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Thoracolumbar Spine & Deformity MCQs

Practice Set 45 of 49

This practice set contains high-yield board review questions covering key concepts in Thoracolumbar Spine & Deformity. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 881

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 882

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 883

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 884

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 885

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 886

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 887

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.

Question 888

Topic: Thoracolumbar Spine & Deformity

A 25-year-old male with chronic L5-S1 isthmic spondylolisthesis (Grade II) complains of persistent mechanical back pain after 1 year of conservative treatment. He has no neurological deficits. Which surgical procedure is most appropriate given his symptoms?

. L5-S1 decompression alone
. L5-S1 posterolateral fusion in situ
. L4-L5 fusion
. Isolated pars repair
. Aggressive reduction and circumferential fusion

Correct Answer & Explanation

. L5-S1 posterolateral fusion in situ

Explanation

For mechanical back pain associated with a stable (non-progressive) Grade II isthmic spondylolisthesis without neurological deficit, the primary goal is stabilization. L5-S1 posterolateral fusion in situ (without attempting reduction unless very specific indications are present) is a well-established and effective procedure that provides stability and high fusion rates while avoiding the risks associated with reduction or unnecessary decompression. Decompression alone does not address mechanical pain from instability. Isolated pars repair is for spondylolysis without slip. Fusion at L4-L5 is incorrect.

Question 889

Topic: Thoracolumbar Spine & Deformity
Which of the following describes Wiltse-Newman Type IV spondylolisthesis?
. Degenerative changes of facet joints
. Stress fracture of the pars interarticularis
. Pathologic bone disease
. Acute fracture of the neural arch other than the pars
. Congenital malformation of the sacrum

Correct Answer & Explanation

. Acute fracture of the neural arch other than the pars

Explanation

Wiltse-Newman Type IV is 'Traumatic' spondylolisthesis, which results from an acute fracture in the neural arch other than the pars interarticularis. This differentiates it from Type II isthmic (pars defect) and Type I dysplastic (congenital malformation). Degenerative (Type III) and pathologic (Type V) are distinct etiologies.

Question 890

Topic: Thoracolumbar Spine & Deformity

What imaging characteristic on MRI helps differentiate an active pars stress reaction (pre-spondylolysis) from a chronic non-union?

. Sclerosis around the defect
. Vertebral body height loss
. Presence of high signal intensity (edema) within and around the pars on T2-weighted images
. Disc dehydration at the affected level
. Endplate changes

Correct Answer & Explanation

. Presence of high signal intensity (edema) within and around the pars on T2-weighted images

Explanation

High signal intensity (edema) on T2-weighted MRI within and around the pars interarticularis is indicative of an active stress reaction or acute/subacute fracture. This suggests ongoing bone healing activity and a potential for successful non-operative management. Chronic non-unions or pseudarthroses typically show no or minimal edema, often appearing sclerotic or with fatty infiltration.

Question 891

Topic: Thoracolumbar Spine & Deformity
In pediatric spondylolisthesis, which of the following is a recognized indication for surgical intervention?
. Asymptomatic Grade I slip, stable over time
. Grade I slip with mild, intermittent back pain responsive to conservative care
. Progressive neurological deficit or high-grade slip with significant lumbosacral kyphosis
. Any radiographic evidence of slip progression, regardless of symptoms
. Adolescent age group

Correct Answer & Explanation

. Progressive neurological deficit or high-grade slip with significant lumbosacral kyphosis

Explanation

Indications for surgery in pediatric spondylolisthesis include progressive neurological deficit, high-grade slips (often Grade III or higher, especially with lumbosacral kyphosis), or persistent, intractable pain despite adequate conservative management, particularly if the slip is progressive. Asymptomatic or mildly symptomatic, stable low-grade slips are typically managed conservatively. Radiographic progression without symptoms is not an absolute indication unless it becomes a high-grade slip.

Question 892

Topic: Thoracolumbar Spine & Deformity

Which surgical technique specifically involves resecting the L5 vertebral body to achieve reduction and decompression in severe L5-S1 spondylolisthesis?

. Posterolateral fusion
. Transforaminal lumbar interbody fusion (TLIF)
. Anterior lumbar interbody fusion (ALIF)
. Vertebrectomy (e.g., L5 vertebrectomy with reconstruction)
. Direct pars repair

Correct Answer & Explanation

. Vertebrectomy (e.g., L5 vertebrectomy with reconstruction)

Explanation

A vertebrectomy, specifically L5 vertebrectomy with reconstruction, is a highly aggressive and complex procedure reserved for the most severe cases of L5-S1 spondylolisthesis (e.g., spondyloptosis with severe neurological compromise or sagittal imbalance) where conventional reduction and fusion techniques are insufficient. It allows for complete decompression and significant reduction, but carries substantial risks. Other listed options are less aggressive fusion or repair techniques.

Question 893

Topic: Thoracolumbar Spine & Deformity

What is a major contributing factor to the 'pelvic tilt' or 'waddling' gait often observed in patients with high-grade spondylolisthesis?

. Quadriceps weakness
. Abdominal muscle atrophy
. Gluteus medius insufficiency
. Compensatory hamstring tightness
. Shortened iliopsoas muscle

Correct Answer & Explanation

. Compensatory hamstring tightness

Explanation

Compensatory hamstring tightness is a very common finding in high-grade spondylolisthesis. It serves as a protective mechanism to limit pelvic rotation and prevent further anterior shear forces. This tightness often leads to a flexed-hip, flexed-knee gait pattern, sometimes described as a 'pelvic tilt' or 'waddling' gait.

Question 894

Topic: Thoracolumbar Spine & Deformity

What is the significance of the 'chevron sign' on a lateral lumbar radiograph in the context of spondylolisthesis?

. Indicates disc space infection
. Signifies sacralization of L5
. Suggests high-grade spondylolisthesis with sagittal plane deformity
. Points to a pars interarticularis fracture
. Identifies a herniated nucleus pulposus

Correct Answer & Explanation

. Suggests high-grade spondylolisthesis with sagittal plane deformity

Explanation

The 'chevron sign' is a radiological finding on a lateral lumbar radiograph in patients with severe L5-S1 spondylolisthesis. It refers to the appearance of the L5 vertebral body superimposed on the S1 vertebral body, creating a 'V' or 'chevron' shape due to the significant anterior displacement and often associated lumbosacral kyphosis. It is a marker of high-grade slip and severe sagittal deformity.

Question 895

Topic: Thoracolumbar Spine & Deformity

What radiographic finding indicates successful fusion following surgery for spondylolisthesis?

. Absence of pain
. Return to full activity
. Bridging bone formation across the fused segment (trabecular continuity) on plain radiographs or CT
. Hardware integrity without loosening
. Restoration of normal lumbar lordosis

Correct Answer & Explanation

. Bridging bone formation across the fused segment (trabecular continuity) on plain radiographs or CT

Explanation

Radiographic evidence of successful fusion (arthrodesis) is typically demonstrated by the presence of solid bridging bone formation (trabecular continuity) between the fused vertebral segments, seen on plain radiographs or, more definitively, on a CT scan. While pain relief and return to activity are clinical goals, they do not directly confirm fusion. Hardware integrity is necessary for stability but doesn't confirm biological fusion. Restoration of lordosis is an alignment goal, not a fusion confirmation.

Question 896

Topic: Thoracolumbar Spine & Deformity

In the context of adult low-grade isthmic spondylolisthesis, what is the significance of significant low back pain (in the absence of neurological deficit) failing conservative management?

. It suggests a high likelihood of concurrent infection.
. It is generally managed by continued pain medication without surgery.
. It is a primary indication for surgical fusion to address mechanical instability.
. It requires immediate aggressive surgical reduction.
. It indicates the need for psychological counseling as the sole intervention.

Correct Answer & Explanation

. It is a primary indication for surgical fusion to address mechanical instability.

Explanation

For adult low-grade isthmic spondylolisthesis, if significant mechanical low back pain persists and profoundly impacts quality of life despite a thorough and prolonged course of conservative management, surgical fusion (typically an in situ posterolateral fusion) is a primary indication. The pain is often attributed to the inherent instability at the slipped segment. While psychological factors can play a role, intractable mechanical pain is a legitimate surgical indication. Immediate aggressive reduction is rarely indicated for low-grade slips without neurological deficit.

Question 897

Topic: Thoracolumbar Spine & Deformity

Which of the following is NOT a common goal of conservative management for spondylolisthesis?

. Pain relief
. Improvement in functional capacity
. Promotion of natural fusion
. Strengthening of core musculature
. Education on activity modification

Correct Answer & Explanation

. Promotion of natural fusion

Explanation

Conservative management for spondylolisthesis aims to alleviate pain, improve function, strengthen the core, and educate on appropriate activity modification. However, it does not promote 'natural fusion' of the vertebral segments. Fusion is a surgical outcome. While some pars defects might heal with bracing, natural fusion of the entire segment is not an expected outcome of conservative care for spondylolisthesis.

Question 898

Topic: Thoracolumbar Spine & Deformity

Which sacral morphological parameter is most strongly correlated with an increased risk of spondylolisthesis progression?

. Pelvic Tilt (PT)
. Sacral Slope (SS)
. Pelvic Incidence (PI)
. Lumbosacral Angle (LSA)
. Vertebral Endplate Angle (VEA)

Correct Answer & Explanation

. Pelvic Incidence (PI)

Explanation

Pelvic Incidence (PI) is a fixed anatomical parameter that defines the orientation of the sacrum relative to the hip axis. A higher pelvic incidence is associated with increased shear forces at the lumbosacral junction, predisposing individuals to a higher risk of developing and progressing spondylolisthesis, especially high-grade slips. It is a key factor in sagittal balance and pathology.

Question 899

Topic: Thoracolumbar Spine & Deformity

What is the role of dynamic flexion-extension radiographs in the evaluation of spondylolisthesis?

. To measure the exact percentage of slip in the static position.
. To assess overall sagittal balance.
. To quantify the amount of instability or segmental motion at the affected level.
. To visualize the pars interarticularis defect.
. To evaluate disc height.

Correct Answer & Explanation

. To quantify the amount of instability or segmental motion at the affected level.

Explanation

Dynamic flexion-extension radiographs are critical for assessing segmental instability. By comparing the amount of slip or angular motion between the flexion and extension views, surgeons can determine if there is excessive pathological motion, which can be an important factor in deciding whether to add fusion to a decompression procedure for degenerative spondylolisthesis, or in evaluating stability in isthmic slips.

Question 900

Topic: Thoracolumbar Spine & Deformity

What is the recommended approach for a pediatric patient with an asymptomatic L5-S1 spondylolisthesis (Grade II) that is not progressing?

. Surgical fusion to prevent future symptoms
. Activity restriction and bracing for 12 months
. Regular observation with periodic clinical and radiographic evaluation
. MRI every 6 months to monitor for neural compression
. Physical therapy focusing on hamstring stretching

Correct Answer & Explanation

. Regular observation with periodic clinical and radiographic evaluation

Explanation

For asymptomatic, non-progressive spondylolisthesis in children, regular observation with periodic clinical and radiographic evaluation is the recommended approach. Many such slips remain stable and asymptomatic throughout life. Surgical intervention is reserved for symptomatic or progressive slips. Bracing/activity restriction is for symptomatic or active pars defects, not necessarily for asymptomatic stable slips. MRI every 6 months is excessive and unnecessary. Hamstring stretching is for symptomatic tightness, not a prophylactic measure for asymptomatic slips.

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