Question 1

A 4-year-old girl is diagnosed with oligoarticular juvenile idiopathic arthritis (JIA). Laboratory testing reveals a high titer of antinuclear antibodies (ANA). Which of the following is the most critical routine screening required for this patient?

Explanation

Patients with early-onset oligoarticular JIA who are ANA positive are at the highest risk for developing chronic, asymptomatic anterior uveitis. Routine slit-lamp screening is mandatory to prevent permanent vision loss.

Question 2

A 35-year-old female with a long-standing history of polyarticular juvenile idiopathic arthritis is scheduled for a total hip arthroplasty. She has severe limitation in multiple joints. What is the most critical pre-operative imaging required prior to intubation?

Explanation

Patients with polyarticular JIA frequently develop cervical spine instability, particularly at the C1-C2 level. Flexion-extension cervical radiographs are essential pre-operatively to evaluate for atlantoaxial subluxation before intubation.

Question 3

A 12-year-old boy with systemic juvenile idiopathic arthritis (JIA) presents to the emergency department with acute high fever, hepatosplenomegaly, and altered mental status. Laboratory results show a sudden drop in ESR, thrombocytopenia, and hypofibrinogenemia. What is the most likely diagnosis?

Explanation

Macrophage activation syndrome (MAS) is a life-threatening complication of systemic JIA characterized by a paradoxical drop in ESR, coagulopathy, and cytopenias. It requires immediate medical intervention.

Question 4

Early-onset juvenile idiopathic arthritis commonly involves the temporomandibular joint (TMJ). Which of the following facial deformities is most characteristically seen as a consequence of this involvement?

Explanation

TMJ arthritis in JIA can cause premature closure of the mandibular condyle growth plate. This leads to restricted mandibular growth, resulting in micrognathia (the classic 'bird-face' deformity).

Question 5

A 16-year-old patient with JIA controlled on Etanercept is scheduled for a posterior spinal fusion for scoliosis. According to current perioperative guidelines, how should this biologic medication be managed?

Explanation

To minimize infection risk, biologic agents like Etanercept (a TNF inhibitor) should be withheld for 1-2 dosing intervals prior to major orthopedic surgery. They are typically restarted once the surgical wound has completely healed.

Question 6

A 15-year-old boy presents with knee pain and a palpable mass in the distal femur. Radiographs reveal a mixed lytic and sclerotic lesion with a 'sunburst' periosteal reaction. Core needle biopsy confirms high-grade, conventional osteosarcoma. What is the standard initial management?

Explanation

The standard of care for high-grade conventional osteosarcoma is neoadjuvant chemotherapy, followed by wide surgical resection, and then adjuvant chemotherapy. The histological response to initial chemotherapy is a major prognostic factor.

Question 7

A 10-year-old girl is diagnosed with Ewing sarcoma of the diaphysis of the humerus. Which specific chromosomal translocation is most classically associated with this malignancy?

Explanation

Ewing sarcoma is driven by a characteristic fusion of the EWS gene with the FLI1 gene. This is caused by the t(11;22)(q24;q12) chromosomal translocation in approximately 85% of cases.

Question 8

A 30-year-old female presents with a large, lytic, expansile lesion in the proximal tibia extending to the subchondral bone. Biopsy demonstrates mononuclear cells interspersed with osteoclast-like multinucleated cells. Which targeted pharmacological agent can be used to downstage this tumor prior to surgery?

Explanation

The diagnosis is Giant Cell Tumor (GCT) of bone. Denosumab, a monoclonal antibody against RANKL, inhibits the recruitment and action of the osteoclast-like giant cells, causing tumor calcification and facilitating surgical curettage.

Question 9

A 65-year-old man presents with a destructive lesion in the proximal humerus. Biopsy confirms metastatic clear cell renal cell carcinoma. He is scheduled for wide resection and endoprosthetic reconstruction. What is the most critical pre-operative step?

Explanation

Metastatic renal cell carcinoma lesions are highly vascular and prone to massive intraoperative hemorrhage. Pre-operative selective arterial embolization, typically 24-48 hours before surgery, significantly reduces surgical blood loss.

Question 10

A 55-year-old man presents with dull pain in the proximal femur. Radiographs show a lytic lesion with 'rings and arcs' calcification. MRI reveals endosteal scalloping involving >2/3 of the cortical thickness. Biopsy confirms grade II chondrosarcoma. What is the primary modality of treatment?

Explanation

Intermediate and high-grade chondrosarcomas (Grades II and III) are largely resistant to both chemotherapy and radiation. Wide surgical resection with negative margins is the definitive standard of care.

Question 11

A 13-year-old boy presents with a rapidly progressive, left-sided thoracic scoliosis and associated upper extremity weakness.

Given the underlying pathology seen on the MRI, what is the most appropriate initial management strategy?

Explanation

The MRI shows a syrinx often associated with a Chiari malformation. The initial treatment for syringomyelia-associated scoliosis is neurosurgical decompression of the foramen magnum, which can halt or occasionally reverse curve progression.

Question 12

A patient with syringomyelia presents with the classic 'cape-like' bilateral loss of pain and temperature sensation over the shoulders and upper extremities.

This specific neurological deficit is caused by the expanding syrinx compressing which structure within the spinal cord?

Explanation

A central cord syrinx initially compresses the crossing spinothalamic fibers in the anterior white commissure. This disruption causes the classic dissociated sensory loss (loss of pain and temperature, with preserved fine touch and proprioception).

Question 13

Syringomyelia, characterized by a fluid-filled cavity within the spinal cord, is most commonly associated with which of the following underlying congenital abnormalities?

Explanation

Syringomyelia is most frequently associated with a Chiari I malformation, where the cerebellar tonsils herniate through the foramen magnum. This alters CSF flow dynamics, leading to central canal expansion.

Question 14

When evaluating an adolescent for scoliosis, certain atypical features should prompt an entire spine MRI to rule out a neuroaxis abnormality such as syringomyelia. These 'red flag' features include all of the following EXCEPT:

Explanation

A right-sided thoracic curve is the standard, typical pattern for adolescent idiopathic scoliosis. A left-sided thoracic curve, rapid progression, or an absent apical lordosis are atypical and strongly warrant an MRI screening.

Question 15

A 45-year-old male with a history of a T12 burst fracture treated non-operatively 15 years ago presents with new-onset ascending spasticity, weakness, and sensory changes in his legs.

What is the most likely diagnosis shown on his current imaging?

Explanation

Post-traumatic syringomyelia can develop months to decades after an initial spinal cord injury. Symptoms typically include ascending myelopathy due to the progressive rostral extension of the fluid-filled syrinx.

Question 16

A 55-year-old diabetic male presents with an acute, red, hot, swollen foot. Radiographs demonstrate bone fragmentation, subluxation, and periarticular debris around the midfoot. According to the Eichenholtz classification of Charcot arthropathy, which stage does this represent?

Explanation

Eichenholtz Stage I (Developmental/Fragmentation stage) is characterized by acute inflammation, joint laxity, bone fragmentation, and debris formation. The foot mimics infection clinically but represents acute neuropathic breakdown.

Question 17

What is the most appropriate initial management for a patient presenting with an acute, non-ulcerated Eichenholtz Stage I Charcot arthropathy of the foot?

Explanation

The cornerstone of management for acute Eichenholtz Stage I Charcot arthropathy is strict offloading and immobilization, ideally utilizing a total contact cast (TCC), to prevent further mechanical breakdown while the acute inflammation subsides.

Question 18

While modern neuropathic (Charcot) arthropathy is most commonly seen in the foot and ankle due to diabetes mellitus, historically, severe Charcot changes of the large joints (knee) and spine were classically associated with which condition?

Explanation

Tabes dorsalis, a manifestation of tertiary syphilis, was classically the most common cause of neuropathic arthropathy in the knee and spine before the antibiotic era. Syringomyelia classically affects the upper extremities (shoulder/elbow).

Question 19

A 4-year-old girl is diagnosed with ANA-positive oligoarticular Juvenile Idiopathic Arthritis (JIA). What is the most critical routine screening required for this patient?

Explanation

ANA-positive oligoarticular JIA carries the highest risk for asymptomatic uveitis/iridocyclitis. Routine slit-lamp examination every 3-4 months is critical to prevent permanent visual impairment or blindness.

Question 20

A 45-year-old man presents with progressive, painless swelling and instability of his right shoulder over 6 months. Exam reveals loss of pain and temperature sensation in a cape-like distribution. X-rays show severe glenohumeral destruction with osseous debris. MRI of the spine will most likely show:

Explanation

Neuropathic (Charcot) arthropathy of the upper extremity, especially the shoulder, is highly associated with syringomyelia (central cord cavitation). The syrinx expands to compress the spinothalamic tracts, leading to dissociated sensory loss in a cape-like distribution.

Question 21

A 14-year-old boy has a high-grade intramedullary osteosarcoma of the distal femur. Following neoadjuvant chemotherapy and wide resection, what histological finding in the resected specimen is the most important prognostic factor for overall survival?

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy (Huvos grading system) is the most significant prognostic factor in osteosarcoma. Greater than 90% necrosis indicates a good response and correlates with better overall survival.

Question 22

A 32-year-old woman presents with an expansive, purely lytic lesion in the distal radius extending to the subchondral bone. Biopsy confirms a Giant Cell Tumor (GCT). For an unresectable or recurrent GCT, which targeted medical therapy is most appropriate?

Explanation

Denosumab is a monoclonal antibody against RANKL. It prevents the RANK-RANKL interaction, inhibiting the osteoclast-like giant cells driving bone destruction in GCT, leading to tumor regression and ossification.

Question 23

In a 12-year-old patient with long-standing, poorly controlled polyarticular Juvenile Idiopathic Arthritis (JIA), what is the most common pattern of cervical spine involvement?

Explanation

While atlantoaxial subluxation can occur, the most characteristic and common cervical spine manifestation in JIA is subaxial ankylosis (fusion of the facet joints). This can lead to altered growth, a hypoplastic cervical spine, and limited neck extension.

Question 24

A 55-year-old diabetic male presents with a swollen, erythematous, and warm left foot without open ulcerations. Radiographs show acute fragmentation and subluxation of the tarsometatarsal joints. What is the initial recommended orthopedic management during this Eichenholtz stage I phase?

Explanation

The mainstay of treatment in the acute fragmentation phase (Eichenholtz stage I) of Charcot arthropathy is strict immobilization and offloading, typically achieved with a total contact cast (TCC). Surgery is contraindicated during the acute inflammatory phase due to a high risk of failure.

Question 25

A 30-year-old female presents with atypical scoliosis and weakness in her intrinsic hand muscles. Neurological exam demonstrates diminished pinprick sensation over her shoulders. Imaging confirms a cervical syrinx. What cranial anomaly is most frequently associated with this condition?

Explanation

Syringomyelia is strongly associated with Chiari I malformations. Herniation of the cerebellar tonsils through the foramen magnum disrupts normal cerebrospinal fluid flow, leading to central cord cavitation.

Question 26

A 10-year-old boy presents with a diaphyseal lytic lesion of the fibula with an "onion-skin" periosteal reaction. Biopsy shows uniform small blue round cells. Which chromosomal translocation is most characteristic of this tumor?

Explanation

Ewing sarcoma is classically characterized by the t(11;22)(q24;q12) translocation, which results in the EWS-FLI1 fusion protein. This molecular marker is used to confirm the diagnosis.

Question 27

A 55-year-old man is found to have a 6 cm calcified intramedullary lesion in his proximal humerus with endosteal scalloping. Biopsy confirms grade II (intermediate-grade) chondrosarcoma. What is the most appropriate definitive management?

Explanation

Conventional chondrosarcomas (especially grade II and III) are notably resistant to both chemotherapy and radiotherapy. The standard of care is wide surgical resection with negative margins.

Question 28

A 9-year-old child with unilateral pauciarticular JIA presents with a 2 cm leg length discrepancy, with the arthritic limb being longer. She also has a mild knee flexion contracture. What is the primary pathophysiological cause of the limb overgrowth?

Explanation

Chronic synovitis in JIA causes local hyperemia and increased vascularity. This local inflammatory environment stimulates the adjacent physes, commonly leading to accelerated growth and limb lengthening on the affected side.

Question 29

Which of the following best describes the 'neurovascular theory' in the pathogenesis of a Charcot neuropathic joint?

Explanation

The neurovascular theory postulates that autonomic neuropathy leads to a loss of sympathetic tone, causing hyperemia and active osteoclastic bone resorption. This weakens the bone, making it susceptible to fractures from minor trauma.

Question 30

A 65-year-old man presents with severe back pain and a solitary lytic lesion in the L3 vertebral body. Laboratory testing reveals an M spike on serum protein electrophoresis. What imaging modality is considered the standard of care for staging skeletal involvement in this disease?

Explanation

Whole-body low-dose CT or PET-CT is the standard imaging modality for the skeletal survey in multiple myeloma. Technetium-99m bone scans are often false-negative because myeloma lesions are purely lytic and lack the osteoblastic activity required for tracer uptake.

Question 31

A 12-year-old girl is evaluated for scoliosis. She has an atypical left thoracic curve and absent abdominal reflexes. An MRI reveals a large syrinx in the thoracic spinal cord. What is the recommended sequence of treatment for her condition?

Explanation

In patients with a syrinx and progressive scoliosis requiring surgery, neurosurgical decompression (e.g., foramen magnum decompression for a Chiari malformation) must be performed first. This significantly reduces the risk of neurologic injury during subsequent spinal deformity correction.

Question 32

A 19-year-old male complains of severe, progressively worsening right thigh pain that occurs primarily at night and is dramatically relieved by NSAIDs. Imaging shows a radiolucent nidus surrounded by dense reactive sclerosis. What is the most definitive, minimally invasive treatment?

Explanation

The clinical and radiographic presentation is classic for an osteoid osteoma. CT-guided radiofrequency ablation (RFA) is the definitive, minimally invasive standard of care, offering excellent success rates and minimal morbidity compared to open surgery.

Question 33

A 5-year-old boy presents with daily spiking fevers, a generalized salmon-pink macular rash, hepatosplenomegaly, and severe polyarthritis. Laboratory tests show markedly elevated ferritin, ESR, and CRP, but negative ANA and RF. Which of the following is the most likely diagnosis?

Explanation

Systemic JIA (Still's disease) is characterized by daily quotidian fevers, an evanescent salmon-pink rash, hepatosplenomegaly, and markedly elevated inflammatory markers (especially ferritin). It is distinct from other JIA subtypes by its prominent systemic manifestations.

Question 34

In a patient with diabetic neuroarthropathy of the foot, serial radiographs demonstrate absorption of fine debris, coalescence of large fracture fragments, and early sclerosis, alongside a clinical reduction in soft tissue edema. This corresponds to which stage of the Eichenholtz classification?

Explanation

Eichenholtz Stage II (Coalescence) is clinically marked by decreasing edema and erythema. Radiographically, it is characterized by the absorption of fine osseous debris, early fusion/coalescence of large fragments, and increasing sclerosis.

Question 35

A 12-year-old boy presents with a left-sided thoracic scoliosis. Neurological examination reveals absent superficial abdominal reflexes and diminished pain and temperature sensation in both upper extremities. Which of the following is the most appropriate next step in evaluation?

Explanation

A left thoracic curve, absent abdominal reflexes, and sensory dissociation (loss of pain/temperature with preserved light touch) strongly suggest an intraspinal anomaly like syringomyelia. A total spine MRI is mandatory to evaluate for a syrinx or Chiari malformation before any scoliosis treatment.

Question 36

Which subtype of Juvenile Idiopathic Arthritis (JIA) carries the highest risk for developing asymptomatic anterior uveitis, thereby requiring the most frequent ophthalmologic screening?

Explanation

Oligoarticular ANA-positive JIA carries the highest risk (approximately 20-30%) for chronic anterior uveitis. Frequent slit-lamp examinations are required as the uveitis is typically asymptomatic and can lead to blindness if untreated.

Question 37

A 14-year-old boy presents with a painful diaphyseal mass in his right femur, low-grade fever, and an elevated erythrocyte sedimentation rate (ESR). Biopsy reveals sheets of uniform small round blue cells. Cytogenetic analysis of this tumor is most likely to demonstrate which of the following translocations?

Explanation

The clinical and histologic findings are diagnostic of Ewing sarcoma. The classic chromosomal translocation associated with Ewing sarcoma is t(11;22), which results in the EWS-FLI1 fusion protein.

Question 38

A 55-year-old patient with long-standing, poorly controlled diabetes presents with a warm, swollen, erythematous, and painless foot. Radiographs demonstrate periarticular debris, bony fragmentation, and midfoot subluxation. According to the Eichenholtz classification, what is the current stage and best initial management?

Explanation

Fragmentation, joint subluxation, and periarticular debris characterize Eichenholtz Stage 1 (Development) Charcot arthropathy. The gold standard initial treatment is immobilization and offloading, typically utilizing a total contact cast.

Question 39

A 45-year-old male presents with a massively swollen, painless shoulder joint. Radiographs show severe destruction of the humeral head with abundant bony debris. He mentions chronic neck stiffness and frequent unrecognized burns on his hands. What is the most likely underlying etiology of his shoulder pathology?

Explanation

Upper extremity Charcot joints are highly characteristic of syringomyelia, which causes sensory dissociation (loss of pain/temperature) in the arms. Diabetic Charcot arthropathy typically affects the foot and ankle.

Question 40

In the multimodal management of high-grade, conventional intramedullary osteosarcoma of the distal femur, which of the following is considered the most critical prognostic factor for long-term patient survival?

Explanation

The histologic response to neoadjuvant chemotherapy, specifically greater than 90% tumor necrosis, is the single most important prognostic factor for overall survival in osteosarcoma. Poor responders have a significantly higher risk of metastasis and mortality.

Question 41

A 9-year-old girl with severe polyarticular JIA is scheduled for bilateral total hip arthroplasty due to debilitating pain and contractures. Prior to general anesthesia, which of the following imaging studies is absolutely mandatory?

Explanation

Patients with polyarticular JIA frequently develop cervical spine involvement, particularly C1-C2 instability or ankylosis. Flexion/extension cervical spine radiographs are essential to assess instability and prevent catastrophic spinal cord injury during intubation.

Question 42

A 60-year-old man presents with dull pain in his proximal humerus. Radiographs reveal a large lytic lesion with intralesional "popcorn" calcifications and endosteal scalloping >2/3 of the cortical thickness. Biopsy confirms grade II chondrosarcoma. What is the most appropriate definitive treatment?

Explanation

Conventional chondrosarcomas (especially grade II and III) are highly resistant to both chemotherapy and radiation. The standard of care is wide surgical resection alone with negative margins.

Question 43

The neurovascular theory of the pathogenesis of Charcot neuroarthropathy postulates that joint destruction is primarily initiated by which of the following mechanisms?

Explanation

The neurovascular theory suggests that autonomic (sympathetic) neuropathy leads to increased blood flow (hyperemia) and active osteoclastic bone resorption, weakening the bone. This contrasts with the neurotraumatic theory, which emphasizes repetitive unperceived microtrauma.

Question 44

A 14-year-old girl presents with a rapidly progressive right thoracic scoliosis. MRI reveals a large fluid-filled cavity within the central spinal cord extending from C4 to T8. Which of the following cranial abnormalities is most commonly associated with this specific spinal finding?

Explanation

Syringomyelia is a fluid-filled cyst within the spinal cord that is most frequently associated with an Arnold-Chiari type I malformation (tonsillar herniation). Treatment often involves suboccipital decompression.

Question 45

A 6-year-old child with oligoarticular JIA presents with a chronic, persistent unilateral knee effusion. Clinical exam reveals a noticeable limb length discrepancy. What is the most common lower extremity deformity pattern observed in this specific clinical scenario?

Explanation

Chronic hyperemia from joint inflammation stimulates the adjacent physes, causing ipsilateral limb overgrowth. Asymmetric stimulation of the distal femoral physis (medial condyle growing faster than lateral) typically produces a valgus deformity.

Question 46

A 32-year-old woman presents with knee pain. Radiographs reveal an eccentric, purely lytic, epiphyseal lesion extending to the subchondral bone of the proximal tibia. Biopsy confirms multinucleated giant cells in a background of mononuclear stromal cells. Which targeted therapy acts as a RANKL inhibitor and is indicated for advanced or unresectable forms of this tumor?

Explanation

Giant cell tumor of bone (GCT) is driven by the overexpression of RANKL by the neoplastic mononuclear stromal cells, which recruits osteoclast-like giant cells. Denosumab, a monoclonal antibody against RANKL, is an effective targeted therapy for advanced or unresectable GCT.

Question 47

In a patient with diabetic Charcot neuroarthropathy, structural collapse of the longitudinal arch resulting in plantar prominence of the cuboid and navicular (rocker-bottom foot deformity) most frequently occurs during which Eichenholtz stage?

Explanation

The active destruction, capsular laxity, and bony fragmentation that lead to midfoot collapse (rocker-bottom foot) occur during Eichenholtz Stage 1. Early offloading is critical to prevent this severe deformity.

Question 48

The pathogenesis of scoliosis in patients with syringomyelia is best explained by which of the following mechanisms?

Explanation

Scoliosis in syringomyelia is believed to result from asymmetric expansion of the syrinx compressing the anterior horn cells. This leads to subtle, asymmetric weakness or paralysis of the paraspinal musculature, causing the spine to curve.

Question 49

An 18-year-old male presents with painful scoliosis. Imaging reveals a 2.5 cm radiolucent lesion with a mineralized matrix in the posterior elements of L3. The pain is persistent and is only partially relieved by nonsteroidal anti-inflammatory drugs (NSAIDs). What is the most likely diagnosis?

Explanation

Osteoblastomas are histologically similar to osteoid osteomas but are distinguished by being larger (>1.5-2.0 cm), exhibiting progressive growth, and causing pain that is less responsive to NSAIDs. They commonly occur in the posterior elements of the spine.

Question 50

Which of the following best describes the characteristic facial morphology of a patient who develops temporomandibular joint (TMJ) ankylosis secondary to severe juvenile idiopathic arthritis (JIA) during early childhood?

Explanation

Early TMJ involvement in JIA causes premature closure of the mandibular growth centers, resulting in micrognathia (undersized jaw), a receded chin, and a convex facial profile, classically described as a "bird-face" deformity.

Question 51

A 62-year-old diabetic male with an Eichenholtz Stage 1 Charcot arthropathy of the midfoot presents with a non-healing, non-infected plantar ulcer directly overlying a massive cuboid prominence. What is the most appropriate surgical management?

Explanation

Arthrodesis during the active, hyperemic fragmentation phase (Stage 1) has a high failure rate due to poor bone quality and active resorption. The preferred management for a recalcitrant ulcer over a prominence in Stage 1 is a simple exostectomy to offload the skin, delaying fusion until the disease coalesces (Stage 2/3).

Question 52

A 65-year-old man presents with new-onset back pain, anemia, and an M-spike on serum protein electrophoresis. Radiographs show a compression fracture of T12 and punched-out lytic skull lesions. Which of the following imaging modalities is most sensitive for detecting additional early osseous lesions in this patient?

Explanation

Whole-body MRI (or PET-CT) is highly sensitive for detecting bone marrow involvement in multiple myeloma. Technetium-99m bone scans are notoriously insensitive because myeloma lesions are purely osteolytic and lack the osteoblastic response needed for tracer uptake.

Question 53

A 4-year-old girl is diagnosed with oligoarticular Juvenile Idiopathic Arthritis (JIA). Her ANA is positive and rheumatoid factor is negative. Which of the following is the most appropriate screening protocol for the most common extra-articular complication in this patient?

Explanation

ANA-positive oligoarticular JIA carries a high risk of asymptomatic anterior uveitis. Routine slit-lamp examinations every 3-4 months are required to prevent permanent visual impairment.

Question 54

A 15-year-old boy presents with a painful mass in his distal femur. Radiographs show a "sunburst" periosteal reaction. He has a history of bilateral enucleation as an infant. Which mutated gene is most directly implicated in both of his neoplastic conditions?

Explanation

The patient has a history of bilateral retinoblastoma, which is strongly associated with mutations in the RB1 tumor suppressor gene. This mutation significantly increases the lifetime risk of developing osteosarcoma.

Question 55

A 35-year-old man presents with progressive weakness and painless burns on his hands. Neurological examination reveals loss of pain and temperature sensation in a cape-like distribution over his shoulders and upper extremities, with preserved light touch. MRI is shown.

What is the most common associated condition?

Explanation

The clinical picture and imaging are classic for syringomyelia, presenting with dissociated sensory loss. Chiari malformation type 1 is the most common condition associated with a cervical syrinx.

Question 56

A 45-year-old patient develops a rapidly progressive, painless, and massively swollen shoulder joint. Radiographs show severe osseous destruction, debris, and subluxation. Which of the following underlying conditions is the most likely etiology for this presentation?

Explanation

Charcot arthropathy of the upper extremity, particularly the shoulder and elbow, is classically caused by syringomyelia. Diabetes mellitus typically affects the foot and ankle, while syphilis historically affected the knee and hip.

Question 57

A 6-year-old boy presents with daily spiking fevers up to 39.5°C, a transient salmon-pink macular rash, and hepatosplenomegaly. He also has bilateral knee effusions. Laboratory tests show elevated ferritin and leukocytosis. What is the most likely diagnosis?

Explanation

Systemic JIA (formerly Still's disease) is characterized by daily quotidian fevers, a migratory salmon-pink rash, hepatosplenomegaly, and arthritis. Elevated ferritin is a hallmark laboratory finding.

Question 58

A 32-year-old woman presents with knee pain. Radiographs reveal an eccentric, expansile lytic lesion in the distal femoral epiphysis extending to the articular surface. Biopsy shows multinucleated giant cells in a stroma of mononuclear cells. Which of the following is the most appropriate targeted medical therapy?

Explanation

This is a giant cell tumor of bone. Denosumab, a monoclonal antibody against RANKL, is an effective targeted medical therapy that inhibits the osteoclast-like giant cells.

Question 59

A 55-year-old diabetic male presents with a warm, erythematous, and swollen foot. Radiographs show periarticular debris, fragmentation of the tarsal bones, and subluxation. According to the Eichenholtz classification, what is the current stage and most appropriate initial management?

Explanation

The patient is in Eichenholtz Stage 1 (fragmentation), characterized by active inflammation, debris, and bone fragmentation. The gold standard initial treatment is offloading with a total contact cast.

Question 60

A 12-year-old boy presents with an atypical, rapidly progressive left thoracic scoliotic curve. He also reports frequent occipital headaches and upper extremity clumsiness. An MRI confirms a syrinx.

What is the most appropriate initial management for his spinal deformity?

Explanation

Atypical scoliosis (e.g., left thoracic curve) driven by a syrinx should be addressed by neurosurgical decompression first. Addressing the underlying syrinx may halt or even reverse the curve progression in younger children.

Question 61

A 60-year-old man presents with dull, aching hip pain. Radiographs show a lytic lesion in the proximal femur with endosteal scalloping and "rings and arcs" calcification. Biopsy confirms a grade II chondrosarcoma. What is the mainstay of treatment?

Explanation

Conventional chondrosarcomas are generally resistant to chemotherapy and radiation. The mainstay of treatment is wide surgical resection with negative margins.

Question 62

A 14-year-old girl with severe, long-standing polyarticular JIA complains of neck pain, myelopathic symptoms, and a "clunking" sensation when nodding. Which of the following radiographic findings is most critical to evaluate before planning any elective surgical procedures requiring intubation?

Explanation

Cervical spine involvement in JIA often leads to atlantoaxial subluxation due to ligamentous laxity and pannus formation. This must be evaluated with flexion/extension radiographs prior to intubation to prevent catastrophic spinal cord injury.

Question 63

A 65-year-old man presents with a massively enlarged, painless knee. He has a history of untreated syphilis in his youth. Radiographs reveal severe joint destruction and large osteophytes. Neurological exam shows loss of proprioception and a positive Romberg sign. Which of the following is the most likely pathophysiological mechanism for his joint destruction?

Explanation

The patient has a Charcot joint secondary to Tabes Dorsalis (neurosyphilis). The "neurotraumatic theory" posits that loss of proprioception and protective pain sensation leads to repeated, unperceived microtrauma and subsequent joint destruction.

Question 64

A 14-year-old girl presents with fever and localized pain in her mid-tibia. Radiographs show a permeative, diaphyseal lytic lesion with an "onion-skin" periosteal reaction. Histology reveals small round blue cells. Which of the following immunohistochemical markers and genetic translocations are characteristic of this tumor?

Explanation

Ewing sarcoma is a small round blue cell tumor typically positive for CD99 (MIC2). It is driven by the t(11;22) translocation resulting in the EWS-FLI1 fusion gene.

Question 65

In a patient with early syringomyelia

experiencing isolated loss of pain and temperature sensation in the upper extremities, which specific spinal cord structure is primarily compressed by the expanding syrinx?

Explanation

A central syrinx expands from the central canal outward, initially compressing the crossing spinothalamic fibers located in the anterior white commissure. This results in the classic bilateral loss of pain and temperature sensation.

Question 66

A 7-year-old boy with systemic JIA suddenly deteriorates, developing lethargy, unremitting fever, and mucosal bleeding. Laboratory findings show profound cytopenias, a rapidly falling erythrocyte sedimentation rate (ESR), hypofibrinogenemia, and markedly elevated serum ferritin. What is the most likely diagnosis?

Explanation

Macrophage activation syndrome (MAS) is a life-threatening complication of systemic JIA. A paradoxical drop in ESR (due to fibrinogen consumption/liver dysfunction) alongside sky-high ferritin and cytopenias is pathognomonic.

Question 67

A 65-year-old man presents with severe back pain and fatigue. Radiographs show multiple "punched-out" lytic lesions in his skull and vertebral bodies. Laboratory studies reveal hypercalcemia, anemia, and an M-spike on serum protein electrophoresis. The osteolytic lesions in this disease are primarily mediated by the upregulation of which factor?

Explanation

Multiple myeloma cells secrete various factors, particularly activating RANKL and inhibiting OPG. This leads to massive osteoclast activation and the classic "punched-out" lytic lesions without reactive bone formation.

Question 68

The pathogenesis of Charcot arthropathy is classically described by two main theories. The "neurovascular theory" attributes the initial bone destruction and fragmentation to which of the following mechanisms?

Explanation

The neurovascular theory posits that autonomic neuropathy leads to loss of sympathetic tone, causing arteriovenous shunting and hyperemia. This hyperemic state washes out bone mineral, leading to osteopenia and susceptibility to fracture.

Question 69

A 22-year-old male presents with dull, aching pain in his mid-back that is constant, night-predominant, and only partially relieved by ibuprofen. CT scan shows a 3.5 cm expansile lytic lesion in the posterior elements of T8 with a distinct radiolucent nidus and surrounding sclerosis. What is the most likely diagnosis?

Explanation

While similar histologically to an osteoid osteoma, an osteoblastoma is larger (typically >2 cm), often found in the posterior elements of the spine, and has pain that is less consistently relieved by NSAIDs.

Question 70

A 40-year-old woman with a history of severe spinal trauma 15 years ago presents with new-onset spasticity in her lower extremities and progressive sensory loss in her hands.

MRI of the cervical and thoracic spine reveals a large cystic cavitation within the spinal cord. What is the most likely diagnosis?

Explanation

Post-traumatic syringomyelia can develop months to years after a spinal cord injury. Fluid accumulates in the spinal cord due to altered CSF dynamics from arachnoid scarring, causing delayed, ascending neurological deficits.

Question 71

A 5-year-old girl with untreated monoarticular JIA of the right knee presents for evaluation. Her parents note a progressive gait abnormality. On examination, the right knee is warm and swollen with a 15-degree flexion contracture. Which of the following limb length discrepancies is most likely to be present?

Explanation

In growing children with monoarticular JIA, chronic inflammation and hyperemia stimulate the adjacent physes. This typically results in limb overgrowth and a longer affected limb.

Question 72

A 4-year-old girl with ANA-positive oligoarticular Juvenile Idiopathic Arthritis (JIA) presents for routine follow-up. Which of the following represents the most critical routine screening recommendation for this patient?

Explanation

Young females with ANA-positive oligoarticular JIA are at the highest risk for asymptomatic anterior uveitis. They require frequent slit-lamp examinations every 3-4 months to prevent synechiae and blindness.

Question 73

A 25-year-old female with severe systemic JIA is undergoing bilateral total hip arthroplasties. Which of the following is the most likely intraoperative finding or technical challenge?

Explanation

Patients with JIA commonly exhibit hypoplastic, narrow medullary canals (stovepipe appearance) and excessive femoral neck anteversion. Custom or modular small-sized implants are often required to accommodate the distorted anatomy.

Question 74

A 14-year-old boy is diagnosed with high-grade osteosarcoma of the distal femur. Following neoadjuvant chemotherapy, what percentage of tumor necrosis is the threshold defining a 'good histological response' according to the Huvos grading system?

Explanation

A good histological response to neoadjuvant chemotherapy in osteosarcoma is defined as greater than 90% tumor necrosis. This is the single most significant prognostic factor for overall survival.

Question 75

A 32-year-old male presents with painless swelling and instability of his left shoulder. He has noted recent burns on his hands that he did not feel. Imaging shows severe joint destruction.

What is the most likely underlying pathophysiology?

Explanation

The patient has a Charcot shoulder secondary to syringomyelia. The syrinx expands to affect the crossing spinothalamic tracts in the anterior white commissure, causing a cape-like loss of pain and temperature sensation.

Question 76

A 55-year-old poorly controlled diabetic presents with an erythematous, warm, and swollen right foot. Radiographs show periarticular fragmentation and debris without signs of coalescence. According to the Eichenholtz classification, what is the appropriate management?

Explanation

The patient is in Eichenholtz Stage I (Developmental/Fragmentation), characterized by erythema, warmth, and bony fragmentation. The standard of care is immobilization via total contact casting and non-weight bearing until the acute phase subsides.

Question 77

A 30-year-old female presents with a lytic lesion in the distal femur extending to the subchondral bone. Biopsy confirms a Giant Cell Tumor. Prior to extended intralesional curettage, the surgeon administers denosumab. What is the mechanism of action of denosumab?

Explanation

Denosumab is a monoclonal antibody that binds to RANKL, preventing its interaction with the RANK receptor. This inhibits the recruitment and maturation of the osteoclast-like giant cells, leading to tumor ossification and easier surgical curettage.

Question 78

A 12-year-old boy with polyarticular JIA complains of progressive neck pain and stiffness. Which of the following cervical spine abnormalities is most characteristic of this disease?

Explanation

Cervical spine involvement in JIA typically presents with early apophyseal joint ankylosis, most commonly at C2-C3. This early fusion leads to altered growth, hypoplasia of the involved vertebral bodies, and secondary instability.

Question 79

A 9-year-old boy presents with a diaphyseal lesion of the fibula with an 'onion skin' periosteal reaction. A biopsy reveals small blue round cells. Which chromosomal translocation is most commonly associated with this malignancy?

Explanation

The presentation is classic for Ewing sarcoma, which is characterized by the t(11;22) translocation resulting in the EWS-FLI1 fusion protein. This anomaly is found in approximately 85-90% of Ewing sarcoma cases.

Question 80

A 14-year-old girl is evaluated for a left-sided thoracic scoliotic curve of 45 degrees. Neurological exam reveals absent abdominal reflexes. An MRI confirms a cervical syrinx.

What is the most appropriate initial management for her spinal deformity?

Explanation

In patients with syringomyelia and scoliosis, atypical features like left-thoracic curves or absent abdominal reflexes indicate neural axis pathology. Neurosurgical decompression is the primary initial treatment and may halt or improve the curve progression.

Question 81

The neurotraumatic and neurovascular theories are postulated for the development of Charcot arthropathy. Which of the following best describes the core principle of the neurovascular theory?

Explanation

The neurovascular theory of Charcot arthropathy suggests that autonomic neuropathy leads to a loss of sympathetic vascular tone. This results in local hyperemia, increased blood flow, and subsequent increased osteoclastic bone resorption and joint weakening.

Question 82

A 60-year-old male presents with dull right hip pain. Radiographs show a large lytic lesion with 'popcorn' calcifications in the right ilium. Biopsy confirms a grade II chondrosarcoma. What is the mainstay of treatment for this condition?

Explanation

Conventional chondrosarcomas are notably resistant to both chemotherapy and radiation therapy. The primary and most effective treatment for intermediate to high-grade chondrosarcoma is wide surgical resection with negative margins.

Question 83

A 9-year-old boy with poorly controlled JIA presents with a progressive unilateral knee deformity. The affected knee exhibits overgrowth and a fixed flexion contracture. Which phenomenon best explains the observed limb length discrepancy?

Explanation

Chronic synovitis in JIA causes intense local hyperemia. This increased regional blood supply stimulates the adjacent open physes, resulting in premature bone overgrowth and a limb length discrepancy.

Question 84

A 16-year-old male complains of severe, aching thigh pain that is worse at night and dramatically relieved by NSAIDs. Radiographs demonstrate a 1-cm radiolucent nidus surrounded by dense sclerotic bone in the femoral diaphysis. What is the preferred definitive treatment if medical management fails?

Explanation

The clinical and radiographic presentation is classic for an osteoid osteoma. If medical management (NSAIDs) is unsuccessful or poorly tolerated, CT-guided radiofrequency ablation (RFA) is the minimally invasive treatment of choice.

Question 85

A 28-year-old female with rapidly progressive scoliosis and intrinsic hand muscle wasting undergoes whole-spine MRI.

The MRI shows a CSF-filled cavity within the spinal cord. What brain malformation is most frequently associated with this finding?

Explanation

Syringomyelia is a CSF-filled cavitation of the spinal cord, most commonly associated with an Arnold-Chiari type I malformation. The herniation of cerebellar tonsils through the foramen magnum alters normal CSF flow dynamics, leading to syrinx formation.

Question 86

A 50-year-old diabetic patient presents with a swollen, warm, and red foot without open ulcers. To differentiate an acute Eichenholtz Stage I Charcot arthropathy from acute osteomyelitis, which imaging modality is most specific?

Explanation

An Indium-111 labeled WBC scan (especially when combined with a Tc-99m bone marrow scan) is highly specific for differentiating osteomyelitis from acute Charcot arthropathy. Charcot arthropathy alone will typically not show focal accumulation of labeled WBCs.

Question 87

In a child with polyarticular JIA who requires a distal femoral extension osteotomy to correct a severe fixed knee flexion contracture, what is a primary concern if performed before skeletal maturity?

Explanation

Performing corrective osteotomies near open physes in children with JIA carries a notoriously high risk of iatrogenic physeal arrest. Surgeons often delay such procedures until skeletal maturity to prevent exacerbating limb length discrepancies.

Question 88

A 65-year-old woman presents with severe back pain. Radiographs reveal multiple punched-out lytic lesions in the skull and a compression fracture of L2. Laboratory workup shows hypercalcemia and a monoclonal spike. What is the most common primary bone malignancy in this age group?

Explanation

Multiple myeloma is the most common primary malignancy of bone overall, particularly in adults over the age of 50. While metastatic bone disease is generally more common, myeloma represents the most common primary tumor arising from the marrow.

Question 89

A 10-year-old boy presents with a left-sided thoracic scoliotic curve. Neurological examination reveals a loss of pain and temperature sensation over his bilateral shoulders and upper extremities with preserved light touch. Which of the following is the most appropriate next step in evaluation?

Explanation

Left-sided thoracic curves and dissociated sensory loss (cape-like distribution) are classic for syringomyelia. MRI of the neuroaxis is required to evaluate for a syrinx and Arnold-Chiari malformation.

Question 90

A 45-year-old male presents with painless swelling and severe crepitus in his right shoulder. He has a history of cervical syringomyelia. Radiographs show severe joint destruction, debris, and dislocation.

What is the primary pathophysiologic mechanism for this joint destruction?

Explanation

Neuropathic (Charcot) arthropathy in the upper extremity is classically associated with syringomyelia. Repetitive microtrauma secondary to loss of protective pain and proprioceptive sensation leads to severe joint destruction.

Question 91

A 14-year-old boy is diagnosed with conventional high-grade osteosarcoma of the distal femur. Genetic testing reveals a mutation in the TP53 gene. Which of the following syndromes is most closely associated with this patient's diagnosis?

Explanation

Li-Fraumeni syndrome is an autosomal dominant disorder caused by mutations in the TP53 tumor suppressor gene. It heavily predisposes patients to osteosarcoma, breast cancer, and soft tissue sarcomas.

Question 92

A 60-year-old male presents with deep thigh pain. Radiographs reveal a large, permeative lytic lesion with "popcorn" calcifications in the proximal femur. Biopsy confirms grade III conventional chondrosarcoma. What is the most appropriate management?

Explanation

Conventional chondrosarcomas are notoriously resistant to both chemotherapy and radiation. The mainstay of treatment for high-grade (Grade III) conventional chondrosarcoma is wide surgical resection alone.

Question 93

A 16-year-old female with polyarticular JIA is scheduled for a bilateral total hip arthroplasty. She is currently managed with methotrexate and etanercept. To minimize the risk of postoperative infection while preventing a severe disease flare, what is the best perioperative medication management strategy?

Explanation

Current ACR/AAHKS guidelines recommend continuing nonbiologic DMARDs like methotrexate perioperatively. Biologics (e.g., etanercept) should be withheld for one dosing cycle before surgery and resumed once the wound has healed.

Question 94

A 55-year-old diabetic patient presents with a swollen, warm, and erythematous left foot. Radiographs show osteopenia, bony fragmentation, and joint subluxation at the midfoot. According to the Eichenholtz classification, what is the current stage and most appropriate initial management?

Explanation

Eichenholtz Stage I (Developmental) is characterized by a warm, swollen extremity with radiographic fragmentation, subluxation, and debris. The gold standard initial treatment is immobilization and offloading, typically with a total contact cast.

Question 95

A 12-year-old girl presents with a destructive diaphyseal lesion of her tibia with an associated "onion-skin" periosteal reaction. A biopsy is performed, and molecular analysis demonstrates a t(11;22) chromosomal translocation. Which of the following fusion proteins is highly specific to this tumor?

Explanation

Ewing sarcoma is classically characterized by the t(11;22) translocation, resulting in the EWS-FLI1 fusion transcript. SYT-SSX is seen in synovial sarcoma, and TLS-CHOP in myxoid liposarcoma.

Question 96

An MRI of the cervical spine is performed on a 28-year-old female presenting with hand weakness and loss of temperature sensation. It demonstrates a large central intramedullary fluid collection extending from C2 to T1.

Which of the following cranial abnormalities is most commonly associated with this condition?

Explanation

Syringomyelia is heavily associated with Chiari I malformations. This involves the caudal herniation of the cerebellar tonsils through the foramen magnum, altering CSF dynamics and leading to syrinx formation.

Question 97

A 32-year-old woman presents with a large, lytic, epiphyseal-metaphyseal lesion of her distal radius. Biopsy confirms a Giant Cell Tumor of bone (GCTB). She is started on Denosumab prior to surgical intervention. What is the mechanism of action of this medication?

Explanation

Denosumab is a human monoclonal antibody that binds to RANKL, preventing it from activating RANK on the surface of osteoclasts. This inhibits the massive osteoclast-like giant cells characteristic of GCTB.

Question 98

A 25-year-old male with a history of long-standing systemic juvenile idiopathic arthritis (JIA) presents with worsening neck stiffness. Radiographs of the cervical spine are most likely to demonstrate which of the following classical findings?

Explanation

Cervical spine involvement in JIA typically presents with apophyseal (facet) joint ankylosis. This classically begins in the upper cervical spine (C2-C3) and progresses caudally, which severely restricts motion.

Question 99

The pathogenesis of neuropathic (Charcot) arthropathy is traditionally described by two main theories: the neurotraumatic theory and the neurovascular theory. Which of the following best describes the core tenet of the neurovascular theory?

Explanation

The neurovascular theory postulates that autonomic neuropathy leads to a loss of sympathetic tone, causing intense regional hyperemia. This increased blood flow stimulates active osteoclastic bone resorption, weakening the bone.

Question 100

A 15-year-old male is suspected of having an osteosarcoma of the proximal tibia. A core needle biopsy is planned. To adhere to standard orthopedic oncology principles and avoid compromising definitive limb-salvage surgery, which of the following is an absolute requirement for the biopsy tract?

Explanation

Biopsy tracts for suspected malignant bone tumors are considered contaminated with tumor cells. They must be placed longitudinally and strictly in line with the planned definitive surgical approach so the entire tract can be excised en bloc during resection.

Orthopaedic Surgery Board Exam Review: ABOS Part I & AAOS OITE Prep Questions | Part 22210

Orthopaedic Board Exam Review: JIA, Bone Tumors, Syringomyelia & Charcot Joints | Part 8

Key Takeaway

Orthopaedic Board Exam Review: JIA, Bone Tumors, Syringomyelia & Charcot Joints | Part 8

Chapter Index