understanding disorders of the spine| anatomy of the spine | chronic back pain
DESCRIPTION
Dr. Donald Corenman, M.D., D.C. (http://neckandback.com 970-479-5895) is a spine surgeon who specializes in the anatomy of the spine. He treats chronic back pain and all conditions associated with the neck, back and spine including arthritis of the spine, slipped disc, degenerative disc disease, degenerative Spondylolysthesis, spinal stenosis, sciatica and scoliosis. He is in private practice at the Steadman Clinic, Spine Institute, in Vail, CO. This presentation was created to help patients, students and physicians gain insight into understanding disorders of the spine, as well as provide a broader understanding relating to the anatomy of the spine. The presentation details the causes of chronic back pain and describes specific causes as they relate to spinal disorders. Ligament stress, strain on the back, annular and disc tears, degenerative changes and aging can lead to chronic back pain. Understanding disorders of the spine and how they are caused will help provide the right treatment option for individual patients.Dr. Corenman is a Colorado spine expert and talented lecturer and researcher. He has written countless medical articles on spine injuries, spine conditions and the surgical options that are available today. He recently launched his own website (http://neckandback.com) to educate patients on spine disorders and to offer second opinions to physicians and colleagues who are seeking additional information on specific spine injuries and treatment options.TRANSCRIPT
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Understanding and Evaluation Understanding and Evaluation of Spinal Disordersof Spinal Disorders
Donald S. Corenman, M.D., D.C.
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Spinal FunctionSpinal Function
Provide enough flexibility to allow positioning of head and trunk in space for ADLs
Must have strong resistance to motion excess that could damage cord and nerves
Ligament and disc- passive resistors and dampeners of motion
Tendons and muscles- active stabilizers and movers
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Spinal AnatomySpinal Anatomy
Vertebral bodies size and mass increase from C1-L5 reflecting the increasing load each level must bear
Thoracic and sacral kyphosis are structural (bodies are trapezoidal)
Cervical and lumbar are result of disc shape (square vertebral bodies)
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Sagittal AlignmentSagittal Alignment Humans need to expend energy in
the form of continuous muscular contraction to maintain static standing posture
Degenerative disc disease causes reduction of lumbar lordosis and positive sagittal balance
L5-S1segment is under greatest shear forces, most likely segment to develop stress fracture (pars interarticularis)
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Annular AnatomyAnnular Anatomy Annular fibers are in lamina
(layers) Approximately 60 layers from
outside to innermost When nucleus loses hydration
(aging)- pressure drops and more stress on annulus
Rotation stretches 50% of fibers (and relaxes the other 50%)
Disc loses 50% of strength by rotation
Flexion loads disc and stretches fibers (possibly to failure)
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Circulatory Changes in the Circulatory Changes in the DiscDisc
Notochord turns into annulus of disc
Vascularity of disc diminishes – arterioles lose their access to the disc as the endplate matures
Disc becomes more avascular over time (largest mass of avascular tissue in the body)
Imbibition- only nutrient exchange after this point
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Discal Changes with AgingDiscal Changes with Aging
After skeletal maturity, type I collagen increases and discal water decreases (stiffens disc)
O2 concentration is 20-30X greater at periphery of disc than at center (imbibition)
Chondrocyte cells decrease and necrotic cells can be identified
Entire disc appears disorganized Large voids appear (vacuum sign) Peripherally- osteophyte formation
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Ligament Stress/Strain CurveLigament Stress/Strain Curve
Motion within the physiologic range is not destructive
Note that the traumatic range may not load to failure, but can cause irreparable damage to ligaments and discs
Once injured, but not to failure, the tissue will deform faster and fail at a much lower strain (load)
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Annular/Discal BiomechanicsAnnular/Discal Biomechanics
Normal disc will resist displacement over time
Degenerative disc has less resistance to displacement- increased possibility to move into zone of injury
Flexion stretches post annulus- greater chance of tearing posterior fibers
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Mechanical Stress with Flexion Mechanical Stress with Flexion on Lumbar Discson Lumbar Discs
Flexion loads the anterior column
Due to distance from fulcrum (femur), anterior load increases logarithmically
Opposition by erector spinae and multifidi with poor lever arm distance from load creates mechanical disadvantage
Load at disc level can cause mechanical failure (especially with rotation)
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Positional Changes and Effect Positional Changes and Effect on Intradiscal Pressureson Intradiscal Pressures
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Instantaneous Centers of Rotation Instantaneous Centers of Rotation
andand Changes with DDD Changes with DDD Normal biomechanics indicate
flexion will open neural canal and compress disc
Extension will unload disc and narrow canal
Degenerative changes can dramatically change center of rotation to make normal biomechanical testing confusing
Note that flexion can put center of rotation in front or in back of canal
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Muscular Responses to Muscular Responses to Degenerative SegmentsDegenerative Segments
Viscoelastic changes to degenerative discs result in faster deformity to plastic stage
More prolonged and quicker muscular contraction needed to achieve same stability
Studies indicate muscular activity reduced prior to fatigue
Spine then susceptible to injury before muscular failure (cramping)
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Nuclear ContentsNuclear Contents
Substance P Metaloproteases Arachidonic acid Histamine Serotonin All noted to be neurotoxins
(application to nerve will cause inflammatory reaction
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Annular TearsAnnular Tears Tears of the posterior annulus
allows nucleus to come into contact with posterior 1/3 nociceptors- sensitizing then
Attempts at repair of the tears of the poorly vascularized tissue allows neovascularization with resultant nociceptor ingrowth into damage areas
Tears also allow aberrant motion of the segment, further stressing the nociceptors
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EnthesopathyEnthesopathy
Sharpie’s fibers connect ligament or annulus to bone
When these pull off by aberrant motion, periosteum is also pulled off
New bone formation occurs at junction of bone and Sharpie’s fibers(spur)
Classic example is annulus pulling off ALL or PLL and spur formation
Most common cause of cervical radiculopathy and lumbar foramenal stenosis
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Pathophysiology of the FacetsPathophysiology of the Facets Articular cartilage is 70% water-
responsible for cushioning bone from impacts
When disc degenerates, increasing pressure and aberrant motion fibrillates cartilage
Enthesopathy occurs causing spur formation
Capsular rents occur allowing outpouching of synovial lining
Ganglion cyst formation occurs Erosion of the facets causes degenerative
spondylolysthesis
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Nerve InjuryNerve Injury In areas of root injury, one
root can induce activity in a neighboring root called an artificial synapse and cause “crosstalk”
Compression causes demyelination causing conduction block of a nerve
Lesions of peripheral nerves or DRG or roots can cause ectopic impulses identical to a neuroma
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Cortical Pain IdentificationCortical Pain Identification
Homunculus of cerebral cortex dedicated to only certain number of receptors in each area
Neck and lower back have minimal number of receptors compared to regional area of coverage
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Pain GeneratorsPain Generators
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Bone Pain GeneratorsBone Pain Generators Bone is innervated by deeply imbedded
nociceptors Bone has some ability to absorb shock but
is overcome when disc completely fails (IDR)
Stress fracturing occurs (MRI- Modec changes)
Becomes sensitive to impact and vibration Pain is deep dull ache that can occur late Impact activities (tennis, running,
basketball) and motor vehicle/airplane passengers
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Root Pain GeneratorsRoot Pain Generators Nerve root sensitive to both chemical
inflammation and compression Normally root has to become sensitized
prior to pain onset (chemical mediators) No blood-nerve barrier at DRG Mechanically, DRG has poor protection Paresthesias may be result of irritation
to proprioceptive nerve Mechanical sensitivity increased by
flexion/ sitting or SLR maneuvers
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Discal Pain GeneratorsDiscal Pain Generators
90% cause of all LBP Instability Patterns- aberrant
motion causes increased stress to the posterior fibers- causing mild tissue damage or stretch of sensitized nociceptors
Pain with cantilever bending, rotation and flexion, load and unexpected (unprotected) motions and axial loading
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Facet Pain GeneratorsFacet Pain Generators
Cervical spine- 40-50% of patients Lumbar spine- less than 10% of
patients Normally asymptomatic in L/S (deg
spondylolysthesis) C2-3 and C3-4 responsible for sub
occipital headaches (greater and lesser occipital neuralgia)
MRI and CT and X ray WNL Most lumbar facet disease associated
with root compression
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Referral PainReferral Pain Thought to be generated
in the cord from strong impulses that spread from internuncial neurons
Somatization phenomenon is generalization of a pain focus (Fibromyalgia and Chronic Pain Syndrome)
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Cervical Uncovertebral Joints Cervical Uncovertebral Joints (Joints of Lushka)(Joints of Lushka)
These are the only joints in the body that are formed after birth
Actually occurs from early degeneration of disc and abutment of cartilaginous endplates of opposing cervical vertebra
Degenerative changes occur similar to any diarthrodial joint
Spur formation causes foramenal stenosis
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Enthesopathy in the Cervical Enthesopathy in the Cervical SpineSpine
Disc herniation or instability (aberrant motion) causes Sharpies fibers to pull away from bone
Uncovertebral joint compression also causes new bone formation
Resultant spur normally occurs in the neurovertebral foramen
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SpondylolysisSpondylolysis
Stress fractures of the pars interarticularis
5-10% of “extension” sport athletes will have
Genetic component Slip normally occurs when
young Pain generators from
pannus, root or disc Unilateral fracture may be
non painful
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Isolated Disc ResorptionIsolated Disc Resorption Common
degenerative change
Disc does not absorb impact
Stress translated onto endplates
Microfractures Pain during
impact and deep dull ache after activity
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Herniated Nucleus PulposisHerniated Nucleus Pulposis Posterior Annular Failure with
a well hydrated disc can lead to a disc herniation
Interestingly, many individuals will have immediate relief of LBP immediately after the disc tear
1-2 days later will be the onset of leg pain (only when the root has become sensitized)
Some individuals will have immediate pain from massive compression
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Cervical HNP Without PainCervical HNP Without Pain Nerve root is made of
fascicles prior to joining at DRG
Anterior fascicles are motor root
HNP can selectively compress motor root
Weakness without pain
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Recurrent HNPRecurrent HNP
Recurrent HNP occurs in 5% of patients
Occurs regardless of surgery or no surgery
Thru and thru tear of annulus does not heal
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Resorption of HNPResorption of HNP
Upper MRI 03-99 Lower MRI 08-02 Extruded fragments
can resorb PLL bulging can
reduce Root can become
“immune” after prolonged exposure
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Endochondral Endochondral Ossification Defect Ossification Defect (Scheuermann’s)(Scheuermann’s) During growth,
endochondral ossification occurs (turns cartilage into bone)
Vertebral endplates are cartilage until 14-16
In some individuals, the strength of the disc is greater that the endplate
Faulty cartilage causes defects in endplate with significant loading (Schereumanns)
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Injury AssessmentInjury Assessment
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Anatomy of the Cord and Anatomy of the Cord and CaudaCauda
Spinal cord from foramen magnum to L1 Conus at L1 for bowel and bladder (nervi
eriganties S3-S5) Peripheral nerves for lower extremities start from
T9-T12 L1 roots start innervation of lower extremities Thoracic blood supply to the cord tenuous at T10-
T12 (artery of Adamkowitz) Lumbar blood supply abundant
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Mechanisms of InjuryMechanisms of Injury
How much energy was imparted into the individual (fall from height vs fall from level skiing vs impact with tree)
What was the loading force (impact onto buttocks vs impact onto flexed neck vs impact from object)
What was the force trajectory (fall from terrain park vs cliff vs tree)
What was the quality of the tissue of the recipient to resist force (young adult vs senior/ preexisting pathology)
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Thoraco-lumbar Injury Thoraco-lumbar Injury Mechanics Mechanics
Direct blow- normally will cause TP fractures- (asso with kidney contusions)
Direct fall onto buttocks causes axial compression- either compression or burst
Direct fall onto buttocks with some flexion causes either simple compression or flexion distraction
Fall onto buttocks with extension can cause facet or pars (spondylolysis) fracture
Fracture dislocations asso with fall from heights Twisting injury can tear annulus
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Patient HistoryPatient History Loss of consciousness Loss of motor strength (temp or present) Sensory changes (temp or present) “burning hands” Incontinence (at scene vs current) Localized pain to other areas Dyspnea (pneumothorax) Past medical history Temp burning on dorsum of hands Feeling of “instability”
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Patient ExaminationPatient Examination ABCs first, then trauma examination Motor strength C5-S1(for suspected
thoracolumbar injury) Sensory C4-S3 Reflexes (hyperreflexia asso. with
preexisting myelopathy) Rectal exam (sensory, tone and
contraction) (missed conus injury) Bulbocavernosis (if necessary) Not
recommended on playing field
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Concordant Spinal InjuriesConcordant Spinal Injuries
3 patterns Watch out for
distracting injuries 10% of patients can
have other spinal injuries
Severity of trauma- splenic/ liver and vessel injury
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Cervical StenosisCervical Stenosis
Cord takes up 9mm, CSF 1mm on each side, Dura- 1mm on each side- total 13mm
Congenital stenosis measure 72 FF distance and reduce by 10%
Torg’s ratio (.75) Controversial allowance to
play contact sports or ski “Neuropraxia of cord”
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Central Cord Central Cord SyndromeSyndrome
Preexisting congenital stenosis predisposes Acute HNP or extension moment narrows
canal Injury is to central portion of cord More central lamina are upper extremity-
more peripheral are lower extremity
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Acute Treatment of Cord or Acute Treatment of Cord or Conus InjuryConus Injury
Methylprednisolone protocol (30 mg/kg loading and 5.4 mg/kg x 24 (or 48) hours as long as injury occurred within 8 hours
Only for central injuries- not peripheral nerve injuries (conus is central injury)
Must be started within 8 hours of injury
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Classification of InjuriesClassification of Injuries Simple Compression (1-2 column injury) Stable burst (2-3 column injury) Unstable burst (3 column injury) Flexion distraction (2 nonconjoined columns) Chance (3 column failure all in tension) Fracture dislocation (3 column injury) Pure Dislocation (rare) (3 column injury) Pathological (any and all) Insufficiency (any and all) Multiple contiguous fractures (nly 1-2 columns)
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Thoracolumbar JunctionThoracolumbar Junction Thoracic spine stiffer in flexion (ribs) than lumbar spine (stress
riser) Lowest 2 thoracic vertebra have less extrinsic stability secondary
to changes in facet orientation and floating ribs (T11-12 have frontal facets but no conjoined ribs to stabilize, therefore less rotational resistance)
In pure axial loading, thoracic spine deforms into kyphosis and lumbar spine into lordosis leaving the transition vertebra exposed to pure compression
Force distributed over 10 thoracic and 4 lumbar vertebra is withstood only by 2 vertebra at the thoracolumbar junction
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