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6. Spine MCQs

Practice Set 277 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 5521

Topic: 6. Spine

A 72-year-old female is evaluated for a primary total hip arthroplasty. She has a history of a prior L2-pelvis posterior spinal fusion for adult degenerative scoliosis. Standing and sitting lateral pelvic radiographs demonstrate a change in pelvic tilt of only 5 degrees. To minimize the risk of posterior dislocation when the patient transitions from standing to sitting, how should the acetabular component be positioned compared to a patient with normal spinopelvic mobility?

. Increased anteversion and increased inclination
. Decreased anteversion and decreased inclination
. Increased anteversion and decreased inclination
. Decreased anteversion and increased inclination
. Standard positioning (15 degrees anteversion, 40 degrees inclination)

Correct Answer & Explanation

. Increased anteversion and increased inclination

Explanation

Correct Answer: Increased anteversion and increased inclinationThis patient has a "stiff spine" due to her prior L2-pelvis fusion, indicated by a change in pelvic tilt of less than 10 degrees between standing and sitting. In a normal patient, transitioning from standing to sitting causes the lumbar spine to flex and the pelvis to tilt posteriorly, which functionally increases acetabular anteversion and accommodates hip flexion, preventing anterior impingement and posterior dislocation. In a patient with a stiff spine, the pelvis fails to tilt posteriorly during sitting. To compensate for this lack of dynamic functional anteversion and prevent posterior dislocation, the surgeon must place the acetabular component in greater operative anteversion and inclination than the standard "safe zone."

Question 5522

Topic: 6. Spine

A 72-year-old female with a previous L2-pelvis spinal fusion presents for a primary total hip arthroplasty. Standing and sitting lateral spinopelvic radiographs demonstrate less than 10 degrees of change in pelvic tilt between positions. What is the most appropriate acetabular component positioning strategy to minimize her postoperative dislocation risk?

. Target the standard Lewinnek safe zone of 15 degrees anteversion and 40 degrees inclination
. Increase the target acetabular anteversion
. Decrease the target acetabular anteversion
. Decrease the target acetabular inclination
. Position the cup in 10 degrees of retroversion

Correct Answer & Explanation

. Increase the target acetabular anteversion

Explanation

A stiff spinopelvic construct prevents normal posterior pelvic tilt during sitting, preventing the functional increase in acetabular anteversion required to clear the femur. Therefore, higher relative cup anteversion (or a dual mobility construct) is required to prevent anterior impingement and posterior dislocation.

Question 5523

Topic: 6. Spine

A 35-year-old male with known psoriatic arthritis develops severe, progressive axial spine pain and asymmetric sacroiliitis. Which human leukocyte antigen (HLA) is most strongly associated with this specific axial presentation?

. HLA-DR4
. HLA-B27
. HLA-Cw6
. HLA-B8
. HLA-DR1

Correct Answer & Explanation

. HLA-B27

Explanation

Spinal and sacroiliac involvement in psoriatic arthritis is strongly associated with the HLA-B27 genotype. In contrast, HLA-DR4 is typically associated with rheumatoid arthritis.

Question 5524

Topic: Cervical Spine

An 8-year-old boy with Down syndrome presents with hyperreflexia, a new wide-based gait, and neck pain.

Dynamic flexion-extension radiographs reveal an atlanto-dens interval (ADI) of 11 mm. What is the most appropriate management?

. Observation and permanent restriction from contact sports
. Rigid cervical collar for 6 weeks followed by re-evaluation
. Anterior cervical discectomy and fusion (ACDF)
. Posterior C1-C2 fusion
. Suboccipital decompression without fusion

Correct Answer & Explanation

. Posterior C1-C2 fusion

Explanation

The patient has symptomatic atlantoaxial instability (AAI) with an ADI greater than 10 mm and myelopathic signs. The gold standard treatment is a posterior C1-C2 arthrodesis to stabilize the joint and decompress the spinal cord.

Question 5525

Topic: Cervical Spine

A 7-year-old boy with Down syndrome presents for cervical spine screening. Radiographs demonstrate an atlanto-dens interval (ADI) of 6 mm and a Space Available for Cord (SAC) of 16 mm. He is neurologically intact. According to AAOS guidelines, what is the most appropriate management?

. Immediate posterior C1-C2 fusion
. Halo-vest immobilization for 6 weeks
. Restriction from contact sports and routine clinical follow-up
. Occipitocervical fusion
. Anterior odontoid screw fixation

Correct Answer & Explanation

. Restriction from contact sports and routine clinical follow-up

Explanation

In asymptomatic children with Down syndrome and an ADI of 5-9 mm (with SAC > 14 mm), the recommended management is restriction from high-risk or contact sports and regular monitoring. Surgical stabilization is indicated for ADI > 10 mm, SAC < 14 mm, or the presence of neurologic symptoms.

Question 5526

Topic: 6. Spine

When performing an atlantoaxial fusion for severe instability in a patient with Down syndrome, what is the most commonly reported significant postoperative complication?

. Vertebral artery injury
. Cerebrospinal fluid (CSF) leak
. High rate of pseudoarthrosis (nonunion)
. Retropharyngeal abscess
. Postoperative blindness

Correct Answer & Explanation

. High rate of pseudoarthrosis (nonunion)

Explanation

Patients with Down syndrome have inherently poor bone quality, ligamentous laxity, and immunologic deficiencies, resulting in a significantly higher risk of pseudoarthrosis (nonunion) following cervical spine fusion compared to the general population.

Question 5527

Topic: 6. Spine

In an adolescent with idiopathic scoliosis, which of the following combinations of congenital vertebral anomalies carries the highest risk for rapid curve progression and often requires early surgical intervention?

. Block vertebra
. Unilateral unsegmented bar with a contralateral hemivertebra
. Single fully segmented hemivertebra
. Incarcerated hemivertebra
. Butterfly vertebra

Correct Answer & Explanation

. Unilateral unsegmented bar with a contralateral hemivertebra

Explanation

A unilateral unsegmented bar combined with a contralateral hemivertebra at the same level provides maximal asymmetric growth potential. This combination carries the highest risk of rapid curve progression in congenital scoliosis.

Question 5528

Topic: 6. Spine

A 13-year-old female is 5 days post-operative from a posterior spinal fusion for adolescent idiopathic scoliosis. She complains of postprandial bilious vomiting and epigastric pain. An upper GI series shows delayed gastric emptying and an abrupt cut-off of contrast in the duodenum. What anatomic structure is responsible for compressing the duodenum?

. Inferior mesenteric artery
. Superior mesenteric artery
. Celiac trunk
. Portal vein
. Right renal artery

Correct Answer & Explanation

. Superior mesenteric artery

Explanation

This patient is presenting with Superior Mesenteric Artery (SMA) syndrome (Cast syndrome). Lengthening of the spine alters the aortomesenteric angle, causing the SMA to compress the third portion of the duodenum.

Question 5529

Topic: Thoracolumbar Spine & Deformity

Which of the following Sanders skeletal maturity stages correlates most closely with the peak height velocity (PHV) and the highest risk of curve progression in Adolescent Idiopathic Scoliosis?

. Sanders Stage 1
. Sanders Stage 3
. Sanders Stage 5
. Sanders Stage 7
. Sanders Stage 8

Correct Answer & Explanation

. Sanders Stage 3

Explanation

Sanders Stage 3 (adolescent rapid growth phase) correlates strongly with peak height velocity (PHV). This stage indicates the period of maximal skeletal growth and the highest risk for scoliosis curve progression.

Question 5530

Topic: 6. Spine

Which of the following clinical or radiographic features most reliably distinguishes psoriatic arthritis from rheumatoid arthritis?

. Symmetric involvement of the metacarpophalangeal joints
. Presence of periarticular osteopenia
. Dactylitis and distal interphalangeal (DIP) joint involvement
. Positive rheumatoid factor in 80% of patients
. High incidence of cervical spine instability

Correct Answer & Explanation

. Dactylitis and distal interphalangeal (DIP) joint involvement

Explanation

Psoriatic arthritis frequently causes dactylitis ("sausage digits") and primarily targets the DIP joints. In contrast, rheumatoid arthritis classically involves the MCP/PIP joints and features significant periarticular osteopenia without dactylitis.

Question 5531

Topic: 6. Spine

An 8-year-old child with Down syndrome presents for clearance to participate in the Special Olympics.

They are completely asymptomatic. Flexion-extension cervical radiographs reveal an atlantodens interval (ADI) of 6 mm. What is the most appropriate next step in management?

. Immediate posterior C1-C2 fusion
. Halo vest immobilization
. Restrict from collision/contact sports and observe
. Total spine MRI to evaluate for syrinx
. Clearance for all athletic activities without restrictions

Correct Answer & Explanation

. Restrict from collision/contact sports and observe

Explanation

In Down syndrome, an ADI between 5 mm and 10 mm in an asymptomatic patient indicates atlantoaxial instability but does not require surgery. The standard of care is restriction from high-risk/collision sports and regular observation.

Question 5532

Topic: 6. Spine

An adult with Down syndrome presents with progressive clumsiness, hyperreflexia, and a positive Babinski sign. Cervical radiographs are obtained. Which radiographic measurement is the strongest indicator of neurologic compromise and risk of spinal cord compression?

. Atlantodens interval (ADI) > 3 mm
. Basion-axial interval (BAI) > 12 mm
. Cervicomedullary angle < 135 degrees
. Power's ratio > 1
. Space available for the cord (SAC) < 14 mm

Correct Answer & Explanation

. Space available for the cord (SAC) < 14 mm

Explanation

While an elevated ADI indicates instability, the Space Available for the Cord (SAC) is the most reliable predictor of neurologic deficit. A SAC of less than 14 mm correlates strongly with an increased risk of spinal cord compression.

Question 5533

Topic: Thoracolumbar Spine & Deformity

In a 9-month-old infant diagnosed with infantile idiopathic scoliosis, which of the following radiographic parameters is the most reliable predictor of curve progression requiring intervention?

. Apical vertebral translation > 2 cm
. Cobb angle > 15 degrees
. Nash-Moe rotation of Grade II
. Rib-vertebral angle difference (RVAD) > 20 degrees
. Thoracic kyphosis > 40 degrees

Correct Answer & Explanation

. Rib-vertebral angle difference (RVAD) > 20 degrees

Explanation

The Rib-Vertebral Angle Difference (RVAD), or Mehta's angle, is the most important prognostic factor in infantile scoliosis. An RVAD > 20 degrees strongly predicts curve progression and typically warrants serial Mehta casting.

Question 5534

Topic: 6. Spine

A 13-year-old boy presents for school scoliosis screening. Radiographs demonstrate a 38-degree left-sided thoracic scoliosis. His neurologic examination is entirely normal. What is the most appropriate next step in his evaluation?

. Proceed to TLSO bracing
. Order a total spine MRI
. Schedule a posterior spinal fusion
. Obtain standing flexion-extension radiographs
. Reassure the patient and observe in 6 months

Correct Answer & Explanation

. Order a total spine MRI

Explanation

A left-sided thoracic curve in a patient with presumed adolescent idiopathic scoliosis is considered "atypical" and carries a high risk of an underlying neural axis abnormality, such as a syrinx or Arnold-Chiari malformation. An MRI of the entire spine is required.

Question 5535

Topic: 6. Spine

During a posterior spinal fusion for a 55-degree thoracic scoliosis, the neuromonitoring technician reports a sudden, bilateral 60% decrease in amplitude and a 15% increase in latency of the somatosensory evoked potentials (SSEPs). Which of the following is the best initial step?

. Immediately perform a wake-up test
. Administer high-dose methylprednisolone
. Alert the surgeon, increase mean arterial pressure (MAP), and check hemoglobin
. Remove all spinal instrumentation immediately
. Continue the procedure as isolated SSEP changes are highly unreliable

Correct Answer & Explanation

. Alert the surgeon, increase mean arterial pressure (MAP), and check hemoglobin

Explanation

A significant change in SSEPs (amplitude drop >50%, latency increase >10%) indicates potential spinal cord compromise. The initial response includes alerting the surgical team, raising MAP to maximize cord perfusion, assessing for anemia/blood loss, and reversing any recent corrective forces.

Question 5536

Topic: 6. Spine

Which of the following immunogenetic markers is most strongly associated with the axial spine manifestations of psoriatic arthritis?

. HLA-DR4
. HLA-B27
. Anti-CCP
. Rheumatoid factor
. ANA

Correct Answer & Explanation

. HLA-B27

Explanation

Psoriatic arthritis is a seronegative spondyloarthropathy. Axial spine involvement is strongly associated with the HLA-B27 haplotype, similar to ankylosing spondylitis.

Question 5537

Topic: 6. Spine

A 7-year-old child with Down syndrome presents for routine orthopedic evaluation.

Cervical spine flexion-extension radiographs are obtained. Which of the following radiographic measurements is the most reliable indicator of impending neurologic compromise and an absolute indication for posterior cervical fusion?

. Atlanto-dens interval (ADI) of 4 mm
. Space available for the cord (SAC) of 13 mm
. Powers ratio of 0.8
. Basion-dental interval of 8 mm
. Wackenheim line passing through the dens

Correct Answer & Explanation

. Space available for the cord (SAC) of 13 mm

Explanation

In patients with Down syndrome, a Space Available for the Cord (SAC) of less than 14 mm is the most reliable predictor of neurologic risk. This finding warrants consideration of posterior C1-C2 fusion.

Question 5538

Topic: 6. Spine

According to the American Academy of Pediatrics (AAP), what is the current recommendation regarding routine cervical spine radiographic screening for asymptomatic children with Down syndrome prior to participation in sports?

. Annual flexion-extension radiographs are mandatory
. Routine radiographic screening in asymptomatic children is no longer recommended
. An MRI of the cervical spine should be performed at age 5
. Screening is only required for contact sports
. Routine screening with an open-mouth odontoid view is sufficient

Correct Answer & Explanation

. Routine radiographic screening in asymptomatic children is no longer recommended

Explanation

The AAP has retired its recommendation for routine cervical spine radiographic screening in asymptomatic children with Down syndrome. Emphasis is now placed on a thorough clinical history and targeted neurologic examination.

Question 5539

Topic: 6. Spine

A 6-month-old infant is diagnosed with infantile idiopathic scoliosis. The rib-vertebral angle difference (RVAD) is calculated at the apical vertebra. An RVAD greater than what threshold suggests a high probability of curve progression?

. 5 degrees
. 10 degrees
. 20 degrees
. 30 degrees
. 40 degrees

Correct Answer & Explanation

. 20 degrees

Explanation

An RVAD (Mehta's angle) greater than 20 degrees in infantile scoliosis is highly predictive of a progressive curve. An RVAD less than 20 degrees typically indicates an resolving curve that may only require observation.

Question 5540

Topic: 6. Spine

When evaluating the spinal radiographic manifestations of a patient with psoriatic arthritis compared to ankylosing spondylitis, psoriatic arthritis is more characteristically associated with which of the following findings?

. Symmetric, thin, marginal syndesmophytes
. Bamboo spine appearance with severe osteopenia
. Bulky, asymmetric, non-marginal syndesmophytes
. Exclusive involvement of the lumbar spine
. Rapidly progressive atlantoaxial subluxation with basilar invagination

Correct Answer & Explanation

. Bulky, asymmetric, non-marginal syndesmophytes

Explanation

Psoriatic arthritis often presents with bulky, asymmetric, non-marginal syndesmophytes (paramarginal ossification). This clearly distinguishes it from the thin, symmetric, marginal syndesmophytes typically seen in ankylosing spondylitis.

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