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6. Spine MCQs

Practice Set 109 of 379

This practice set contains high-yield board review questions covering key concepts in 6. Spine. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2161

Topic: 6. Spine

A 39-year-old male falls off his bicycle and complains of neck pain and tingling in his fingers. Trauma series radiographs are seen in Figures A and B. Which of the following is likely to be true? Review Topic

. Examination would likely reveal a short neck, low posterior hairline and limited neck motion.
. Serum human leukocyte antigen B27 is likely to be positive.
. He is likely to be of Japanese descent.
. The disease is defined by flowing ossification of the anterior longitudinal ligament at 4 consecutive levels.
. Rheumatoid factor is likely to be positive.

Correct Answer & Explanation

. Examination would likely reveal a short neck, low posterior hairline and limited neck motion.

Explanation

This patient has ankylosing spondylitis (AS). HLA-B27 is positive in 90% of patients with this disease. This tends to occur in younger patients (as opposed to DISH, which happens in older male patients).Cervical spine fractures are not uncommon in ankylosing spondylitis because of osteoporosis and the long lever arm from fused vertebrae. They commonly occur because of hyperextension of the cervical spine (usually C5-7) and have a high rate of neurologic injury. AS fractures have a higher rate of neurologic injury than DISH fractures. Posterior decompression and stabilization with long constructs is necessaryWhang et al. reviewed spine injuries in 12 patients with AS and 18 patients with DISH. Most injuries involved C5-C7. Patients with AS were more likely to have severe neurologic injury (41% ASIA A) than DISH (44% ASIA E). There was 81% good-excellent outcome and 4 deaths related to halo vest use.Caron et al. reviewed spine fractures in patients with ankylosing spine disorders (AS and DISH). AS patients were younger than DISH patients. Spinal cord injury was present in 58%. Surgery was performed on 67% and comprised instrumentation 3 levels above/below the injury. Mortality correlated with age. Mortality was 32%.Westerveld et al. performed a systematic review on spine injuries in ankylosing spinal disorders. Most patients had sustained low energy trauma (fall from sitting/standing). In DISH, most fractures were through the vertebral body. In AS, vertebral body fractures equaled those through the disc. Surgery was performed for neurological deterioration, unstable fracture and the presence of an epidural hematoma.Figure A shows a hyperextension injury at C6-7 (Type I, disc or Type IV,anterior disc, posterior body) cervical spine fracture in ankylosis spondylitis. Visible radiographic characteristics include osteopenia, bamboo spine, marginal syndesmophytes and ossfication of the disc space. Figure B is a chest radiograph showing thoracic syndesmophytes consistent with ankylosing spondylitis. Figure C shows bilateral sacroilitis and hip joint space narrowing typical of ankylosing spondylitis. Illustration A shows the Caron classification of spine fractures in ankylosing spondylitis (Type A, disc injury; Type B, body injury; Type C, anterior body, posterior disc injury; Type D, anterior disc, posterior body injury). Illustration B shows the difference between the marginal osteophytes of AS and nonmarginal osteophytes of DISH in the cervical spine. If you have osteophytes that are building up, and project out anterior to the anterior cortex of the vertebral bodies, like "flowing wax" it is DISH.Incorrect Answers:1:ThisischaracteristicofKlippel-Feilsyndrome

Question 2162

Topic: 6. Spine

Which of the following is a true statement regarding thoracic disk herniations? Review Topic

. Are most commonly discovered during the fifth to seventh decades of life
. Occur with similar frequency as cervical disk herniations
. Occur most commonly in the midthoracic or apical region of the spine
. Can be found in 40% of asymptomatic individuals
. Are best treated surgically with posterior laminectomy and excision

Correct Answer & Explanation

. Are most commonly discovered during the fifth to seventh decades of life

Explanation

Symptomatic herniations of the thoracic spine are much less common than those of the cervical or lumbar region. They tend to occur most commonly during the third to fifth decades of life and although they can be found at all levels, they are mostcommon in the lower third near the thoracolumbar region. Posterior laminectomy and disk excision has the highest rate of neurologic deterioration and is not recommended. Multiple studies have shown that herniated thoracic disks can be found at one or more levels in 40% of asymptomatic individuals.

Question 2163

Topic: 6. Spine

Which of the following areas of the vertebral segment has the highest ratio of cortical to cancellous bone? Review Topic

. Thoracic vertebral bodies
. Lumbar vertebral bodies
. Sacrum
. Pedicles of the lower lumbar spine
. Pedicles of the thoracic spine

Correct Answer & Explanation

. Thoracic vertebral bodies

Explanation

The weight-bearing potential of bone is influenced by the ratio of cortical to cancellous bone. The area of the spinal anatomy that has the highest ratio is the pedicles of the thoracic spine. This is followed by the lumbar pedicles. The vertebral bodies have a lower ratio than the pedicles, with the sacrum having the very lowest ratio.

Question 2164

Topic: 6. Spine

What is the most common presenting problem in patients with cauda equina syndrome? Review Topic

. Urinary retention
. Urinary incontinence
. Saddle numbness
. Lower extremity numbness and weakness
. Back and leg pain

Correct Answer & Explanation

. Urinary retention

Explanation

In one recent retrospective cohort study of 42 patients with cauda equina syndrome, 83% had low back pain at presentation, 90% had radicular lower extremity pain, 60% had urinary retention, and 55% had urinary incontinence. Objective findings at presentation included 55% with leg weakness, 62% with sensory deficit, 62% with absent ankle jerk reflexes, 76% with perianal sensory deficit, and 50% with decreased rectal tone.

Question 2165

Topic: 6. Spine

The spinal cord terminates as the conus medullaris at what vertebral level in adults? Review Topic 1 T12

. L1
. L2
. L3
. L4

Correct Answer & Explanation

. L1

Explanation

The spinal cord anatomy changes at the thoracolumbar junction. The spinal cord terminates as the conus medullaris at the lower portion of L1 in women and the pedicle of L1 in men.

Question 2166

Topic: 6. Spine

The AP radiograph of a 5-year-old boy shows a 20-degree left thoracic scoliosis. He was noted by his pediatrician to have asymmetry on a forward bend test. On examination he is neurologically intact except for decreased sensation on the lateral aspect of both flanks and to pinprick in both hands. He has no pain. What is the best initial step in treatment at this time? Review Topic

. Observation
. Initiate bracing
. MRI scan of the entire spine
. Spinal instrumentation with growing rod construct

Correct Answer & Explanation

. Observation

Explanation

This patient has atypical scoliosis, given his young age and left thoracic curve. In addition, he has abnormal neurologic findings. MRI scan to evaluate for neural axis abnormalities is indicated. Abnormal MRI findings are present in 2% to 3.8% of all patients with presumed idiopathic scoliosis. Abnormal MRI findings are more likely if specific clinical factors are present, such as absence of thoracic apical segment lordosis, atypical curve pattern, an abnormal neurologic examination, male gender, and age younger than 11. In a patient with an atypical curve and neurologic indicators, the yield of MRI scan for a neuraxis abnormality has been shown to be 25%. This patient had both syringomyelia and a Chiari malformation that were treated neurosurgically. Observation would have missed these findings. Bracing or spinal instrumentation may eventually be treatment options for scoliosis given his young age, but establishing a diagnosis first with an MRI scan of the spine is the most appropriate initial step.

Question 2167

Topic: 6. Spine

An 81-year-old man with severe low back pain reports right extensor hallucis longus and anterior tibialis weakness and difficulty urinating over the past 24 hours. He has a temperature of 101 degrees F (38.3 degrees C). MRI scans are shown in Figures 31a and 31b. Management should consist of

. hospital admission for IV antibiotics and observation.
. an epidural steroid.
. anterior diskectomy and fusion with autologous bone graft.
. laminectomy for decompression and debridement.
. laminectomy for decompression with an instrumented posterolateral fusion.

Correct Answer & Explanation

. hospital admission for IV antibiotics and observation.

Explanation

DISCUSSION: An epidural abscess with neurologic deficit represents a medical and surgical emergency.  The prognosis is related to the timeliness of diagnosis and treatment.  Once identified, the primary treatment is surgical decompression of the abscess, followed by organism-specific antibiotics.  In the absence of a significant anterior process such as diskitis or vertebral osteomyelitis, lumbar epidural abscesses generally can be drained through a posterior approach.  Delayed stabilization usually is not required unless, in the course of decompression, removal of too much of the facets creates an instability; this is an uncommon occurrence.REFERENCES: Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 257-271.Reihsaus E, Waldbaur H, Seeling W: Spinal epidural abscess: A meta-analysis of 915 patients.  Neurosurg Rev 2000;23:175-204.

Question 2168

Topic: 6. Spine

Which of the following agents increases the risk for a nonunion following a posterior spinal fusion?

. Ibuprofen
. Intranasal calcitonin
. Simvastatin
. Gentamycin
. Tamoxifen

Correct Answer & Explanation

. Ibuprofen

Explanation

DISCUSSION: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to increase the risk of pseudarthrosis.  In a controlled rabbit study, nonunions were reported with the use of toradol and indomethacin.  NSAIDs are commonly used medications with the potential to diminish osteogenesis.  Studies clearly have demonstrated inhibition of spinal fusion following the postoperative administration of several NSAIDs, including ibuprofen.  Cigarette smoking is another potent inhibitor of spinal fusion.REFERENCES: Glassman SD, Rose SM, Dimar JR, et al: The effect of postoperative nonsteroidal anti-inflammatory drug administration on spinal fusion.  Spine 1998;23:834-838.Martin GJ Jr, Boden SD, Titus L: Recombinant human bone morphogenetic protein-2 overcomes the inhibitory effect of ketorolac, a nonsteroidal anti-inflammatory drug (NSAID), on posterolateral lumbar intertransverse process spine fusion.  Spine 1999;24:2188-2193.

Question 2169

Topic: 6. Spine

Which of the following forms of nonsurgical management is considered best for acute low back pain without radiculopathy?

. Acupuncture
. Epidural steroid injections
. Facet joint injections
. Sclerosant injections
. Bed rest

Correct Answer & Explanation

. Acupuncture

Explanation

DISCUSSION: Temporary bed rest (less than 4 days) with gradual resumption of activities can be efficacious.  Epidural steroid injections may be indicated for acute low back pain with radiculopathy.  Acupuncture, facet joint injections, or ligamentous (sclerosant) injections are not indicated.REFERENCES: Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, Appendix A15.Helfgott SM: Sensible approach to low back pain.  Bull Rheum Dis 2001;3:50.

Question 2170

Topic: 6. Spine

During an anterior retroperitoneal approach to the low lumbar spine, the iliac vessels are mobilized along the lateral side, allowing them to be retracted toward the midline. To gain adequate mobility of the common iliac vein for exposure of L5, it is important to identify which of the following structures?

. Obturator artery
. Central sacral vessels
. Internal iliac vein
. Ascending lumbar vein
. Iliolumbar vein

Correct Answer & Explanation

. Obturator artery

Explanation

DISCUSSION: The iliolumbar vein is a large tributary that sits along the lateral surface of the common iliac vein.  It can be quite substantial in size and must be identified prior to mobilizing the common iliac vein toward the midline.  The other structures are not of surgical significance in performing this exposure.REFERENCE: Gray H: Anatomy of the Human Body.  Philadelphia, PA, Lea & Febiger,1918, 2000.

Question 2171

Topic: 6. Spine

A patient who was involved in a motor vehicle accident 2 weeks ago now reports neck pain. Work-up reveals no evidence of nerve root involvement or acute radiographic abnormality. The patient appears to have a hyperextension soft-tissue injury of the neck (whiplash). What is the best course of treatment at this time?

. No immobilization, no time off from work, and instructions to go about normal activities
. Part-time soft collar immobilization and modified duty at work for 1 to 2 weeks
. Full-time soft collar immobilization and modified duty at work for 1 to 2 weeks
. Full-time rigid collar immobilization and time off from work for 1 to 2 weeks
. Repeat MRI to assess for occult disk or ligamentous injury

Correct Answer & Explanation

. No immobilization, no time off from work, and instructions to go about normal activities

Explanation

DISCUSSION: Early mobilization and resumption of normal activities immediately after neck sprain has been shown to improve functional outcome and decrease subjective symptoms as measured 6 months after injury.REFERENCES: Borchgrevink GE, Kaasa A, McDonagh D, Stiles TC, Haraldseth O, Lereim I: Acute treatment of whiplash neck injuries: A randomized trial during the first 14 days after a car accident.  Spine 1998;23:25-31.Mealy K, Brennan H, Fenelon GC: Early mobilization of acute whiplash injuries.  Br Med J 1986;292:656-657.

Question 2172

Topic: Thoracolumbar Spine & Deformity

Evaluation of an 8-year-old girl for scoliosis reveals a normal gestation, birth, and family history. Her parents state that she stopped gaining new motor skills at age 6 months. Examination shows the patient can sit independently, but she is nonverbal and she makes repetitive hand clapping movements. She has a 30-degree thoracolumbar kyphoscoliosis, and mildly increased tone in the hamstrings and gastrocnemius-soleus complex. What is the most likely diagnosis?

. Rett syndrome
. Cerebral palsy
. Myotonic dystrophy
. Fragile-X syndrome
. Adrenoleukodystrophy

Correct Answer & Explanation

. Rett syndrome

Explanation

Rett syndrome is a progressive encephalopathy of unknown etiology observed only in girls, who are apparently normal physically and mentally until the age of 6-18 months. It is characterized by autism, gait apraxia, dementia, stereotypical hand movements, loss of hand motor skills, hyperreflexia, spasticity, jerky trunk ataxia, seizures, and acquired microcephaly. Neurologically, abnormal development starts with hypotonia and is followed by ataxia and finally spasticity. The orthopaedic aspects of Rett syndrome have been mentioned only briefly in the literature. They include scoliosis, kyphosis, flexion contractures of the joints, and bilateral tight heel cords. Scoliosis is the major orthopaedic deformity in Rett syndrome. Eight of Ten girls in one series had developed scoliosis at the average age of 11 years. All eight girls had C-shaped thoracolumbar neuromuscular curves with pelvic obliquity. The right thoracolumbar curve was by far the most common pattern, occurring in seven patients (88%), whereas only one patient (12%) had a left thoracolumbar curve.

Question 2173

Topic: 6. Spine

Which of the following lumbar disk components has the highest tensile modulus to resist torsional, axial, and tensile loads?

. Nucleus pulposus
. Cartilaginous end plate
. Anterior longitudinal ligament
. Annulus fibrosis
. Cellular matrix

Correct Answer & Explanation

. Nucleus pulposus

Explanation

DISCUSSION: The annulus fibrosis has a multilayer lamellar architecture mode of type I collagen fibers.  Each successive layer is oriented at 30 degrees to the horizontal in the opposite direction, leading to a “criss-cross” type pattern.  This composition allows the annulus, which has the highest tensile modulus, to resist torsional, axial, and tensile loads.REFERENCE: Rhee JM, Schaufele M, Abdu WA: Radiculopathy and the herniated lumbar disc: Controversies regarding pathophysiology and management. J Bone Joint Surg Am 2006;88:2070-2080.

Question 2174

Topic: 6. Spine

A 58-year-old woman with rheumatoid arthritis has progressive neck pain, upper extremity and lower extremity weakness, and difficulty with fine motor movements. Examination reveals hyperreflexia with mild to moderate objective weakness but the patient has no difficulty with ambulation for short distances. What is the most important preoperative imaging finding that predicts full neurologic recovery with surgical stabilization?

. Basilar invagination of less than 1 cm
. Anterior atlanto-dens interval of 4 mm
. Posterior atlanto-dens interval of greater than 14 mm
. Rotatory subluxation of less than 10 degrees
. Subaxial subluxation of less than 3.5 mm

Correct Answer & Explanation

. Basilar invagination of less than 1 cm

Explanation

DISCUSSION: Boden and associates’ article presents compelling evidence that patients with rheumatoid arthritis and neurologic deterioration in C1-2 instability are more likely to achieve some improvement if the posterior atlanto-dens interval is greater than 10 mm on preoperative studies.  All the patients in their series who had neurologic deterioration and a preoperative posterior atlanto-dens interval of greater than 14 mm achieved complete motor recovery.REFERENCES: Boden SD, Dodge LD, Bohlman HH, et al: Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery.  J Bone Joint Surg Am 1993;75:1282-1297.Boden SD, Clark CR: Rheumatoid arthritis of the cervical spine, in Clark CR (ed): The Cervical Spine, ed 3.  Philadelphia, PA, Lippincott Raven, 1998, pp 755-764.Monsey RD: Rheumatoid arthritis of the cervical spine.  J Am Acad Orthop Surg 1997;5:240-248.

Question 2175

Topic: 6. Spine

A 20-year-old man involved in a motor vehicle accident is brought to the emergency department with a C6-7 unilateral facet dislocation. His neurologic examination reveals a focal left-sided C7 nerve root palsy. He is awake and cooperative with questioning and has no other obvious traumatic injuries. What is the most appropriate treatment at this time?

. Further imaging studies, including MRI
. An awake closed reduction with Gardner-Wells traction with neurologic examination
. Immobilization in a halo skeletal fixation for definitive treatment
. Closed reduction under general anesthesia
. Immediate open reduction and internal fixation in the surgical suite

Correct Answer & Explanation

. Further imaging studies, including MRI

Explanation

DISCUSSION: In the patient who is neurologically intact or has an incomplete injury from a cervical facet dislocation, a closed reduction with weighted tong traction is appropriate when the patient is awake, alert, and cooperative.  Although there is a risk that a cervical facet dislocation could occur with an underlying cervical disk herniation, Vaccaro and associates have shown that closed reduction can be safely carried out in the awake, responsive patient.  Closed reduction can be performed in the emergency department with traction with skull tongs or a halo ring.  A slow stepwise application of weight is added until a reduction is achieved.  Any worsening of the neurologic status of the patient requires immediate termination of the closed reduction and further diagnostic imaging before proceeding with further treatment.REFERENCES: Vaccaro AR, Falatyn SP, Flanders AE, et al: Magnetic resonance evaluation of the intervertebral disc, spinal ligaments, and spinal cord before and after closed traction reduction of cervical spine dislocations.  Spine 1999;24:1210-1217.Hart RA: Cervical facet dislocation: When is magnetic resonance imaging indicated?  Spine 2002;27:116-117.Cotler JM, Herbison GJ, Nasuti JF, et al: Closed reduction of traumatic cervical spine dislocation using traction weights up to 140 pounds.  Spine 1993;18:386-390.

Question 2176

Topic: 6. Spine

A 10-year-old girl who is Risser stage 0 has back deformity associated with neurofibromatosis type 1 (NF1). She has no back pain. Examination shows multiple cafe-au-lait nevi with normal lower extremity neurologic function and reflexes. Standing radiographs of the spine show a short 50-degree right thoracic scoliosis with a kyphotic deformity of 55 degrees (apex T8). A 10-degree progression in scoliosis has occurred during the past 1 year. There is no cervical deformity. MRI shows mild dural ectasia, primarily in the upper lumbar region. Management should consist of Review Topic

. observation with repeat radiographs in 6 months.
. a thoracolumbosacral orthosis (TLSO).
. in situ posterior spinal fusion without instrumentation, followed by full-time TLSO bracing.
. anterior spinal convex hemiepiphysiodesis.
. combined anterior and posterior spinal arthrodesis with instrumentation.

Correct Answer & Explanation

. observation with repeat radiographs in 6 months.

Explanation

Scoliotic deformities in patients with NF1 are often dysplastic with short, angular curves. Posterior arthrodesis is made more difficult by the presence of kyphosis and of weak posterior elements caused by dural ectasia. Combined anterior and posterior spinal arthrodesis is generally preferred for progressive dysplastic curves to maximize deformity correction and to decrease the risk of pseudarthrosis. Anterior fusion may also prevent crankshaft phenomenon in young children. Brace treatment is not effective for large, rigid, or dysplastic curves.

Question 2177

Topic: 6. Spine

A 62-year-old man has cervical myelopathy with no evidence of cervical radiculopathy. MRI reveals stenosis at C4-5 and C5-6 with severe cord compression. Examination will most likely reveal which of the following findings?

. Spastic gait and a positive Hoffman’s sign
. Severe arm pain with upper extremity hyporeflexia
. Normal neurologic findings
. Hyperactive jaw jerk reflex with extremity numbness
. Flaccid paraparesis

Correct Answer & Explanation

. Spastic gait and a positive Hoffman’s sign

Explanation

DISCUSSION: Cervical myelopathy involves compression of the spinal cord and presents as an upper motor neuron disorder.  Patients commonly have extremity spasticity and problems with ambulation and balance.  Hoffman’s sign is often present and is elicited by suddenly extending the distal interphalangeal joint of the middle finger; reflexive finger flexion represents a positive finding.  The extremities are usually hyperreflexic with myelopathy.  With cervical radiculopathy (lower motor neuron disorder), reflexes are hyporeflexic, and patients report pain along a dermatomal distribution.  A hyperactive jaw jerk reflex indicates pathology above the foramen magnum or in some cases, systemic disease.  Flaccid paraparesis suggests a lower motor neuron problem.REFERENCES: Sachs BL: Differential diagnosis of neck pain, arm pain and myelopathy, in Clark CR (ed): The Cervical Spine, ed 3.  Philadelphia, PA, Lippincott Raven, 1998, pp 741-742.Beaty JH (ed): Orthopaedic Knowledge Update 6.  Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 673-680.

Question 2178

Topic: 6. Spine

During the revision surgical procedure, thoracic pedicle screws are placed. Following placement, triggered electromyography (EMG) is performed by stimulating the pedicle screw heads. During testing the right T2 pedicle screw head returns a threshold of 2 mA. What does this reading indicate?

. The right T2 pedicle screw is well seated within the pedicle.
. The right T2 pedicle screw has breached the pedicle wall and has violated the costovertebral junction.
. There is a breach in the right T2 pedicle wall, but the screw is not in contact with a neural structure.
. There is a breach in the right T2 pedicle and the screw is in contact with a neural structure.

Correct Answer & Explanation

. The right T2 pedicle screw is well seated within the pedicle.

Explanation

DISCUSSIONThis patient has developed a proximal junctional kyphosis following a long posterior fusion performed for treatment of degenerative lumbar scoliosis. Risk factors for proximal junctional kyphosis in the setting of instrumented fusions performed for degenerative scoliosis include advanced age, 360-degree fusions, extension of fusion constructs to the sacrum, and upper instrumented vertebrae at the level of T1-3. The patient's junctional kyphosis is attributable to failure of the disk and ligamentous structures at T2-3 and would be graded as type I using the classification system of Yagi and associates. Most symptomatic proximal junctional kyphoses are treated with posterior extension of the fusion construct to a more proximal level spanning the kyphosed region. The use of orthoses or simple removal of instrumentation is unlikely to substantively impact symptoms or address the proximal kyphosis. Diabetes and obesity are known factors that increase risk for postsurgical infection following a spine fusion procedure. The most frequent complication following revision surgery for proximal junctional kyphosis, however, is the need for further surgery. In the study by Yagi and associates, 48% of patients who underwent revision surgery for proximal kyphosis developed further adjacent segment degeneration. In the proximal thoracic spine, where the pedicle may be narrow, triggered EMG testing of inserted pedicle screws may be used to assess for violation of the pedicle wall during insertion. In the setting of triggered EMG, thresholds exceeding 10 mA indicate a well-placed pedicle screw. Thresholds lower than 4 mA to 6 mA indicate that a screw is directly contacting a neural structure. Thresholds between 9 mA and 10 mA suggest that a breach of the pedicle may be present, but the screw is not contacting a neural structure.RECOMMENDED READINGSYagi M, Rahm M, Gaines R, Maziad A, Ross T, Kim HJ, Kebaish K, Boachie-Adjei O; Complex Spine Study Group. Characterization and surgical outcomes of proximal junctional failure in surgically treated patients with adult spinal deformity.Spine (Phila Pa 1976). 2014 May 1;39(10):E607-14. doi: 10.1097/BRS.0000000000000266. PubMed PMID: 24525992.ViewAbstract at PubMedCammarata M, Aubin CÉ, Wang X, Mac-Thiong JM. Biomechanical risk factors for proximal junctional kyphosis: a detailed numerical analysis of surgical instrumentation variables. Spine (Phila Pa 1976). 2014 Apr 15;39(8):E500-7. doi: 10.1097/BRS.0000000000000222. PubMedPMID: 24480964.View Abstract at PubMedKim HJ, Lenke LG, Shaffrey CI, Van Alstyne EM, Skelly AC. Proximal junctional kyphosis as a distinct form of adjacent segment pathology after spinal deformity surgery: a systematic review. Spine (Phila Pa 1976). 2012 Oct 15;37(22 Suppl):S144-64. doi: 10.1097/BRS.0b013e31826d611b. PubMed PMID: 22885829.View Abstract at PubMedSchoenfeld AJ, Carey PA, Cleveland AW 3rd, Bader JO, Bono CM. Patient factors, comorbidities, and surgical characteristics that increase mortality and complication risk after spinal arthrodesis: a prognostic study based on 5,887 patients. Spine J. 2013 Oct;13(10):1171-9. doi: 10.1016/j.spinee.2013.02.071. Epub 2013 Apr 9. PubMed PMID:

Question 2179

Topic: 6. Spine
Vertebral fractures are common in the thoracolumbar spine. What is the most important factor that determines the strength of the cancellous bone in the vertebral body?
. Mineral content
. Rate of loading
. Anatomic level of the vertebra
. Apparent density
. Trabecular number

Correct Answer & Explanation

. Apparent density

Explanation

DISCUSSION: Cancellous bone strength and stiffness are determined primarily by the apparent density (the amount of bone per unit volume). Strength varies approximately as the square of the density, and stiffness as the cube of the density; therefore, these are very strong relationships. Cancellous bone strength also depends on the mineral content, the rate of loading (it is viscoelastic), the anatomic level, and the trabecular number (a histomorphometry term), but all to a markedly lesser extent than density.

Question 2180

Topic: 6. Spine

A 39-year-old man presents with back pain radiating to the left lower extremity for the past 6 weeks. Magnetic resonance images of the pathology are

. Pain/parasthesias near the medial malleolus due to impingement of L4 nerve root
. Pain/parasthesias near the medial malleolus due to impingement of L3 nerve root
. Pain/parasthesias near the medial epicondyle of femur due to impingement of L4 nerve root
. Pain/parasthesias near the medial epicondyle of femur due to impingement of L3 nerve root
. Intermittent claudication due to impingement on segmental vessel

Correct Answer & Explanation

. Pain/parasthesias near the medial malleolus due to impingement of L4 nerve root

Explanation

The patient presents with MRI suggestive of far lateral disc herniation at the L3-L4 disc space. He would be expected to have symptoms in L3 nerve distribution, near the medial epicondyle of the femur. Associated motor manifestations may include quadriceps weakness and/or diminished patellar reflex.Far lateral disc herniations constitute approximately 5-10 percent of disc hernations in the lumbar spine. Given the more vertical anatomy of lumbar nerve roots, at a given disc level, a central or paracentral herniation will affect the traversing nerve root (e.g. nerve root of level below) and a far lateral herniation will affect the exiting nerve root (e.g. nerve root of the level above). Similar to the more common central and paracentral herniations, approximately 90% of patients will improve without surgical intervention. When surgical intervention is needed, the paraspinal approach of Wiltse is utilized.Marquadt et al. reported long term outcomes of surgical management of far lateral disc herniations. At an average of 146 months follow up, 56.3% of patients had complete relief of symptoms and 27.6% had permanent residual symptoms. Over 75% of patients subjectively rated their outcomes as excellent.Figure A and B are T2 and T1 axial MRI images, respectively, showing the L3-L4 disc space with a left far lateral disc herniation. Figure C is a left parasagittal T2 MRI image showing impingement on the L3 nerve root. Structures are labeled in illustration A. Illustration B shows the dermatomes of the lower extremity.Incorrect Answers:

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