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6. Spine MCQs

Practice Set 303 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 6041

Topic: 6. Spine

A 40-year-old man presents with severe lower back pain, bilateral sciatica, and perineal numbness. He mentions he cannot feel toilet paper when wiping. Which of the following represents the most appropriate initial management step to confirm the diagnosis and plan treatment?

. Immediate laminectomy
. Urgent administration of high-dose methylprednisolone
. Urgent MRI of the lumbar spine
. Post-void residual bladder volume ultrasound
. Lumbar puncture

Correct Answer & Explanation

. Urgent MRI of the lumbar spine

Explanation

While post-void residual volume supports the clinical suspicion of urinary retention in Cauda Equina Syndrome, an urgent MRI is definitively required. The MRI confirms the level and extent of compression, which is essential before emergent surgical decompression.

Question 6042

Topic: 6. Spine

A 45-year-old male presents with acute back pain, bilateral sciatica, and urinary retention following a heavy lifting injury. An MRI confirms a massive L4-L5 disc herniation compressing the cauda equina. What is the most critical factor determining the postoperative return of normal bladder function?

. Timing of surgery within 12 hours of the lifting injury
. Preoperative severity of bilateral leg pain
. Time interval between the onset of urinary symptoms and surgical decompression
. The specific anatomical level of the disc herniation
. Use of high-dose intravenous steroids preoperatively

Correct Answer & Explanation

. Time interval between the onset of urinary symptoms and surgical decompression

Explanation

The time interval from the onset of autonomic symptoms (like urinary retention) to surgical decompression is the most critical factor for functional recovery in cauda equina syndrome. Decompression within 24 to 48 hours of symptom onset significantly improves bladder outcomes.

Question 6043

Topic: 6. Spine

A 6-year-old boy presents with back pain. Radiographs reveal a severe collapse of the T8 vertebral body, often termed 'vertebra plana.' Biopsy of the lesion demonstrates a prominent population of large cells with grooved nuclei mixed with eosinophils. Electron microscopy of these cells is most likely to reveal which of the following ultrastructural features?

. Weibel-Palade bodies
. Howell-Jolly bodies
. Birbeck granules
. Auer rods
. Heinz bodies

Correct Answer & Explanation

. Birbeck granules

Explanation

The clinical and radiographic presentation of 'vertebra plana' in a young child combined with grooved nuclei and eosinophils on histology is diagnostic of Langerhans Cell Histiocytosis (Eosinophilic Granuloma). On electron microscopy, the diagnostic ultrastructural finding is Birbeck granules, which have a characteristic 'tennis racket' appearance. These cells also classically stain positive for CD1a and S-100.

Question 6044

Topic: 6. Spine

A 40-year-old asymptomatic female undergoes a lumbar spine MRI for mild lower back pain. An incidental lesion is found in the L3 vertebral body. On plain radiographs, this lesion has a coarse, vertically striated 'corduroy' appearance. What are the expected signal characteristics of this lesion on a non-contrast MRI?

. Low T1, High T2 signal
. High T1, High T2 signal
. Low T1, Low T2 signal
. High T1, Low T2 signal
. Intermediate T1, Intermediate T2 signal

Correct Answer & Explanation

. High T1, High T2 signal

Explanation

The lesion described is a vertebral hemangioma, characterized by prominent vertical trabeculae appearing as 'corduroy' on plain film or 'polka dots' on axial CT. Due to their high adipose (fat) content, benign intraosseous hemangiomas characteristically demonstrate high signal intensity on both T1-weighted and T2-weighted MRI sequences.

Question 6045

Topic: 6. Spine

A 70-year-old female is evaluated for a primary THA. She has a history of a solid multilevel lumbar spinal fusion from L2 to the sacrum. How should the surgeon adjust the target acetabular cup position to minimize the risk of posterior dislocation?

. Increase cup anteversion and increase cup abduction
. Decrease cup anteversion and increase cup abduction
. Increase cup anteversion and decrease cup abduction
. Decrease cup anteversion and decrease cup abduction
. No adjustment is needed; place in standard 40/15 position

Correct Answer & Explanation

. Increase cup anteversion and increase cup abduction

Explanation

Patients with a lumbosacral spinal fusion have a stiff spinopelvic junction. Normally, moving from standing to sitting involves posterior pelvic tilt, which functionally increases acetabular anteversion to clear the anterior femur. In a fused spine, this dynamic tilt does not occur, leading to a high risk of anterior impingement and posterior dislocation when seated. The surgeon must compensate by placing the cup in higher static anteversion and slightly higher abduction.

Question 6046

Topic: 6. Spine

A 68-year-old man with advanced ankylosing spondylitis undergoes primary THA. Preoperative radiographs demonstrate a fully fused lumbar spine. Which of the following best describes his spinopelvic biomechanics and the optimal surgical strategy to minimize dislocation risk?

. He will have excessive posterior pelvic tilt when sitting; the cup should be placed in more anteversion.
. He will have a lack of posterior pelvic tilt when sitting; the cup should be placed in more anteversion.
. He will have a lack of posterior pelvic tilt when sitting; the cup should be placed in less anteversion.
. He will have excessive posterior pelvic tilt when sitting; the cup should be placed in less anteversion.
. He will have normal spinopelvic motion; the cup should be placed in standard Lewinnek safe zone parameters.

Correct Answer & Explanation

. He will have a lack of posterior pelvic tilt when sitting; the cup should be placed in more anteversion.

Explanation

A stiff spinopelvic junction limits the normal posterior pelvic tilt that occurs during sitting. Normally, posterior pelvic tilt increases relative acetabular anteversion, clearing the anterior femur and preventing anterior impingement and posterior dislocation. Because this patient cannot tilt his pelvis posteriorly, he is at high risk for anterior impingement and posterior dislocation when sitting. The surgeon should compensate by placing the acetabular component in more anteversion and slightly more inclination than the standard safe zone.

Question 6047

Topic: 6. Spine

A 70-year-old male with a history of multi-level instrumented lumbar fusion from L2 to the Pelvis presents for a primary THA. Which of the following describes his expected spinopelvic biomechanics, and how should acetabular component positioning be adjusted?

. The pelvis will over-tilt anteriorly when standing; decrease the cup anteversion
. The pelvis will not tilt posteriorly when sitting; increase the cup anteversion and inclination
. The spine will compensate with hyperlordosis; use a standard Lewinnek safe zone
. The pelvis will tilt excessively posteriorly when sitting; decrease the cup anteversion
. The anterior pelvic plane will remain unchanged; no adjustment is needed

Correct Answer & Explanation

. The pelvis will not tilt posteriorly when sitting; increase the cup anteversion and inclination

Explanation

A spinopelvic fusion or stiff spine prevents the normal posterior pelvic tilt that occurs when moving from standing to sitting. Without this posterior tilt, the acetabular cup fails to 'open up' (gain anteversion) to accommodate hip flexion, leading to a high risk of anterior impingement and subsequent posterior dislocation. The surgeon must compensate by placing the cup with increased anteversion (and often inclination) or consider a dual mobility construct.

Question 6048

Topic: 6. Spine

Which of the following spinopelvic conditions represents the greatest risk for anterior impingement and posterior dislocation following total hip arthroplasty?

. Normal spinopelvic mobility
. Increased posterior pelvic tilt when transitioning from standing to sitting
. A hypermobile lumbar spine
. A stiff lumbar spine causing decreased posterior pelvic tilt when sitting
. Excessive femoral anteversion

Correct Answer & Explanation

. A stiff lumbar spine causing decreased posterior pelvic tilt when sitting

Explanation

Normally, transitioning from standing to sitting causes the lumbar spine to flex and the pelvis to tilt posteriorly, effectively increasing acetabular anteversion and clearing the anterior space for the femur. A stiff lumbar spine (e.g., from fusion) prevents this posterior tilt, leading to anterior bony impingement and subsequent posterior dislocation when sitting.

Question 6049

Topic: Thoracolumbar Spine & Deformity

A 70-year-old female with a previous L2-Pelvis fusion presents for a primary THA. Standing and sitting lateral radiographs reveal less than 10 degrees of change in her sacral slope. Due to her stiff spinopelvic complex, she is at the highest risk for which of the following complications, and how should cup position be adjusted?

. Anterior dislocation; increase cup anteversion
. Posterior dislocation; increase cup anteversion
. Anterior dislocation; decrease cup anteversion
. Posterior dislocation; decrease cup anteversion
. Superior dislocation; increase cup inclination

Correct Answer & Explanation

. Anterior dislocation; increase cup anteversion

Explanation

A stiff spinopelvic complex with prior lumbar fusion prevents normal posterior pelvic tilt during sitting. This lack of functional acetabular anteversion increases the risk of posterior dislocation, necessitating compensatory increased cup anteversion during surgery.

Question 6050

Topic: 6. Spine

A 45-year-old male presents following a high-speed motor vehicle collision with a T6 burst fracture and complete paraplegia. In the trauma bay, his blood pressure is 80/50 mmHg, heart rate is 55 bpm, and his extremities are warm and flushed. Which of the following best describes the pathophysiology of his current hemodynamic state?

. Hypovolemia secondary to occult intra-abdominal hemorrhage
. Loss of sympathetic tone resulting in unopposed parasympathetic activity
. Complete loss of the bulbocavernosus reflex (spinal shock)
. Release of systemic inflammatory cytokines from massive tissue trauma
. Compression of the inferior vena cava from an epidural hematoma

Correct Answer & Explanation

. Loss of sympathetic tone resulting in unopposed parasympathetic activity

Explanation

The patient is exhibiting classic signs of neurogenic shock, which occurs in spinal cord injuries typically at or above the T6 level. It is characterized by a loss of descending sympathetic outflow to the splanchnic bed and heart, leading to unopposed vagal (parasympathetic) tone, profound vasodilation, bradycardia, hypotension, and warm extremities.

Question 6051

Topic: 6. Spine

A 55-year-old male presents with acute onset of severe low back pain, bilateral flaccid lower extremity weakness, absent ankle reflexes, and overflow urinary incontinence. Examination reveals decreased perianal sensation. The underlying pathophysiology of this specific neurologic syndrome represents compression of which of the following nervous system elements?

. Upper motor neurons within the descending spinal tracts
. Sympathetic chain ganglia in the retroperitoneum
. Lower motor neurons within the lumbar spinal canal
. Parasympathetic splanchnic nerves arising from the sacrum
. Anterior horn cells of the lower thoracic spinal cord

Correct Answer & Explanation

. Lower motor neurons within the lumbar spinal canal

Explanation

This patient is presenting with Cauda Equina Syndrome, caused by compression of the lumbosacral nerve roots below the termination of the spinal cord (conus medullaris, usually at L1-L2). Because these nerve roots have already exited the spinal cord, the syndrome represents a peripheral, lower motor neuron (LMN) lesion, characterized by flaccid paralysis, areflexia, and loss of sphincter tone.

Question 6052

Topic: 6. Spine

A 45-year-old male presents to the emergency department with severe lower back pain and bilateral sciatica. Which of the following clinical findings has the highest sensitivity for diagnosing cauda equina syndrome?

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

Correct Answer & Explanation

. Saddle anesthesia

Explanation

Urinary retention (typically with a post-void residual volume > 200 mL) is the most sensitive finding in cauda equina syndrome. Its absence has a high negative predictive value for ruling out the condition.

Question 6053

Topic: 6. Spine

Traumatic spondylolisthesis of the axis (Hangman's fracture) typically involves bilateral fractures of the C2 pars interarticularis. The classic mechanism of injury leading to a Type I Hangman's fracture is:

. Hyperextension and axial loading
. Hyperflexion and rotation
. Axial distraction and hyperflexion
. Lateral bending and compression
. Pure rotational shear

Correct Answer & Explanation

. Hyperextension and axial loading

Explanation

A Type I Hangman's fracture classically results from hyperextension and axial loading, commonly seen in motor vehicle accidents when the chin strikes the dashboard.

Question 6054

Topic: 6. Spine
A patient presents with a traumatic spondylolisthesis of the axis (Hangman's fracture) demonstrating 4 mm of translation and 15 degrees of angulation on lateral radiographs. According to the Levine-Edwards classification, what is the injury type and optimal management?
. Type I; rigid cervical collar
. Type II; closed reduction and halo vest immobilization
. Type IIa; traction followed by halo vest
. Type III; surgical stabilization
. Type I; surgical stabilization

Correct Answer & Explanation

. Type II; closed reduction and halo vest immobilization

Explanation

A Levine-Edwards Type II fracture is characterized by greater than 3 mm of translation and significant angulation. It is typically managed with careful closed reduction and halo vest immobilization.

Question 6055

Topic: Thoracolumbar Spine & Deformity

According to Sorensen's criteria, the strict radiographic diagnosis of classic Scheuermann's kyphosis requires anterior wedging of at least 5 degrees in a minimum of how many consecutive vertebrae?

. Two
. Three
. Four
. Five
. Six

Correct Answer & Explanation

. Two

Explanation

Sorensen's diagnostic criteria for Scheuermann's disease strictly require the presence of anterior wedging of 5 degrees or more in at least three consecutive vertebral bodies on a lateral radiograph.

Question 6056

Topic: 6. Spine

During an anterior approach to the cervical spine (Smith-Robinson approach), blunt dissection is carried down to the prevertebral fascia. This dissection naturally passes between which two distinct anatomical sheaths/layers?

. Between the sternocleidomastoid and the strap muscles
. Between the carotid sheath (lateral) and the visceral fascia/axis (medial)
. Between the internal jugular vein and the common carotid artery
. Between the trachea and the esophagus
. Between the sternocleidomastoid and the platysma

Correct Answer & Explanation

. Between the sternocleidomastoid and the strap muscles

Explanation

The standard anterior approach to the cervical spine utilizes the relatively avascular interfascial plane between the carotid sheath (containing the common carotid artery, internal jugular vein, and vagus nerve) located laterally, and the visceral axis (trachea, esophagus, and thyroid gland) located medially.

Question 6057

Topic: 6. Spine

A 45-year-old male presents with a posterolateral disc herniation at the L4-L5 level. Which nerve root is most commonly compressed by this specific pathology?

. L3
. L4
. L5
. S1
. S2

Correct Answer & Explanation

. L3

Explanation

In the lumbar spine, a typical posterolateral disc herniation affects the traversing nerve root. Therefore, an L4-L5 herniation will most commonly compress the L5 nerve root.

Question 6058

Topic: Cervical Spine

During an anterior cervical discectomy and fusion (ACDF), aggressive lateral dissection past the uncinate process risks catastrophic injury to the vertebral artery. At which cervical level does the vertebral artery typically enter the transverse foramen?

. C7
. C6
. C5
. C4
. C3

Correct Answer & Explanation

. C7

Explanation

The vertebral artery arises from the first part of the subclavian artery and typically enters the transverse foramen of the cervical spine at the C6 level, bypassing the C7 transverse foramen.

Question 6059

Topic: 6. Spine

During a lateral transpsoas approach to the lumbar spine, the lumbar plexus is at risk of injury as it lies within the substance of the psoas major. At the L4-L5 disc space, where is the lumbar plexus generally located relative to the psoas muscle?

. Anterior third
. Middle third
. Posterior third
. Medial to the psoas
. Superficial to the anterior psoas fascia

Correct Answer & Explanation

. Anterior third

Explanation

In the lateral transpsoas approach, the lumbar plexus predictably migrates anteriorly as it descends. At the L4-L5 level, the plexus is located in the posterior third of the psoas major, requiring the surgeon to stay in the anterior half of the muscle.

Question 6060

Topic: Thoracolumbar Spine & Deformity

A patient with a history of long-segment lumbar fusion (L2-Pelvis) is planned for a total hip arthroplasty. Because of spinopelvic stiffness, how does the pelvis normally respond when transitioning from standing to sitting, and what specific instability is this patient at highest risk for due to their fusion?

. Normal posterior pelvic tilt; anterior dislocation
. Lack of posterior pelvic tilt; posterior dislocation
. Excessive posterior pelvic tilt; posterior dislocation
. Lack of anterior pelvic tilt; anterior dislocation
. Excessive anterior pelvic tilt; anterior dislocation

Correct Answer & Explanation

. Lack of posterior pelvic tilt; posterior dislocation

Explanation

In a normal spinopelvic relationship, when a person transitions from standing to sitting, the lumbar spine flexes and the pelvis tilts posteriorly. This posterior pelvic tilt functionally increases acetabular anteversion, allowing the anterior femur to clear the acetabulum during deep hip flexion. A patient with a fusion to the pelvis has a stiff spine and cannot posteriorly tilt the pelvis when sitting. Therefore, the functional anteversion does not increase, leading to anterior bony/component impingement and subsequent posterior dislocation.

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