ABOS Orthopedic Board Review: Scoliosis, Ankylosing Spondylitis, Bone Tumors & Dysplasias | Part 31

Correct Answer: B

Rationale: In infantile idiopathic scoliosis (IIS), the rib vertebral angle difference (RVAD) is a critical prognostic indicator. An RVAD greater than 20 degrees (as in this case, 25 degrees) indicates a high likelihood of curve progression and a low chance of spontaneous resolution. These curves often require intervention, such as serial casting or growth-friendly surgery, to prevent severe deformity. Spontaneous resolution is more likely with an RVAD less than 20 degrees. Bracing can be used but often follows casting or is for less severe curves. Physical therapy does not prevent progression. Therefore, the curve is likely to progress and will likely require early intervention.

Correct Answer: C

Rationale: Juvenile Idiopathic Scoliosis (JIS) is diagnosed in children between 3 and 9 years of age. Unlike infantile idiopathic scoliosis, JIS has a high rate of progression, with up to 70% of curves progressing to require surgical intervention if left untreated. Spontaneous resolution is rare. Therefore, a 35-degree progressive curve in a 7-year-old (Risser 0) carries a high risk of progression. Bracing is often the first line of treatment for progressive curves in this age group, and serial casting may also be considered. Surgical fusion is typically reserved for larger, progressive curves that fail non-operative management or are already severe, and is generally avoided if possible to allow for spinal growth.

Correct Answer: C

Rationale: For adolescent idiopathic scoliosis (AIS) curves between 10-25 degrees in skeletally immature patients (Risser 0-2), observation with serial clinical and radiographic follow-up every 4-6 months is the standard of care. Bracing is typically indicated for curves >25 degrees in skeletally immature patients or for documented progression of curves between 20-25 degrees. Surgical consultation is reserved for larger, progressive curves, typically >45-50 degrees. Physical therapy alone has not been shown to alter the natural history of AIS. An MRI is indicated for atypical curves, rapid progression, neurological symptoms, or very young patients, none of which are present here.

Correct Answer: B

Rationale: Bracing is indicated for skeletally immature patients (Risser 0-2, premenarchal) with progressive curves between 25-45 degrees. This patient has a 32-degree curve and a Risser 1, making her an ideal candidate for bracing to prevent further progression. Continuing observation is inappropriate given the documented progression and curve magnitude. Surgical evaluation is typically for curves >45-50 degrees. Physical therapy and anti-inflammatories do not alter curve progression. An MRI is not indicated unless there are atypical features or neurological symptoms.

Correct Answer: B

Rationale: Surgical intervention is generally recommended for skeletally mature or nearly mature patients with progressive curves greater than 45-50 degrees, especially if associated with pain or significant cosmetic deformity. This patient meets these criteria, having failed bracing and exhibiting a 55-degree curve. Continuing bracing is unlikely to be effective given the progression. Physical therapy and chiropractic adjustments do not correct structural scoliosis. A bone scan is not indicated. Spontaneous stabilization is unlikely for a curve of this magnitude.

Correct Answer: A

Rationale: Congenital scoliosis is frequently associated with other congenital anomalies, particularly those affecting the VACTERL association (Vertebral, Anorectal, Cardiac, Tracheoesophageal, Renal, Limb). Renal anomalies (e.g., absent kidney, horseshoe kidney) and cardiac anomalies (e.g., septal defects) are among the most common and clinically significant. Therefore, a renal ultrasound and cardiac evaluation (echocardiogram) are essential components of the initial workup. The other options are not routinely indicated unless specific symptoms or findings suggest them.

Correct Answer: C

Rationale: Neuromuscular scoliosis, especially in non-ambulatory patients with severe cerebral palsy, is often rapidly progressive and can lead to significant functional impairment, including seating difficulties, skin breakdown, and respiratory compromise. Curves typically progress beyond 40-50 degrees and often require surgical correction, frequently involving fusion to the pelvis to address pelvic obliquity and provide a stable base for seating. Observation and bracing are generally ineffective in preventing progression in severe neuromuscular scoliosis. Physical therapy and botulinum toxin injections may help with spasticity but do not correct structural deformity.

Correct Answer: C

Rationale: The clinical presentation of rigid kyphosis and the radiographic findings of anterior wedging of at least three consecutive vertebrae by 5 degrees or more, along with irregular endplates (Schmorl's nodes), are pathognomonic for Scheuermann's kyphosis. Adolescent idiopathic scoliosis primarily involves coronal plane deformity. Congenital kyphosis would typically present earlier and with different vertebral anomalies. Postural kyphosis is flexible and corrects with hyperextension. A spinal tumor is less likely given the diffuse vertebral changes and lack of other red flag symptoms.

Correct Answer: D

Rationale: Untreated AIS curves, particularly those greater than 30-40 degrees, can progress in adulthood, often leading to degenerative changes, disc herniation, spinal stenosis, and the development of adult degenerative scoliosis. This can result in significant back pain, radiculopathy, and coronal and sagittal imbalance, which explains her symptoms. Neurological deficits are rare in AIS unless the curve is very severe or there's an underlying condition. Thoracic curves generally stabilize in adulthood, but lumbar curves may progress. Pulmonary compromise is typically seen with curves >80-90 degrees. Compensatory curves do not spontaneously resolve.

Correct Answer: C

Rationale: New-onset neurological deficit after scoliosis surgery is a surgical emergency. The most critical immediate step is to reduce any potential compression on the spinal cord. This often involves loosening or removing instrumentation to decompress the spinal cord. While an MRI is important for diagnosis, it should not delay decompression if instrumentation is suspected to be the cause. High-dose corticosteroids are sometimes used for spinal cord injury but are secondary to decompression. Monitoring for spontaneous recovery is inappropriate, and physical therapy is not an immediate treatment for acute neurological deficit.

Correct Answer: C

Rationale: This patient presents with severe adult degenerative scoliosis with significant sagittal imbalance and neurological symptoms (leg pain, difficulty standing upright) that have failed extensive non-operative management. Surgical correction, often involving long instrumented fusion and osteotomies to restore sagittal balance, is indicated to alleviate pain and improve function. Observation, bracing, and epidural injections are appropriate for less severe symptoms or as initial non-operative treatments, but not for this advanced stage. Reassurance is inappropriate given her severe symptoms.

Correct Answer: D

Rationale: This patient has early-onset scoliosis (EOS) with a severe, progressive curve and signs of pulmonary compromise. Definitive spinal fusion at this age would severely restrict thoracic growth and lung development, leading to thoracic insufficiency syndrome. Growing rod surgery (or other growth-friendly techniques like VEPTR) is the preferred treatment to control curve progression while allowing continued spinal and thoracic growth. Observation and bracing are unlikely to control such a severe, progressive curve. Vertebral body tethering is typically for larger, flexible curves in older, but still growing, adolescents.

Correct Answer: D

Rationale: A positive Adam's forward bend test indicates a potential spinal deformity and warrants further evaluation. The next appropriate step is to refer the patient to their primary care physician or an orthopedic specialist for a formal clinical examination and standing posteroanterior and lateral radiographs of the spine to measure the Cobb angle and confirm the diagnosis of scoliosis. Reassurance is inappropriate. Surgical consultation and bracing are premature without radiographic confirmation and curve measurement. Physical therapy alone does not correct structural scoliosis.

Correct Answer: C

Rationale: Bracing for AIS works by applying three-point corrective forces to the curve, aiming to prevent further progression of the curve during the remaining growth period. It does not typically reverse the curve or remodel vertebral bodies, nor does it work by traction or muscle strengthening. The primary goal is to hold the curve stable and prevent it from worsening, allowing the spine to grow straighter. It is not merely passive support, but an active corrective force.

Correct Answer: C

Rationale: For adult degenerative scoliosis with mild to moderate symptoms and no significant functional limitations, non-operative management is the first-line treatment. This includes observation, physical therapy (focusing on core strengthening, flexibility, and posture), and pain management with NSAIDs or other analgesics. Epidural steroid injections and nerve blocks can be considered for radicular symptoms if initial conservative measures fail. Surgical intervention is reserved for severe, progressive symptoms, neurological deficits, or significant deformity that has failed extensive non-operative treatment. Bracing is generally not effective for adult degenerative scoliosis. Vertebroplasty is for vertebral compression fractures, not scoliosis.

Correct Answer: B

Rationale: The gold standard for intraoperative spinal cord monitoring during scoliosis surgery involves a combination of Somatosensory Evoked Potentials (SSEPs) and Transcranial Motor Evoked Potentials (TcMEPs). SSEPs monitor the dorsal columns (sensory pathways), while TcMEPs monitor the corticospinal tracts (motor pathways). The combination provides comprehensive assessment of both sensory and motor function of the spinal cord, allowing for early detection of potential injury. EEG and EMG are less specific for spinal cord function. NCS and QST are diagnostic tools, not typically used for intraoperative monitoring. VEPs, BAEPs, and intracranial monitoring are not relevant to spinal cord function during scoliosis surgery.

Correct Answer: C

Rationale: The type of vertebral anomaly is the most significant factor influencing curve progression in congenital scoliosis. Fully segmented hemivertebrae, especially those with contralateral bar formation, have the highest risk of progression due to continuous asymmetric growth. Block vertebrae or unsegmented bars without hemivertebrae have a lower risk. While initial curve magnitude can be a factor, the underlying anomaly dictates the growth potential. Gender and location (thoracic vs. lumbar) are less predictive than the specific anomaly. Associated cardiac anomalies are important for overall health but do not directly predict curve progression.

Correct Answer: B

Rationale: This patient's presentation is highly suggestive of Marfan syndrome. Patients with Marfan syndrome often have rapidly progressive scoliosis that is less responsive to bracing. Due to the rapid progression and potential for severe deformity, surgical intervention (spinal fusion) is often considered at lower curve magnitudes (e.g., 40-45 degrees) compared to idiopathic scoliosis. Marfan patients also have an increased risk of dural ectasia, which can complicate surgery, and a higher risk of pseudarthrosis due to poor bone quality. Postoperative pulmonary complications can be more common due to underlying lung issues.

Correct Answer: C

Rationale: The patient's symptoms (persistent, localized pain, loss of correction) combined with radiographic findings (lucency around hardware, lack of bony bridging on CT) are classic for pseudarthrosis, which is a failure of bony fusion. Adjacent segment disease would typically involve symptoms and degenerative changes at a level immediately above or below the fusion. Spinal infection would present with systemic signs (fever, elevated inflammatory markers) and different radiographic features. Hardware failure can be a consequence of pseudarthrosis, but the underlying issue is the lack of fusion. Normal post-fusion pain typically resolves over time, and new or persistent pain with loss of correction is concerning.

Correct Answer: C

Rationale: The "Syndrome of Seven Symptoms" explicitly lists dysplasia of the hip as one of its characteristic components, alongside scoliosis, lumbodorsal kyphosis, inclined position of the head (torticollis), asymmetry of the skull, asymmetry of the pelvis, and foot deformity. Craniosynostosis (D) can cause skull asymmetry but is not listed as a primary component of this specific syndrome.

Correct Answer: C

Rationale: For infants up to 4-6 months of age, dynamic ultrasound of the hips is the gold standard for diagnosing and assessing developmental dysplasia of the hip (DDH). This is because the femoral head and acetabulum are largely cartilaginous at this age, making radiographs (A) less reliable for visualizing the bony anatomy and stability. MRI (B) and CT (D) are typically reserved for more complex cases or pre-operative planning, and arthrography (E) is an invasive procedure usually performed in the operating room.

Correct Answer: C

Rationale: The initial recommended treatment for congenital muscular torticollis in infants is physical therapy, focusing on passive stretching of the sternocleidomastoid muscle and active range of motion exercises. This approach is successful in the vast majority of cases. Surgical release (A) is reserved for refractory cases, typically after 6-12 months of failed conservative treatment. Observation (E) without active intervention is inappropriate as it can lead to persistent deformity and secondary issues like plagiocephaly.

Correct Answer: B

Rationale: The Ponseti method, involving serial manipulation and casting, is the universally accepted initial non-operative treatment for congenital clubfoot. It aims to gradually correct all components of the deformity. Surgical release (A) is typically reserved for cases that fail Ponseti treatment or for recurrence. Dynamic bracing (C) is used *after* casting to maintain correction, not as the initial treatment. Observation and passive stretching (E) are insufficient for a true clubfoot deformity.

Correct Answer: D

Rationale: For non-ambulatory infants, supine anteroposterior (AP) and lateral spine radiographs are the most appropriate initial imaging studies to evaluate scoliosis. Standing radiographs (A) are not feasible for a 3-month-old. MRI (B) is indicated if there are neurological symptoms, rapid progression, or suspicion of congenital anomalies, but not as the initial screening for a flexible curve. Ultrasound (C) has limited utility for bony spinal deformities, and CT (E) involves higher radiation and is typically reserved for detailed bony anatomy assessment.

Correct Answer: C

Rationale: The Syndrome of Seven Symptoms explicitly includes inclined position of the head (torticollis), asymmetry of the skull, and dysplasia of the hip. The vignette describes torticollis and skull asymmetry, making dysplasia of the hip a highly consistent additional finding from the syndrome's listed components. The other options are not listed components of this specific syndrome.

Correct Answer: C

Rationale: The Syndrome of Seven Symptoms explicitly lists "scoliosis" and "lumbodorsal kyphosis" as components. The vignette describes a C-shaped spinal curve (scoliosis) and a flattened skull (asymmetry of the skull), which are consistent with the syndrome. Lumbodorsal kyphosis is the other specific spinal deformity mentioned. Spondylolisthesis, Scheuermann's kyphosis, congenital block vertebrae, and atlantoaxial instability are not listed components of this specific syndrome.

Correct Answer: C

Rationale: The Syndrome of Seven Symptoms explicitly lists "foot deformity (e.g., clubfoot or calcaneal deformity)" as one of its components. Clubfoot is one of the two specific examples provided. Metatarsus adductus, vertical talus, pes planus, and tarsal coalition are not specifically mentioned in the description of this syndrome.

Correct Answer: D

Rationale: The Syndrome of Seven Symptoms includes scoliosis, asymmetry of the pelvis, dysplasia of the hip, and inclined position of the head. Genu varum (bowlegs) is not mentioned as one of the seven symptoms that define this specific syndrome.

Correct Answer: C

Rationale: The clinical context for the Syndrome of Seven Symptoms explicitly refers to "a 3-month-old child" in the figure description, indicating this is the age at which these deformities are observed and the syndrome is described in this case. While some components might be present at birth, the syndrome is presented in the context of a 3-month-old.

Correct Answer: C

Rationale: The Syndrome of Seven Symptoms includes inclined position of the head (torticollis), asymmetry of the skull, lumbodorsal kyphosis, and asymmetry of the pelvis. The vignette describes torticollis, skull asymmetry, and lumbodorsal kyphosis. Asymmetry of the pelvis is another listed component. Polydactyly, syndactyly, craniosynostosis, and brachial plexus palsy are not listed components of this specific syndrome.

Correct Answer: C

Rationale: The image (Fig. 13.7) clearly demonstrates a significant lateral curvature of the spine, which is consistent with scoliosis, one of the described symptoms of the Syndrome of Seven Symptoms. The other options are not clearly visible or suggested in the provided image.

Correct Answer: D

Rationale: The clinical presentation of inflammatory back pain (worse with rest, better with activity, morning stiffness), decreased spinal mobility, bilateral sacroiliitis on radiographs, elevated ESR, and positive HLA-B27 are classic diagnostic criteria for Ankylosing Spondylitis. Mechanical low back pain typically worsens with activity and improves with rest. Lumbar disc herniation usually presents with radicular symptoms. DISH is characterized by flowing ossification along the anterolateral spine and typically spares the sacroiliac joints. Psoriatic arthritis can involve the spine but often presents with asymmetric sacroiliitis and peripheral joint involvement, and the overall picture is less typical than for AS.

Correct Answer: D

Rationale: HLA-B27 is the most strongly associated genetic marker with Ankylosing Spondylitis, found in over 90% of Caucasian patients with the disease. While its presence is not diagnostic alone, it is a key predisposing factor. Rheumatoid Factor and Anti-CCP antibodies are associated with rheumatoid arthritis. HLA-DR4 is associated with rheumatoid arthritis. ANA is associated with systemic lupus erythematosus and other autoimmune conditions.

Correct Answer: C

Rationale: Bilateral sacroiliitis, characterized by erosions, sclerosis, and joint space narrowing of the sacroiliac joints, is typically the earliest and most characteristic radiographic finding in Ankylosing Spondylitis. Squaring of vertebral bodies and syndesmophytes ("bamboo spine") are later manifestations of spinal involvement. Atlantoaxial subluxation is a rare, late complication. Diffuse osteopenia can occur but is not the earliest or most specific sign.

Correct Answer: D

Rationale: "Bamboo spine" refers to the classic appearance of the spine in advanced Ankylosing Spondylitis, caused by extensive syndesmophyte formation and ossification of the spinal ligaments, leading to complete spinal fusion. Andersson lesions are destructive lesions of the vertebral bodies and discs. Romanus lesions (shiny corner sign) are early erosions at the vertebral body corners. Carrot stick fracture is a type of spinal fracture seen in fused spines, not the overall appearance of the fused spine itself.

Correct Answer: C

Rationale: Anterior uveitis (or iritis) is the most common extra-articular manifestation of Ankylosing Spondylitis, affecting up to 40% of patients. While Inflammatory Bowel Disease, aortic insufficiency, and pulmonary fibrosis can occur, they are less common than uveitis. Psoriasis is a primary feature of psoriatic arthritis, another spondyloarthropathy, but not the most common extra-articular manifestation of AS itself.

Correct Answer: D

Rationale: Nonsteroidal Anti-inflammatory Drugs (NSAIDs) are the first-line pharmacologic treatment for pain and stiffness in Ankylosing Spondylitis. They are effective in reducing inflammation and improving symptoms in many patients. TNF-α inhibitors are typically reserved for patients who have an inadequate response to NSAIDs. Methotrexate is generally not effective for axial symptoms of AS. Oral corticosteroids are used for acute flares or specific extra-articular manifestations but not as a long-term first-line treatment due to side effects. Opioid analgesics are not recommended for chronic management due to risks of dependence and lack of anti-inflammatory effect.

Correct Answer: C

Rationale: For patients with Ankylosing Spondylitis who have persistent high disease activity despite an adequate trial of NSAIDs, biologic agents, particularly TNF-α inhibitors (e.g., etanercept, adalimumab, infliximab), are the recommended next step. Sulfasalazine and hydroxychloroquine are generally ineffective for axial symptoms of AS. Oral prednisone is used for short-term flares but not as a long-term disease-modifying agent. Colchicine is used for gout.

Correct Answer: C

Rationale: Spinal fractures in patients with Ankylosing Spondylitis, even from low-energy trauma, are highly unstable and carry a significant risk of neurological compromise. The fused, osteoporotic spine acts as a long lever arm, concentrating stress at the fracture site, often leading to a three-column injury. These fractures are often difficult to diagnose on plain radiographs and require CT or MRI. They are rarely managed non-operatively due to the inherent instability.

Correct Answer: D

Rationale: Unstable spinal fractures in patients with Ankylosing Spondylitis, especially those with neurological deficits, require urgent surgical stabilization. The fused, osteoporotic spine is highly susceptible to unstable three-column injuries, and non-operative management carries a very high risk of further neurological deterioration and poor outcomes. Surgical fixation provides stability and allows for early mobilization. Steroids may be considered for acute spinal cord injury but do not address the instability.

Correct Answer: C

Rationale: For severe, fixed kyphosis in Ankylosing Spondylitis, vertebral column resection techniques, such as pedicle subtraction osteotomy (PSO) or Ponte osteotomy, are commonly performed. These procedures involve removing a wedge of bone from the vertebral body and posterior elements to achieve significant angular correction and restore sagittal balance. Laminectomy and discectomy are not designed for kyphosis correction. Spinal fusion alone would not correct the fixed deformity. Kyphoplasty is used for vertebral compression fractures, not for correcting severe fixed kyphosis.

Correct Answer: C

Rationale: Total hip arthroplasty (THA) is a highly effective surgical intervention for severe, end-stage hip osteoarthritis secondary to Ankylosing Spondylitis, providing significant pain relief and functional improvement. Hip arthroscopy is typically for milder conditions or labral tears. Core decompression is for avascular necrosis. Hip fusion would eliminate motion and is generally not preferred for bilateral disease. Femoral osteotomy is used for specific deformities but not end-stage arthritis.

Correct Answer: C

Rationale: Diffuse Idiopathic Skeletal Hyperostosis (DISH) is a crucial differential diagnosis for Ankylosing Spondylitis, especially in older patients, due to its characteristic flowing ossification along the spine. However, DISH typically spares the sacroiliac joints, involves the right side of the thoracic spine more often, and does not present with inflammatory back pain or elevated inflammatory markers. Ankylosing Spondylitis is characterized by sacroiliitis and thin, vertical syndesmophytes, often with inflammatory symptoms. Rheumatoid arthritis primarily affects peripheral joints. Psoriatic and reactive arthritis are spondyloarthropathies but have distinct clinical and radiographic features. Osteoarthritis is degenerative and does not involve ligamentous ossification in this manner.

Correct Answer: C

Rationale: The described maneuver is the Schober test, which is used to assess lumbar spine flexion. A normal increase in distance between the two marks is typically 5 cm or more. In Ankylosing Spondylitis, reduced lumbar flexion due to spinal stiffness and fusion results in a smaller increase, indicating impaired mobility. The Faber test and Gaenslen test assess sacroiliac joint pain. The straight leg raise test assesses sciatic nerve irritation. The Trendelenburg test assesses hip abductor strength.

Correct Answer: C

Rationale: Enthesitis is the inflammation at the site where tendons, ligaments, or joint capsules insert into bone. It is a hallmark feature of Ankylosing Spondylitis and other spondyloarthropathies, commonly affecting the Achilles tendon, plantar fascia, and costochondral junctions. Bursitis is inflammation of a bursa. Tendinitis is inflammation of a tendon body. Synovitis is inflammation of the synovial membrane. Osteomyelitis is bone infection.

Correct Answer: B

Rationale: The Erythrocyte Sedimentation Rate (ESR) and C-reactive protein (CRP) are non-specific markers of inflammation. While they can be elevated in active Ankylosing Spondylitis, they are not consistently elevated in all patients, and their levels do not always correlate with disease activity. Therefore, they are less reliable for diagnosis than clinical features and imaging. HLA-B27 is a genetic marker, not an inflammatory marker, and while strongly associated, its presence alone is not diagnostic. Rheumatoid Factor and Anti-CCP antibodies are specific for rheumatoid arthritis.

Correct Answer: C

Rationale: Cauda equina syndrome is a rare but recognized late complication of long-standing Ankylosing Spondylitis. It is thought to be caused by chronic arachnoiditis leading to dural ectasia and compression of the cauda equina nerve roots. The symptoms of bilateral lower extremity weakness, sensory deficits (especially saddle anesthesia), and bowel/bladder dysfunction are classic for cauda equina syndrome. While disc herniation or spinal stenosis can cause similar symptoms, the context of severe, long-standing AS with dural ectasia points strongly to AS-related cauda equina syndrome. Transverse myelitis and peripheral neuropathy have different clinical presentations and underlying pathologies.

Correct Answer: C

Rationale: Atlantoaxial subluxation (AAS) is a serious, albeit rare, complication of advanced Ankylosing Spondylitis due to inflammatory erosion and laxity of the transverse ligament and other supporting structures at the C1-C2 level. The symptoms of neck pain, occipital headaches, and myelopathy (fine motor difficulty, hyperreflexia, Babinski sign, Lhermitte's sign) are indicative of spinal cord compression at the craniocervical junction. While cervical disc herniation or spinal stenosis can cause myelopathy, AAS is a specific and critical concern in AS patients with these symptoms. Thoracic outlet syndrome and vertebral artery dissection have different presentations.

Correct Answer: C

Rationale: The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is a validated, patient-reported questionnaire specifically designed to measure disease activity in Ankylosing Spondylitis. It assesses fatigue, spinal pain, peripheral joint pain/swelling, enthesitis, and morning stiffness. While VAS for pain is a general pain measure, and ODI is a general back pain disability index, BASDAI is specific to AS disease activity. WOMAC is for osteoarthritis, and ASA is for surgical risk assessment.

Correct Answer: C

Rationale: Squaring of vertebral bodies is an early and characteristic radiographic finding in Ankylosing Spondylitis. It results from erosion of the anterior superior and inferior vertebral body corners (Romanus lesions) followed by reactive new bone formation, leading to a loss of the normal anterior concavity of the vertebral body. Vertebral body collapse is typically due to trauma or osteoporosis. Schmorl's nodes are disc herniations into the vertebral body. Hemivertebrae are congenital anomalies. Degenerative osteophytes are different in morphology and etiology.

Correct Answer: C

Rationale: Syndesmophytes are the characteristic bony bridges seen in Ankylosing Spondylitis. They are typically thin, vertical, and marginal, arising from the outer fibers of the annulus fibrosus and eventually bridging adjacent vertebral bodies, leading to spinal fusion and the "bamboo spine" appearance. Oste

Correct Answer: C

Rationale: In a patient with inflammatory back pain suggestive of ankylosing spondylitis, MRI of the sacroiliac joints is the most sensitive imaging modality for detecting early inflammatory changes (bone marrow edema) that may not be visible on plain radiographs. This allows for earlier diagnosis and initiation of appropriate treatment. Lumbar spine MRI would be less specific for early AS, and plain radiographs are often normal in early disease. HLA-B27 is a genetic marker associated with AS but is not diagnostic on its own, as many HLA-B27 positive individuals do not develop AS. EMG is used for nerve root compression, not inflammatory arthritis.

Correct Answer: D

Rationale: Acute anterior uveitis (iritis) is the most common extra-articular manifestation of ankylosing spondylitis, affecting up to 40% of patients. Symptoms typically include acute onset of unilateral eye pain, redness (ciliary flush), photophobia, and blurred vision. It requires prompt treatment with topical corticosteroids to prevent complications. Conjunctivitis is usually bilateral and lacks severe pain and photophobia. Glaucoma, cataract, and retinal detachment are less common or present differently.

Correct Answer: C

Rationale: Syndesmophytes are characteristic radiographic findings in ankylosing spondylitis, representing ossification of the outer annulus fibrosus and longitudinal ligaments, leading to bony bridges between vertebral bodies. These typically start at the thoracolumbar and cervicothoracic junctions and progress upwards and downwards. This is distinct from degenerative osteophytes, which are typically larger, more irregular, and arise from the vertebral endplates. Disc space narrowing is a degenerative change, and spondylolisthesis is vertebral slippage. Schmorl's nodes are disc herniations into the vertebral body.

Correct Answer: C

Rationale: The Schober test is a specific and widely used clinical measure to assess lumbar spine flexion. A normal increase in distance between the two marks (10 cm apart, with an additional 5 cm mark above) should be at least 5 cm (total 15 cm) upon maximal flexion. In ankylosing spondylitis, reduced lumbar flexion is an early and common finding, making the Schober test a valuable diagnostic and monitoring tool. The other tests listed assess different aspects: Straight Leg Raise for sciatica, FABER and Gaenslen for sacroiliac joint pain, and Trendelenburg for hip abductor weakness.

Correct Answer: B

Rationale: HLA-B27 is the strongest known genetic risk factor for ankylosing spondylitis, present in 90-95% of Caucasian patients with the disease. While its presence is not diagnostic (as many HLA-B27 positive individuals do not develop AS), it significantly increases susceptibility and is often used as a supportive diagnostic criterion. The other HLA alleles are associated with different autoimmune conditions or have a weaker association with AS.

Correct Answer: C

Rationale: Non-steroidal anti-inflammatory drugs (NSAIDs) are considered the first-line pharmacological treatment for patients with active ankylosing spondylitis, especially those with axial symptoms. They effectively reduce pain and stiffness and can slow radiographic progression in some patients. Methotrexate and sulfasalazine are typically used for peripheral arthritis in spondyloarthropathies but are less effective for axial disease. TNF-alpha inhibitors are biologics reserved for patients who have failed adequate trials of NSAIDs. Oral prednisone is generally not recommended for long-term management due to side effects, though it may be used for acute flares or specific extra-articular manifestations.

Correct Answer: C

Rationale: The "bamboo spine" appearance is a classic radiographic finding in advanced ankylosing spondylitis, resulting from diffuse ossification of the annulus fibrosus and anterior longitudinal ligament, leading to complete fusion of the vertebral bodies. Romanus lesions (erosions at vertebral corners) and Andersson lesions (inflammatory lesions at disc-vertebral body junctions) are earlier or less common findings. A "carrot stick fracture" refers to a specific type of spinal fracture in a rigid AS spine, and "pugilistic spine" is not a recognized term for AS.

Correct Answer: E

Rationale: Patients with long-standing ankylosing spondylitis develop a rigid, osteoporotic spine that acts as a single, long bone. Even minor trauma can lead to unstable fractures, often through a fused segment (sometimes called a "carrot stick fracture"). These fractures are highly unstable and carry a significant risk of neurological injury, including spinal cord injury or cauda equina syndrome. While compression fractures can occur, the concern for an unstable fracture through a fused segment with neurological compromise is paramount. Disc herniation is less likely in a fused spine. Atlantoaxial subluxation is a known complication but typically presents differently and is less likely to be acutely triggered by a low-energy fall in the lumbar region. Spinal stenosis exacerbation is also less likely to cause acute, severe neurological deficits from a fall.

Correct Answer: C

Rationale: TNF-alpha inhibitors (e.g., adalimumab, etanercept, infliximab) are the most established and widely used class of biologic agents for ankylosing spondylitis when NSAIDs fail. They have demonstrated significant efficacy in reducing disease activity, improving function, and slowing radiographic progression. While other biologics like IL-17 inhibitors (e.g., secukinumab, ixekizumab) are also effective and approved for AS, TNF-alpha inhibitors remain the most common and often first-choice biologic class. IL-6 inhibitors, B-cell inhibitors, JAK inhibitors, and T-cell costimulation blockers are primarily used for other rheumatic conditions like rheumatoid arthritis, though some JAK inhibitors are approved for AS.

Correct Answer: C

Rationale: The patient's presentation with inflammatory back pain, sacroiliitis, and a history of psoriatic skin lesions (rashes on elbows/knees, nail pitting) is highly suggestive of Psoriatic Arthritis (PsA). PsA is a seronegative spondyloarthropathy that can affect the axial skeleton, mimicking ankylosing spondylitis, and is also associated with HLA-B27. While Reactive Arthritis can also cause sacroiliitis and skin lesions (keratoderma blennorrhagicum), the description of the rash is more consistent with psoriasis. Rheumatoid arthritis typically affects small joints symmetrically and is seropositive. Osteoarthritis is degenerative, and DISH involves ossification of ligaments but typically spares the SI joints and presents in older individuals without inflammatory markers or skin manifestations.

Correct Answer: C

Rationale: Upper lobe pulmonary fibrosis (also known as apical fibrobullous disease) is a recognized, albeit uncommon, pulmonary complication of long-standing ankylosing spondylitis. It typically presents with progressive dyspnea and cough, and imaging shows fibrotic changes in the upper lung fields. The restrictive pattern on PFTs can also be exacerbated by reduced chest wall expansion due to costovertebral joint involvement in AS. Asthma and COPD are common but not specific to AS. Pleural effusion is not a characteristic pulmonary manifestation of AS. Pulmonary hypertension can be a secondary complication but is not the primary lung pathology described.

Correct Answer: C

Rationale: Aortic insufficiency (or aortic regurgitation) is the most common cardiac manifestation of ankylosing spondylitis, particularly in long-standing disease. It results from inflammation and dilation of the aortic root and valve leaflets. The diastolic murmur at the right sternal border and echocardiographic findings are classic for aortic insufficiency. Pericarditis can occur but is less common. Mitral valve prolapse, myocarditis, and atrial fibrillation are not specifically associated with AS as primary cardiac complications.

Correct Answer: D

Rationale: For severe, fixed kyphosis in ankylosing spondylitis that significantly impairs function and quality of life, a spinal osteotomy (e.g., pedicle subtraction osteotomy) is the most effective surgical option. This procedure involves removing a wedge of bone from the vertebral column to correct the sagittal imbalance and restore a more upright posture, allowing the patient to look forward. Laminectomy and discectomy are typically performed for spinal decompression. Spinal fusion is often part of the osteotomy procedure but is not the primary corrective maneuver for severe kyphosis. Vertebroplasty is used for vertebral compression fractures, not for correcting fixed kyphotic deformities.

Correct Answer: C

Rationale: Sacroiliitis (inflammation of the sacroiliac joints) is the hallmark and earliest radiographic change seen in ankylosing spondylitis. It typically begins with blurring of the subchondral bone, followed by erosions, sclerosis, and eventually fusion of the sacroiliac joints. This is often bilateral and symmetric. Syndesmophytes and "bamboo spine" are later manifestations of axial disease. Disc space narrowing and facet joint fusion are also later or less specific findings.

Correct Answer: D

Rationale: Cauda equina syndrome is a rare but serious neurological complication of long-standing ankylosing spondylitis. It is thought to result from chronic inflammation leading to dural ectasia, arachnoiditis, and compression of the nerve roots in the lumbosacral region. The classic symptoms include bilateral lower extremity weakness, saddle anesthesia, and bowel/bladder dysfunction. Spinal cord compression and myelopathy are less likely in the lumbar region. Lumbar radiculopathy would typically be unilateral or affect a single nerve root distribution. Peripheral neuropathy is a more generalized nerve disorder.

Correct Answer: D

Rationale: A daily, structured exercise program, including stretching, strengthening, and aerobic exercises, is paramount in the management of ankylosing spondylitis. It helps maintain spinal mobility, reduce stiffness, improve posture, and enhance overall physical function. Bed rest can worsen stiffness and deconditioning. While heat therapy can provide symptomatic relief, it's not a primary management strategy. Spinal bracing is generally discouraged as it can lead to muscle atrophy and further stiffness. Elimination diets lack strong evidence for widespread efficacy in AS.

Correct Answer: C

Rationale: The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) is a validated, patient-reported questionnaire specifically designed to assess disease activity in ankylosing spondylitis. It includes questions about fatigue, spinal pain, peripheral joint pain/swelling, localized tenderness, and morning stiffness. While VAS for pain is a component, BASDAI provides a comprehensive measure of disease activity. HAQ is a general functional assessment. DAS28 is used for rheumatoid arthritis. WOMAC is for osteoarthritis.

Correct Answer: B

Rationale: Osteofibrous dysplasia (OFD) is a benign fibro-osseous lesion almost exclusively found in the tibia (and rarely fibula) of young children, typically under 10 years old. It presents as an eccentric, lytic lesion with cortical thickening and bowing, often with a sclerotic rim. It is histologically similar to fibrous dysplasia but contains osteoblast-lined woven bone trabeculae within a fibrous stroma. Fibrous dysplasia can occur in the tibia but is less common to present with bowing and cortical thickening in

Correct Answer: C

Rationale: The clinical presentation of a lytic, expansile lesion with a "ground-glass" matrix in the metaphysis of a long bone in an adolescent, without other systemic findings, is classic for monostotic fibrous dysplasia. Enchondromas typically have a chondroid matrix (rings and arcs calcification) and are often asymptomatic. Aneurysmal bone cysts are expansile and lytic but typically multiloculated and fluid-filled. Non-ossifying fibromas are usually cortically based, eccentric, and have a sclerotic rim. Low-grade chondrosarcomas are less common in this age group and would typically show more aggressive features or chondroid matrix calcifications.

Correct Answer: C

Rationale: The classic triad of polyostotic fibrous dysplasia, café-au-lait skin pigmentation, and precocious puberty (due to endocrine hyperfunction) is diagnostic of McCune-Albright syndrome. Ollier disease and Maffucci syndrome involve multiple enchondromas, not fibrous dysplasia. Neurofibromatosis type 1 can have café-au-lait spots but typically presents with neurofibromas and different skeletal manifestations (e.g., pseudarthrosis, scoliosis). Paget's disease is a disorder of bone remodeling, typically affecting older adults, and does not present with precocious puberty or café-au-lait spots.

Correct Answer: C

Rationale: Malignant transformation of fibrous dysplasia is rare but a recognized complication, particularly in polyostotic forms or those treated with radiation. The most common malignant transformation is osteosarcoma, followed by chondrosarcoma and fibrosarcoma. The presentation of rapid growth, new pain, and aggressive radiographic features in a pre-existing fibrous dysplasia lesion is highly suspicious for malignant degeneration. Ewing sarcoma is typically a tumor of childhood and adolescence, and malignant fibrous histiocytoma is a less common transformation.

Correct Answer: C

Rationale: The presence of multiple enchondromas, often unilateral or asymmetric, leading to limb deformity and shortening, without associated soft tissue hemangiomas, is characteristic of Ollier disease (enchondromatosis). Maffucci syndrome is similar but includes soft tissue hemangiomas. Multiple hereditary exostoses involve osteochondromas, not enchondromas. Dysplasia epiphysealis hemimelica is a localized epiphyseal osteochondroma. Fibrous dysplasia has a different radiographic appearance ("ground-glass").

Correct Answer: C

Rationale: Maffucci syndrome is characterized by the combination of multiple enchondromas and soft tissue hemangiomas. Ollier disease involves multiple enchondromas but lacks the hemangiomas. Klippel-Trenaunay syndrome involves capillary malformations, venous malformations, lymphatic malformations, and limb overgrowth, but not typically enchondromas. Proteus syndrome is a complex overgrowth syndrome with various manifestations, but not specifically enchondromas and hemangiomas as the primary defining features. Sturge-Weber syndrome involves facial port-wine stain, leptomeningeal angiomatosis, and ocular involvement.

Correct Answer: C

Rationale: Patients with Ollier disease have a significantly increased risk of malignant transformation of their enchondromas into chondrosarcomas. The reported risk ranges from 25% to 50%, with some studies suggesting even higher rates, especially in Maffucci syndrome. This risk is a critical consideration in the long-term management and monitoring of these patients.

Correct Answer: D

Rationale: The presence of multiple osteochondromas (exostoses) with an autosomal dominant inheritance pattern (father also affected) is characteristic of multiple hereditary exostoses (MHE), also known as hereditary multiple osteochondromas. Solitary osteochondroma is a single lesion. Ollier disease involves multiple enchondromas. Fibrous dysplasia has a different radiographic appearance. Dysplasia epiphysealis hemimelica is a localized epiphyseal osteochondroma-like lesion, typically unilateral and affecting a single joint.

Correct Answer: C

Rationale: Ulnar shortening and radial head dislocation are common complications of multiple hereditary exostoses affecting the forearm, due to growth disturbance caused by osteochondromas at the distal ulna. This leads to relative overgrowth of the radius, bowing of the radius, and subsequent dislocation of the radial head. While Madelung deformity can involve ulnar shortening and radial bowing, it is a specific congenital growth disturbance of the distal radius and ulna, distinct from the direct effects of osteochondromas in MHE. Carpal tunnel syndrome, scaphoid nonunion, and distal radius fracture are less directly related to the primary pathology of MHE in the forearm.

Correct Answer: C

Rationale: The most common malignant transformation of an osteochondroma in patients with multiple hereditary exostoses is chondrosarcoma. The risk of malignant transformation is estimated to be around 1-5% in MHE, significantly higher than in solitary osteochondromas. Rapid growth, new pain, and radiographic signs of aggression in a previously stable osteochondroma are red flags for malignant degeneration. Osteosarcoma, fibrosarcoma, and Ewing sarcoma are much less common transformations.

Correct Answer: C

Rationale: Dysplasia epiphysealis hemimelica (Trevor's disease) is a rare, localized developmental anomaly characterized by an osteochondroma-like growth arising from an epiphysis, often affecting a single joint and causing deformity. The key features are its epiphyseal origin and unilateral involvement. Solitary osteochondromas typically arise from the metaphysis. Multiple hereditary exostoses involve multiple metaphyseal osteochondromas. Ollier disease involves enchondromas. Fibrous dysplasia has a distinct radiographic appearance.

Correct Answer: D

Rationale: Dysplasia epiphysealis hemimelica most commonly affects the lower extremities, with the knee (distal femur or proximal tibia) and ankle (distal tibia or talus) being the most frequent sites. The medial side of the joint is more commonly involved. While other joints can be affected, the knee is the most prevalent location.

Correct Answer: C

Rationale: The classic radiographic description of "flowing candle wax" or "dripping candle wax" appearance, characterized by irregular cortical hyperostosis and sclerosis, is pathognomonic for melorheostosis. Osteopoikilosis presents as multiple small, round or ovoid sclerotic foci. Osteopathia striata shows linear striations of increased density. Fibrous dysplasia has a ground-glass appearance. Paget's disease involves disorganized bone remodeling with cortical thickening and trabecular coarsening, but not the "flowing" pattern of melorheostosis.

Correct Answer: D

Rationale: Melorheostosis is a sclerosing bone dysplasia that can affect bone, soft tissue, and skin. Common clinical features include chronic pain, joint contractures, limb length discrepancy (either shortening or lengthening), and characteristic scleroderma-like skin changes (thickening and induration) overlying the affected areas. Vascular malformations can also be associated. Therefore, all the listed options are common associated clinical features.

Correct Answer: C

Rationale: The radiographic finding of multiple small, well-defined, round or ovoid sclerotic foci, typically in the epiphyses and metaphyses, in an asymptomatic patient, is characteristic of osteopoikilosis (also known as osteopathia condensans disseminata). Osteoblastic metastases would be a primary concern, but they are usually more irregular in shape, vary in size, and often associated with a known primary malignancy. Bone infarcts can cause sclerotic areas but are typically more irregular and often have a serpiginous border. Melorheostosis has a "flowing candle wax" appearance. Osteopathia striata shows linear striations.

Correct Answer: D

Rationale: Osteopoikilosis is inherited in an autosomal dominant pattern, often associated with mutations in the LEMD3 gene. The family history provided (mother and maternal grandfather affected) is consistent with autosomal dominant inheritance, where the trait appears in every generation and affects both males and females.

Correct Answer: C

Rationale: The radiographic appearance of linear striations of increased bone density, running longitudinally in the metaphyses and diaphyses, is characteristic of osteopathia striata. Osteopoikilosis presents as small, round sclerotic foci. Melorheostosis has a "flowing candle wax" appearance. Stress fractures would typically be localized, painful, and show a different pattern of periosteal reaction or callus. Osteoblastic metastases are usually more irregular and associated with a primary malignancy.

Correct Answer: C

Rationale: Localized gigantism, or macrodactyly when affecting digits, is characterized by the progressive overgrowth of all mesenchymal tissues (bone, soft tissue, nerve, fat, and often associated with vascular anomalies) in a localized segment or digit. It is not merely isolated hypertrophy of one tissue type. The involvement of all tissues distinguishes it from simple vascular malformations or isolated bone/soft tissue lesions.

Correct Answer: B

Rationale: The clinical text states that Ewing's sarcoma "most commonly present in the first three decades of life." This encompasses children, adolescents, and young adults, which aligns with the typical presentation of this tumor. Main Distractor: A) While Ewing's sarcoma is common in the first decade, the text specifies "first three decades" as the broader, most common range, making option B more accurate.

Correct Answer: C

Rationale: The clinical text and the description for Fig. 8.98a explicitly state that Ewing's sarcoma presents with a "permeative pattern, broad zone of transition, and periosteal reaction." The image clearly demonstrates these features. Main Distractor: A) A well-defined sclerotic margin with a narrow zone of transition is characteristic of a benign or slow-growing lesion, which is contrary to the aggressive nature of Ewing's sarcoma.

Correct Answer: C

Rationale: The clinical text and the description for Fig. 8.101 explicitly state that histologically, Ewing's sarcoma tumors are "composed of small, round, blue cells." The image also shows this uniform population. Main Distractor: A) Spindle cell proliferation with osteoid formation is characteristic of osteosarcoma, a different type of bone tumor.

Correct Answer: B

Rationale: The clinical text states, "Lesions typically present in the diaphysis or metadiaphysis of long bones, although flat bones such as the pelvis and scapula may also be involved." Main Distractor: A) The epiphysis of long bones is a less common location for Ewing's sarcoma, being more typical for tumors like chondroblastoma.

Correct Answer: C

Rationale: The clinical text explicitly states, "Most patients will have pain at rest or at night." This is a classic symptom of malignant bone tumors, including Ewing's sarcoma. Main Distractor: A) Pain exclusively with activity and relieved by rest is more characteristic of mechanical issues, stress fractures, or benign conditions, not typically a malignant bone tumor.

Correct Answer: D

Rationale: Ewing's sarcoma is classified as a "round cell sarcoma." Lymphoma is another prominent member of the "small, round, blue cell tumor" differential diagnosis in bone, especially in children and young adults. Other common small round blue cell tumors include rhabdomyosarcoma, neuroblastoma,

Question 95

A 14-year-old male presents with progressive pain in his proximal forearm. Radiographs are obtained.

• A) Well-defined sclerotic margins.
• B) Broad zone of transition.
• C) Primarily epiphyseal involvement.
• D) Absence of periosteal reaction.
• E) Cortical thickening without bone destruction.

View Answer & Explanation

Correct Answer: B

Rationale: As described in the clinical context for Fig. 8.98a, Ewing's sarcoma typically presents with a permeative pattern, a broad zone of transition, and periosteal reaction on radiographs, indicating an aggressive lesion. Well-defined sclerotic margins are characteristic of benign or less aggressive lesions, and epiphyseal involvement is uncommon.

Question 95

A biopsy is performed on a 12-year-old girl with a diaphyseal lesion of the tibia. Low-power microscopic examination of the tissue is shown.

• A) Spindle-shaped cells with abundant eosinophilic cytoplasm.
• B) Uniform population of small, round, blue cells.
• C) Chondroid matrix production.
• D) Osteoid formation with atypical osteoblasts.
• E) Multinucleated giant cells.

View Answer & Explanation

Correct Answer: B

Rationale: As stated in the clinical context for Fig. 8.101, Ewing's sarcoma is histologically characterized by a uniform population of small, round, blue cells. Spindle cells, chondroid matrix, osteoid formation, and giant cells are characteristic features of other bone tumors.

Question 95

Further high-power microscopic examination of the same biopsy specimen from the 12-year-old girl is performed.

• A) Marked cellular pleomorphism and high mitotic activity.
• B) Prominent nucleoli and uniform cell appearance.
• C) Abundant intercellular collagen.
• D) Extensive fatty differentiation.
• E) Formation of true rosettes.

View Answer & Explanation

Correct Answer: B

Rationale: As described in the clinical context for Fig. 8.102, high-power microscopy of Ewing's sarcoma typically shows uniform cells and prominent nucleoli, often with little mitotic activity. Marked pleomorphism and high mitotic activity are characteristic of many high-grade sarcomas but the uniformity is a key feature of Ewing's. True rosettes are more characteristic of neuroblastoma.

Question 95

A 13-year-old girl presents with pain and swelling in her proximal radius. An MRI is performed.

• A) A well-encapsulated lesion confined to the bone.
• B) Extensive bone destruction and a large associated soft tissue mass.
• C) Primarily an intra-articular lesion with synovial hypertrophy.
• D) Multiple small, discrete lesions throughout the bone.
• E) Marrow edema without cortical breach.

View Answer & Explanation

Correct Answer: B

Rationale: As described in the clinical context for Fig. 8.98b, the MRI clearly shows significant bone destruction and a large soft tissue mass extending beyond the bone, which is characteristic of aggressive bone sarcomas like Ewing's.

Correct Answer: B

Rationale: Ewing's sarcoma often presents with signs and symptoms that mimic infection, such as pain, swelling, fever, and elevated inflammatory markers, leading to diagnostic challenges. While pathologic fractures can occur, they are not the most common initial presentation. Joint effusions are not typical, and the tumor is rarely asymptomatic.

Correct Answer: B

Rationale: As described in the clinical context for Fig. 8.98a, Ewing's sarcoma typically presents with a permeative pattern, a broad zone of transition, and periosteal reaction on radiographs, indicating an aggressive lesion. Well-defined sclerotic margins are characteristic of benign or less aggressive lesions, and epiphyseal involvement is uncommon.

Correct Answer: B

Rationale: As stated in the clinical context for Fig. 8.101, Ewing's sarcoma is histologically characterized by a uniform population of small, round, blue cells. Spindle cells, chondroid matrix, osteoid formation, and giant cells are characteristic features of other bone tumors.

Correct Answer: B

Rationale: As described in the clinical context for Fig. 8.102, high-power microscopy of Ewing's sarcoma typically shows uniform cells and prominent nucleoli, often with little mitotic activity. Marked pleomorphism and high mitotic activity are characteristic of many high-grade sarcomas but the uniformity is a key feature of Ewing's. True rosettes are more characteristic of neuroblastoma.

Correct Answer: C

Rationale: Ewing's sarcoma typically presents in the diaphysis or metadiaphysis of long bones. Epiphyseal involvement is rare for this tumor, distinguishing it from other pediatric bone tumors like chondroblastoma.