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6. Spine MCQs

Practice Set 258 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 5141

Topic: 6. Spine
A 14-year-old gymnast presents with severe mechanical back pain and L5 radiculopathy. Radiographs reveal a Grade III L5-S1 isthmic spondylolisthesis with a slip angle of 55 degrees. Nonoperative management has failed. What is the most appropriate surgical treatment?
. L5-S1 laminectomy without fusion
. Pars interarticularis repair (Buck's procedure)
. L4-S1 posterior spinal fusion with instrumentation
. L5-S1 posterior in situ spinal fusion without instrumentation
. L5-S1 anterior lumbar interbody fusion (ALIF) alone

Correct Answer & Explanation

. L4-S1 posterior spinal fusion with instrumentation

Explanation

Symptomatic high-grade spondylolisthesis (Grade III-V) in adolescents typically requires decompression and instrumented posterior fusion. Fusing from L4 to S1 is often necessary to obtain adequate fixation and counteract severe shear forces.

Question 5142

Topic: 6. Spine

An 8-month-old boy with achondroplasia presents with hypotonia, sleep apnea, and hyperreflexia. An MRI reveals severe stenosis at the foramen magnum with T2 signal changes in the upper cervical cord. What is the most appropriate next step?

. Continuous positive airway pressure (CPAP) at night
. Urgent suboccipital decompression and C1 laminectomy
. Bracing with a cervical collar
. Observation with repeat MRI in 6 months
. Somatotropin (growth hormone) therapy

Correct Answer & Explanation

. Urgent suboccipital decompression and C1 laminectomy

Explanation

Foramen magnum stenosis leading to cervicomedullary compression is a critical complication in infants with achondroplasia. Signs of myelopathy and MRI cord signal changes mandate urgent surgical decompression to prevent sudden death or permanent neurological injury.

Question 5143

Topic: 6. Spine

A child presents with short stature, rhizomelic limb shortening, frontal bossing, and a trident hand deformity. What is the most critical and life-threatening cervical spine abnormality associated with this skeletal dysplasia?

. Foramen magnum stenosis leading to cervicomedullary compression
. Atlantoaxial instability due to odontoid hypoplasia
. Cervical kyphosis requiring early posterior fusion
. Basilar invagination
. Congenital fusion of C2-C3 (Klippel-Feil anomaly)

Correct Answer & Explanation

. Foramen magnum stenosis leading to cervicomedullary compression

Explanation

The clinical picture describes Achondroplasia. The most critical cervical spine issue in these infants is foramen magnum stenosis, which can cause severe cervicomedullary compression, leading to central apnea or sudden death.

Question 5144

Topic: Thoracolumbar Spine & Deformity
A 14-year-old gymnast is diagnosed with an L5-S1 isthmic spondylolisthesis with a 60 percent slip (Grade III). She reports persistent mechanical back pain and L5 radiculopathy despite 6 months of rest and therapy. What is the most appropriate surgical management?
. Continued rigid bracing for 6 additional months
. Pars interarticularis defect repair (Buck procedure)
. L5-S1 in situ posterolateral fusion
. L4-L5-S1 wide laminectomy without fusion
. Epidural steroid injections alone

Correct Answer & Explanation

. L5-S1 in situ posterolateral fusion

Explanation

High-grade spondylolisthesis (greater than 50 percent slip) with refractory symptoms is generally managed with an in situ posterolateral fusion, often with decompression if radicular symptoms are profound. Pars repair is reserved for Grade 0 or I slips.

Question 5145

Topic: Cervical Spine

A 7-year-old child presents with torticollis and severe neck stiffness one week after undergoing a tonsillectomy. A CT scan confirms atlantoaxial rotatory subluxation. What is the primary pathophysiologic mechanism of this condition (Grisel's syndrome)?

. Congenital aplasia of the odontoid process
. Rupture of the transverse ligament due to minor trauma
. Hyperemia and inflammation leading to ligamentous laxity
. Ischemic necrosis of the atlas
. Facet joint osteoarthrosis

Correct Answer & Explanation

. Hyperemia and inflammation leading to ligamentous laxity

Explanation

Grisel's syndrome is a non-traumatic atlantoaxial rotatory subluxation associated with head and neck infections or recent ENT surgery. Pharyngeal inflammation causes local hyperemia, which leads to laxity of the transverse ligament and subsequent C1-C2 subluxation.

Question 5146

Topic: 6. Spine

A 72-year-old woman is evaluated for a primary total hip arthroplasty. She has a history of a long spinal fusion from T10 to the pelvis for adult spinal deformity. How does this spinopelvic stiffness affect her acetabular component positioning compared to a patient with normal spinal mobility?

. The cup should be placed in less anteversion
. The cup should be placed in more anteversion
. The cup should be placed in less abduction
. Spinopelvic stiffness does not alter target cup position
. The cup should be placed in more retroversion

Correct Answer & Explanation

. The cup should be placed in more anteversion

Explanation

Patients with lumbopelvic fusions cannot increase posterior pelvic tilt when sitting, which functionally decreases their acetabular anteversion and increases the risk of posterior dislocation. To accommodate this stiffness and prevent dislocation during seated activities, the cup should be placed in relatively more anteversion.

Question 5147

Topic: 6. Spine

A patient with a fused lumbar spine from L2 to the sacrum is scheduled for a total hip arthroplasty. How does this spinopelvic stiffness alter the target cup positioning to minimize dislocation risk?

. It requires standard placement as spinopelvic motion is irrelevant
. It requires decreased acetabular inclination
. It requires decreased acetabular anteversion
. It requires increased acetabular anteversion
. It requires a dual mobility cup in all cases regardless of version

Correct Answer & Explanation

. It requires increased acetabular anteversion

Explanation

A fused lumbar spine prevents normal posterior pelvic tilt during sitting, which normally functionally increases acetabular anteversion. To prevent anterior impingement and posterior dislocation during sitting, the cup must be placed with increased anteversion.

Question 5148

Topic: 6. Spine

A 68-year-old female with a long spinal fusion from T10 to the pelvis requires a total hip arthroplasty.

Flexion-extension lateral spine radiographs show a failure of the pelvis to tilt posteriorly when moving from standing to sitting. How should the acetabular component be positioned to minimize dislocation risk?

. Decrease anteversion and decrease inclination relative to standard
. Increase anteversion and increase inclination relative to standard
. Maintain standard anteversion but increase inclination
. Increase anteversion only
. Decrease inclination only

Correct Answer & Explanation

. Increase anteversion and increase inclination relative to standard

Explanation

Patients with a stiff spinopelvic complex fail to increase pelvic tilt during sitting, resulting in a relative lack of functional acetabular anteversion. To prevent anterior impingement and posterior dislocation, the cup should be placed in more anteversion and inclination than the traditional safe zone.

Question 5149

Topic: 6. Spine

A 70-year-old man with ankylosing spondylitis and a fused lumbar spine is scheduled for a primary THA. His pelvis remains in a neutrally tilted position and fails to retrovert when he transitions from standing to sitting. To prevent posterior instability, how should the acetabular component positioning be adjusted?

. Increase the anteversion
. Decrease the anteversion
. Decrease the inclination
. Place the cup in neutral version
. Use a constrained liner with standard version

Correct Answer & Explanation

. Increase the anteversion

Explanation

Normally, the pelvis retroverts during sitting to accommodate hip flexion by functionally increasing acetabular anteversion. In patients with a stiff spine who cannot retrovert, the surgeon must increase the cup anteversion to prevent posterior impingement and dislocation.

Question 5150

Topic: 6. Spine

A 72-year-old woman with a history of an L2 to pelvis spinal fusion presents for a total hip arthroplasty. How does her multi-level spinal fusion alter her spinopelvic mechanics, and what modification in acetabular component positioning is recommended to prevent dislocation?

. The pelvis will exhibit increased posterior tilt when sitting; the cup should be placed in less anteversion.
. The pelvis will be unable to posteriorly tilt when sitting; the cup should be placed in more anteversion and inclination.
. The pelvis will exhibit increased anterior tilt when sitting; the cup should be placed in less inclination.
. The pelvis will be unable to anteriorly tilt when standing; the cup should be placed in more retroversion.
. Spinopelvic mechanics are unaffected if the fusion is above S1; no modification is necessary.

Correct Answer & Explanation

. The pelvis will be unable to posteriorly tilt when sitting; the cup should be placed in more anteversion and inclination.

Explanation

In a normal spine, sitting induces posterior pelvic tilt, which increases functional acetabular anteversion and clears the anterior impingement plane. A rigid lumbopelvic fusion prevents posterior tilt, increasing the risk of anterior impingement and posterior dislocation when sitting; thus, the cup should be placed in more anteversion and inclination.

Question 5151

Topic: 6. Spine

A 65-year-old man with a solid L2-S1 spinal fusion undergoes a total hip arthroplasty. Preoperative standing and sitting lateral radiographs demonstrate less than 5 degrees of change in pelvic tilt. Based on his spinopelvic mechanics, what is the most appropriate acetabular component positioning strategy?

. Target standard Lewinnek safe zone parameters
. Increase cup anteversion and inclination
. Decrease cup anteversion and inclination
. Increase cup inclination but decrease anteversion
. Decrease cup inclination but increase anteversion

Correct Answer & Explanation

. Increase cup anteversion and inclination

Explanation

Patients with a stiff lumbosacral spine fail to increase pelvic tilt during sitting, creating a high risk of anterior impingement and posterior dislocation. Compensating by increasing acetabular cup anteversion and inclination helps accommodate the fixed pelvis and prevents posterior instability during flexion.

Question 5152

Topic: 6. Spine

A 65-year-old female is evaluated for recurrent posterior THA dislocations. Radiographs demonstrate a stiff lumbar spine with loss of normal spinopelvic mobility. When transitioning from standing to sitting, how does a stiff spine abnormally affect acetabular version?

. The pelvis fails to tilt posteriorly, resulting in relative acetabular retroversion compared to a normal spine.
. The pelvis hyper-tilts anteriorly, causing excessive acetabular anteversion.
. The pelvis tilts laterally, leading to a functional leg length discrepancy.
. The pelvis fails to tilt anteriorly, resulting in relative acetabular retroversion.
. The lumbar spine flexes excessively, leading to an anterior pelvic tilt.

Correct Answer & Explanation

. The pelvis fails to tilt posteriorly, resulting in relative acetabular retroversion compared to a normal spine.

Explanation

Normally, moving from standing to sitting involves lumbar flexion and posterior pelvic tilt, which increases acetabular anteversion to accommodate hip flexion. A stiff spine prevents this posterior tilt, leaving the cup relatively retroverted and prone to posterior dislocation.

Question 5153

Topic: 6. Spine

In a patient undergoing total hip arthroplasty, dynamic spinopelvic assessment reveals a stiff, fused lumbar spine in a kyphotic position. How does this condition affect the functional position of the acetabulum when the patient transitions from standing to sitting?

. The pelvis fails to tilt posteriorly, leading to functional acetabular relative retroversion and increased risk of anterior dislocation.
. The pelvis tilts excessively posteriorly, increasing the risk of posterior dislocation.
. The pelvis fails to tilt posteriorly, causing the cup to remain relatively less anteverted, increasing the risk of anterior impingement and posterior dislocation.
. The pelvis tilts anteriorly, increasing functional anteversion and anterior instability.
. Spinopelvic mechanics are unaffected by lumbar fusion.

Correct Answer & Explanation

. The pelvis fails to tilt posteriorly, causing the cup to remain relatively less anteverted, increasing the risk of anterior impingement and posterior dislocation.

Explanation

In a stiff lumbar spine, the pelvis fails to undergo normal posterior tilt when sitting. This lack of posterior tilt means the acetabulum does not gain functional anteversion, risking anterior impingement and subsequent posterior dislocation.

Question 5154

Topic: Thoracolumbar Spine & Deformity

A 65-year-old woman is evaluated for a total hip arthroplasty. She has a history of L3-S1 lumbar fusion. Sitting and standing lateral radiographs show a change in pelvic tilt of 5 degrees. How should the acetabular cup be positioned compared to a patient with normal spinopelvic mobility?

. Increased anteversion and increased inclination
. Decreased anteversion and decreased inclination
. Decreased anteversion and increased inclination
. Increased anteversion and normal inclination
. Normal positioning as fusion does not affect cup dynamics

Correct Answer & Explanation

. Increased anteversion and increased inclination

Explanation

A stiff lumbar spine (change in pelvic tilt <10 degrees) prevents normal posterior pelvic rollback during sitting. This increases the risk of anterior impingement and posterior dislocation; therefore, the cup should be placed in increased anteversion and inclination.

Question 5155

Topic: Thoracolumbar Spine & Deformity

A patient is scheduled for a THA. Preoperative standing and sitting lateral spinopelvic radiographs demonstrate a stiff lumbar spine with less than 10 degrees of pelvic tilt change between standing and sitting. How does this condition affect acetabular component positioning?

. The cup should be placed in less anteversion to prevent anterior dislocation in standing.
. The cup must be placed in a patient-specific safe zone with increased anteversion to accommodate the lack of posterior pelvic tilt in sitting.
. A dual mobility bearing is absolutely contraindicated due to restricted pelvic motion.
. The cup should be placed in more retroversion to improve posterior coverage.
. Standard Lewinnek safe zone parameters (40 degrees inclination, 15 degrees anteversion) remain optimal.

Correct Answer & Explanation

. The cup must be placed in a patient-specific safe zone with increased anteversion to accommodate the lack of posterior pelvic tilt in sitting.

Explanation

A stiff spinopelvic junction prevents the normal posterior pelvic tilt required to accommodate hip flexion when sitting, increasing the risk of anterior impingement and posterior dislocation. The acetabular component typically requires higher anteversion and inclination to compensate for this stiffness.

Question 5156

Topic: 6. Spine

A 65-year-old male with a history of an L2-L5 spinal fusion undergoes preoperative planning for a THA. Standing and sitting lateral radiographs demonstrate less than 10 degrees of change in his pelvic tilt. How should the acetabular cup placement be modified to minimize the risk of posterior dislocation?

. The cup should be placed in increased relative retroversion
. The cup should be placed in more anteversion and higher inclination than standard targets
. The cup should be placed perfectly horizontal (0 degrees inclination)
. The cup requires standard positioning as spinal fusion does not affect the safe zone
. The cup should be placed in relative retroversion and low inclination

Correct Answer & Explanation

. The cup should be placed in more anteversion and higher inclination than standard targets

Explanation

Patients with stiff lumbar spines lack normal spinopelvic mobility and cannot dynamically alter pelvic tilt (posterior tilt) when sitting. To accommodate hip flexion and clear the anterior impingement limit, the acetabular component requires increased anteversion.

Question 5157

Topic: 6. Spine

A 24-year-old man sustains a Denis Zone 3 sacral fracture following a fall. Which of the following neurologic deficits is most commonly associated with this specific injury zone?

. Foot drop
. Quadriceps weakness
. Bowel and bladder dysfunction
. Loss of sensation over the lateral thigh
. Weakness of great toe extension

Correct Answer & Explanation

. Bowel and bladder dysfunction

Explanation

Denis Zone 3 sacral fractures involve the central sacral canal and are highly associated with cauda equina injury, leading to bowel, bladder, and sexual dysfunction.

Question 5158

Topic: 6. Spine

A trauma patient sustains a U-type sacral fracture (spinopelvic dissociation). Which neurological complication is most specifically associated with this classic fracture pattern?

. Isolated femoral nerve palsy
. Isolated L5 nerve root injury
. Cauda equina syndrome with bowel and bladder dysfunction
. Sural nerve palsy
. Complete sciatic nerve transection

Correct Answer & Explanation

. Cauda equina syndrome with bowel and bladder dysfunction

Explanation

U-type sacral fractures typically involve the central sacral canal, frequently compressing the sacral nerve roots. This results in cauda equina syndrome, characterized by bowel, bladder, and sexual dysfunction.

Question 5159

Topic: Cervical Spine

A 30-year-old unrestrained driver sustains a traumatic spondylolisthesis of C2 with severe angulation and minimal translation (Levine-Edwards Type IIa). What is the most appropriate initial management?

. Immediate heavy longitudinal cervical traction
. Gentle reduction with extension and compression in a halo vest
. Immediate anterior cervical discectomy and fusion (ACDF)
. C1-C2 posterior instrumentation and fusion
. Application of a rigid cervical collar only

Correct Answer & Explanation

. Gentle reduction with extension and compression in a halo vest

Explanation

Type IIa Hangman's fractures involve a flexion-distraction mechanism. Axial traction is strictly contraindicated as it worsens the deformity; treatment requires gentle extension and compression, typically in a halo vest.

Question 5160

Topic: 6. Spine

A 24-year-old male is brought to the trauma bay with scapulothoracic dissociation following a motorcycle accident. What is the most critical immediate life-threatening concern associated with this injury?

. Complete brachial plexus avulsion
. Subclavian artery or vein disruption
. Flail chest
. Cervical spine fracture
. Tension pneumothorax

Correct Answer & Explanation

. Subclavian artery or vein disruption

Explanation

Scapulothoracic dissociation involves a massive disruption of the shoulder girdle from the axial skeleton. Vascular injury, particularly massive hemorrhage from subclavian artery or vein disruption, is the most immediate life-threatening concern.

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