and the age of the patients was younger than 22 years. He reported that the

incidence of ASD is decreased in patients over 30 years old (12%). The incidence of

ASD and recurrent dislocation is high in young athletes who overuse the shoulder in sport

activities. The implications of high incidence of ASD justify the investigation of the

complex shoulder joint. Aa early diagnosis of neuromuscular instability could prevent

recurrent dislocation and subsequent dysfunction.

1.3.4 Pathophysiology of Anterior Shoulder Dislocation

Anterior shoulder didocation is a result of a MI or a blow on the abducted arm.

When the fkl1 o m s on the outstretched hand with the elbow extended, the humeral head

is pushed on the anterior and antero-inferior structure of the capsule. When the arm is

abducted and externally rotated the humeral head is forced downward on the inferior side

of the capsule (Post. 1988). In abduction and external rotation the capsule and

glenohumeral ligaments are strong enough to prevent dislocation and to maintain the

humeral head in the glenoid cavity (Matsen et d. 1991). Repetitive stresses in this arm

position like throwing, are related to glenohumeral tearing or detachment from the

labrum and may result in subluxation and dislocation (O'Driscoll, 1993). The normal

anatomic structures that hold the humeral head in the glenoid cavity are affected by

repetitive dislocation when the anterior capsule with or without the glenoid labrum

becomes detached h m the glenoid (Bankart, 1938). De Pdma (1963) emphasized the

role of the musculotendinous cuff that becomes lax and detached f?om the glenoid fossa

in recurrent dislocation.

O'Driscoll (1993) studied the role of muscles around the shoulder in joint

stability. He divided the shoulder muscles into primary movers and primary stabilizers.

The major primary movers are the deltoid, pectoralis major, latismus dorsi, and teres

major. These muscles are active when the arm moves in ail positions and they move the

humeral head out of the glenoid. The primary stabilizers are supraspinatus, infraspinatus,

teres minor and subscapularis. Their contractions center the humeral head in the glenoid.

The action of primary stabilizers is opposed to primary movers. The primary stabilizers

have an important role in external rotation of the a m Celli et al. (1990) suggested that

deltoid and supraspinatus muscles act in synergy centering and lowering the humerd

head in abduction on the vertical plane. During elevation of the arm produced by deltoid,

the supraspinatus maintains the head centered and away fiom the acromion. In the

horizontal plane the infraspinatus is important in stability of the joint and its action is

controlled by teres major. The infkaspinatus is also active in extrarotation associated with

rebopositioning of the head.

The anterior security in abduction and external rotation is produced by

subscapul ark (Sarrafian, 1988). Turkel et aL (1 98 1) suggested that subscapularis

provides an anterior support of the humeral head in the middle range of abduction. At

4S0 abduction the subscapularis muscle, the MGHL, and the anterior fibers of the IGHL

work against anterior dislocation At 900 of abduction the axillary pouch of the inferior

glenohumeral ligament maintains the anterior stability. Symeonides (1972) fiom

experiments on cadavers, suggested that stretching the subscapularis decreases its power.

Remurent dislocation is related to laxity and lengthening of the subscapularis muscle.

Injuries at the GH3 are associated with pathologic changes in static and dynamic

constraints of the joint that de-center the humeral head (Celli et d. 1990). The pathologic

changes in the capsule and ligament structures can be associated with joint laxity or

limitation of external rotation due to retraction and fibrosis of the glenohumeral ligaments

and coracohumeral ligament. The imbalance between stabilizer and mover muscles can

alter the stability of the GHJ.

Another type of pathologic change during shoulder dislocation is the decrease of

neuromuscular stabilization of the shoulder joint (Liber & Friden, 1993). The authors

postulated that "variable stiffness position and force regulators" are present while the

shoulder joint is moved in different positions. The stiflkess was suggested to be an

interrelationship between intrafusal fiber innervation and contractility. The muscle

stiflhess is an intrinsic property and the C N S through muscle spindle feedback controls

its action. The feedback mechanism is also important to stabilize muscle force and

regulate muscle fiber recruitment.

In wnclusion the macroscopic changes at the capsule, ligaments, and muscles of

the shoulder joint might be associated with alteration of sensory receptors. This

microtrauma could be related to a decrease of proprioception in the dislocated shoulder

(Jerosch et al. 1993).

13.5. Previous studies of proprioception in non-affected shoulder and in Anterior

Shoulder Dislocation

Different tests of position sense have been used in routine neurological

assessment, but they are not all sensitive in determining proprioceptive abnormalities.

Therefore investigators have tried to develop customized tests to assess proprioception.

Specific tests have been developed for the shoulder, which could be used to evaluate

whether there are deficits subsequent to trauma

Cohen (1958) attempted to study proprioception of the shoulder joint by using

reaching movements in normal subjects and found a mean error of 2-98 centimeters (cm)

for 4 targets (1 0 trialdtarget). When adding weight to the limb and skin tape to interfere

with muscle and skin receptors, the mean error was increased (4.0Icm) which implied

that not only joint receptors are important in proprioception, but also skin and muscle

receptors could have a significant contribution to position sense. The authors reported

large variability £?om subject to subject that was related to the medio-lateral translation

movement in the shoulder joint and change of the position ofthe body during movement.

In recent years more studies of shoulder proprioception have been conducted in

order to understand the role of proprioception in ASD. Smith and Brunolli (1989)

suggested that recument dislocations result, not only fiom alteration of gross anatomical

structure of the joint, but also from the disruption of peripheral sensory receptors and

decrease of neuromuscular coordination. Tests of angular reproduction (AR), threshold to

sensation of movement (TSM), and end-range reproduction (ERR) were used to test the

proprioception on eight subjects with ASD and ten non-affected subjects. The subjects

had to reproduce passively an angular movement, bilaterally and without visual feedback

at different velocities (20°/s for AR and l.SO/s for TSM and ERR). There was a

significant difference between the uninvolved and dislocated shoulder @< 0.001) for all

three tests (AR, TSM, ERR). The TSM was between 0.91" and 1 .OSO in uninvolved

shoulders compared to 2.5S0 in the affected shoulders. The increase of the ERR deficit in

the dislocated shoulder was explained based on articular receptors, damaged, fiom

dislocation. The error in the non-affected side for AR was 1.08O and in dislocated

shoulders was 2.75O. The A . deficit at intermediate range of movement in the affected

side was repolted as being related to the decrease in activity of muscle receptors, since

the joint receptors are thought to be more sensitive to extremes of ROh4 The data

suggested a deficit of proprioception in ASD, but intra-subject comparison was not done.

Furthermore the ERR test has been criticized because performing the test at end range of

motion could be associated with apprehension or fear of recurrent dislocation. On the

other hand a decrease of proprioception in ERR in DS could be associated with pain

rather thm a decrease in proprioception-

Using the same methods, Lephart et al. (1994) measured proprioception of the

shoulder joint in three experimental groups (group I healthy subjects, group IT, patients

with shoulder dislocation, and group III, patients who had surgical reconstruction). TSM

and reproduction of passive positioning (RPP) was executed fiom the neutral position to

internal @It) and external rotation (ER). In the healthy group there was no significant

mean difference for TSM between the dominant and non-dominant shoulder (mean value

1.43O k 0.2O vs. 2.20" f 0.4O). In the group with ASD the threshold to detect passive

movements was greater in the affected side compared to the contralateral shoulder IR

(2X0 k 0.3O vs. 1.P f 0.6O) and for ER (2.6' f 0.6* vs. 1.8O f 0.2O). In the same group

RPP was significantly different between the two shoulders fiom a starting position of 30"

ER: W @S: 4.1' f l.OO vs. N-AS: 3.3O f 0.4O) and ER (DS: 2.S0 + 0.7O vs. N-AS: 2.2* + 0.4O). No significant difference was seen between shoulders for RPP fkom a starting

position of neutral position. In the surgical repair group there was no si,gnificant

difference between shoulders for TSM and RPP. Lephart et al. (1994) suggested that the

dislocation of the shoulder affect the peripheral sensory receptors located in articular,

muscular and cutaneous structures. The results in the group after surgical repair

suggested that the surgery and a rehabilitation program for ASD could restore not only

the anatomical finction but also the proprioceptive feedback mechanism. However the

test was for passive movement and did not assess the contribution of all neurosensory

receptors as occurs during active movement.

Blasier et al. (1994) performed a similar tea in normal subjects and subjects with

joint laxity. The authors observed that in the group without joint laxity subjects had

significantly smaller detection threshold for the movement. This group had the

pefiormance score of 0.78". The sensitivity was decreased (1.08") in the group of

subjects with joint laxity, because the capsular structures were loose and therefore joint

receptors were less active. Furthermore proprioception for ER was more accurate than

proprioception for IR @< 0.001). When the movement required more ER of the shoulder

the detection was more accurate. Blasier et d. (1994) suggested that the joint receptors

are more sensitive when the capsule is tightened because more receptors provided

information related to position of the joint which confirmed previous studies (Burgess &

Clark, 1969; Burke et al. 1988). Blasier et al. (1994) confirmed the view of Jerosch et. al;

(1993) who observed an increase of anterior translation when anesthetic solution was

injected into the shoulder joint.

On the other hand Forwell and Carnahan (1996) investigated temporal, spatial,

and kinematic data associated with voluntary (self-paced) reaching movements (matching

test to 3 targets) in normal subjects and in those with ASD. The task was performed with

and without visual feedback and with vibration of the posterior deltoid muscle.

Movement time to a given target was increased as the target distance increased in no

vision trials and it was no different when vibration was applied. The authors postulated

that vibration increased the velocity of muscle contraction, which compensated for the

lack of vision. The highest degree of accuracy was seen at the 100' target and the least at

150" target suggesting that distance influence proprioceptive performance. Furthermore,

vision decreased the emor in the reaching movements (1 8.9 & 2.3mm vs. 28.0 f 1.7mm)

indicating that vision is an important factor related to accuracy of movement. The

temporal and spatial data did not reveal any significant differences between the control

and the ASD group. The kinematic data (peak finger velocity, time to peak finger

velocity, and normalized time to peak finger velocity) showed that there was a significant

difference between the two groups. An increase of peak finger velocity and a negative

effect of vibration in accurate movements were seen on the affected side. In the normal

group there was no sigruficant difference when vibration was applied. The authors

suggested that the control shoulder had the ability to compensate for the effect of

vibration that contradicts with previous studies (Paillard & Brouchon, 1974; Inglis &

Frank, 1990) who postulated that vibration affects the proprioception due to the influence

of group Ia afferent fibers.

Forwell and Camahan (1996) related their findings in DS to a proprioceptive

deficit implying that recurrent dislocations may occur as a result of lack of

neuromuscular control.

Other studies investigated the use of a Kincorn dynamometer in assessing

shoulder position sense actively and passively in normal subjects and in subjects with

surgical repair after ASD (Alvemalm et aI. 1996). The accuracy of reproduction of joint

angle for the dominant arm was measured in three trials without vision and on thee

consecutive days. Statistically significant differences were found between the normal and

the patient group, active and passive test (p< 0.00 1). and between day 1 and day 3 (p<

0.05). No significant difference was seen between day 1 and day 2 and between day 2

and day 3 and perhaps could be associated with learning efkt over repetitive testing.

However, the magnitude of error in day 1 was greater than day 3. The difference

between active and passive reproduction of joint angles (active movement: error mean in

normal subjects 1 -64" k 0.86O vs. patients 2.75O * 1.07O compared to passive movement

in n o d subjects 2.48" * 1.44" vs. patients 4.08O k 1.65') supported the view of

Gandevia et. al; (1992) who postulated that active movement is more accurate than

passive because all the receptors are activated. However, we do not know whether the

1.2O difference between the two groups is related to decrease of sensory receptors due to

trauma or damage associated with surgical repair of the recurrent dislocated shoulder or

some other phenomen.

In conclusion, studies in normal subjects and those with dislocated shoulders, or

joint laxity using passive movement have supported the role of peripheral sensory

receptors in propnoaption (Smith & Brunolli, 1989; Lephart et al. 1994; Blasier et al.

1994). Recent work has been suggested that conscious awareness of joint position is

strongly dependent on muscle spindles discharge. This awareness appears to be

dependent on the amplitude or number of spindles activated (Macefield et al. 1990).

Therefore, more sophisticated proprioception tests have been created to demonstrate the

importance of all peripheral sensory receptors in proprioception. The active tests of

reaching points or angular reproduction of movement (Forwell & Carnahan, 1996;

Alvemalm et al. 1996) support the view of Gandevia et al. (1992) that active movement

involves all sensory receptors and not only joint and skin receptors. The above studies

suggested that there was a decrease in shoulder proprioception in patients with DS, that

could be related to repetitive dislocations.

1.3.6 Research questions

This study addressed the following questions:

How accurate is proprioception in the N-AS?

How does proprioception in the DS compare to the N-AS?

What is the accuracy of proprioception for larger movements in the WAS?

What is the variability of "end point targef' in both shoulders?

CHAPTER2: METHODS

2-1. Subjects

Nine males and one female with ASD were recruited fiom the Orthopaedic and

Arthritic Hospital and assessed by Dr Paul Marks (Appendix A). All patients were

between 21 and 33 years of age (mean 26.4 4.3). they had repeated dislocations (mean

6.6 * 3.4), and they were engaged in different sport activities (Table 2.1). Age of first

dislocation was between 13 to 32 (mean 19.8 * 5.5).

The inclusion criteria were ASD patients that: 1) were clinically diagnosed with

recurrent (two or more episodes) ASD, 2) presented a history of dislocation with a

positive anterior apprehension sign at physical examination, 3) had had no prior surgical

treatment at the indicated site, 4) were between 18-40 years of age, 5) were able to follow

instructions, 6) were in good nutritional and general health status, 7) were able to return

to the clinic for follow-up examinations, and 8) had consented to participate in the study.

Exclusion criteria were patients that: 1) had an active infection, 2) were diagnosed

with any of the following: osteomyelitis, voluntary dislocations, posterior shoulder

instability, impingement syndrome, multidirectional instability, irregularities of previous

fracture of the glenoid, connective tissue diseases (M;ufan's syndrome, Ehlers-Danlos

syndrome), ipsilateral rotator cuff tears or concomitant injury, Paget's disease, or

neoplasm, and 3) were experiencing pain throughout the range of motion to the

apprehension zone.

The unaffected side of the same subjects served as the control as all subjects had

unilateral ASD .

Table 2.1 Demographic data for subjects with ASD

lab be 95 34 I

2.2. Experimental Procedure

All patients were tested in the Restorative Motor Control Laboratory in the

Department of Physical Therapy, University of Toronto. Patients were asked to read the

information sheet, to sign the consent form, and fill out the demographic data (Appendix

B). They were seated in a chair with a seat belt across their pelvis and their back against

the back of the chair to avoid the rotation and movement of the thorax (Appendix C).

The ann was placed on the table in 90" of shoulder abduction, and with the elbow flexed

at 90°. The forearm was at O0 of supination and pronation (neutral position). Maximum

external rotation of the GHJ was obtained by using goniometric measurements using the

olecran and styloid process for reference points. The patients were asked to externally

rotate their shoulders and the maximum was recorded bilaterally.

The 65%, 75%, and 85% angle of maximum external rotation of the dislocated

joint was used as the three movement end targets for both shoulders. The non-affected

shoulder had two more end targets. One was 40% of the maximum external rotation of

the dislocated shoulder. The last target was two thirds of the difference between the

maximum external rotation of the non-affected shoulder and the maximum external

rotation of the dislocated shoulder (Table 3.1-2). The end targets represent specific target

angles.

A plastic board, which was placed behind the am, was marked with the five end

targets for the unaflFected shoulder and the three end targets for the dislocated shoulder.

For the detection of limb position three light emitting diodes (LEDs) were taped on the

arm at the fifth metacarpophalangeal joint, the ulnar styloid and the olecran, and a

Kinematics System was used to record the movement. Two LED'S were placed on the

board: one was different for each target (defined as a target angle), and the other LED

was fixed on the plastic glass.

Prior to testing each subject, a randomized order of target angles was determined.

The dislocated shoulder was tested first. Following an auditory cue the patients were

directed to rotate the arm externally (self-paced movement) &om a resting position to the

end target (Appendix C). They held the arm for 1 second at the end target. Subjects were

instructed to start the external rotation-fiom the same referece position in order to get a

consistent measurement of each angular movement. It is well known that shoulder

abduction and external rotation is associated with medio-lateral translation of the

shoulder, which may change the starting point and the magnitude of the angular

movement. The first fifteen trials were conducted with visual feedback and the next

fifteen were without visual feedback. Each angular movement to target was recorded.

2.3 Data Collection

A Selspot II System was used to measure the kinematics. The Selspot II System

measures the position and movement of the LED with a temporal (1000 Hz) and spatial

resolution (0.025% of measuring range) respectively. The cameras detect the center of

the light image and generate output signals that represent x and y coordinates that are

later converted into precise 3-D positional information using an algorithm. Data were

captured on a PDP-11/73, transformed and transferred to a PC in ASCII format. The

ASCII data were imported into Sigma-plot (Jandel). A subroutine was used to calculate

the degree of movement (target angle).

The target position is planer and it is composed of x and y components. The

angle reproduced by each subject at each trial was calculated according to the formula

below (O'Neil, 1995):

where: xlyl are the coordinates &om the board

x2y2 are the coordinates tiom the arm movement as seen in the next figure

Figure 2.3-2 Diagrnm of coordinates of planar angular movement

After the two cameras were set up and calibrated with a 3-D calibration fiame of

know specifications, a picture of the experimental set up was taken to detect the error in

the system due to experimental procedure (Appendix C). For most experiments the range

of error was between -1.4' and +0.2". The duration of time recorded for each movement

from resting position to the target angle was 3000 or 4000 ms. For each subject the end

position was measured as seen in the figure below.

Figure 2.3-2 Shoulder angular movement to target (93")

-- . - - E n d

0 ' 1000 2000 3000 4000 ! Tim (rn S) r

- 3 .

i Start pomWi.m

2.4 Data Analysis

The target error was calculated by subtracting the reproduced angle &om the

target angle. Underestimation occurred when the error was < 0" and an overestimation

when the error was > OO. Because the data were not normal1y distributed a Mann-Whitney

U-test was used to test the significance between mean data collected for each target with

visual and without visual feedback, and between DS and WAS. To reduce the probability

of type I error a Bonferroni correction was applied. The p 5 0.05 was divided by 12

which represented the level of independent variable (two sides, both conditions) and three

targets. The "p" value was established at the p s 0.004 level to determine the significance

between DS and N-AS for three targets. The N-AS had three independent variables (one

side, both conditions) and two extra targets, and therefore the p 5 0.05 was divided by 6.

For N-AS the significance level was set p I 0.008.

In addition, the overall dserence in ability of the subjects to reach the targets for

the DS and N-AS was compared using the paired t-test for each target individually. Since

only three targets are being compared the alpha level for statistical significance was set to

p S 0.0513 = 0.015. Ifthe "p" value associated with the t-statistic was leu than or equal

to 0.015, then the result was considered to be statistically significant. For target II the t-

value was 4.848 and the p S 0.0005. The t-value for target III was 2.842 and p z; 0.0 1.

For target IV the t-value was 4.217 and p s 0.005. The p-values are reported in Appendix

E and F.

CHAPTER3: RESULTS

3.1 Characteristics of study sample: clinical evaluation and pathology

had to

Ten subjects performed the task of reaching to the end targets bilaterally. Subjects

externally rotate the shoulder to three targets with the affected shoulder and five

targets with the non-&ected shoulder. The velocity of shoulder movement was for N-AS

between 33*/s to 5g0/s and for DS was between 3S0/s to 68*/s. Targets E, III, and N

represented 65%, 75%, and 85% of angular movement fiom maximum ROM of the

dislocated side. Targets I

shoulder, The clinical and

the table below,

and V were the two additional targets for the non-affected

radiological evaluations of al l the patients are summarized in

Table 3.1-1 Clinical and pathological evaluation of the dislocated shoulder

Three patients had a HiLSachTs defect, two patients had a Bankart lesion and one

a superior labrum, anterior and posterior (SLAP) lesion (Appendix D). Most of the

patients had an apprehension sign and a positive relocation test. One patient had a visible

atrophy of supraspinatus, infraspinatus and deltoid and a limited ROM in DS (48"). No

correlation was found between the magnitude of the MTEO and the number of

dislocations. The maximum ROM was measured for both shoulders (see table below).

Tabk 3.1-2 Maximum range of movement in N-AS and DS, and target angles

MEAN 115' 98' 16- 39' 64- 74" 84' 111' 21 So 9.9 20' 20" 8' 1 3' 1 5" 17" 9'

TARGET t 40% of maximum ROM of DS ,TARGET I I 65% of maximum ROM of DS TARGET 111 75% of maximum ROM of DS TARGET IV 85% of maximum ROM of DS TARGFT V 213 ( maximum ROM contralateral shoulder - maximum ROM ds) + maximum ROM ds

SUM. NO.

The mean maximum ROM in N-AS was 1 1 SO+O.SO, and in DS was 98OSO0. The mean

degree of difference between N-AS and DS was 16"eO0. The patient (P9) with restricted

ROM on DS (48O) had 14 recurrent dislocations over 16 years without seeking

intervention and was the subject demonstrating the most pathology and clinically aspect.

DIFF. OEGR

MAX, EXT. ROT.

1 2

, 3 4

TARGET N-A SHOULDER I

36- 36- 44' 44' 44' 42- 40' 40- 19- 48'

DS

100' 120' 11 0' 116'

II

58' 90' 90' 110' 110'

5 I 130'

1 Om 30- 0' 6.

110'' 104' 100" 99' 48' 121'

6 7 8 9 10

V

9 7

ill

68'

20' 4' 12. 6- 70' V

108' 112' 105' 11 8' 127'

110' 108' 114' 123' 107' 108' ,

103'

127'

tV

78' 78' 93' 93' 93' 88' 85'

58- I 68' 71' 1 8T 71' 1 8T 71' 68' 65'

8 2 78' 75'

m" 31' 79-

74' 1 84' 36" 41' 91' 1 103'

3.2 Comparison of target error in two conditions in the non-affected shoulder

The results discussed below represent the data obtained fiom all 10 subjects for all

targets in N-AS with the exception of target V in subject 9 (data error). Target error was

defined as the dserence between the calculated target angle and the calculated angle

reproduced by each subject for all targets in DS

mean target error in degrees (MTEO) for I5 trials

feedback

and N-AS. The table below shows the

for each subject with and without visual

Table 3.2-1 MTEO for .U subjects in the N-AS

The MTEO in the task performed with visual feedback was significantly different fiorn that

performed without visual feedback for almost all targets and all subjects @ 5 0.004),

(Appendix E). The MTEO for target I was statistically different for almost aIl subjects

(iK 0.008) and for target V the significance difference was observed only in 4 snbjects

(Appendix E). A negligi'ble aror of lo was seen for last target (V). The data f?om Table

3.2-1 are displayed graphically in Figure 3.2-1

Figure 3.2-1 MTEO for u c h subject uith and without v i s d feedback h the N-AS

Most of the tasks were underestimated when the movement to the target was

performed without visual feedback. Overestimation occuned on 5 1% of the tasks with

visual feedback and an underestimation of 74% without visual feedback Wlthout visual

feedback the target error and the variability increased as seen in Table 3.2-2.

Table 3.2-2 MTEO for dl subjects with and without visual feedback in the N-AS

Figure 3.2-2 shows a box plot graph of the median target error. The rectangle

shows the interquartile range; the upper line of the rectangle is the 75* percentile and the

lower Line is 25& percentile. The line in between the lines showing 75" and 25& shows the

median value of the data. When the median is in the middle of the rectangle the data is

normally distributed and the mean and median are the same. Outside of the rectangle are

two vertical lines which show the range when other value might be observed, given the

median and interquartile range of the distribution. The open dots show outliers in the

data. The plot clearly shows the increase in variability in the tasks without visual feedback

in most cases.

me.-.....

I

....... VISUAL ..,,--,.. FEEDBACK .-..- ................ ...-.. ...............- ------.--___._.-_._I_

*--.-..--*w ....

wm~out - . .......................

" 'S. !k ., ..

FEED.BA~.K

...-.-.............-......- TARGETNO.

.--.---.--.- MEAN .....,,.,.,,..,.-, 1fS.D. --..-....-..-..-..-.- RANGE ...........................................

TARGETNO. , mw. . ,

,!.?S*!?*.. MGE. . , .

V

,-.----.-a. .... ..... 553

6.06 ............. 17.61

...............................

V . . . . . . . . . . . . . . . . .

4 A 5 , . 637 . 17-34

I ---r--

2.74 .--.-. 4.10 ...... - --..

14.12

............................................................

I

. . . . . . . . . . . . . . . . . . . , . . , . -1 -99

. ,3147 , . 9.76

n/

..-,--.-A,..

E!?- 3:6*

10.41 .-.-....---..-,.-..-.--~.--~-.-.,-~_f..-f-*-------I---.---~---.-----

,....

IV

,

..... , -?*0 . , 8-56 . 23-83

II 1 Ill

---.-.---4.-----.---.

1.99 1.--.,

3.48 024 --..----. 4.47 . ....-.-. -. ........-..-.,..-...

10.50' 15.37 I....

II

...............

1U I

. . . . . . . . . . . . . . . . . . . . . . . . . . . . -6.92

. . 5 1 7 ~

, .

...... -7-97, . - 0 . . 22.45

Figure 3.2-2 Median target error for a11 subjects in the N-AS

Target number

3.3 Comparison of proprioception in the dislocated shoulder versus the non-affected

shoulder

Table 3.3-1 summarizes the MTEo for each subject for three targets examined in DS.

Table 3.3-1 MTEO in the DS with and without visual feedback

The MTEO in the tasks achieved with visual feedback was significantly different from that

achieved without visual -back for almost all targets @S 0.004), (Appendix E). The

data fiom Table 3.3-1 is displayed graphically in Figure 3 -3-1

Figure 3.3-1 MTEO in the DS with and without visual feedback

In the task performed without visual feedback the subjects underestimated the

target in 90% of the trials and the mean and variability was high for these tasks.

Table 3.3-2 shows the MTEO for all subjects in the DS with a high degree of

difference between vision and no vision conditions.

The next box

Table 3.3-2 MTEa in the DS for all subjects in both conditions

without visual feedback, again underestimated.

I

plot graph shows the increase in variability in the tasks performed

TARGET NO.

Figure 3.3-2 Median target error in the DS for all subjects in both conditions

A I IU I IV , I I

Visual feedback 1s 1 1

Without visual feedback

I

Target number

There was a significant diierence (p~0.004) between the DS and N-AS in the

tasks performed without visual feedback for almost all patients and all targets

(Appendix F). The t-test (Appendix E) shows also a significant difference between the

two shoulders with less magnitude for target II.

Figure 3.3-3 Median for ail subjects in DS and WAS witbout visual feedback

Target number

As seen in Figure 3 -3-2 target LI and IV were underestimated to a greater degree

when the subjects used their DS. Target II was also underestimated but the median in

both shoulders was almost similar: DS (-8.4Z0) and N-AS (-8.56O). The "p" value was

significant only in four subjects for this target (Appendix F). The mean difference of the

A4TE0 for targets I& JII, and TV in the tasks performed without visual feedback in DS

(10.71°, 10.97O, 6. lo0) for all subjects was 3.4" greater than in N-AS (6.92O, 7.97O,

2-80').

3.4 Stability of end point in both shoulders related to both conditions

The end target angle achieved by all subjects was stable over the 15 trials for al l

targets in the tasks performed with visual feedback The end point variability was

increased in the tasks without visual f d b a c k The increase in variability was observed in

both shoulders and it was not target specific.

Figure 3.4-1 End point variability for each subject in the N-AS target: II,

botb conditions

Fipre 3.4-2 End point variability for each subject in DS target: 1CI, IV in both

conditions

Number trkb Number mas

Summary of results:

There was a significant difference between the MTEO in the tasks performed with visual

compared to those without visual feedback in both shoulders.

An increase of end target angle variability was observed in both shoulders in no visual

feedback tasks.

The difference in MTEO between visual and no visual feedback tasks for all subjects for

target (V) in N-AS was negligible (1 .OO)

The mean diffkrence of the MTEO was higher for the DS (3.4O) versus N-AS in the

tasks performed without visual feedback.

CHAPTER 4: DISCUSSION

Lephart et al. (1994) have suggested that proprioception of the shoulder joint plays

an important role in the stabiity of this multiple degreeof-fieedom joint. The angular

reproduction of active movement of subjects with DS and N-AS was measured in the

present experiment. The major finding was the difference in the average MTEO of3.4" for

the three targets, between DS and N-AS, in the tasks performed without visual feedback.

The other findings ofthis study were:

1) a statistically significant difference between the MTEO in the tasks performed with

vision compared ta those without vision in both shoulders,

2) an increase of end target variability in tasks without vision in both shoulders, and

3) a negligible MTEO (1 .OO) between visual and no visual feedback for target V in N-AS.

Averaae difference in MTEO of 3 -4' in the tasks without visual feedback between DS and

N-AS for three targets -

In recent years, functional proprioception tests have been developed to compare

the difference of proprioceptive performance in normal subjects and subjects with

dislocated shoulders. These studies have reported a decrease of proprioception in DS

(Smith & Brunolli, 1989; Lephart et al. 1994; ForweU. & Camahan, 1996; Alvernalrn et al.

1996). Except for the study of Alvemalm et d. (1996), and Forwell and Camahan (1996),

all the studies have used a passive movement task, which could not require the activity of

all the receptors compared to those activated during a natural movement. The present

study was performed using an active movement of the shoulder joint. It has been

suggested that an active matching movement is more accurate than a passive one (Paillard

& Brouchoq 1974; Alvemalm et al. 1996) and indeed Gandevia et al. (1992) proposed

that tests of proprioception should be performed using active movement because the

muscle spindle activity related to proprioception is increased during an active movement.

The active movement activates the joint, and cutaneous receptors, as well as the muscle

spindle and thus the reproduction of the position of the joint has the potential to be more accurate (Gandevia et aL 1983; 1992).

The methodology used in the present study was similar to that used by Alvemalm

et d- (1996) who also found a difference, although of smaller magnitude (1.2O) between

normal and DS group. However, one difference was that Alvemalm's DS group had

previously undergone surgical repair. The reason for the slight difference in MTEO

between the two studies remains unclear. The Aivemah et al. (1996) study used a

different measurement system, which may have been more accurate. However it is

unlikely that measurement accuracy was the cause of the digerence in the present study,

since multiple measurements in both sides showed a significant difference between DS and

N-AS. Another explanation could be related to the characteristics of the groups involved

in the studies. As mentioned AIvemdm et al. (1996) used a control group of normals and

a patient group represented by patients who had had surgical repair, rather than no-

surgically group, as in the present study. The control group in our study was the non-

&ected side. From the previous studies it is not known if the decrease in proprioception

on the & i e d side is related to damage to receptors arising from recurrent dislocations

and to damage resulting from the surgical repair. It has been suggested (Lephart et al.

1994) that surgical repair restores the shoulder stability and this may result in improved

proprioception but for biomechanical reasons. If this is the case then one would predict

that the surgically repaired group could have had a smaller magnitude in degree of error.

Forwell and Camahan (1996) also used an active movement (reaching task) in

assessing the proprioception in normal subjects and those with a previous DS. The

kinematic data (peak finger velocity, time to peak finger velocity, and normalized time to

peak finger velocity) showed that there was a difference between the two groups. The

hding was associated with a proprioception deficit in DS. In the present study we did

not investigate differences between shoulders in terms of initiation time, velocity, and how

long it took for subjects to stabilize the shoulder when they reached the end point target

which could be measured in future to enhance insight into the differences.

It is more difficult to compare the present result with results of Smith and Brunolli

(1989) and Lephart et al. (1994) studies, who measured proprioception in normals and

subjects with DS, using passive angular reproduction tests because they used very

different measurement techniques. Nevertheless they found deficits in proprioception in

the dislocated shoulder and concluded that recurrent dislocations r d t e d in an alteration

of sensory receptors, due to trauma Since both techniques (passive and active) showed a

dBerence between the DS and WAS, this suggests that multiple dislocations may lead to

alteration of peripheral sensory receptors: It would be important to find a method for

distinguishing between neural and biomechanical intluences. It would however, seem

reasonable to speculate that proprioception might be decreased with an increased number

of dislocations+

From the present study it is not known how clinically significant the MTEO

diierence in proprioceptive performance of 3.4' between the two sides would be, and

future investigation would be useful to determine the relationship between the degree gf

shoulder pathology, the proprioception alteration and the functional significance.

A sieniticant difference between the MTEO in the tasks performed with vision compared to

those without vision in both shoulders

Another £inding in the present study is the difference between the MTEO in the

tasks perfonneci, with vision in comparison to those without visual feedback in both

shoulders as was evidenced in Figures -3 -2- 1 and 3 -3- 1 and Tables 3 -2-2 and 3 -3-2. It has

been well known and not surprising that vision improves the accuracy of reaching the

target (Keele et al. 1968; Carlton, 1981). Our findings confirm those of Forwell and

Camahan (1996) and others who have shown that vision decreases the error in active

reaching movement of the shoulder joint (1 8.9 * 2.3mm with vision vs. 28.0 * 1 . 7 m

without vision in study of Forwell and Camahan, 1996).

Increase of end target variability in no vision tasks in both shoulders

In the present study it was noticed in tasks performed with visual feedback that the

end-point is relatively stable and the variability is increased in the tasks without visual

feedback These findings confirm those of others (Gordon et al. 1995; Ghez et al- 1995)

who demonstrated that vision decreased the end-point error in deaerented patients. In

the same studies after the vision was occluded the error increased indicating that vision

had a small effect over time. The authors concluded that the subjects needed continuous

visual sensory information related to limb position in order to have an accurate

proprioception of movement. The present study confirms the findings of the above studies

because the variability was increased for both control shoulders and DS in the tasks with

no visual feedback

Another finding of this study was that in the tasks performed with visual feedback

overestimation was predominant in both shoulders whereas in the tasks without visual

feedback underestimation in the DS was usually predominant. This finding is at variance

with that of Alvemalm et aL (1996) who reported that most subjects with surgical repair

overestimated the target. The difference between the two studies may be related to the

different test procedures and this tinding needs hrther investigation.

Negligible difrence in MTEO (1 -09 between visual and non-visual feedback for target V

in N-AS

Another observation in the present paper is related to the negligible MTEO at the

last target (V), between visual and non-visual feedback in WAS, as seen in Figure 3.2-2.

This finding suggests that joint receptors may be more sensitive when the capsule is

stretched, especially near the end range of joint movement, and supports previous studies

(Burgess & Clark, 1969; Burke et al. 1988). Burgess and Clark (1 969) recorded single

joint fibers in cats and found that most of the afFerents responded to marked flexion and

extension. Later Burke et d. (1 988) used mimneurographic techniques from afferents

associated with the distal interphalangeal joint in humans. They found that the majority of

afferents were sensitive only at the limits of joint rotation. Thus it is reasonable to observe

a decrease of detection error in the normal shoulder where the sensory receptors provide

accurate information related to joint movement and position sense.

Ierosch et al. (1993) who used lidocaine intra-artidarly at the shoulder joint

during a clinical study found that passive anteroposterior translation of the shoulder joint

was increased in the group where the anaesthetic solution was injected, compared to the

group where no anaesthetic was used (13.2 * 6.3mm vs. 6.8 3.2mm) implying that joint

receptors were "disrupted" by the anaesthetic solution. Smith and Bmnolli (1989) tested

proprioception at the extreme range of movement in DS patients passively but in the

present experiment the proprioceptive performance near the end range of motion in DS

was not tested in order to ensure that a dislocation would not occur. Exploration of end

range would be essential to wntinn this hypothesis.

Factors affectine the proprioceptive testing in the present study

The hctional proprioception tests of the shoulder joint are affected by multiple

fhctors. Factors related to the test procedures are associated with the configuration of the

set up of the Selspot II System. The plexi glass board where the targets are set should be

in the center of calibration h e in order to avoid errors. In the present study, the error

of the system was measured between -1.4" and +O.ZO, which was less than the MTEO

difference. Another f u o r is related to the center of angular movement that could be

different due to medio-lateral translation in external rotation of the shoulder joint. In the

present study this is not the case because the subjects were instructed to start the

movement fiom the same position.

Other factors could be attributed to physiological changes of the subject's

perception. These could be related to age, vision, fatigue, memory and learning

disruptions, and speed of movement. Voigh et d- (1996) suggested that proprioception

can be altered by muscle fatigue. Muscle fatigue changes the ability of muscle receptors to

detect an accurate positioning of the shoulder joint. The authors observed a signi6cant

difference in the perception of arm position between pre and post fatigue. Cohen (1 958)

noticed an increase of error in reaching the target of shoulder joint when subjects began to

sway more than usual. This is not likely the case in the present study as no subjects

reported any fatigue at the end of the test.

McCloskqr (1978) and later Alvemalrn et al. (1996) suggested that memory and

learning effects are thought to be important factors in proprioception. One type of

memory, visual memory, based on "mental maps'' has been thought to have implications in

task reproduction (Chase, 1986). In the present experiment an increase of variability of

angular reproduction was noticed in the tasks without vision, as seen in Figure 3.4-1 and

3 -4-2. This finding supports the view of Ghez at. al. (1995), who suggested that visual

memory for Limb position, is transitory. A Wher study (Blouin et al, 1996) demonstrated

the accufacy of ann movements that is being re!ated to various types of oculomotor

behaviors. These included fixation, saccade and pursuit condition preding the

movement. The authors estimated the accuracy of arm movement related to different

movements of the eyes during reaching the targets in normal and deafferented patients.

The authors emphasized that patients used different eye movement strategies. Patients

had a good accuracy of arm movement in saccade condition and a large error in pursuit

and fixation condition compared to normal subjects who had a better performance in

fixation condition. This finding suggests that the accuracy of reaching the target in

patient's group was infhenced by visual feedback to compensate the lack in

proprioception compare to the normal subjects who did not rely on vision The group of

normal subjects had an accurate movement in the fixation condition-

Clark and Horch (1986) described "memory for limb position". The authors

suggested that this type of memory is related to proprioception sensory information

because, without vision, subjects could match the remembered position of the limb even

after many hours. The authors also postdated that in matching tests of position of the

two limbs, the memory for limb position is more accurate than the absolute position of a

single limb. They could not explain the mechanism of this memory. Alvemalm et al.

(1996), in repetitive testihg, did not find a significant difference between day 1 and day 2,

and between day 2 and day 3, however there was a difference between day 1 and 3 and

therefore they emphasized the effect of leaming/memory in improving proprioception. In

the present study the memory effect was not tested because the test was not repeated over

days but it would be important in the future to test for "memory o f limb position", both

short intermediate and long term.

Age is another factor that may a@& proprioception. Kaplan et d. (1985)

suggested that the elderly (mean age of 70) had an increase of deficit in proprioception

compared to young subjects (mean age of 24). The error of passive reproduction

movement of the knee was 7 O + 1 in elderly and 4' + 1 in young subjects. In the present

experiment, the mean-age was 26.4 + 4.3 years, and therefore unlikely to influence the

conclusions of this study.

Speed of movement may influence proprioceptive performance. In the present

experiment, the subjects used a self-paced movement that has been suggested by Hall and

McCloskey (1983), to be optimal for better performance because it is adequate time for

the afferent information fkom the sensory receptors to be transmitted and processed. In

the present experiment all patients were requested to peform the tasks in both shoulders

at comparable speeds, and therefore velocity should not have influenced the difference in

proprioception between the two sides but in the future it could be measured in detail.

Limitations of the present stud^ The present study has some limitations related to the apparent diierence in the position of

an object when it is viewed fiom different points. This may explain some of the

overestimation error observed in the tasks performed with visual feedback. McCloskey

(1978) mentioned that the mechanism for the location of the target is important in

accurately reproducing the joint position. The mobile center of the angular movement that

is related to the medio-lateral translation of the arm is another limitation observed but

allowed for naturally occurring knctional movement. Each test started with the afYected

shoulder. In this manner it may have allowed the patients to have a better understanding

o$ and a better performance in N-AS.

Future research

Future experiments should use proprioceptive inputs in learning the tasks as Bard et al.

(1995) have suggested and avoid the problems with vision (e.g. parallax). These

experiments should use a fixed center point, and randomize the order of testing two

shoulders. These experiments could be performed at different velocities of movement in

order to characterize the effect of velocity on the performance of proprioception. Future

studies could measure the initiation time, the movement time, and the variability of end

point Another recommendation is related to the implication of recurrent dislocations on

shoulder proprioception. Comparative studies should be performed in subjects after first

and multiple dislocations to determine if there is a cumulative effect as Wirth and

Rockwood (1993) suggested that eariy repair after an initial dislocation may allow the

patients to have comptete fiction of the shoulder joint.

CHAPTER V: SIMMARY AND CONCLUSIONS

1) The aim of this paper was to measure the position sense (proprioception) in ten subjects

with previous ASD. The control group was the non-affected arm.

2) The subjects had to perform an active movement that resembled a throwing motion

with and without visual feedback (15 trials).

3) The clinical data revealed that the mean ROM in the dislocated shoulder was decreased

(mean 98O) compared to N- AS (mean 1 1 5 O ) . One subject had very limited ROM (48O)

perhaps due to multiple dislocations.

4) In the DS the MTEO was increased by 3.4' compared to the N-AS in the tasks

performed without visual feedback. This finding suggests that there may be a deficit of

proprioception in DS.

5) As expected the m0 was decreased in the tasks with visual feedback in both

shoulders.

6) A negligible error of ME0 was observed at the last target in N-AS and suggests that

the contribution of activity from joint receptors is enhanced at the end oEROM confirming

previous studies that have postulated that joint receptors are more sensitive to the end of

ROM.

7) The present paper has some limitations related to visual feedback in learning trials and

technical procedure.

8) Future studies should examine the effect of learning (repeated trials longer over time

frames) on proprioception. Future experiments should test subjects after initial and

multiple dislocations to characterize the performance of proprioception in recurrent

dislocations and include subjects before and after surgical repair to see if treatment

approaches alter proprioception.

9) The present study suppons the findings of previous studies and suggests that ASD is

associated with a decrease in proprioception. The present study also provides a better

understanding of proprioception during active movement of the upper limb. It also opens

up the question whether that could be helpll in navomuscular training of patients with

ASD before and post surgical repair.

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APPENDIX A

PAULEMARI<SBmMD,FBCSC SHOULDER PROTOCOL SHEET

APPENDIX B

PROPRIOCEPTION FOLLOWING ANTERIOR SHOULDER DISLOCATION

Subject Information S W

This study is being conducted by Prof Molly Verrier @kctor, Restorative Motor Control Laboratory, Department of Physical Therapy), Dr. Paul Marks (Oahopaedc Surgeon, The Orthopedic and Arthritic Hmital), and Oaaa Scafesi, Graduate Student, Department of Rehabilitation Science at the University of Toronto.

The purpose of-this study is to determine if patients with shoulder instability (people who are prone to dislocating their shoulder) have a d m sense of shoulder and arm position when they m o t see their a m Normally the detection of shoulder position is important since it prevents straining of the shoulder. If someone has injured his or her shoulder, a decreased sense of position may lead to in- Nain on the shoulder and hrr(her injury- If this holds tme, then th& to in- the ability to sense shoulder pusition may be in order for people who hjwe their shoulders.

As a participant in this study, I will be asked to perform 30 trials (each trial lasting 10 seconds) of moving my arm in a throwing motion while I will sit in a cbair. These tests will occur at the University of Toronto. I will be able to rest in between each trial if necessary. While I am sitting in a chair with a seat belt across my pelvis, the shoulder will be abducted 90° and external rotated at 65% 75% and 85% of maximum external rotation ,with elbow flexed 90°. The test will be done on both shoulders. Motion of my arm will be recorded by a motion analysis system in which markers will be taped to skin on my elbow,

and the 5th metacarpophdangeal joint. These markers will be used b determine the speed and accuracy of my movements. Muscle activity will be monitored using M a c e eleztmdes taped on the skin. over the shoulder (deltoid, infiaspinatus, supraspinatus, biceps, teres minor, teres major) muscles. Application of the markers and electrodes is by a non-allergenic adhesive and will not cam any discomfort. I will be asked general demographic questions regarding my shoulder (please see attached sheet), -

The risks to me as a participant in @is study are very minimal and no more than may be encountered in a routine medical examination or physical therapy treatment. My anus may feel tired at the end of the session and I may develop a slight rash on nty skin-in response to the adhesive on the marker. The tests may help me understand more about my ability, or inability, to detect the position of my shoulder joint while I am moving it.

The study wi l l be ongoing at the University of Toronto laboratory, but my involvement will be to one 60 minutes testing session. If you have any questions I may contact Prof. M. Verrier at 978-5837 or Dr. P. Marks at 972-7233.

PROPRIOCEPTION FOLLOWING ANTERIOR SHOIKDER DISLOCATION

Subject Consent Form

I have been asked to participate in a study that invlestigates the sensation of movement and position in the shoulder join during a tbrowing motioa This study is being conducted by Prof- Molly Verrier (Director, Restorative Motor Control Laboratory, Deparbnent of Physical Therapy). Dr. Paul Marks (Orthopedic Surgeon, The Orthopaedic and Arthritic Hospital), and Oana Scafesi, Graduate Student in the Department of Rehabilitation Science at the University of Toronto.

As a participant in the study, I will be asked to undergo movement tasks at the University of Toronto. The testing session win take apprordmately 90 minutes, including preparation and clean-up time. I will be asked to wear a short-deeve-d shirt for the session, I will sit in a chair with a seat belt across my pelvis. The shoulder will be abducted WO, and the elbow flex to 90". I will be asked to rotate my arm about the elbow (like a throwing motion) and I will be asked to rotate my ann at 65% 75% and 85% from maximum extemal rotation. For the detection of limb position and speed of movement, 3 markers will be taped to the skin on my arm using non-ailergenic tape. The application of these markCrs is non-invasive and will not cause any discomfort Muscle activity wi l l be monitored using Surface electrodes taped on the skin over the shoulder (deltoid, infiaspinatus, supraspinatus, biceps, teres minor, teres major) musdes. I will &en be asked to move the arm under visual control for IS times, between three Merent positions of external rotation 1 will then be asked to move my arm between three different positions with vision occluded by a blind fold, and there will be 15 trials, I will be asked to move the contralateral shoulder between five merent positions with vision and without vision. I will be asked general demographic questions about my shoulder the answers will be recorded on the attached sheet

It has been explained to me that I may ask questions about the procedures throughout the testing p e r i d I understand tbat my name will not be used in any publication or discussion about this study, and that aU information abut me will remain confidential. I am under no obligation to sign this consent form and understand tbat not participating in the study will not affect my treatment. I may' withdraw h m the study at any time. I have read the attached information sheet and my questions about it have been answered to my satisfaction by Prof. M. Verrier or Dr. P. Marks, If I have any M e r questions 1 may contact M. Verrier at 978-2763 or 978-5837 or Dr. P. Marks at 927-7233,

I consent to participate in this study dated:

,19%

Name of Participant or Guardian Signature of Participant or Guardian

Name of Witness Signature of Witness

Shoulder Proprioception Study Subject Lnfonnation Sheet

Subject Name (Last m e , k t name)

Occupation: Date of Experiment:

DOB (m:d:y) Dominant Side: L R

Athletic Status: ProfessionaI Amateur Recreational N/A

Types of sports/activities

Healthy Shoulder Shoulder Instability (Afkcted side: L R)

Type of injury

Age of injury

Treatment

Medications

Severity of pain: mild moderate severe constant intermittent nocturnal

dull sharp achy gnawing

Aggravating factors

Alleviating factors

APPENDIX C

Proprioceptive testing using Selspot II system

Subject sitting behind the experimental board (marked with target angles) with the arm externally rotating using visual feedback

APPENDIX D

FUNCTIONAL ASSESSMENT OF ANTERIOR SHOULDER DISLOCATION

Neer test: The examiner stands behind the patient, who is seated. Rotation of

the scapula is blocked with one band, while the other lifts the arm

of the subject forwards, producing anterior flexion and abduction

which create a conflict between the trochiter and the anteroinferior

border of the acromion (Neer, 1972).

Hawkins test: The examiner stands in front of the patient and brings his arm at

90" of anterior flexion with the elbow flexed at 90°, obtaining

internal rotation movement of the GHJ. Thus, conflict between

the trochiter and the acromiowracoid ligament is produced

(Hawkins & Abrams, 1987).

Lift off test:

Suicus sign:

The ability to actively lift the internally rotated arm off the

patient's back (test of firmtion of subscapularis muscle)

Widening ofthe subacromial space between the acrornion and

humeral head with dimpling of the overlying skin when inferior

traction to the shoulder is applied (Neer & Silliman, 1996)

Anterior I posterior The patient lies in supine position, the humerus head is grasped

transIation : and compressed into the glenoid fossa. In this 'loaded' position,

anterior and posterior stresses are applied

(Boublik & Silliman, 1996).

Apprehension A positive test is indicated by a look or feeling of apprehension or

test (Crank) alarm on the patient's face and the patient 's resistance to fiuther

motion (Magee, 1992). The test can be performed with the

patient in the supine or seated position. The examiner raises the

arm to 90" of abduction and begins to externally rotate the

humerus. The right hand of the examiner is placed over the

humeral head with the thumb pushing fiom posterior, and with

the fingers anterior to control the instability of the shoulder

(SIlliman & Hawlcins, 1994).

Relocation test : When the apprehension test is positive the examiner applies a

posterior stress to the arm, the patient will lose the apprehension,

and fbrther externat rotation will be possible before the

apprehension returns (Magee, 1 992).

Anterior slide test: The patient lies supine and the examiner places the hand ofthe

affected shoulder in the examiner's axilla holding the patient's

hand. The shoulder to be tested is abducted between 80 and

120° f o m d flexed, 0 and 20"; and laterally rotated, 0 and 30".

The examiner's thumb exerts counterpressure on the patient's

coracoid process and with the other arm draws the humerus

forward (Magee, 1 992).

Speed's test: Resisted forward elevation of the humerus with the elbow

extended and the forearm supinated (Boublik & Silliman, 1996).

Yergason's test: Resisted forearm suppination with elbow flexed to 90'

(IBoubIik & Silliman, 1996).

PATHOLOGICAL LESIONS OF ANTERIOR SHOULDER DISLOCATION

Bankart lesion: It is characterized by avulsion of the capsule and labrum from

the anterior glenoid rim (Rowe, 1980).

Hill-Sacbs lesion: It is a compression hcture of the lateral superior aspect of the

humeral head @owe, 3980).

SLAP: It is a superior labrum, anterior and posterior (SLAP) lesion that

begins posteriorly and extends anteriorly and involves the 'anchor'

of the biceps tendon to the labrum (Snyder et. al. 1990).

APPENDIX E

"p" VALUE - THE COMPARISON OF PROPRlOCEPTlON BETWEEN VISUAL AND NON VISUAL FEEDBACK IN

SUW NO.

TARGET NO. T I

T I1

T Ill

TIV

T V P

T I

T II

T 111

T N

T V -.I1cI

T I

T II

T Ill

T W

T V - T I

T I1

T IN

T IV

T V

N - AS AND DS N - A SHOULDER

P value DS

P value

Not statistically significant p r 0.004 for T II, T Ill and T IV p $0.008 for T I and T V

TARGET NO. T I

T II

T HI

T N

T V

N - A SHOULDER P value

P = 0.0001

DS P value

' Not statistically significant

SUBJ NO.

TARGET NO. T I

T I1

T Ill

T N

T V - TI

T II

T 111

T W

TV

N - A SHOULDER P value

P = 0.0001

No data P = O.385Oa

DS P value

Not statistically significant

COMPARJSON OF PROPRIOCEPTION BETWEEN N-AS AND DS USING t - TEST

TARGET NO.

T II

T 111

T N

SD I "t" VALUE "p" VALUE

APPENDIX F

"p" VALUE - THE COMPARISON OF PROPRIOCEPTION BETWEEN N - AS AND DS WITH AND WITHOUT VISUAL FEEDBACK

TARGE' NO.

BETWEEN N - AS AND D.S. P VALUE

- SUBJ

NO. - 6

7

8

9

10

TARGET NO.

* Not statistically significant -

BETWEEN N -AS AND D.S. P VALUE

fll

T Ill

T IV

TI1

V - visual feedback OV - without vision

V ov V OV V ov

V

-I

-.

I

I

-

I

1

I \

i 1

1