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6. Spine MCQs

Practice Set 336 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 6701

Topic: 6. Spine

What is the primary rationale for using instrumented fusion over non-instrumented fusion for lumbar spondylolisthesis?

. To avoid the need for bone graft
. To reduce operative time
. To increase fusion rates and provide immediate stability
. To eliminate the need for postoperative bracing
. To decrease blood loss

Correct Answer & Explanation

. To increase fusion rates and provide immediate stability

Explanation

Instrumented fusion, typically using pedicle screws and rods, provides immediate rigid internal fixation, which significantly enhances spinal stability, promotes higher fusion rates by minimizing motion at the fusion site, and facilitates early mobilization, potentially reducing the need for external bracing. It does not eliminate the need for bone graft, nor does it inherently reduce operative time or blood loss (often the opposite).

Question 6702

Topic: 6. Spine

A 40-year-old construction worker with chronic L4-L5 degenerative spondylolisthesis (Grade II) and bilateral L5 radiculopathy undergoes L4-L5 posterior decompression and instrumented fusion. Postoperatively, he develops increased bilateral foot drop and numbness in the lateral calves. What is the most likely cause?

. Epidural hematoma
. Dural tear with CSF leak
. L5 nerve root stretch injury during instrumentation or reduction attempts
. Deep surgical site infection
. Persistent spinal stenosis

Correct Answer & Explanation

. L5 nerve root stretch injury during instrumentation or reduction attempts

Explanation

New or worsened foot drop and numbness in the lateral calves (consistent with L5 radiculopathy/palsy) immediately post-op following a decompression and fusion for spondylolisthesis, especially Grade II, strongly suggests an iatrogenic L5 nerve root injury. This can occur due to excessive retraction during decompression, direct trauma, or stretch injury during screw placement or reduction maneuvers. Epidural hematoma or persistent stenosis could cause symptoms, but an acute worsening immediately post-op points more to an iatrogenic event. Infection typically presents later and with systemic signs.

Question 6703

Topic: Thoracolumbar Spine & Deformity
Which of the following describes a 'high-grade' spondylolisthesis?
. A slip of less than 25% (Meyerding Grade I)
. A slip of 25-50% (Meyerding Grade II)
. A slip of greater than 50% (Meyerding Grade III-V)
. Any symptomatic spondylolisthesis
. A spondylolisthesis with associated spinal stenosis

Correct Answer & Explanation

. A slip of greater than 50% (Meyerding Grade III-V)

Explanation

High-grade spondylolisthesis refers to a slip of greater than 50% (Meyerding Grades III, IV, and V). These slips are often associated with more severe symptoms, lumbosacral kyphosis, and a higher risk of complications with surgical reduction compared to low-grade slips (Grades I and II).

Question 6704

Topic: 6. Spine

What is the primary indication for surgical reduction of a high-grade spondylolisthesis?

. Intractable mechanical back pain alone
. Asymptomatic radiographic progression
. Significant neurological deficit with progressive weakness or cauda equina syndrome
. Cosmetic deformity due to trunk shortening
. Patient preference for anatomical restoration

Correct Answer & Explanation

. Significant neurological deficit with progressive weakness or cauda equina syndrome

Explanation

While high-grade slips can cause mechanical pain and cosmetic issues, the primary indication for reduction (especially with its increased risks) is a progressive neurological deficit, such as worsening weakness or the development of cauda equina syndrome, where reduction may be necessary to decompress and stabilize the neural elements. In situ fusion is often preferred for pain or stable neurological symptoms due to the risks of reduction.

Question 6705

Topic: 6. Spine

A 16-year-old male presents with a painful L5-S1 Grade II isthmic spondylolisthesis and mild, non-progressive S1 radiculopathy. He has failed 6 months of physical therapy and bracing. Given his persistent pain and radiculopathy, which surgical option is generally considered the most appropriate initial treatment in this adolescent?

. Decompression alone
. L5-S1 in situ posterolateral fusion without decompression
. L5-S1 posterior decompression and instrumented posterolateral fusion
. L5-S1 anterior lumbar interbody fusion
. Pars repair

Correct Answer & Explanation

. L5-S1 posterior decompression and instrumented posterolateral fusion

Explanation

For symptomatic Grade II isthmic spondylolisthesis with radiculopathy that has failed conservative management in adolescents, the standard of care is L5-S1 posterior decompression (if radicular symptoms are present) and instrumented posterolateral fusion. Fusion is necessary to stabilize the unstable segment and prevent further progression. Decompression alone without fusion is prone to failure and re-operation due to instability. Pars repair is typically for spondylolysis without significant slip. In situ fusion without decompression may not adequately relieve radiculopathy.

Question 6706

Topic: 6. Spine

Which of the following is considered the gold standard for diagnosing a pars interarticularis defect if plain radiographs are equivocal in a symptomatic patient?

. MRI with gadolinium
. CT scan of the lumbar spine
. Bone scintigraphy (SPECT/CT)
. Discography
. Myelogram

Correct Answer & Explanation

. CT scan of the lumbar spine

Explanation

While SPECT/CT is very sensitive for identifying active pars lesions, a CT scan of the lumbar spine is considered the gold standard for clearly visualizing the bony anatomy of the pars interarticularis and definitively diagnosing a pars defect. MRI is excellent for soft tissue but less precise for fine bony detail. SPECT/CT shows metabolic activity but not always the defect itself with the same clarity as CT.

Question 6707

Topic: 6. Spine

In a patient undergoing surgery for L5-S1 high-grade spondylolisthesis, what intraoperative monitoring technique is most critical to prevent neurological injury during reduction maneuvers?

. Somatosensory Evoked Potentials (SSEPs)
. Electromyography (EMG) monitoring of lower extremity muscles
. Motor Evoked Potentials (MEPs)
. Intraoperative CT scanning
. Direct nerve stimulation

Correct Answer & Explanation

. Motor Evoked Potentials (MEPs)

Explanation

Motor Evoked Potentials (MEPs) are crucial for monitoring the motor tracts of the spinal cord and nerve roots, especially during high-risk maneuvers like reduction of high-grade spondylolisthesis. Changes in MEPs can indicate impending motor nerve injury, allowing the surgeon to adjust the reduction. SSEPs monitor sensory tracts, and EMG monitors nerve root irritation but not directly the motor integrity of the spinal cord as effectively as MEPs.

Question 6708

Topic: 6. Spine
A 70-year-old female presents with severe back and leg pain, positive sagittal imbalance, and Grade III L4-L5 degenerative spondylolisthesis with severe stenosis. She is otherwise healthy. What is the most comprehensive surgical approach for this patient?
. L4-L5 decompression alone
. L4-L5 posterolateral fusion in situ
. L4-L5 anterior lumbar interbody fusion (ALIF)
. L4-L5 posterior decompression, reduction, and circumferential fusion (anterior and posterior)
. L4-L5 transforaminal lumbar interbody fusion (TLIF) with decompression and pedicle screw fixation

Correct Answer & Explanation

. L4-L5 transforaminal lumbar interbody fusion (TLIF) with decompression and pedicle screw fixation

Explanation

For a Grade III degenerative spondylolisthesis with severe stenosis and sagittal imbalance in an otherwise healthy 70-year-old, a comprehensive stabilization and decompression is required. TLIF with decompression and pedicle screw fixation provides direct decompression of the neural elements, restores disc height, potentially corrects sagittal balance, and offers robust segmental stability with a high fusion rate. While circumferential fusion can be considered, TLIF often achieves similar goals with a single approach. Decompression alone leads to instability. Posterolateral fusion in situ may not address severe stenosis or kyphosis adequately. ALIF alone does not decompress posteriorly.

Question 6709

Topic: Thoracolumbar Spine & Deformity

What is the typical angle measured on a lateral radiograph to assess the severity of lumbosacral kyphosis associated with high-grade spondylolisthesis?

. Lumbar Lordosis (LL)
. Sacral Slope (SS)
. Pelvic Incidence (PI)
. Lumbosacral Angle (LSA) or Slip Angle (Dubousset's Angle)
. T1 Pelvic Angle (TPA)

Correct Answer & Explanation

. Lumbosacral Angle (LSA) or Slip Angle (Dubousset's Angle)

Explanation

The Lumbosacral Angle (also known as the Slip Angle or Dubousset's Angle) is specifically used to quantify lumbosacral kyphosis in spondylolisthesis. It is formed by the intersection of a line drawn along the inferior endplate of L5 and a line drawn along the superior endplate of S1. Increased kyphosis (a negative angle) is a sign of instability and often correlates with higher-grade slips. Other angles like LL, SS, PI, TPA are measures of overall sagittal balance but not specific to L5-S1 kyphosis due to slip.

Question 6710

Topic: Thoracolumbar Spine & Deformity

In the context of degenerative spondylolisthesis, which level is most commonly affected?

. L2-L3
. L3-L4
. L4-L5
. L5-S1
. T12-L1

Correct Answer & Explanation

. L4-L5

Explanation

Degenerative spondylolisthesis most commonly occurs at the L4-L5 level. This is thought to be due to the orientation of the L4-L5 facet joints, which are more sagittally oriented and thus less resistant to anterior shear forces, combined with the greater mobility and stress at this segment.

Question 6711

Topic: 6. Spine

A patient with L5-S1 high-grade spondylolisthesis presents with progressive cauda equina syndrome. Which surgical approach is generally indicated for rapid decompression and stabilization?

. L5-S1 anterior lumbar interbody fusion (ALIF) only
. L5-S1 posterolateral fusion in situ
. Urgent posterior decompression and instrumented fusion, potentially with reduction
. Laminoplasty without fusion
. Conservative management with high-dose steroids

Correct Answer & Explanation

. Urgent posterior decompression and instrumented fusion, potentially with reduction

Explanation

Progressive cauda equina syndrome is a surgical emergency. Urgent decompression of the compressed neural elements is paramount. For high-grade spondylolisthesis, this typically involves a posterior approach with decompression (e.g., laminectomy/foraminotomy) and instrumented fusion to provide immediate stability. While reduction carries risks, it might be necessary to adequately decompress in some severe cases. ALIF alone would not achieve rapid posterior decompression. Laminoplasty is for cervical spine. Conservative management is inappropriate for progressive cauda equina.

Question 6712

Topic: Thoracolumbar Spine & Deformity

What is the main concern with surgical reduction of high-grade spondylolisthesis in terms of achieving optimal spinal balance?

. Increased risk of non-union
. Difficulty in achieving adequate decompression
. Potential for pelvic retroversion
. Overcorrection leading to flatback syndrome
. Difficulty in achieving correct sacral slope

Correct Answer & Explanation

. Overcorrection leading to flatback syndrome

Explanation

A significant concern with aggressive reduction of high-grade spondylolisthesis, particularly in patients with compensatory hyperlordosis above the slip, is the potential for overcorrection of the lumbosacral kyphosis. This can lead to a 'flatback syndrome' or sagittal imbalance if the overall lumbar lordosis is excessively restored without considering the patient's global sagittal alignment. It's often more about restoring a balanced sagittal alignment than just maximal reduction of the slip.

Question 6713

Topic: Thoracolumbar Spine & Deformity

When is an isolated direct pars repair (e.g., Buck's technique, Scott wiring) considered in the management of spondylolysis?

. For high-grade spondylolisthesis with neurological deficit
. For degenerative spondylolisthesis with central stenosis
. For symptomatic spondylolysis without significant slip (Grade I or less) after failed conservative management, especially in younger patients
. As a primary treatment for symptomatic spondylolisthesis of any grade
. In older patients with chronic pars defects

Correct Answer & Explanation

. For symptomatic spondylolysis without significant slip (Grade I or less) after failed conservative management, especially in younger patients

Explanation

Isolated pars repair is typically reserved for young, active patients with symptomatic spondylolysis (a pars defect without significant anterior translation or only a very minimal Grade I slip) who have failed conservative treatment. The goal is to heal the pars defect and restore its integrity without fusing the segment. It is not indicated for significant spondylolisthesis or degenerative conditions where stability is the primary issue.

Question 6714

Topic: Thoracolumbar Spine & Deformity

Which anatomical structure is most commonly implicated in the compression of the L5 nerve root in L5-S1 isthmic spondylolisthesis?

. Hypertrophic ligamentum flavum
. Herniated L4-L5 disc
. The pars interarticularis defect and associated pseudarthrosis/scar tissue
. Vertebral body osteophytes
. Facet joint cysts

Correct Answer & Explanation

. The pars interarticularis defect and associated pseudarthrosis/scar tissue

Explanation

In L5-S1 isthmic spondylolisthesis, the L5 nerve root exits above the slipped L5 vertebral body. It can be compressed as it passes through the L5-S1 foramen, primarily by the pars interarticularis defect itself, the hypertrophic pseudarthrosis tissue at the defect, or the superior aspect of the S1 body or disc. While other structures can contribute to stenosis, the pars defect is specific to this type of spondylolisthesis at this level.

Question 6715

Topic: 6. Spine

What is the typical timeframe for conservative management of symptomatic spondylolisthesis before considering surgical intervention?

. 1-2 weeks
. 4-6 weeks
. 2-3 months
. 6 months to 1 year
. Immediately, if symptoms are present

Correct Answer & Explanation

. 6 months to 1 year

Explanation

For most cases of symptomatic spondylolisthesis (especially low-grade isthmic or degenerative), a trial of comprehensive conservative management, including physical therapy, activity modification, NSAIDs, and potentially epidural injections, for 6 months to 1 year is generally recommended before surgical intervention is considered. Exceptions are progressive neurological deficits or cauda equina syndrome, which require more urgent evaluation.

Question 6716

Topic: Thoracolumbar Spine & Deformity
Which type of spondylolisthesis is most commonly associated with a 'vertical sacrum' or high sacral inclination?
. Type I Dysplastic
. Type II Isthmic
. Type III Degenerative
. Type IV Traumatic
. Type V Pathologic

Correct Answer & Explanation

. Type I Dysplastic

Explanation

Type I (Dysplastic) spondylolisthesis is characterized by congenital anomalies that predispose to instability, including abnormal sacral morphology such as a more vertically oriented sacrum (high sacral inclination) and a domed sacrum, which reduce the shear resistance and facilitate anterior slippage of L5 on S1.

Question 6717

Topic: Thoracolumbar Spine & Deformity

What is the main advantage of an Anterior Lumbar Interbody Fusion (ALIF) over a posterior approach for treating L5-S1 spondylolisthesis?

. It allows for direct decompression of the posterior neural elements.
. It avoids abdominal incisions.
. It allows for better restoration of lumbar lordosis and disc height.
. It has a lower risk of pseudarthrosis.
. It is associated with less blood loss.

Correct Answer & Explanation

. It allows for better restoration of lumbar lordosis and disc height.

Explanation

An ALIF approach at L5-S1 allows for excellent access to the anterior column, enabling aggressive discectomy, release of the anterior longitudinal ligament, and placement of a large interbody cage. This is highly effective in restoring disc height, correcting L5-S1 lordosis, and indirectly decompressing the foramina. While it has advantages, it does not directly decompress posterior neural elements and requires an abdominal incision. Pseudarthrosis rates are comparable to other fusion types, and blood loss can vary.

Question 6718

Topic: Thoracolumbar Spine & Deformity

Which of the following is considered a relative contraindication for surgical reduction of a high-grade spondylolisthesis in adults?

. Severe intractable mechanical back pain
. Progressive neurological deficit
. Significant lumbosacral kyphosis
. Long-standing, non-progressive neurological symptoms with significant dural adhesion
. Cosmetic deformity

Correct Answer & Explanation

. Long-standing, non-progressive neurological symptoms with significant dural adhesion

Explanation

Long-standing, non-progressive neurological symptoms, especially if associated with significant dural scarring and adhesions (common in chronic high-grade slips), represent a relative contraindication to reduction. Attempts at reduction in such cases carry a significantly higher risk of neurological injury due to the adherent and tethered nerve roots/dura. In these situations, in situ fusion with adequate posterior decompression is often preferred. Other options listed are indications for surgery (pain, deficit, kyphosis) or less compelling (cosmetic).

Question 6719

Topic: Thoracolumbar Spine & Deformity

What is the primary objective of a 'Gaines procedure' (dome osteotomy) in the treatment of high-grade L5-S1 spondylolisthesis?

. To perform an isolated pars repair
. To decompress the central spinal canal
. To achieve anatomical reduction of the slip in a single stage with minimal risk
. To correct the lumbosacral kyphosis and allow for safer reduction of the vertebral body
. To perform anterior column reconstruction only

Correct Answer & Explanation

. To correct the lumbosacral kyphosis and allow for safer reduction of the vertebral body

Explanation

The Gaines procedure (dome osteotomy) is a surgical technique for severe high-grade L5-S1 spondylolisthesis. It involves an S1 dome osteotomy (removal of a wedge of the S1 superior vertebral body) to effectively 'hinge' the L5 vertebral body posteriorly, allowing for correction of the lumbosacral kyphosis and safer reduction of the L5 on S1 without excessive stretch on the L5 nerve roots. It is a complex procedure aimed at correcting sagittal alignment and facilitating reduction.

Question 6720

Topic: Thoracolumbar Spine & Deformity

Which spinal deformity is commonly seen in patients with high-grade L5-S1 spondylolisthesis due to the slip and compensatory mechanisms?

. Thoracic kyphosis
. Cervical lordosis
. Lumbosacral kyphosis
. Scoliosis
. Excessive lumbar lordosis above the slip

Correct Answer & Explanation

. Lumbosacral kyphosis

Explanation

High-grade L5-S1 spondylolisthesis often leads to an abnormal sagittal alignment characterized by lumbosacral kyphosis, meaning the L5-S1 segment angles forward rather than maintaining the normal lordotic curve. This is often accompanied by compensatory hyperlordosis in the segments above the slip and pelvic retroversion to maintain overall sagittal balance.

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