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6. Spine MCQs

Practice Set 366 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 7301

Topic: 6. Spine

A 4-year-old girl is evaluated for a skeletal dysplasia. She has significant atlantoaxial instability, short stature, and distinctive stippled calcifications of the epiphyses on initial radiographs. Furthermore, lateral spine radiographs reveal coronal clefts in the vertebral bodies. Which of the following is the most likely diagnosis?

. Kniest dysplasia
. Chondrodysplasia punctata
. Campomelic dysplasia
. Metatropic dysplasia
. Achondroplasia

Correct Answer & Explanation

. Chondrodysplasia punctata

Explanation

Chondrodysplasia punctata is characterized by stippled epiphyses in infancy and early childhood. Spinal manifestations commonly include coronal clefts of the vertebral bodies and significant atlantoaxial instability requiring vigilant monitoring.

Question 7302

Topic: Cervical Spine

In patients with mucopolysaccharidoses (MPS), upper cervical instability is a well-documented risk. The pathogenesis of odontoid hypoplasia and subsequent atlantoaxial instability in Morquio syndrome (MPS IV) is primarily due to the accumulation of which of the following?

. Dermatan sulfate
. Heparan sulfate
. Keratan sulfate
. Hyaluronic acid
. Chondroitin-4-sulfate

Correct Answer & Explanation

. Keratan sulfate

Explanation

Morquio syndrome (MPS IV) is caused by a defect in keratan sulfate degradation, leading to its accumulation in tissues. This disrupts normal chondrogenesis, particularly affecting the odontoid process and leading to hypoplasia and severe C1-C2 ligamentous instability.

Question 7303

Topic: 6. Spine

During the evaluation of a 45-year-old male with achondroplasia complaining of neurogenic claudication, lumbar radiographs are obtained. Which of the following anatomic abnormalities is the primary driver of his spinal stenosis?

. Decreasing interpedicular distance from L1 to L5
. Hypertrophy of the ligamentum flavum
. Congenital pars interarticularis defects
. Dural ectasia
. Anterior wedging of the vertebral bodies

Correct Answer & Explanation

. Decreasing interpedicular distance from L1 to L5

Explanation

In achondroplasia, there is a failure of normal endochondral ossification leading to abnormally short pedicles and a characteristic decrease in the interpedicular distance from L1 to L5. This congenital narrowing strictly limits the spinal canal volume, predisposing patients to early-onset symptomatic spinal stenosis.

Question 7304

Topic: 6. Spine

A 7-year-old child with Morquio syndrome (MPS IV) presents with progressive clumsiness, broad-based gait, and bilateral Babinski signs. Flexion-extension radiographs of the cervical spine demonstrate 8 mm of atlantoaxial instability. What is the primary underlying cause of this instability?

. Transverse ligament laxity
. Odontoid hypoplasia
. Occipitocervical assimilation
. Cervical facet joint dysplasia
. Pathological fracture of the dens

Correct Answer & Explanation

. Odontoid hypoplasia

Explanation

Odontoid hypoplasia is a hallmark of Morquio syndrome, occurring in almost all affected individuals due to defective endochondral ossification. Combined with severe ligamentous laxity, this predictably leads to profound atlantoaxial instability and potential myelopathy, requiring posterior cervical fusion.

Question 7305

Topic: Thoracolumbar Spine & Deformity

A 6-year-old patient with Hurler syndrome (MPS I) successfully underwent hematopoietic stem cell transplantation (HSCT) at age 2. Which of the following spinal deformities is most likely to persist and potentially progress despite successful HSCT?

. Atlantoaxial rotatory fixation
. Thoracolumbar kyphosis
. Spondylolisthesis
. Cervical lordosis
. Dystrophic scoliosis

Correct Answer & Explanation

. Thoracolumbar kyphosis

Explanation

While hematopoietic stem cell transplantation (HSCT) resolves many systemic and visceral manifestations of Hurler syndrome, it has limited effect on skeletal dysplasias. Thoracolumbar kyphosis, driven by anterior vertebral body hypoplasia (bullet-shaped vertebrae), frequently progresses and often requires surgical intervention.

Question 7306

Topic: 6. Spine

A newborn is diagnosed with Larsen syndrome. In addition to multiple major joint dislocations and spatulate fingers, orthopedic evaluation must immediately prioritize imaging of the spine to rule out which potentially lethal deformity?

. Atlantooccipital dissociation
. Mid-thoracic scoliosis
. Cervical kyphosis
. Lumbosacral agenesis
. Thoracolumbar kyphosis

Correct Answer & Explanation

. Cervical kyphosis

Explanation

Larsen syndrome is heavily associated with a severe, potentially lethal congenital cervical kyphosis caused by hypoplastic cervical vertebrae. If left unbraced or unfused, this deformity can progress rapidly to cause catastrophic spinal cord compression and tetraplegia.

Question 7307

Topic: 6. Spine
A 25-year-old female with Osteogenesis Imperfecta Type III complains of lower cranial nerve deficits, suboccipital headache, and hyperreflexia. A sagittal MRI of the brain and cervical spine is most likely to demonstrate which of the following?
. Odontoid hypoplasia
. Basilar invagination
. Chiari malformation type II
. Os odontoideum
. Subaxial cervical subluxation

Correct Answer & Explanation

. Basilar invagination

Explanation

Basilar invagination is a dangerous complication of severe osteogenesis imperfecta, caused by progressive softening and upward yielding of the skull base. This results in the dens migrating upwards through the foramen magnum, causing direct brainstem and lower cranial nerve compression.

Question 7308

Topic: 6. Spine

A 10-year-old boy with Neurofibromatosis Type 1 presents with a rapidly progressing, sharp angular thoracic scoliosis of 60 degrees. Radiographs reveal penciling of the ribs, dural ectasia, and severe apical vertebral wedging. What is the most appropriate surgical strategy?

. Posterior spinal fusion alone
. Anterior and posterior spinal fusion
. Growing rod instrumentation
. Vertebral body tethering
. Bracing until skeletal maturity

Correct Answer & Explanation

. Anterior and posterior spinal fusion

Explanation

Dystrophic scoliosis in NF1 is characterized by short, sharp curves that are highly prone to progression and pseudoarthrosis after surgery. An anterior release and fusion combined with a solid posterior spinal fusion (APSF) is strongly recommended to achieve rigid stabilization and prevent pseudoarthrosis.

Question 7309

Topic: 6. Spine

A 9-year-old girl with pseudoachondroplasia presents for a routine orthopedic evaluation. She has a normal facial appearance, severe disproportionate short stature, and joint laxity. Which of the following cervical spine anomalies is most prevalent in this condition?

. Atlantoaxial instability due to odontoid hypoplasia
. Cervical kyphosis due to vertebral body wedging
. Subaxial instability due to facet dysplasia
. C1-C2 rotatory subluxation
. Klippel-Feil anomaly

Correct Answer & Explanation

. Atlantoaxial instability due to odontoid hypoplasia

Explanation

Unlike achondroplasia, patients with pseudoachondroplasia frequently have odontoid hypoplasia combined with severe ligamentous laxity. This combination makes them highly susceptible to atlantoaxial instability, necessitating flexion-extension cervical radiographs to screen for subluxation.

Question 7310

Topic: 6. Spine

A 4-year-old boy with diastrophic dysplasia presents with an unresolved, rigid mid-cervical kyphosis of 65 degrees that has progressed over the last year. Neurological examination is currently normal. What is the recommended management?

. Continued observation until symptomatic
. Application of a Minerva cast
. Anterior and posterior cervical spinal fusion
. Posterior cervical tethering
. Cervical laminectomy without fusion

Correct Answer & Explanation

. Anterior and posterior cervical spinal fusion

Explanation

While mild cervical kyphosis in diastrophic dysplasia often resolves spontaneously, curves exceeding 50 degrees or those failing to resolve and becoming rigid generally progress. Surgical stabilization, typically with an anterior and posterior fusion, is required to prevent severe myelopathy.

Question 7311

Topic: 6. Spine

A 50-year-old female with achondroplasia requires surgery for severe, medically refractory lumbar spinal stenosis at L2-L5. Which of the following specific technical considerations is mandatory during surgical decompression to avoid iatrogenic complications?

. Preservation of the lamina to maintain stability
. Routine use of interbody cages at all decompressed levels
. Wide laminectomy extending laterally into the pedicles (pediculectomy)
. Exclusive use of an anterior retroperitoneal approach
. Simultaneous correction of thoracolumbar kyphosis

Correct Answer & Explanation

. Wide laminectomy extending laterally into the pedicles (pediculectomy)

Explanation

The primary pathology in achondroplastic spinal stenosis is extremely short pedicles and thickened articular processes. Adequate decompression requires a wide laminectomy that extends laterally to include the medial aspect of the pedicles (pediculectomy) to fully decompress the traversing and exiting nerve roots.

Question 7312

Topic: 6. Spine

Spondyloepiphyseal dysplasia congenita (SEDC) is caused by mutations in the COL2A1 gene. Which of the following radiographic findings of the spine is a classic hallmark of this condition?

. Platyspondyly with pear-shaped vertebrae
. Bullet-shaped vertebrae with central beaking
. Coronal clefts in the vertebral bodies
. Posterior scalloping of the vertebral bodies
. Decreasing interpedicular distance

Correct Answer & Explanation

. Platyspondyly with pear-shaped vertebrae

Explanation

SEDC is typically characterized by generalized platyspondyly, and the vertebral bodies often have a characteristic pear shape (or hump-shaped) on lateral radiographs. Odontoid hypoplasia is also a critical and consistent finding that must be evaluated.

Question 7313

Topic: 6. Spine

A 4-month-old infant with achondroplasia presents with hyperreflexia, generalized hypotonia, and episodes of central sleep apnea. What is the most appropriate imaging modality to evaluate the primary cause of these symptoms?

. Cervical spine flexion-extension radiographs
. MRI of the craniocervical junction
. CT scan of the temporal bones
. Plain radiographs of the thoracolumbar spine
. Ultrasound of the spinal cord

Correct Answer & Explanation

. MRI of the craniocervical junction

Explanation

Infants with achondroplasia are at high risk for foramen magnum stenosis, which can cause cervicomedullary compression manifesting as sleep apnea and hyperreflexia. MRI of the craniocervical junction is the gold standard for diagnosis and evaluating the extent of cord compression.

Question 7314

Topic: 6. Spine

A 6-year-old child with Morquio syndrome (MPS IV) requires general anesthesia for a dental procedure. Which of the following preoperative evaluations is most critical to prevent catastrophic neurologic injury?

. Thoracolumbar scoliosis radiographs
. Flexion-extension cervical spine radiographs
. Lumbar spine MRI
. DEXA scan
. Pulmonary function tests

Correct Answer & Explanation

. Flexion-extension cervical spine radiographs

Explanation

Morquio syndrome is frequently associated with odontoid hypoplasia and ligamentous laxity, leading to atlantoaxial instability. Flexion-extension cervical radiographs are critical prior to intubation to identify instability and prevent spinal cord injury.

Question 7315

Topic: 6. Spine

A 35-year-old man with achondroplasia presents with severe, progressive bilateral leg pain and weakness that worsens with standing and walking. What anatomic abnormality primarily drives this condition in achondroplastic patients?

. Premature fusion of the neurocentral synchondroses
. Hypertrophy of the facet joints
. Redundant and buckled ligamentum flavum
. Isthmic spondylolisthesis
. Degenerative scoliosis

Correct Answer & Explanation

. Premature fusion of the neurocentral synchondroses

Explanation

Spinal stenosis in achondroplasia is driven by abnormal endochondral ossification leading to premature fusion of the neurocentral synchondroses. This results in shortened pedicles and a progressively narrowed interpedicular distance in the lumbar spine.

Question 7316

Topic: 6. Spine

An asymptomatic 8-year-old girl with Spondyloepiphyseal Dysplasia Congenita (SEDC) is found to have an atlantodens interval (ADI) of 9 mm on dynamic cervical radiographs. What is the most appropriate management?

. Observation and annual radiographic follow-up
. Application of a rigid cervical collar
. Posterior C1-C2 spinal fusion
. Occipitocervical fusion
. Anterior odontoid screw fixation

Correct Answer & Explanation

. Posterior C1-C2 spinal fusion

Explanation

In Spondyloepiphyseal Dysplasia Congenita, asymptomatic atlantoaxial instability with an ADI greater than 8 mm is an indication for prophylactic posterior C1-C2 fusion. This prevents the high risk of sudden, irreversible spinal cord injury.

Question 7317

Topic: 6. Spine

A 15-year-old boy with severe Osteogenesis Imperfecta presents with lower cranial nerve palsies, nystagmus, and hyperreflexia. Which of the following radiographic parameters best confirms the suspected diagnosis?

. The tip of the odontoid projects 6 mm above Chamberlain line
. The atlantodens interval (ADI) is 4 mm
. The clivus-canal angle is 160 degrees
. There is a fixed C2-C3 kyphosis
. Widening of the predental space

Correct Answer & Explanation

. The tip of the odontoid projects 6 mm above Chamberlain line

Explanation

Basilar invagination is a severe complication of Osteogenesis Imperfecta, caused by the skull settling onto the cervical spine. It is diagnosed when the odontoid tip projects more than 3-5 mm above Chamberlain line or crosses McRae line, resulting in brainstem compression.

Question 7318

Topic: 6. Spine

A 10-year-old child with pseudoachondroplasia is evaluated in the orthopedic clinic. Despite having normal facies and intelligence, this patient must be meticulously screened for which of the following spinal conditions?

. Foramen magnum stenosis
. Odontoid hypoplasia and atlantoaxial instability
. Severe rigid thoracic scoliosis
. Lumbar spondylolisthesis
. Tethered cord syndrome

Correct Answer & Explanation

. Odontoid hypoplasia and atlantoaxial instability

Explanation

Unlike achondroplasia, patients with pseudoachondroplasia have normal craniofacial features but are at high risk for odontoid hypoplasia and atlantoaxial instability. Cervical spine flexion-extension radiographs are essential for screening in these patients.

Question 7319

Topic: 6. Spine

A 2-year-old boy with Hurler syndrome (MPS I) develops a sharp thoracolumbar kyphosis. Lateral spine radiographs reveal anteroinferior beaking of the apical lumbar vertebrae. What is the primary underlying pathomechanism for this deformity?

. Defective type II collagen synthesis
. Premature fusion of the neurocentral synchondroses
. Accumulation of glycosaminoglycans in developing vertebral bodies
. Mutation in the diastrophic dysplasia sulfate transporter
. Ligamentous laxity from fibrillin-1 defect

Correct Answer & Explanation

. Accumulation of glycosaminoglycans in developing vertebral bodies

Explanation

Hurler syndrome results from alpha-L-iduronidase deficiency, causing toxic accumulation of dermatan and heparan sulfate (glycosaminoglycans). This disrupts endochondral ossification, leading to anteroinferior vertebral beaking and progressive kyphosis.

Question 7320

Topic: 6. Spine

A 6-year-old child diagnosed with diastrophic dysplasia presents for a routine orthopedic evaluation. Which combination of cervical spine anomalies is considered a classic characteristic of this specific dysplasia?

. Odontoid hypoplasia and atlantoaxial instability
. Cervical kyphosis and spina bifida occulta
. Basilar invagination and Klippel-Feil anomaly
. C1-C2 rotatory subluxation and dural ectasia
. Foramen magnum stenosis and pedicle narrowing

Correct Answer & Explanation

. Cervical kyphosis and spina bifida occulta

Explanation

Diastrophic dysplasia classically features cervical kyphosis, which often resolves spontaneously but can become rigidly progressive, alongside spina bifida occulta of the cervical vertebrae. Odontoid hypoplasia is more typical of SED and Morquio syndrome.

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