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6. Spine MCQs

Practice Set 131 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 2601

Topic: 6. Spine

In the evaluation of adult spinal deformity, achieving optimal sagittal balance is critical for long-term patient outcomes. A 65-year-old woman is being planned for a long posterior spinal fusion from T10 to the pelvis. Her pelvic incidence (PI) is 58 degrees. To minimize the risk of proximal junctional kyphosis (PJK) and mechanical failure, her post-operative lumbar lordosis (LL) should ideally be targeted within what range?

. 20 to 30 degrees
. 35 to 45 degrees
. 48 to 68 degrees
. 70 to 80 degrees
. 85 to 95 degrees

Correct Answer & Explanation

. 20 to 30 degrees

Explanation

The goal in correcting adult spinal deformity is to restore global sagittal balance. A key parameter is matching Lumbar Lordosis (LL) to Pelvic Incidence (PI). The Schwab SRS adult spinal deformity classification sets the ideal PI-LL mismatch at < 10 degrees (PI - LL = +/- 9 degrees). Since her PI is 58, her LL should be targeted at 58 +/- 10 degrees, meaning roughly 48 to 68 degrees. An LL of 35-45 would leave her with a significant flatback deformity and predispose her to PJK and poor clinical outcomes.

Question 2602

Topic: 6. Spine

A 24-year-old man is brought to the trauma bay intubated and sedated (GCS 3T) following a high-speed motorcycle crash. CT scan of the cervical spine reveals a unilateral C5-C6 facet dislocation. What is the most appropriate next step in management to address the cervical spine injury?

. Awake closed traction reduction using Gardner-Wells tongs
. Closed traction reduction under general anesthesia with neuromonitoring
. MRI of the cervical spine
. Immediate posterior open reduction and fusion
. Application of a halo vest

Correct Answer & Explanation

. Awake closed traction reduction using Gardner-Wells tongs

Explanation

In a patient with a cervical facet dislocation who is unexaminable (e.g., intubated, sedated, or obtunded), an MRI of the cervical spine must be obtained prior to any reduction maneuvers. This is to rule out a compressive anterior lesion, such as a herniated intervertebral disc. Performing a closed reduction or a posterior open reduction in the presence of a herniated disc in an unexaminable patient carries a high risk of catastrophic spinal cord injury by drawing the disc into the spinal canal. In an awake and cooperative patient, an MRI is not strictly necessary prior to attempted closed traction reduction.

Question 2603

Topic: 6. Spine

A 5-year-old boy is placed in a halo vest for a rigid atlantoaxial rotatory subluxation (AARS) that failed soft collar treatment and halter traction. Three days after halo application, the mother notices the child is keeping his right eye turned inward and complains of seeing double when looking to the right. Which of the following cranial nerves is most likely injured?

. Trochlear nerve (CN IV)
. Trigeminal nerve (CN V)
. Abducens nerve (CN VI)
. Facial nerve (CN VII)
. Glossopharyngeal nerve (CN IX)

Correct Answer & Explanation

. Trochlear nerve (CN IV)

Explanation

Cranial nerve VI (abducens) palsy is a known complication of halo traction or halo vest application, particularly if excessive traction is applied. The abducens nerve has a long intracranial course and is tethered at Dorello's canal, making it uniquely susceptible to stretching when the cervical spine is distracted. Injury to CN VI results in weakness of the lateral rectus muscle, leading to an esotropia (inward deviation) of the affected eye and horizontal diplopia, especially on lateral gaze toward the affected side.

Question 2604

Topic: 6. Spine

A 58-year-old male undergoes a complex 10-level posterior spinal fusion for adult degenerative scoliosis. The surgery lasts 11 hours, with an estimated blood loss of 3.5 liters. He is positioned on a Jackson table. On postoperative day 1, the patient complains of painless, bilateral vision loss. Pupillary light reflexes are sluggish. What is the most common cause of this complication in this clinical scenario?

. Retinal detachment
. Acute angle-closure glaucoma
. Central retinal artery occlusion
. Ischemic optic neuropathy
. Cortical blindness

Correct Answer & Explanation

. Retinal detachment

Explanation

Postoperative visual loss (POVL) is a rare but devastating complication of complex spine surgery performed in the prone position. The most common cause is ischemic optic neuropathy (ION), which accounts for almost 90% of cases. Risk factors for ION include prolonged operative time (typically >6 hours), substantial blood loss, use of a Wilson frame (which lowers the head below the heart), hypotension, obesity, and male sex. Central retinal artery occlusion (CRAO) is another cause of POVL but is usually unilateral and associated with direct mechanical pressure on the globe.

Question 2605

Topic: 6. Spine
Recombinant human bone morphogenetic protein-2 (rhBMP-2) is frequently used off-label in spine surgery to enhance fusion rates. When used in anterior cervical discectomy and fusion (ACDF), which of the following is the most widely recognized and significant complication associated with its use?
. Retrograde ejaculation
. Severe prevertebral soft tissue swelling and dysphagia
. Pseudarthrosis
. Osteolysis of the adjacent vertebral bodies
. Postoperative radiculitis

Correct Answer & Explanation

. Severe prevertebral soft tissue swelling and dysphagia

Explanation

The use of rhBMP-2 (INFUSE) in the anterior cervical spine is associated with significant prevertebral soft tissue swelling, which can lead to severe dysphagia, airway compromise, and occasionally the need for re-intubation or tracheostomy. Because of this life-threatening risk, the FDA issued a warning regarding its use in the anterior cervical spine. Postoperative radiculitis and ectopic bone formation are more commonly associated with its use in posterior lumbar interbody fusions (PLIF or TLIF).

Question 2606

Topic: 6. Spine

A 45-year-old intravenous drug user presents with 2 weeks of worsening back pain, fevers, and new-onset bilateral lower extremity weakness with urinary retention. MRI reveals a large epidural fluid collection with peripheral enhancement from L1 to L4 compressing the cauda equina. He is hemodynamically stable. Blood cultures are drawn. What is the most appropriate next step in management?

. Broad-spectrum intravenous antibiotics and close observation
. CT-guided aspiration of the fluid collection
. Urgent surgical decompression and evacuation
. Initiation of systemic corticosteroids
. Placement of a lumbar drain

Correct Answer & Explanation

. Broad-spectrum intravenous antibiotics and close observation

Explanation

This patient presents with a spinal epidural abscess (SEA) causing acute neurologic deficits (cauda equina syndrome), as evidenced by bilateral lower extremity weakness and urinary retention. The standard of care for SEA with new or progressive neurologic deficit is urgent surgical decompression and evacuation. Medical management alone (antibiotics) is only appropriate for carefully selected patients who are neurologically intact, poor surgical candidates, or have pan-spinal disease without focal severe compression. Corticosteroids are contraindicated in active pyogenic infections.

Question 2607

Topic: Thoracolumbar Spine & Deformity
A 14-year-old gymnast presents with progressive lower back pain and a noticeable 'step-off' on her lower spine. Imaging confirms a Grade III L5-S1 isthmic spondylolisthesis. During surgical intervention involving reduction of the slip and L5-S1 instrumented fusion, the patient is at highest risk for injury to which of the following nerve roots?
. L3
. L4
. L5
. S1
. S2

Correct Answer & Explanation

. L5

Explanation

Reduction of high-grade L5-S1 isthmic spondylolisthesis carries a significant risk of iatrogenic L5 nerve root injury. This occurs due to stretching of the L5 nerve root as the L5 vertebral body is pulled posteriorly and superiorly during the reduction maneuver. The L5 nerve is tethered by the lumbosacral ligament and can be stretched over the sacral ala. S1 nerve root injury is less common during the actual reduction maneuver.

Question 2608

Topic: 6. Spine
A 50-year-old woman presents with progressive myelopathy, hyperreflexia, and a sensory level at the umbilicus. MRI demonstrates a large, calcified central thoracic disc herniation at T9-T10 causing severe spinal cord compression. Which of the following surgical approaches is CONTRAINDICATED in the management of this pathology?
. Costotransversectomy
. Transpedicular approach
. Standard posterior laminectomy
. Lateral extracavitary approach
. Anterior thoracotomy

Correct Answer & Explanation

. Standard posterior laminectomy

Explanation

Standard posterior laminectomy is absolutely contraindicated for a central thoracic disc herniation, particularly if calcified. Removing the posterior elements alone does not remove the anterior compression and allows the spinal cord to drape over the calcified disc, which inevitably leads to catastrophic neurologic worsening or paralysis. Appropriate approaches require access ventral to the spinal cord without retracting it, such as anterior (thoracotomy) or posterolateral approaches (costotransversectomy, lateral extracavitary, or transpedicular).

Question 2609

Topic: 6. Spine

A 12-year-old boy with Duchenne Muscular Dystrophy (DMD) presents for evaluation of a progressive 45-degree thoracolumbar scoliosis. He recently became wheelchair-dependent. His forced vital capacity (FVC) is 45% of predicted. What is the most appropriate recommendation regarding his spinal deformity?

. Custom-molded TLSO brace to halt progression.
. Observation until the curve reaches 60 degrees.
. Immediate posterior spinal fusion to the pelvis.
. Observation, as surgery is contraindicated due to his poor pulmonary function.
. Anterior spinal fusion alone to save motion segments.

Correct Answer & Explanation

. Custom-molded TLSO brace to halt progression.

Explanation

In Duchenne Muscular Dystrophy, scoliosis almost universally progresses rapidly once the child loses ambulation and becomes wheelchair-bound. Bracing does not halt progression and is poorly tolerated. Surgery (posterior spinal fusion from the upper thoracic spine to the pelvis) is indicated for curves >20-30 degrees in non-ambulatory patients to maintain sitting balance and comfort. It is critical to perform surgery before the FVC drops below 30-35%, as pulmonary complications and perioperative mortality increase significantly below this threshold. Early intervention is ideal.

Question 2610

Topic: 6. Spine

In the evaluation of a patient with cervical ossification of the posterior longitudinal ligament (OPLL), the 'K-line' is determined on a lateral cervical radiograph. The K-line connects the midpoints of the spinal canal at C2 and C7. A patient is considered 'K-line negative' if the OPLL mass crosses anterior to this line. What is the clinical significance of a K-line negative finding?

. The patient will have an excellent outcome with a posterior cervical laminoplasty.
. The OPLL is highly likely to resorb spontaneously over time.
. A posterior approach alone (e.g., laminoplasty) is less likely to yield adequate indirect decompression, favoring an anterior or combined approach.
. The patient has a concurrent tethered spinal cord.
. The K-line indicates a high risk of vertebral artery injury.

Correct Answer & Explanation

. The patient will have an excellent outcome with a posterior cervical laminoplasty.

Explanation

The K-line is a critical concept in evaluating OPLL. It connects the mid-points of the spinal canal at C2 and C7 on a neutral lateral radiograph. If the OPLL mass crosses posterior to the K-line (the line intersects the mass), the spine is 'K-line negative.' This means the cervical sagittal alignment is kyphotic or the mass is so large that posterior drift of the spinal cord will not occur after a posterior decompression (laminectomy/laminoplasty). In K-line negative patients, posterior surgery alone results in poor neurologic recovery, and an anterior decompression (or combined) is typically required.

Question 2611

Topic: Thoracolumbar Spine & Deformity

A 4-year-old girl with early-onset idiopathic scoliosis and a 65-degree curve undergoes implantation of magnetically controlled growing rods (MCGR). What is the primary advantage of this technology compared to traditional growing rods (TGR)?

. It provides a definitive rigid fusion at an earlier age.
. It significantly reduces the number of repeated surgical procedures for lengthenings.
. It allows for continuous real-time distraction over months.
. It entirely eliminates the risk of proximal junctional kyphosis.
. It is safe for use in patients requiring serial MRI imaging.

Correct Answer & Explanation

. It provides a definitive rigid fusion at an earlier age.

Explanation

The primary advantage of magnetically controlled growing rods (MCGR, e.g., MAGEC) over traditional growing rods is the ability to perform lengthenings non-invasively in an outpatient clinic using an external remote control. This avoids the need for repetitive operative lengthenings every 6 months under general anesthesia, thereby reducing surgical risks, infection rates, and psychological trauma to the child. MCGRs do not eliminate PJK and are generally MRI conditional or contraindicated due to the internal magnet.

Question 2612

Topic: 6. Spine

A 68-year-old male with a long-standing history of ankylosing spondylitis presents with localized, progressive lower back pain over the past 6 months without recent acute trauma. Inflammatory markers (CRP, ESR) are normal. Radiographs reveal a radiolucent defect and localized kyphosis at the L3-L4 intervertebral disc space with adjacent endplate sclerosis. There is no large paraspinal mass. What is the most likely diagnosis?

. Pyogenic spondylodiscitis
. Tuberculous spondylitis
. Andersson lesion (pseudarthrosis)
. Metastatic prostate cancer
. Multiple myeloma

Correct Answer & Explanation

. Pyogenic spondylodiscitis

Explanation

An Andersson lesion is a non-infectious inflammatory or post-traumatic pseudarthrosis seen in patients with ankylosing spondylitis. Because the spine is completely fused and rigid, a minor, unrecognized stress fracture can lead to a localized area of micro-motion. Over time, this non-union causes bone resorption, endplate sclerosis, and localized kyphosis, mimicking an infection (spondylodiscitis). However, inflammatory markers are typically normal, and there is no infectious fluid collection. Treatment often requires posterior instrumentation to stabilize the segment.

Question 2613

Topic: 6. Spine

A 19-year-old male presents with slowly progressive, unilateral weakness and atrophy of his right hand and forearm intrinsic muscles over the past 2 years. He denies pain, sensory loss, or lower extremity symptoms. MRI of the cervical spine in neutral is unremarkable, but a flexion MRI demonstrates anterior displacement of the posterior dura compressing the lower cervical cord. What is the most likely diagnosis?

. Amyotrophic lateral sclerosis
. Syringomyelia
. Parsonage-Turner syndrome
. Hirayama disease
. Ossification of the posterior longitudinal ligament

Correct Answer & Explanation

. Amyotrophic lateral sclerosis

Explanation

Hirayama disease (juvenile muscular atrophy of distal upper extremity) is a rare cervical myelopathy that predominantly affects young males. It presents with asymmetric weakness and wasting of the intrinsic hand and forearm muscles, sparing the brachioradialis (oblique amyotrophy). The classic pathophysiologic mechanism is a tight posterior dural sac that displaces anteriorly during neck flexion, compressing the lower cervical cord against the vertebral bodies, leading to chronic microvascular ischemia of the anterior horn cells. Diagnosis requires a dynamic flexion MRI showing this forward dural shift.

Question 2614

Topic: 6. Spine
A newborn is diagnosed with multiple hemivertebrae and a unilateral unsegmented bar in the thoracic spine on screening radiographs. Given the high association of VACTERL and other congenital anomalies, which of the following screening tests is mandatory in the initial workup of this patient?
. MRI of the brain
. Echocardiogram and renal ultrasound
. Upper GI series
. Karyotype analysis
. Pulmonary function tests

Correct Answer & Explanation

. Echocardiogram and renal ultrasound

Explanation

Congenital scoliosis is caused by failures of formation (hemivertebra) and/or failures of segmentation (unsegmented bars). It occurs during the first 6 weeks of gestation, concurrent with the development of the cardiac and genitourinary systems. Consequently, up to 30% of these patients have genitourinary anomalies, and 10-15% have congenital heart defects (part of the VACTERL association). Routine screening with renal ultrasound and echocardiography is mandatory for any child diagnosed with congenital scoliosis. Neural axis anomalies (tethered cord) are also common, warranting a spinal MRI.

Question 2615

Topic: 6. Spine

A 35-year-old man dives into a shallow pool and sustains an isolated C1 (atlas) burst fracture. An open-mouth odontoid view demonstrates a combined lateral mass overhang of 8 mm. According to the Rule of Spence, what structure is presumed to be incompetent, dictating the need for more rigid stabilization?

. Alar ligament
. Apical ligament
. Transverse atlantal ligament (TAL)
. Tectorial membrane
. Posterior atlantooccipital membrane

Correct Answer & Explanation

. Alar ligament

Explanation

A C1 burst fracture (Jefferson fracture) involves fractures of the anterior and posterior arches. The Rule of Spence states that if the sum of the overhang of the bilateral C1 lateral masses on the C2 superior articular facets is greater than or equal to 6.9 mm (often practically rounded to 7 mm) on an AP open-mouth radiograph, the transverse atlantal ligament (TAL) is likely ruptured. TAL rupture indicates atlantoaxial instability requiring rigid stabilization (e.g., halo or C1-C2 fusion). In modern practice, an MRI is usually obtained to definitively visualize the TAL.

Question 2616

Topic: Thoracolumbar Spine & Deformity

A 65-year-old woman undergoes corrective surgery for severe adult spinal deformity. To minimize the risk of adjacent segment disease, proximal junctional kyphosis, and mechanical failure, the pelvic incidence minus lumbar lordosis (PI-LL) should ideally be corrected to within what range?

. ± 5 degrees
. ± 10 degrees
. ± 20 degrees
. ± 30 degrees
. ± 45 degrees

Correct Answer & Explanation

. ± 5 degrees

Explanation

According to the Schwab criteria for adult spinal deformity, adequate sagittal balance correction requires a PI-LL mismatch of less than 10 degrees (ideally ± 10 degrees) to optimize outcomes and minimize mechanical complications.

Question 2617

Topic: 6. Spine

A 55-year-old man presents with cervical myelopathy due to severe ossification of the posterior longitudinal ligament (OPLL) from C3-C6. Sagittal MRI and CT show the OPLL mass anteriorly exceeds the K-line (K-line negative). What is the most appropriate surgical approach?

. Anterior cervical discectomy and fusion (ACDF)
. Posterior laminoplasty alone
. Posterior laminectomy without fusion
. Anterior corpectomy and fusion or posterior decompression with instrumented fusion
. Cervical disc arthroplasty

Correct Answer & Explanation

. Anterior cervical discectomy and fusion (ACDF)

Explanation

A negative K-line implies the anterior compressive OPLL mass is too large and the cervical kyphosis is too significant for the spinal cord to drift backward adequately after a posterior laminoplasty alone. An anterior approach or posterior decompression with instrumented fusion is required.

Question 2618

Topic: 6. Spine

A 15-year-old girl undergoes posterior spinal fusion for a 65-degree thoracic scoliosis. On post-operative day 5, she develops bilious vomiting, significant abdominal distension, and rapid weight loss. What is the most likely anatomic cause of her symptoms?

. Compression of the duodenum between the superior mesenteric artery and the aorta
. Compression of the left renal vein between the superior mesenteric artery and the aorta
. Paralytic ileus secondary to heavy opioid use
. Intestinal malrotation with midgut volvulus
. Cecal volvulus secondary to autonomic dysfunction

Correct Answer & Explanation

. Compression of the duodenum between the superior mesenteric artery and the aorta

Explanation

Superior mesenteric artery (SMA) syndrome occurs when corrective lengthening of the spine stretches the SMA, reducing the aortomesenteric angle and causing obstruction of the third portion of the duodenum. Symptoms include bilious vomiting and weight loss.

Question 2619

Topic: 6. Spine

A 25-year-old man presents after a high-speed motor vehicle collision with quadriparesis. Imaging shows a C5-C6 bilateral facet dislocation. He is fully alert, cooperative, and medically stable.

What is the most appropriate next step in management?

. Immediate MRI before any reduction attempt
. Awake closed cranial traction reduction
. Immediate posterior open reduction and fusion
. Immediate anterior cervical discectomy and fusion
. Administration of high-dose methylprednisolone

Correct Answer & Explanation

. Immediate MRI before any reduction attempt

Explanation

In an awake, cooperative patient with a cervical facet dislocation and a neurologic deficit, urgent awake closed reduction via cranial traction is indicated to quickly decompress the spinal cord without delaying for an MRI.

Question 2620

Topic: Thoracolumbar Spine & Deformity

A 45-year-old man falls from a height. CT shows an L1 burst fracture with 40% loss of height and 30% canal compromise. He is neurologically intact. MRI confirms the posterior ligamentous complex (PLC) is intact. What is his Thoracolumbar Injury Classification and Severity (TLICS) score, and what is the recommended treatment?

. TLICS 2, non-operative management
. TLICS 4, surgical management
. TLICS 5, surgical management
. TLICS 2, surgical management
. TLICS 4, non-operative management

Correct Answer & Explanation

. TLICS 2, non-operative management

Explanation

The TLICS score is 2: 2 points for a burst fracture mechanism, 0 points for intact neurology, and 0 points for an intact PLC. A score of 3 or less is an indication for non-operative management (e.g., bracing).

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