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6. Spine MCQs

Practice Set 146 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 2901

Topic: 6. Spine

A 72-year-old male with long-standing ankylosing spondylitis presents to the emergency department after a minor fall from a standing height. He reports severe neck pain but has a normal neurologic examination. CT scan reveals a displaced fracture through the C6-C7 disc space extending through the posterior elements. What is the most appropriate definitive management?

. Rigid cervical collar for 12 weeks
. Halo vest immobilization
. Anterior cervical discectomy and fusion (ACDF) at C6-C7
. Posterior short-segment fusion (C6-C7)
. Long-segment posterior cervical instrumentation and fusion

Correct Answer & Explanation

. Long-segment posterior cervical instrumentation and fusion

Explanation

Spinal fractures in patients with ankylosing spondylitis are highly unstable due to the altered biomechanics of the completely fused spinal column, acting like a long bone. They are prone to translation and shear forces, leading to high rates of neurologic deterioration if not definitively stabilized. Conservative management (collar, halo) is associated with high mortality and failure rates. The standard of care is long-segment posterior instrumentation and fusion (typically spanning at least 3 levels above and 3 levels below the fracture) to provide adequate lever-arm control.

Question 2902

Topic: 6. Spine

A 60-year-old male with severe cervical spondylotic myelopathy is being evaluated for surgical decompression. Which of the following preoperative MRI findings of the spinal cord is most strongly associated with a poor potential for neurologic recovery?

. T2-weighted hyperintensity alone
. T1-weighted hypointensity
. Loss of the posterior subarachnoid space
. Hypertrophy of the ligamentum flavum
. Foraminal stenosis at multiple levels

Correct Answer & Explanation

. T1-weighted hypointensity

Explanation

In the context of cervical spondylotic myelopathy, T2-weighted hyperintensity in the spinal cord indicates edema, ischemia, or gliosis, and has a variable prognostic value. However, T1-weighted hypointensity indicates permanent tissue destruction (myelomalacia or cystic necrosis) and is strongly associated with permanent neurologic deficits and poor recovery potential following surgical decompression.

Question 2903

Topic: 6. Spine

Pathologic examination of the hypertrophied ligamentum flavum in a patient with degenerative lumbar spinal stenosis is most likely to demonstrate which of the following histologic changes?

. Amyloid deposition
. Increase in the ratio of elastin to collagen
. Fibrosis with a decrease in the ratio of elastin to collagen
. Extensive neovascularization and acute inflammatory infiltrates
. Chondroid metaplasia and endochondral ossification

Correct Answer & Explanation

. Fibrosis with a decrease in the ratio of elastin to collagen

Explanation

The normal ligamentum flavum is composed predominantly of elastic fibers (roughly 80% elastin and 20% collagen). In the pathogenesis of degenerative lumbar spinal stenosis, mechanical stress and aging lead to a loss of elastic fibers and a corresponding increase in collagen (fibrosis). This fibrotic change causes the ligament to lose its elasticity, leading to hypertrophy and buckling into the spinal canal during extension, thereby contributing to neural compression.

Question 2904

Topic: 6. Spine

A 45-year-old male presents with acute onset of severe low back pain and bilateral leg radiculopathy. Which of the following clinical findings has the highest sensitivity for the diagnosis of cauda equina syndrome?

. Saddle anesthesia
. Decreased anal sphincter tone
. Urinary retention
. Bilateral absent ankle reflexes
. Fecal incontinence

Correct Answer & Explanation

. Urinary retention

Explanation

Urinary retention is considered the most sensitive early clinical sign for cauda equina syndrome (CES), with a sensitivity of approximately 90%. While saddle anesthesia and decreased anal sphincter tone are highly specific and classically associated with the condition, they may present later. A patient with normal bladder function (specifically, a post-void residual volume of less than 100-200 mL) is highly unlikely to have established cauda equina syndrome.

Question 2905

Topic: Thoracolumbar Spine & Deformity

A 45-year-old female presents with an L1 burst fracture following a fall from height. Neurological examination is completely normal. MRI reveals an intact posterior ligamentous complex (PLC). According to the Thoracolumbar Injury Classification and Severity (TLICS) score, what is her total score and the recommended management?

. Score 2; non-operative management
. Score 4; operative management
. Score 4; conservative management
. Score 5; operative management
. Score 7; operative management

Correct Answer & Explanation

. Score 2; non-operative management

Explanation

The TLICS system scores three categories: Morphology, Neurology, and PLC integrity. Morphology: Burst fracture = 2 points. Neurological status: Intact = 0 points. PLC: Intact = 0 points. Total score = 2. A score of 3 or less indicates non-operative management. A score of 4 can be treated non-operatively or operatively based on surgeon preference/clinical scenario. A score of 5 or more favors operative treatment.

Question 2906

Topic: Thoracolumbar Spine & Deformity

In a pediatric patient with an L5-S1 isthmic spondylolisthesis, which of the following spinopelvic parameters is typically fixed morphologically, significantly increased compared to the general population, and strongly correlates with progression of the slip?

. Pelvic tilt
. Sacral slope
. Pelvic incidence
. Lumbar lordosis
. Thoracic kyphosis

Correct Answer & Explanation

. Pelvic incidence

Explanation

Pelvic incidence (PI) is a fixed morphological parameter unique to each individual, defined as the angle between a line perpendicular to the sacral plate and a line connecting the midpoint of the sacral plate to the center of the bicoxofemoral axis. Patients with developmental isthmic spondylolisthesis generally have a significantly higher PI. A high PI leads to an increased sacral slope and higher shear forces at the lumbosacral junction, predisposing to slip progression.

Question 2907

Topic: 6. Spine

A 62-year-old male with a history of uncontrolled diabetes mellitus presents with severe back pain, fever, and radicular leg pain. MRI with contrast reveals a lumbar epidural abscess. The patient is neurologically intact. A trial of non-operative management with IV antibiotics is considered. Which of the following factors at presentation is most strongly predictive of failure of medical management?

. Patient age greater than 50 years
. Presenting C-reactive protein (CRP) level greater than 115 mg/L
. Abscess located anterior to the thecal sac
. Concomitant diagnosis of uncomplicated vertebral osteomyelitis
. Positive blood cultures for Streptococcus species

Correct Answer & Explanation

. Presenting C-reactive protein (CRP) level greater than 115 mg/L

Explanation

Non-operative management of a spinal epidural abscess (SEA) can be attempted in neurologically intact patients. However, risk factors for failure of medical management (leading to neurological deterioration requiring emergency decompression) include: age > 65, diabetes, MRSA infection, positive blood cultures, and a highly elevated CRP (> 115 mg/L) or ESR (> 85 mm/hr). A CRP > 115 mg/L is a very strong independent predictor of medical failure.

Question 2908

Topic: Cervical Spine

A 60-year-old man presents with progressive clumsiness in his hands and a wide-based gait. Imaging reveals multi-level ossification of the posterior longitudinal ligament (OPLL) from C3 to C6. The K-line on the sagittal T1 MRI is negative. What is the most appropriate surgical management?

. C3-C6 posterior laminoplasty
. C3-C6 posterior laminectomy without fusion
. Anterior cervical corpectomy and fusion
. Posterior cervical laminectomy and instrumented fusion
. C1-C2 transarticular screw fixation

Correct Answer & Explanation

. Anterior cervical corpectomy and fusion

Explanation

A negative K-line indicates that the anterior compressive lesion (OPLL) is so large that the spinal cord will not shift posteriorly enough to be adequately decompressed by a posterior approach alone. Therefore, an anterior decompression and fusion (or combined approach) is required.

Question 2909

Topic: 6. Spine

A 65-year-old man presents with progressive difficulty buttoning his shirts and a worsening gait. Examination shows a positive Hoffman's sign, hyperreflexia in the lower extremities, and ankle clonus. An MRI of the cervical spine is most likely to show compression at which level to explain both upper and lower extremity findings?

. C3-C4
. C6-C7
. T1-T2
. L4-L5
. L5-S1

Correct Answer & Explanation

. C3-C4

Explanation

The patient's symptoms indicate cervical spondylotic myelopathy. Compression at a higher cervical level like C3-C4 affects the long tracts to the lower extremities (hyperreflexia, gait issues) as well as the upper extremity fine motor skills.

Question 2910

Topic: 6. Spine

A 50-year-old woman presents with acute low back pain radiating down the lateral aspect of her right leg to the dorsum of her foot. She has weakness in the extensor hallucis longus (EHL) but normal ankle and patellar reflexes. Which nerve root is most likely compressed, and at which classic disc herniation level?

. L4 nerve root at L3-L4
. L4 nerve root at L4-L5
. L5 nerve root at L4-L5
. S1 nerve root at L5-S1
. S1 nerve root at L4-L5

Correct Answer & Explanation

. L5 nerve root at L4-L5

Explanation

Weakness in the extensor hallucis longus and pain radiating to the dorsum of the foot are classic signs of L5 radiculopathy. In the lumbar spine, a posterolateral disc herniation at the L4-L5 level most commonly compresses the traversing L5 nerve root.

Question 2911

Topic: Cervical Spine

A 72-year-old man sustains a Type II odontoid fracture after a ground-level fall. The fracture is displaced 6 mm posteriorly. What is the most significant risk factor for non-union if this fracture is treated non-operatively with a rigid cervical collar?

. Posterior direction of displacement
. Patient age greater than 65 years
. Mechanism of injury
. Associated mandible fracture
. Patient gender

Correct Answer & Explanation

. Patient age greater than 65 years

Explanation

In Type II odontoid fractures, age greater than 65 years is one of the most significant risk factors for non-union, with non-union rates exceeding 50% in this demographic when treated non-operatively. Displacement greater than 5 mm is also a major risk factor.

Question 2912

Topic: 6. Spine

A 25-year-old male is brought to the ED after a motor vehicle collision. He is awake, alert, and neurologically intact. Radiographs reveal a bilateral C5-C6 facet dislocation. What is the most appropriate next step in management?

. Urgent MRI of the cervical spine
. Closed traction reduction
. Open reduction and internal fixation
. Application of a halo vest
. CT angiogram of the neck

Correct Answer & Explanation

. Closed traction reduction

Explanation

In an awake, alert, and cooperative patient with a cervical facet dislocation, urgent closed reduction with skeletal traction is indicated before an MRI. MRI is required prior to open reduction or in a patient with altered mental status to evaluate for disc herniation.

Question 2913

Topic: 6. Spine

When planning corrective surgery for adult spinal deformity, sagittal balance is a critical parameter for postoperative clinical outcomes. The surgical goal should aim for a mismatch between Pelvic Incidence (PI) and Lumbar Lordosis (LL) of:

. PI - LL > 20 degrees
. PI - LL = 15 to 20 degrees
. PI - LL < 10 degrees
. LL - PI > 20 degrees
. LL - PI = 15 to 20 degrees

Correct Answer & Explanation

. PI - LL < 10 degrees

Explanation

In adult spinal deformity surgery, achieving a Pelvic Incidence to Lumbar Lordosis (PI-LL) mismatch of less than 10 degrees is highly correlated with improved health-related quality of life scores. Failure to restore this balance increases the risk of adjacent segment disease and hardware failure.

Question 2914

Topic: Cervical Spine

The distal tibiofibular syndesmosis is stabilized by several key ligamentous structures. During biomechanical testing, which specific ligament provides the greatest proportion of resistance (approximately 42%) against lateral displacement of the fibula (diastasis)?

. Anterior inferior tibiofibular ligament (AITFL)
. Posterior inferior tibiofibular ligament (PITFL)
. Interosseous membrane
. Interosseous ligament
. Inferior transverse ligament

Correct Answer & Explanation

. Posterior inferior tibiofibular ligament (PITFL)

Explanation

While the Anterior Inferior Tibiofibular Ligament (AITFL) is the most commonly injured ligament in syndesmotic sprains, biomechanical studies demonstrate that the Posterior Inferior Tibiofibular Ligament (PITFL) provides the greatest structural resistance to diastasis (lateral displacement), contributing approximately 42% of the overall syndesmotic strength. The AITFL contributes roughly 35%, and the interosseous ligament contributes about 22%.

Question 2915

Topic: Thoracolumbar Spine & Deformity

A surgeon is evaluating a 65-year-old man for a THA. Standing and sitting lateral spinopelvic radiographs are obtained. From the standing to the sitting position, the pelvic incidence minus lumbar lordosis (PI-LL) mismatch increases by 15 degrees, and the sacral slope decreases by 15 degrees. How would you categorize this patient's spinopelvic mobility?

. Stiff spine
. Normal spinopelvic mobility
. Hypermobile spine
. Kyphotic decompensation
. Fixed anterior pelvic tilt

Correct Answer & Explanation

. Normal spinopelvic mobility

Explanation

Normal spinopelvic mobility involves a decrease in sacral slope of 10 to 30 degrees when transitioning from standing to sitting, accommodating hip flexion by posterior pelvic tilt and reduction of lumbar lordosis.

Question 2916

Topic: 6. Spine

A 70-year-old female with long-standing ankylosing spondylitis and a completely fused lumbosacral spine is scheduled for a primary total hip arthroplasty. Her pelvis is fixed in a retroverted position. Which of the following component positioning strategies is most appropriate to minimize the risk of anterior impingement and posterior dislocation during sitting?

. Increase acetabular cup anteversion relative to the standard Lewinnek safe zone.
. Decrease acetabular cup anteversion relative to the standard Lewinnek safe zone.
. Maintain standard acetabular cup anteversion but use a larger diameter femoral head.
. Increase femoral stem retroversion.
. Position the acetabular cup in neutral version.

Correct Answer & Explanation

. Increase acetabular cup anteversion relative to the standard Lewinnek safe zone.

Explanation

A fused spine prevents the normal posterior pelvic tilt that accommodates hip flexion when sitting. To compensate and prevent anterior impingement with subsequent posterior dislocation, the acetabular cup must be placed in increased anteversion.

Question 2917

Topic: 6. Spine
A 19-year-old man who sustained a spinal cord injury in a motor vehicle accident 3 days ago has 5/5 full strength in the deltoids and biceps bilaterally, 4/5 strength in wrist extension bilaterally, 1/5 triceps function on the right side, and 2/5 triceps function on the left side. The patient has no detectable lower extremity motor function. Based on the American Spinal Injury Association’s classification, what is the patient’s functional level?
. C4
. C5
. C6
. C7
. C8

Correct Answer & Explanation

. C6

Explanation

By convention when determining the motor level, the key muscle must be at least 3/5. The next most rostral level must be 4/5. Therefore, this patient’s functional level is C6.

Question 2918

Topic: 6. Spine
Which of the following statements about injury of the anterior vascular structures during lumbar disk surgery is true?
. An arteriovenous fistula formation is more likely to form than acute, life-threatening bleeding.
. The L5-S1 level is the most common site.
. Use of a curette in the disk space is the most common cause.
. It is rarely associated with patient death.
. Brisk bleeding from the disk space always occurs as a result.

Correct Answer & Explanation

. The L5-S1 level is the most common site.

Explanation

Vascular injury most commonly occurs at L4-L5, followed by L5-S1 and are associated with use of the pituitary rongeur. Formation of an arteriovenous fistula is the most common vascular injury resulting from lumbar disk surgery but is usually not recognized until months after surgery. Cardiomegaly and high output cardiac failure are common presenting symptoms.

Question 2919

Topic: 6. Spine
Which of the following findings is the best radiographic indicator of segmental instability at L4-L5?
. Anterior marginal osteophytes
. Modic end plate changes on MRI
. Disk space narrowing
. More than 3.5 mm of translation or 11° of angulation compared with adjacent levels on flexion/extension radiographs
. More than 4 mm of translation or 10° of angulation compared with adjacent levels on flexion/extension radiographs

Correct Answer & Explanation

. More than 4 mm of translation or 10° of angulation compared with adjacent levels on flexion/extension radiographs

Explanation

DISCUSSION: Motion segments that demonstrate more than 4 mm of translation or 10° of angulation compared with adjacent motion segments on flexion-extension radiographs have excessive motion and instability. Anterior marginal osteophytes form at the insertion of the annulus from increased forces but do not indicate increased motion. A spondylolisthesis or lateral listhesis is often static without increased motion. More than 3.5 mm of translation or 11° of angulation is considered instability criteria for the cervical spine. Internal disk disruption does not denote instability. REFERENCES: Boden SD, Wiesel SW: Lumbosacral segmental motion in normal individuals. Have we been measuring instability properly? Spine 1990;15:571-576. Garfin SR, Rauschning W: Spinal stenosis. Instr Course Lect 2001;50:145-152.

Question 2920

Topic: 6. Spine
A 42-year-old woman underwent an instrumented posterior spinal fusion at L3-S1 with transforaminal lumbar interbody fusion. She had an excellent clinical result with complete resolution of leg pain. Three months later she now reports increasing back pain and weakness in her legs. Examination reveals weakness in the quadriceps and tibialis anterior. Radiographs show no interval changes in the position of the hardware. MRI scans are shown in Figures 2a through 2c. What is the next most appropriate step in management?
. Observation
. Oral antibiotics only
. IV antibiotics only
. Irrigation and debridement of the surgical site
. Irrigation and debridement of the surgical site with hardware removal

Correct Answer & Explanation

. Irrigation and debridement of the surgical site

Explanation

DISCUSSION: The MRI scans reveal a postoperative infection. Observation and antibiotics are not appropriate choices. There is a large fluid collection and this requires decompression because the patient has neurologic changes. There is considerable debate regarding the removal of hardware. Many contend that biofilm on the implants can harbor the infection. However, these complications usually can be treated with serial irrigations, debridements, and IV antibiotics. The incidence of infection has been widely studied with varying rates in fusions with instrumentation. Rates appear to be increased with instrumentation, yet these infections usually can be managed without hardware removal. REFERENCES: Glassman SD, Dimar JR, Puno RM, et al: Salvage of instrumental lumbar fusions complicated by surgical wound infection. Spine 1996;21:2163-2169. Fang A, Hu SS, Endres N, et al: Risk factors for infection after spinal surgery. Spine 2005;30:1460-1465.

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