gross anatomy of the elbow capsule

SCIENTIFIC ARTICLE

Gross Anatomy of the Elbow Capsule:

A Cadaveric Study

Lee M. Reichel, MD, Omar A. Morales, MD

Purpose The elbow is an inherently stable joint because of its bony articulation and sur-rounding capsuloligamentous structures. Anatomic and biomechanical studies have focusedon the medial and lateral collateral ligamentous contributions to stability. In 1918, Grayprovided a qualitative description of the elbow capsule and its fibers. Our study wasperformed to detail the gross anatomy of the elbow capsule.

Methods We evaluated the elbow capsule of 6 paired, fresh-frozen cadaveric specimens todetail gross capsular anatomy.

Results We identified 3 distinct bands within the anterior capsule and 3 distinct bands withinthe posterior capsule.

Conclusions Further study is needed to delineate the functional meaning of these anatomicfindings.

Clinical relevance Greater understanding of elbow capsule gross anatomy may lead to im-proved understanding of acute and chronic elbow pathoanatomy and treatment modalities. (JHand Surg 2013;38A:110–116. Copyright © 2013 by the American Society for Surgery ofthe Hand. All rights reserved.)

Key words Anterior elbow capsule, elbow anatomy, elbow capsule, elbow stability, posteriorelbow capsule.

THE ELBOW IS an inherently stable joint becauseof its bony articulation and surrounding capsu-loligamentous structures. Anatomic and biome-

chanical studies have focused on the medial and lateralcollateral ligamentous contributions to elbow stability,but a paucity of literature exists regarding the anatomyand function of the elbow capsule excluding the collat-eral ligaments. It has been noted that oblique and trans-verse fibrous bands exist in the anterior capsule of the

From the Department of Orthopedic Surgery, Baylor College of Medicine, Ben Taub General Hospital,Houston, TX.

Received for publication July 12, 2012; accepted in revised form September 25, 2012.

The authors thank Scotty Bolleter, Chief, Office of Clinical Direction, Centre for Emergency HealthSciences, Bulverde Spring Branch Emergency Medical Service.

No benefits in any form have been received or will be received related directly or indirectly to thesubject of this article.

Correspondingauthor:LeeM.Reichel,MD,DepartmentofOrthopedicSurgery,BaylorCollegeofMedicine, Ben Taub General Hospital, 1504 Taub Loop, Houston, TX 77030; e-mail:[email protected].

0363-5023/13/38A01-0019$36.00/0
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elbow.1 Clinically, the elbow capsule is an importantcontributor in the development of posttraumatic elbowcontractures and acutely has been used to augmentstability in complex elbow fracture dislocations withcoronoid fractures. To better understand this structure,which encompasses the entire elbow joint, we evaluatedthe capsular gross anatomy of 6 paired, fresh-frozencadaveric elbows.

MATERIALS AND METHODSWe dissected 12 fresh-frozen cadaveric elbows (averageage, 73 y; 4 female and 2 male) of all structures except thecapsuloligamentous covering. None of the specimens hadevidence of prior surgery or injury to the elbow. We noteddistinct grossly identifiable anatomic capsular bands ex-cluding the medial and lateral collateral ligamentous com-plexes on each specimen. We measured the lengths ofeach structure. The authors performed all measurementsand agreed on them. Using a digital caliper with a resolu-tion of 0.01 mm and accuracy of 0.1 mm, measurements
were repeated and averaged for each defined structure. We
mailto:[email protected]

http://dx.doi.org/10.1016/j.jhsa.2012.09.031

e, an

ANATOMY OF ELBOW CAPSULE 111

took anterior capsular band measurements in full extensionand took posterior capsular band measurements in full

FIGURE 1: Anterior lateral, anterior medial obliqu

TABLE 1. Raw Length Measurement (Average)of Anterior Capsular Bands, Lateral, MedialOblique, and Transverse

Specimen

AnteriorLateral

Band (mm)

Anterior MedialOblique

Band (mm)

AnteriorTransverseBand (mm)

1a 19.3 16.0 34.5

1b 24.4 23.3 35.3

2a 20.7 18.9 36.4

2b 18.4 15.1 38.3

3a 16.0 23.0 28.0

3b 15.5 15.3 26.7

4a 16.1 17.4 30.1

4b 18.2 22.0 24.8

5a 17.5 18.0 28.0

5b 19.9 28.9 25.9

6a 17.6 19.2 25.2

6b 15.6 17.9 19.7

Average 18 20 29

flexion to maximize respective lengths. In 3 specimens, the

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entire elbow was painted with black paint, and we resectedthe elbow capsuloligamentous structures, creating a nega-tive template of the capsular dimensions for visualizationpurposes only.2 Before any painting, we then measuredmidline distances from proximal to distal of the entireanterior and posterior capsule in both full flexion and fullextension.

We detailed gross anatomical descriptions of the elbowcapsule. We measured average lengths of distinct identifi-able bands of the anterior and posterior capsule and cal-culated gross percent excursion (percent difference in cap-sular length in full flexion vs extension) of the anterior andposterior capsule in full extension and flexion.

RESULTS

Anterior capsule

We identified 3 bands on all specimens. One bandoriginated on the anterior lateral surface of the distalhumerus near the lateral supracondylar ridge and con-tinued distal to insert on the anterior superior annularligament. We defined this band as the anterior lateralband. A second band originated at the anterior medialside of the elbow near the lateral part of the superiormedial trochlear ridge and continued laterally and dis-

d anterior transverse bands of the anterior capsule.

tally to insert on the anterior central and medial annular

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112 ANATOMY OF ELBOW CAPSULE

ligament. We defined this band as the anterior medialoblique band. The third band was a transverse bandcrossing the elbow medially to laterally from the centraland inferior anterior medial trochlear ridge to the ante-rior medial annular ligament. It also gave a contributioninsertion distal to the coronoid tip. We defined this bandas the anterior transverse band. In 2 of 12 specimens (1matched pair), the anterior transverse band was nar-rower and thicker and had an appearance of an acces-sory annular ligament, except that it originated from theanterior capsule rather than the ulna, but there was a

FIGURE 2: Posterior transverse, posterior medial oblique, andolecranon fossa.

TABLE 2. Raw Length Measurements ofPosterior Capsular Bands, Transverse, MedialOblique, and Lateral Oblique

SpecimenTransverseBand (mm)

Medial ObliqueBand (mm)

Lateral ObliqueBand (mm)

1a 24.0 20.0 18.0

1b 24.0 21.0 18.2

2a 21.0 17.8 15.1

2b 24.0 19.2 15.3

3a 18.0 16.0 18.0

3b 17.5 15.9 12.4

4a 20.8 13.3 15.9

4b 19.8 17.0 20.5

5a 24.7 19.6 20.8

5b 20.6 17.3 20.7

6a 19.4 18.2 20.1

6b 21.0 15.5 13.9

Average 21 18 17

distinct separation from the annular ligament. These

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findings were consistent in the 12 specimens (Fig. 1).Although all specimens contained each of the bands,there was variability in their degree of development. Ingeneral, the anterior lateral band was the least substan-tial and well developed compared with the anteriormedial oblique and anterior transverse bands.

Table 1 presents individual lengths. The anterior lateralband averaged 18 mm in length, the anterior medialoblique band averaged 20 mm, and anterior transverseband measured 29 mm.

In full extension, the mean midline distance from themost proximal capsular attachment on the humerus tothe most distal capsular attachment on the anterior ulnain full extension measured 50.2 mm, and 14.2 mm infull flexion. This corresponded to a 28% excursion ofthe anterior capsule in the midline.

Posterior capsule

The posterior capsule also had 3 distinct bands (Fig. 2).A transverse band crossed inferior to the olecranonfossa from medial to lateral, originating and inserting onthe medial and lateral posterior trochlear ridges. Theother 2 bands were opposing bands, 1 originating at themedial posterior trochlear ridge and the other originat-ing at the lateral posterior trochlear ridge, both insertingon the posterior superior ridge of the olecranon tip.These 3 bands formed an inverted triangular shape. Wedefined these bands as the posterior transverse, poste-rior medial oblique, and posterior lateral oblique.

Table 2 presents individual lengths of the posteriorbands. The posterior transverse band length averaged21 mm. The posterior medial oblique band, measuredfrom the posterior medial origin to its ulnar insertion,

rior lateral oblique bands, which lie at the distal portion of the
poste
averaged 18 mm in length. The posterior lateral band,

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ith th


measured from the lateral humeral origin to the ulnarinsertion, averaged 17 mm in length.

The midline posterior capsular distance averaged 9.7mm in full extension and 42.5 mm in full flexion (Fig.3). This corresponded to a 23% excursion of the pos-terior capsule in the midline.

DISCUSSIONAnatomic studies of the elbow osseous, capsuloligamen-tous, and muscular structures have been well documented,but there is a paucity of literature detailing the anatomy ofthe elbow capsule and its function. In 1918, Gray3 pro-vided a detailed qualitative description of the elbow cap-sule, which he referred to as the anterior ligament andposterior ligament, and provided a description of bandssimilar to this report but without quantifying the structuresand with different nomenclature. Regarding the anteriorcapsule, Gray stated, “Its superficial fibers pass obliquelyfrom the medial epicondyle of the humerus to the annularligament. The middle fibers, vertical in direction, passfrom the upper part of the coronoid depression and be-come partly blended with the preceding, but are insertedmainly into the anterior surface of the coronoid process.The deep or transverse set intersects these at right angles.”Gray described the posterior capsule: “This posterior lig-ament is thin and membranous, and consists of transverseand oblique fibers. . . . It is attached to the humerus imme-diately behind the capitulum and close to the medial mar-

FIGURE 3: Anterior and posterior view of a painted specimen w

gin of the trochlea, to the margins of the olecranon fossa,

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and to the back of the lateral epicondyle some distancefrom the trochlea. Below, it is fixed to the upper and lateralmargins of the olecranon. . . . Transverse fibers form astrong band which bridges across the olecranon fossa;under cover of this band a pouch of synovial membraneand a pad of fat project into the upper part of the fossawhen the joint is extended.” Morrey noted “the anteriorcapsule inserts proximally above the coronoid and radialfossae. Distally, the capsule attaches to the anterior marginof the coronoid medially as well as the annular ligamentlaterally.”1 He also described the anterior capsule as a thintransparent structure with strength provided by transverseand obliquely directed fibrous bands. King et al4 reportedthat “the anterior capsule has transverse and obliquelydirected bands that have significant strength and providean important stabilizing effect when the capsule becomestaut in extension. The posterior capsule similarly becomestaut in flexion and may also have an important role as astatic stabilizer in this position.” Morrey and An5 dem-onstrated the importance of the anterior capsule as astabilizer to varus stress and demonstrated that theanterior capsule contributed 32% resistance to varusstress and 85% of resistance to distraction in fullextension.

The focus of this anatomic cadaveric study was todescribe the gross anatomy of the anterior and posteriorcapsular bands, excluding the medial and lateral collat-eral ligaments. Three distinct bands have been identi-

e capsule excised, demonstrating the area covered by the capsule.

fied on the anterior capsule of each specimen: the an-

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terior lateral band, anterior medial oblique band, andanterior transverse band. Each of these bands had aprimary insertion point on annular ligament. In mostspecimens, the anterior transverse band also inserted onthe coronoid tip as it crossed. Although we did notevaluate them in this study, anterior capsular insertionpoints on the annular ligament and coronoid processand the behavior of the anterior capsule in variousamounts of flexion may explain why capsular repair tothe footprint of a coronoid fracture in complex elbowfracture dislocations may help provide stability to theelbow.6 Studies are needed to evaluate what portion ofthe anterior capsule and in what degree of elbow flexionthe capsule should be fixed to the footprint of a coro-noid fracture. In addition, in 2 specimens (1 matchedpair), the anterior transverse band was narrower andthicker and had the appearance of an accessory annularligament, except that it originated from the anteriorcapsule rather than the ulna, but there was a distinct

FIGURE 4: Anterior capsular re

separation from the annular ligament.

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We also identified 3 bands in the posterior capsule: theposterior transverse, posterior medial, and posterior lateralbands. These bands formed an inverted triangle inferior tothe olecranon fossa attaching from the humerus to theposterior superior ridge of the olecranon tip. The posteriorcapsule extended proximal to the olecranon fossa, but the3 identifiable bands resided inferior to the fossa. Theybecame tight in flexion and bunched up into the superiorportion of the olecranon fossa superior to the olecranon tipwhen the elbow was extended.

Based on their anatomical course, the anterior bandsmay function as secondary ligamentous stabilizers ofthe lateral collateral ligament, keeping the radial head(and proximal radius and ulna) held anterior in a check-rein fashion when the annular ligament is competent.This is evident during elbow extension, because theyare visualized becoming taut, but this is only an obser-vation. Biomechanical and sectioning studies areneeded to demonstrate the contribution of the anterior

ancy from extension to flexion.

capsular bands to elbow stability. In addition, tightening

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of the anterior capsule and ligamentous bands in exten-sion may function to counteract hyperextension of theelbow, preventing the ulna from levering out of thetrochlea when the olecranon tip contacts with the olec-ranon fossa. Conversely, the posterior bands were tautin flexion and may prevent the ulna from levering offthe trochlea during hyperflexion. Safran and Baillar-geon7 postulated that the posterior capsule may serve asa restraint to flexion and posterior directed forces.

From extension to flexion, there was a considerableredundancy in anterior capsule, which folded on itselfto accommodate the shortened distance in flexion (Fig.4). The excursion of the anterior capsule was approxi-mately 28% from flexion to extension. This observationmay be relevant to capsular repair in terrible triad inju-ries. The location of suture placement in the capsule andthe amount of elbow flexion at time of suture placementmay greatly affect how tight the repair is. Conversely,from flexion to extension, the posterior capsule foldedon itself in the olecranon fossa superior to the tip of theolecranon in full extension (Fig. 5). We calculated pos-terior capsular excursion of 23%.

We saw discrete bands in all specimens but reportedonly band lengths because they could reliably and re-producibly be measured with visual inspection. We did

FIGURE 5: Posterior capsular re

not report band widths because band width was variable

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along the course of the band and there was no reliableway to reproducibly obtain measurements. We mea-sured capsular bands in specimens with intact capsules;therefore, we did not measure capsular thickness. Dis-rupting the capsule to measure thickness would result infolding and redundancy, making thickness measurementsunreliable in this study. Small length differences wereattributed to differences in the specimen sizes (ie, largespecimens had longer lengths), but calculating averagesminimized these differences across all specimens.

Clearly, this is a small sample size, and examinationof more specimens might reveal other anatomical vari-ations. In addition, because we performed the dissec-tions and measurements together, we calculated no in-traobserver or interobserver error.

This cadaveric study demonstrated the presence of 3distinct bands present in both the anterior capsule andposterior capsule, excluding the medial and lateral collat-eral ligaments. Their functional contribution has not beenevaluated. Based on their anatomic course (origin on thehumerus and insertion on the annular ligament, which is anattachment point for the lateral collateral ligament), wepresume that the anterior capsular bands are importantsecondary ligamentous stabilizers to the annular ligamentand lateral collateral ligament, as well as a checkrein to

ancy from flexion to extension.

hyperextension of the elbow joint. Posterior ligaments

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structures are presumed to function as a checkrein coun-tering hyperflexion. More study is needed to define thecontribution of these bands to elbow stability.

REFERENCES1. Morrey B. Anatomy of the elbow joint. In: Morrey B, Sanchez-Sotelo

J, eds. The Elbow and Its Disorders. Philadelphia, PA: SaundersElsevier; 2009:18–23.

2. Fuss FK. The ulnar collateral ligament of the human elbow joint:
anatomy, function, and biomechanics. J Anat. 1991;(175):203–212.
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3. Gray H. Gray’s Anatomy. 20th ed. New York, NY: Lea & Febiger;1918:321–322.

4. King G, Morrey BF, An K. Stabilizers of the elbow. J Shoulder ElbowSurg. 1993;2(3):165–174.

5. Morrey BF, An K. Articular and ligamentous contributionsto the stability of the elbow joint. Am J Sports Med. 1983;11(5):315–319.

6. Cage DJ, Abrams RA, Callahan JJ, Botte MJ. Soft tissue attachementsof the ulnar coronoid process: an anatomic study with radiographiccorrelations. Clin Orthop Relat Res. 1995;(320):154–158.

7. Safran MR, Baillargeon D. Soft-tissue stabilizers of the elbow. J
Shoulder Elbow Surg. 2005;14(1 suppl S):S179–S185.
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gross anatomy of the elbow capsule

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