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6. Spine MCQs

Practice Set 9 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 161

Topic: 6. Spine

Which imaging modality is usually the least sensitive in diagnosing discitis:

. Plain radiograph
. C omputed tomography (C T) scan
. Magnetic resonance image (MRI)
. Technetium bone scan
. Tomograms

Correct Answer & Explanation

. Plain radiograph

Explanation

The least helpful modality in diagnosing early discitis is the plain radiograph. Fluoroscopy does not give insight into the state of the intervertebral disk. It can suggest loss of disk height or involvement of the vertebral bone but will not reveal infection limited to the disk. The CT scan is useful because of its excellent resolution of bony structures and associated changes secondary to disk infection. MRI is the best modality to characterize the soft tissues in the cervical spine.

Question 162

Topic: 6. Spine

Potts disease is most commonly treated by:

. Decompression
. Antibiotic therapy and immobilization
. Antibiotic therapy only
. Spinal orthosis
. Decompression and fusion

Correct Answer & Explanation

. Antibiotic therapy and immobilization

Explanation

The treatment of tuberculous involvement of the spine is rarely surgical. Most commonly, the spine remains stable and fusion is not necessary. However, orthosis in combination with long-term antibiotic therapy is the key for successful treatment. A collar is sufficient to provide enough stability and comfort for the lesion to heal.

Question 163

Topic: 6. Spine

Which of the following is characteristic of patients with Klippel-Feil syndrome:

. Absence of the vertebral pedicles
. Absence of intervertebral joints
. Shortened pedicles
. A narrow spinal canal
. Increased interpediculate distance

Correct Answer & Explanation

. Absence of intervertebral joints

Explanation

Klippel-Feil syndrome is a rare disorder characterized by the congenital fusion of any two of the seven cervical vertebrae. The cause is a failure in the early segmentation during fetal development. The fused segments show absence of intervertebral joints. Associated abnormalities may include scoliosis; spina bifida; anomalies of the kidneys and ribs; and other midline anomalies.

Question 164

Topic: 6. Spine

Which of the following strictly defines the boundaries of Kambin's working triangle utilized in transforaminal endoscopic and minimally invasive spine procedures?

. Superior endplate of the inferior vertebra, exiting nerve root, and traversing nerve root
. Superior endplate of the inferior vertebra, exiting nerve root, and superior articular process
. Inferior pedicle, superior pedicle, and exiting nerve root
. Superior articular process, traversing nerve root, and inferior pedicle
. Pars interarticularis, superior endplate, and exiting nerve root

Correct Answer & Explanation

. Superior endplate of the inferior vertebra, exiting nerve root, and superior articular process

Explanation

Kambin's triangle is bound anteriorly by the exiting nerve root, inferiorly by the superior endplate of the inferior vertebral body, and posteriorly by the superior articular process of the inferior vertebra. It serves as a safe corridor for transforaminal access to the disc space.

Question 165

Topic: Thoracolumbar Spine & Deformity

Cortical bone trajectory (CBT) pedicle screws are increasingly used in minimally invasive lumbar fusions. Which of the following best describes the starting point and trajectory of a CBT screw compared to a traditional pedicle screw?

. More lateral starting point, trajectory directed medially and caudad
. More lateral starting point, trajectory directed medially and cephalad
. More medial starting point, trajectory directed laterally and cephalad
. More medial starting point, trajectory directed laterally and caudad
. Identical starting point, trajectory directed strictly cephalad

Correct Answer & Explanation

. More lateral starting point, trajectory directed medially and cephalad

Explanation

CBT screws are inserted with a medial-to-lateral and caudad-to-cephalad trajectory, starting at the junction of the pars interarticularis and superior articular process. This maximizes engagement with high-density cortical bone, increasing pullout strength.

Question 166

Topic: 6. Spine

A 62-year-old male presents with neurogenic claudication and L5-S1 isthmic spondylolisthesis. Why is a standard lateral lumbar interbody fusion (LLIF) approach generally contraindicated at this specific level?

. High risk of bowel perforation
. Inability to mobilize the great vessels
. Obstruction by the iliac crest
. Anomalous course of the sciatic nerve
. Excessive psoas muscle bulk

Correct Answer & Explanation

. Obstruction by the iliac crest

Explanation

The standard transpsoas lateral approach (LLIF) is generally contraindicated at L5-S1 due to the anatomical obstruction caused by the iliac crest, which prevents direct orthogonal access to the disc space. ALIF or TLIF are preferred alternatives.

Question 167

Topic: Thoracolumbar Spine & Deformity

Review the provided imaging.

In managing a patient with symptomatic L4-L5 degenerative spondylolisthesis, which of the following is a proven advantage of utilizing a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) over an open approach?

. Reduced incidence of adjacent segment disease
. Superior restoration of coronal balance
. Decreased postoperative narcotic use and shorter hospital stay
. Lower rate of long-term pseudarthrosis
. Decreased intraoperative fluoroscopy time

Correct Answer & Explanation

. Decreased postoperative narcotic use and shorter hospital stay

Explanation

Extensive literature comparing MIS TLIF to open TLIF for degenerative spondylolisthesis demonstrates that MIS approaches lead to less intraoperative blood loss, decreased postoperative narcotic consumption, and a shorter hospital length of stay. Long-term fusion rates and ASD incidence remain similar.

Question 168

Topic: 6. Spine

Which of the following is the most appropriate indication for utilizing an interlaminar endoscopic approach rather than a transforaminal endoscopic approach for a lumbar discectomy?

. Far lateral extraforaminal disc herniation at L3-L4
. Central disc herniation at L1-L2
. Paracentral disc herniation at L5-S1 with a high iliac crest
. Recurrent disc herniation with extensive epidural fibrosis
. Degenerative spondylolisthesis requiring fusion

Correct Answer & Explanation

. Paracentral disc herniation at L5-S1 with a high iliac crest

Explanation

The interlaminar approach is preferred at L5-S1 because the wide interlaminar window allows excellent access, while the transforaminal approach is often obstructed at this level by a high-riding iliac crest and large L5 transverse process.

Question 169

Topic: 6. Spine

During a percutaneous transforaminal endoscopic discectomy or MIS approach, the surgeon accesses the disc space via Kambin's triangle. Which of the following structures forms the medial (posterior) boundary of this working zone?

. The exiting nerve root
. The superior endplate of the caudal vertebra
. The traversing nerve root
. The pedicle of the cranial vertebra
. The pars interarticularis

Correct Answer & Explanation

. The traversing nerve root

Explanation

Kambin's triangle is an anatomical corridor bounded anteriorly/laterally by the exiting nerve root, inferiorly by the superior endplate of the caudal vertebra, and medially/posteriorly by the traversing nerve root and thecal sac.

Question 170

Topic: 6. Spine



When establishing the operative corridor for a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) using a tubular retractor system, what is the primary initial bony docking point?

. The spinous process of the cranial vertebra
. The lateral border of the pars interarticularis
. The facet joint complex (inferior articular process of the cranial vertebra and superior articular process of the caudal vertebra)
. The base of the transverse process
. The medial wall of the pedicle

Correct Answer & Explanation

. The facet joint complex (inferior articular process of the cranial vertebra and superior articular process of the caudal vertebra)

Explanation

In an MIS TLIF, the tubular retractor is typically docked directly over the facet complex (specifically the junction of the pars and the facet joint). This allows direct access for a unilateral facetectomy to expose the intervertebral disc and neuroforamen.

Question 171

Topic: Thoracolumbar Spine & Deformity

Cortical bone trajectory (CBT) screws have gained popularity in minimally invasive lumbar fusions. Which of the following best describes the entry point and trajectory of a CBT pedicle screw compared to a traditional pedicle screw?

. Lateral to medial, aimed caudally
. Lateral to medial, aimed parallel to the endplate
. Medial to lateral, aimed cephalad
. Medial to lateral, aimed caudally
. Directly posterior to anterior, avoiding the pars

Correct Answer & Explanation

. Lateral to medial, aimed caudally

Explanation

The CBT screw entry point is in the pars interarticularis, starting medially and aiming laterally and cephalad. This maximizes contact with higher-density cortical bone, increasing pullout strength.

Question 172

Topic: 6. Spine

A surgeon is performing a lateral lumbar interbody fusion (LLIF/XLIF). At which of the following operative levels is the patient at the highest risk for postoperative lumbar plexus injury or severe psoas weakness?

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

Correct Answer & Explanation

. T12-L1

Explanation

The lumbar plexus courses more anteriorly within the psoas muscle as it descends the lumbar spine. Consequently, the L4-L5 level carries the highest risk for iatrogenic plexus injury during a transpsoas lateral approach.

Question 173

Topic: 6. Spine

A 55-year-old patient undergoes an uncomplicated L4-L5 MIS TLIF for right-sided radiculopathy. Postoperatively, the patient develops severe new-onset left-sided (contralateral) radicular leg pain. What is the most likely intraoperative cause of this complication?

. Inadequate decortication of the L4 endplate
. Over-distraction of the disc space
. Incidental durotomy without primary repair
. Use of an undersized interbody cage
. Placement of a transfascial wound drain

Correct Answer & Explanation

. Inadequate decortication of the L4 endplate

Explanation

Over-distraction of the intervertebral space with a large cage during a unilateral MIS TLIF can cause indirect compression or traction on the contralateral traversing nerve root, leading to new-onset contralateral radiculopathy.

Question 174

Topic: 6. Spine

Oblique lumbar interbody fusion (OLIF) was developed as an alternative to the transpsoas lateral approach (LLIF). What is the primary anatomical advantage of OLIF over LLIF?

. It approaches the spine anterior to the psoas muscle, minimizing lumbar plexus injury risk
. It utilizes a transperitoneal approach, allowing direct visualization of the great vessels
. It requires partial resection of the psoas, providing better access to the neuroforamen
. It avoids the sympathetic chain entirely in the upper lumbar spine
. It allows for direct bilateral decompression of the central canal

Correct Answer & Explanation

. It approaches the spine anterior to the psoas muscle, minimizing lumbar plexus injury risk

Explanation

OLIF approaches the lumbar spine through an oblique corridor anterior to the psoas muscle. This largely avoids the lumbar plexus, reducing the risk of postoperative psoas weakness and groin numbness associated with LLIF.

Question 175

Topic: 6. Spine

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is frequently used off-label as a bone graft extender in MIS TLIF procedures. Which of the following is a recognized complication specifically associated with its use in the posterior lumbar spine?

. Systemic anaphylaxis
. Accelerated adjacent segment degeneration
. Postoperative radiculitis or ectopic bone formation
. Increased rate of surgical site infection
. Pseudomeningocele formation

Correct Answer & Explanation

. Systemic anaphylaxis

Explanation

When used in posterior or transforaminal approaches, rhBMP-2 leakage near neural elements can cause a robust localized inflammatory response resulting in severe postoperative radiculitis, as well as the risk of ectopic heterotopic ossification.

Question 176

Topic: 6. Spine

Minimally invasive spine surgery heavily relies on intraoperative fluoroscopy, increasing radiation exposure to the surgeon. According to the inverse square law, stepping back 1 meter from the C-arm during exposure reduces the radiation dose by approximately what factor compared to standing 0.5 meters away?

. It reduces the dose to one-fourth (1/4)
. It reduces the dose to one-half (1/2)
. It reduces the dose to one-eighth (1/8)
. It reduces the dose to one-third (1/3)
. It has no significant effect on scatter radiation

Correct Answer & Explanation

. It reduces the dose to one-fourth (1/4)

Explanation

The inverse square law states that radiation exposure is inversely proportional to the square of the distance from the source. Doubling the distance (e.g., 0.5m to 1m) reduces the radiation exposure to one-fourth.

Question 177

Topic: 6. Spine

Computer-assisted navigation with intraoperative CT (O-arm) is increasingly used for percutaneous pedicle screw placement in MISS. What intraoperative maneuver is most likely to cause a "registration error" resulting in inaccurate screw navigation?

. Changing the fluoroscopy bed height
. Aggressive distraction or decompression after acquiring the CT scan but before screw placement
. Use of a radiolucent carbon fiber retractor
. Administering intravenous contrast during the scan
. Placement of the reference array on the spinous process of the target vertebra

Correct Answer & Explanation

. Changing the fluoroscopy bed height

Explanation

Navigation systems rely on the fixed spatial relationship between the reference frame and the bony anatomy. Any manipulation (distraction, translation, or decompression) that alters the alignment of the vertebrae after the spin will compromise navigational accuracy.

Question 178

Topic: Thoracolumbar Spine & Deformity

For a patient with an L5-S1 isthmic spondylolisthesis and significant loss of segmental lordosis, an Anterior Lumbar Interbody Fusion (ALIF) may be preferred over an MIS TLIF. What is the primary biomechanical advantage of ALIF at this specific level?

. Higher rate of successful posterior decompression
. Reduced risk of retrograde ejaculation
. Superior ability to restore segmental sagittal lordosis
. Avoidance of major vascular structures
. Lower risk of postoperative abdominal hernia

Correct Answer & Explanation

. Higher rate of successful posterior decompression

Explanation

ALIF at L5-S1 allows for the placement of a large, highly lordotic cage and release of the anterior longitudinal ligament (ALL), providing far superior restoration of segmental lordosis compared to a posterior/transforaminal approach.

Question 179

Topic: 6. Spine

During the placement of percutaneous pedicle screws, a Kirschner wire (K-wire) is impacted into the pedicle. What is the most devastating complication associated with poor K-wire control during this step?

. Medial breach into the spinal canal causing dural tear
. Breakage of the K-wire in the pedicle
. Unrecognized ventral advancement through the vertebral body causing vascular or visceral injury
. Lateral breach into the psoas muscle
. Thermal necrosis of the pedicle wall

Correct Answer & Explanation

. Medial breach into the spinal canal causing dural tear

Explanation

Loss of K-wire control during tapping or screw placement can lead to ventral migration through the anterior vertebral body cortex, risking catastrophic injury to the great vessels (aorta/vena cava) or bowel.

Question 180

Topic: 6. Spine

Which of the following clinical scenarios represents a relative contraindication to a minimally invasive transforaminal lumbar interbody fusion (MIS TLIF)?

. Grade I degenerative spondylolisthesis
. Recurrent lumbar disc herniation with radiculopathy
. One-level fusion in a morbidly obese patient (BMI > 40)
. Severe fixed sagittal imbalance requiring a pedicle subtraction osteotomy (PSO)
. Bilateral foraminal stenosis at L4-L5

Correct Answer & Explanation

. Grade I degenerative spondylolisthesis

Explanation

While MIS TLIF is excellent for single-level degenerative disease, severe fixed sagittal deformity requiring major 3-column osteotomies (like PSO) necessitates extensive bilateral exposure and is best treated with an open approach.

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