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6. Spine MCQs

Practice Set 240 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 4781

Topic: Thoracolumbar Spine & Deformity

A 68-year-old man presents with recurrent posterior instability of his THA. He has a history of L5-S1 fusion prior to his THA. What is the most likely biomechanical cause of his recurrent instability?

. Decreased pelvic tilt in sitting position leading to functional retroversion of the acetabular component.
. Increased pelvic tilt in standing position leading to functional anteversion of the acetabular component.
. Anterior impingement of the femoral neck on the acetabulum during extension.
. Decreased spinopelvic mobility leading to hyperlordosis in sitting.
. Impaired abductor function due to superior gluteal nerve injury.

Correct Answer & Explanation

. Decreased pelvic tilt in sitting position leading to functional retroversion of the acetabular component.

Explanation

Patients with stiff spinopelvic segments (e.g., prior lumbar fusion) lack the normal posterior pelvic tilt that occurs when moving from standing to sitting. Normally, posterior pelvic tilt increases functional anteversion to accommodate hip flexion and prevent anterior impingement. In patients with a stiff spine, the pelvis fails to tilt posteriorly during sitting, leaving the cup relatively retroverted and the hip prone to anterior impingement and posterior dislocation.

Question 4782

Topic: 6. Spine

A 66-year-old man who underwent an L4-S1 posterior spinal fusion three years ago now requires a total hip arthroplasty for severe osteoarthritis. Which of the following biomechanical considerations is most critical when planning his acetabular component positioning to minimize the risk of posterior dislocation?

. He will likely have excessive pelvic retroversion when moving from sitting to standing
. He will have a fixed anterior pelvic tilt in the sitting position, requiring increased cup anteversion
. He will have increased spinopelvic mobility, requiring a constrained liner
. The acetabular component should be placed in neutral version
. The femoral stem should be placed in 15 degrees of retroversion

Correct Answer & Explanation

. He will have a fixed anterior pelvic tilt in the sitting position, requiring increased cup anteversion

Explanation

Patients with prior lower lumbar and sacral fusions suffer from spinopelvic stiffness. Normally, when moving from a standing to a sitting position, the pelvis retroverts, effectively opening the acetabulum (increasing anteversion) to accommodate hip flexion without impingement. A stiff spine with a fixed anterior pelvic tilt prevents this compensatory retroversion. As a result, the patient is at a high risk for anterior impingement and subsequent posterior dislocation during hip flexion. Surgeons must typically increase the target anteversion of the acetabular cup to compensate for this lack of dynamic mobility.

Question 4783

Topic: 6. Spine

A 25-year-old equestrian falls from a horse and sustains a Denis Zone 3 sacral fracture (longitudinal fracture medial to the neural foramina). She complains of perineal numbness and difficulty voiding. Which of the following statements best describes the risk of neurologic injury in this specific sacral fracture zone?

. The risk of neurologic injury is less than 5%, typically affecting the L5 nerve root.
. It carries the highest risk of neurologic injury among Denis zones, frequently resulting in bowel and bladder dysfunction.
. It predominantly causes an isolated S1 nerve root palsy presenting as weak plantarflexion.
. The risk of neurologic injury is moderate, primarily involving the sciatic nerve.
. Neurologic injuries in this zone almost always resolve spontaneously without intervention.

Correct Answer & Explanation

. It carries the highest risk of neurologic injury among Denis zones, frequently resulting in bowel and bladder dysfunction.

Explanation

The Denis classification of sacral fractures predicts neurologic deficit based on location. Zone 1 (alar) has the lowest risk (~6%, often L5). Zone 2 (foraminal) has a higher risk (~28%, often S1/S2 causing radiculopathy). Zone 3 involves the central sacral canal and carries the highest risk of neurologic injury (>50%). Because the fracture involves the central canal, it frequently damages the sacral roots responsible for sphincter tone, leading to cauda equina syndrome with bowel, bladder, and sexual dysfunction.

Question 4784

Topic: 6. Spine

A 65-year-old man presents with progressive gait difficulties and loss of fine motor skills over the past 18 months. Examination reveals positive Hoffmann and Babinski signs. Figure 1 shows a sagittal T2-weighted MRI of his cervical spine.

What is the most critical clinical prognostic factor regarding his expected functional recovery following surgical decompression?

. Duration of symptoms prior to surgical intervention
. Presence of hyperintensity on T2-weighted MRI
. The specific surgical approach utilized (anterior vs. posterior)
. The absolute number of stenotic levels involved
. The presence of positive upper motor neuron signs preoperatively

Correct Answer & Explanation

. Duration of symptoms prior to surgical intervention

Explanation

In cervical spondylotic myelopathy (CSM), the duration of symptoms prior to surgery is the most consistently reported clinical predictor of postoperative functional recovery. A shorter duration of symptoms (typically less than 12 months) correlates strongly with better neurological outcomes. While T2 hyperintensity is common, T1 hypointensity (indicating myelomalacia) is a stronger imaging prognosticator. Surgical approach and number of levels do not dictate functional recovery as strongly as preoperative symptom duration.

Question 4785

Topic: Cervical Spine

An 82-year-old woman falls from a standing height and presents with localized neck pain. She is neurologically intact. A CT scan of the cervical spine reveals a Type II odontoid fracture with 2 mm of posterior displacement. She has a history of severe COPD, osteoporosis, and congestive heart failure. What is the most appropriate definitive management?

. Halo vest immobilization for 12 weeks
. Rigid cervical collar for 8 to 12 weeks
. Posterior C1-C2 transarticular screw fixation
. Anterior odontoid screw fixation
. Occipitocervical fusion with structural grafting

Correct Answer & Explanation

. Rigid cervical collar for 8 to 12 weeks

Explanation

In elderly patients (typically >80 years) with multiple comorbidities, halo vest immobilization is associated with high morbidity and mortality (up to 26%). Anterior odontoid screw fixation is contraindicated due to osteoporosis. While posterior C1-C2 fusion provides highest union rates, surgical risks must be weighed against nonoperative management. For a minimally displaced Type II odontoid fracture in an elderly, highly comorbid patient, a rigid cervical collar provides the best balance of safety and acceptable outcomes. Even if a fibrous non-union occurs, it is usually clinically stable and asymptomatic.

Question 4786

Topic: Thoracolumbar Spine & Deformity
When planning corrective surgery for adult spinal deformity, achieving optimal sagittal balance has been shown to strongly correlate with improved health-related quality of life (HRQOL) scores. According to the SRS-Schwab classification, which of the following is a primary radiographic target for sagittal realignment?
. Pelvic incidence minus lumbar lordosis (PI - LL) less than or equal to 10 degrees
. Sagittal vertical axis (SVA) greater than 5 cm
. Pelvic tilt (PT) greater than 25 degrees
. Thoracic kyphosis less than 20 degrees
. Lumbar lordosis greater than 60 degrees regardless of pelvic incidence

Correct Answer & Explanation

. Pelvic incidence minus lumbar lordosis (PI - LL) less than or equal to 10 degrees

Explanation

The SRS-Schwab classification of adult spinal deformity emphasizes three key sagittal modifiers that correlate closely with pain and disability: 1) Sagittal vertical axis (SVA) < 50 mm, 2) Pelvic Tilt (PT) < 20 degrees, and 3) Mismatch between Pelvic Incidence and Lumbar Lordosis (PI - LL) ≤ 10 degrees. Achieving a PI-LL mismatch of less than 10 degrees is a critical surgical target to restore proper spinopelvic harmony.

Question 4787

Topic: 6. Spine

A 72-year-old male complains of bilateral leg and buttock pain that progressively worsens with walking and is promptly relieved by sitting or leaning forward over a shopping cart. Pedal pulses are 2+ bilaterally. An axial MRI of his lumbar spine is shown in Figure 2.

Which of the following anatomic structures is primarily responsible for the neural compression observed in the lateral recess?

. Ligamentum flavum and superior articular facet
. Posterior longitudinal ligament and disc annulus
. Pedicle and transverse process
. Herniated nucleus pulposus and uncinate process
. Interspinous ligament and facet joint capsule

Correct Answer & Explanation

. Ligamentum flavum and superior articular facet

Explanation

The patient's clinical presentation is classic for neurogenic claudication secondary to lumbar spinal stenosis. Lateral recess stenosis is most commonly caused by hypertrophy of the superior articular facet and infolding or hypertrophy of the ligamentum flavum. The lateral recess is bounded laterally by the pedicle, posteriorly by the superior articular facet and ligamentum flavum, and anteriorly by the vertebral body and intervertebral disc.

Question 4788

Topic: Thoracolumbar Spine & Deformity

A 14-year-old female gymnast presents with persistent lower back pain for 8 months. She has no radiating leg pain and a normal neurologic examination. Radiographs reveal a Grade I isthmic spondylolisthesis at L5-S1. She has exhausted 6 months of nonoperative management, including bracing and physical therapy. What is the most appropriate surgical intervention?

. L5-S1 anterior lumbar interbody fusion (ALIF)
. L5-S1 posterior instrumented fusion with autogenous bone graft
. Direct repair of the pars interarticularis (pars repair)
. L5 laminectomy without fusion
. L4-S1 posterior instrumented fusion

Correct Answer & Explanation

. L5-S1 posterior instrumented fusion with autogenous bone graft

Explanation

For an adolescent with symptomatic Grade I isthmic spondylolisthesis at L5-S1 that has failed extensive nonoperative management, an in situ L5-S1 posterior instrumented fusion with autogenous bone grafting is the gold standard of treatment. A direct pars repair (e.g., Buck's or Scott's wiring) is typically reserved for symptomatic L1-L4 spondylolysis without a significant slip. Laminectomy alone in a pediatric patient is contraindicated as it exacerbates instability.

Question 4789

Topic: Thoracolumbar Spine & Deformity

A 35-year-old male is evaluated after falling from a ladder. Examination demonstrates completely intact motor and sensory function in his bilateral lower extremities, with normal rectal tone. CT scan reveals a T12 burst fracture with 30% canal compromise and 10 degrees of focal kyphosis. MRI confirms an intact posterior ligamentous complex (PLC). According to the Thoracolumbar Injury Classification and Severity (TLICS) system, what is the patient's score and the recommended treatment?

. Score 2, non-operative management
. Score 4, operative or non-operative management
. Score 5, operative management
. Score 7, operative management
. Score 3, non-operative management

Correct Answer & Explanation

. Score 2, non-operative management

Explanation

The TLICS system assigns points based on three categories: 1) Morphology: Burst fracture = 2 points. 2) Neurologic status: Intact = 0 points. 3) Posterior Ligamentous Complex (PLC): Intact = 0 points. The total score is 2. A TLICS score of 3 or less is typically managed non-operatively (e.g., TLSO brace). A score of 4 is indeterminate (surgeon's choice), and a score of 5 or more dictates operative intervention.

Question 4790

Topic: 6. Spine

A 55-year-old man with a 20-year history of severe ankylosing spondylitis presents to the emergency department after a low-speed motor vehicle collision. He complains of severe lower cervical pain but exhibits no neurologic deficits. Plain radiographs of the cervical spine appear unchanged from previous films, showing diffuse syndesmophytes and a 'bamboo spine' appearance. What is the most appropriate next step in management?

. Discharge with a soft cervical collar and oral NSAIDs
. Perform flexion-extension cervical radiographs to evaluate for dynamic instability
. Obtain a CT scan of the entire cervical spine
. Reassure the patient and prescribe outpatient physical therapy
. Perform a diagnostic medial branch block

Correct Answer & Explanation

. Obtain a CT scan of the entire cervical spine

Explanation

Patients with ankylosing spondylitis have highly rigid, osteopenic spines that act like long bones. They are exceptionally susceptible to highly unstable fractures, even from low-energy trauma. Plain radiographs are frequently inadequate and notoriously insensitive for detecting fractures in this population due to the altered, obscured anatomy. A CT scan of the spine is mandatory to rule out occult fractures. Flexion-extension views are strictly contraindicated due to the high risk of catastrophic neurologic injury.

Question 4791

Topic: 6. Spine

A 60-year-old diabetic male presents with 5 days of severe midthoracic back pain, low-grade fevers, and new-onset bilateral lower extremity weakness (motor grade 3/5). MRI with gadolinium confirms a posterior epidural abscess from T6 to T9 causing severe spinal cord compression and cord signal change. What is the most appropriate and definitive management?

. CT-guided needle aspiration followed by 6 weeks of targeted intravenous antibiotics
. Emergent posterior laminectomy for decompression and debridement
. Empiric intravenous antibiotics with close serial neurologic monitoring
. Anterior thoracic corpectomy and strut grafting
. Lumbar puncture to isolate the organism followed by tailored antibiotics

Correct Answer & Explanation

. Emergent posterior laminectomy for decompression and debridement

Explanation

This patient presents with a spinal epidural abscess accompanied by an acute, progressive neurologic deficit (spinal cord compression). This constitutes a surgical emergency. Emergent posterior laminectomy with decompression and debridement is required to prevent irreversible paralysis. Nonoperative management (IV antibiotics alone or needle aspiration) is only considered for patients who are neurologically intact with no impending cord compression, or those who are medically unfit for surgery.

Question 4792

Topic: 6. Spine

A 45-year-old man presents with severe, burning anterior thigh pain, accompanied by weakness in knee extension. Examination reveals a diminished patellar tendon reflex and a positive femoral nerve stretch test. MRI of the lumbar spine demonstrates a far lateral (extraforaminal) disc herniation at the L3-L4 level. Which specific nerve root is most likely compressed by this pathology?

. L2
. L3
. L4
. L5
. S1

Correct Answer & Explanation

. L3

Explanation

In the lumbar spine, a paracentral or posterolateral disc herniation typical affects the traversing nerve root (e.g., an L3-L4 paracentral herniation affects the L4 root). However, a far lateral (extraforaminal) disc herniation impinges upon the exiting nerve root at the same level. Therefore, an L3-L4 far lateral disc herniation will compress the exiting L3 nerve root, manifesting as L3 radiculopathy (anterior thigh pain, weak quadriceps, decreased patellar reflex).

Question 4793

Topic: 6. Spine

A 12-year-old girl with adolescent idiopathic scoliosis (AIS) undergoes a posterior spinal fusion from T4 to L1. On postoperative day 4, she develops acute abdominal pain, bilious vomiting, and significant abdominal distension. Upright abdominal radiographs reveal marked dilation of the stomach and proximal duodenum, with an abrupt cutoff in the third portion of the duodenum. What is the primary pathophysiologic mechanism of this complication?

. Adynamic ileus secondary to prolonged opioid analgesic use
. Compression of the duodenum by the superior mesenteric artery
. Intra-abdominal organ perforation from a malpositioned pedicle screw
. Development of a large retroperitoneal hematoma
. Acute cholecystitis exacerbated by surgical stress

Correct Answer & Explanation

. Compression of the duodenum by the superior mesenteric artery

Explanation

The clinical presentation is classic for Superior Mesenteric Artery (SMA) syndrome, also known as Cast syndrome. It is a well-documented complication following corrective spinal surgery for scoliosis. The acute lengthening of the spine during deformity correction decreases the aortomesenteric angle, which mechanically compresses the third portion of the duodenum between the aorta and the superior mesenteric artery, leading to proximal obstruction.

Question 4794

Topic: Cervical Spine

A 72-year-old male sustains a trauma to the neck after a fall from a standing height. Radiographs and CT imaging demonstrate a Type II odontoid fracture with 6 mm of posterior displacement.

If surgical intervention is considered, which of the following findings is an absolute contraindication to anterior odontoid screw fixation?

. Age greater than 65 years
. Associated rupture of the transverse atlantal ligament
. Posterior displacement greater than 5 mm
. Presence of an acute sub-axial cervical spine fracture
. Delayed presentation of 2 weeks post-injury

Correct Answer & Explanation

. Associated rupture of the transverse atlantal ligament

Explanation

Anterior odontoid screw fixation relies on an intact transverse atlantal ligament (TAL) to maintain C1-C2 stability after the dens fracture is reduced and fixed. If the TAL is ruptured, the C1 ring can still translate anteriorly relative to C2, rendering isolated anterior screw fixation mechanically insufficient. In cases of TAL rupture, a posterior C1-C2 fusion is indicated. Advanced age and posterior displacement are risk factors for nonunion but not absolute contraindications for anterior screw fixation, though bone density must be considered.

Question 4795

Topic: 6. Spine

A 65-year-old woman presents with worsening back pain and a progressive forward-stooping posture. Standing full-length spine radiographs reveal a 'flatback' deformity.

Her Pelvic Incidence (PI) is measured at 62 degrees. To achieve a harmonious sagittal profile and minimize the risk of adjacent segment disease and mechanical failure after a long-segment fusion, her post-operative Lumbar Lordosis (LL) should ideally be targeted within what range?

. 10 to 20 degrees
. 30 to 40 degrees
. 52 to 72 degrees
. 75 to 90 degrees
. Matched exactly to her Pelvic Tilt (PT)

Correct Answer & Explanation

. 52 to 72 degrees

Explanation

In adult spinal deformity surgery, achieving proper sagittal balance is critical for good clinical outcomes and preventing implant failure or adjacent segment disease. The Schwab criteria dictate that the pelvic incidence (PI) and lumbar lordosis (LL) should be matched within 10 degrees (PI - LL < 10°). For a patient with a PI of 62 degrees, the ideal LL should be approximately 52 to 72 degrees. Attempting to under-correct or over-correct outside of this matching range leads to compensatory mechanisms like increased pelvic tilt or knee flexion, which result in poor outcomes.

Question 4796

Topic: 6. Spine

A 25-year-old male sustains a cervical spine injury following a diving accident. On examination in the trauma bay, he has 0/5 motor strength in his lower extremities and 2/5 strength in the C5 and C6 muscle groups bilaterally. He has absent pinprick and light touch sensation below the T4 dermatome. A digital rectal examination reveals no voluntary anal contraction, but deep anal pressure (sensory) is intact. According to the American Spinal Injury Association (ASIA) Impairment Scale, what is his correct grade?

. ASIA A
. ASIA B
. ASIA C
. ASIA D
. ASIA E

Correct Answer & Explanation

. ASIA B

Explanation

The ASIA Impairment Scale classifies spinal cord injuries based on motor and sensory findings. ASIA A is a complete injury with no sensory or motor function preserved in the sacral segments (S4-S5). ASIA B is an incomplete injury where sensory function is preserved below the neurologic level (including S4-S5, such as deep anal pressure) but no motor function is preserved below the neurologic level, and there is no voluntary anal contraction. Since this patient has deep anal pressure but no voluntary anal contraction and no motor function below the level of injury, he is classified as ASIA B. If he had voluntary anal contraction or any motor function >3 levels below the motor level, he would be motor incomplete (ASIA C or D).

Question 4797

Topic: 6. Spine

A 48-year-old man presents with sharp, shooting neck pain radiating down his right arm that has persisted for 6 weeks despite conservative management. On physical examination, he demonstrates weakness in elbow extension and wrist flexion. His triceps reflex is 1+ (diminished compared to the contralateral side), and he has decreased sensation to light touch over the middle finger of his right hand. Which of the following cervical nerve roots is most likely compressed?

. C5
. C6
. C7
. C8
. T1

Correct Answer & Explanation

. C7

Explanation

This clinical scenario describes a classic C7 radiculopathy. The C7 nerve root primarily supplies motor innervation to the triceps (elbow extension), flexor carpi radialis (wrist flexion), and extensor digitorum communis (finger extension). It is also responsible for the triceps reflex. Sensory innervation for C7 covers the middle finger. In contrast, C6 radiculopathy typically affects wrist extension and elbow flexion (biceps/brachioradialis), with sensory loss over the thumb and index finger. C8 radiculopathy affects finger flexion and interossei, with sensory loss over the ulnar side of the hand.

Question 4798

Topic: Thoracolumbar Spine & Deformity
A 14-year-old female gymnast presents with progressive low back pain and tight hamstrings. Standing lateral lumbar radiographs reveal an isthmic spondylolisthesis at L5-S1 with a 60% slip (Meyerding Grade III). Which of the following radiographic parameters is the most significant predictor of further slip progression in this patient?
. High slip angle (lumbosacral kyphosis)
. Low pelvic incidence
. Presence of spina bifida occulta
. Sacral doming
. Increased lumbar lordosis

Correct Answer & Explanation

. High slip angle (lumbosacral kyphosis)

Explanation

In pediatric and adolescent isthmic or dysplastic spondylolisthesis, a high slip angle (also known as lumbosacral kyphosis) is the most significant radiographic predictor for the risk of further progression of the slip. A high slip angle indicates severe local kyphotic deformity at the lumbosacral junction, which alters the biomechanical shear forces, making progressive anterior translation highly likely. Other risk factors for progression include high pelvic incidence, age (immature skeleton), and female gender, but slip angle remains the strongest radiographic predictor.

Question 4799

Topic: 6. Spine

A 62-year-old male with a long-standing history of ankylosing spondylitis presents to the emergency department complaining of new-onset lower neck pain after a low-speed rear-end motor vehicle collision. He has no neurological deficits. Initial plain radiographs of the cervical spine (AP, lateral, and odontoid views) are interpreted by the radiologist as 'no acute fracture or dislocation.' What is the most appropriate next step in the management of this patient?

. Discharge home with a soft cervical collar and NSAIDs
. Perform dynamic flexion-extension radiographs
. Obtain a CT scan of the entire cervical spine
. Obtain an MRI of the cervical spine with contrast
. Administer a prophylactic dose of intravenous methylprednisolone

Correct Answer & Explanation

. Obtain a CT scan of the entire cervical spine

Explanation

Patients with ankylosing spondylitis have highly brittle, osteoporotic, and fused spines that behave mechanically like long bones. Even trivial or low-energy trauma can cause highly unstable, through-and-through fractures (often extension-distraction injuries). These fractures are notoriously difficult to visualize on plain radiographs due to altered anatomy, osteopenia, and baseline deformity. The standard of care for any patient with ankylosing spondylitis presenting with neck or back pain after trauma, regardless of normal-appearing plain films, is a CT scan of the entire involved spine to rule out an occult fracture.

Question 4800

Topic: Thoracolumbar Spine & Deformity

A 35-year-old roofer falls 15 feet, sustaining an L1 burst fracture. On physical examination in the emergency department, his neurological examination is completely intact (ASIA E). A CT scan and MRI demonstrate 30% loss of anterior vertebral body height, 15 degrees of focal kyphosis, retropulsion of bone into the spinal canal narrowing it by 20%, and an intact posterior ligamentous complex (PLC). According to the Thoracolumbar Injury Classification and Severity (TLICS) score, what is his total score and the recommended management?

. Score 2; non-operative management
. Score 4; operative or non-operative management
. Score 5; operative management
. Score 7; operative management
. Score 1; non-operative management

Correct Answer & Explanation

. Score 2; non-operative management

Explanation

The Thoracolumbar Injury Classification and Severity (TLICS) score guides treatment based on three categories: injury morphology, neurological status, and posterior ligamentous complex (PLC) integrity. In this scenario: Morphology is a burst fracture = 2 points. Neurological status is intact = 0 points. PLC is intact = 0 points. The total score is 2. According to TLICS, a score of 3 or less is an indication for non-operative management (e.g., TLSO brace). A score of 4 is indeterminate (either operative or non-operative), and a score of 5 or greater is an indication for operative management.

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