Question 1

A 45-year-old female with a history of scaly skin plaques presents with asymmetric oligoarthritis and dactylitis of her right hand. Radiographs demonstrate central erosions of the proximal phalanx with distal bone proliferation creating a "pencil-in-cup" appearance. Which joint is classically most affected in this condition?

Explanation

Psoriatic arthritis frequently involves the distal interphalangeal (DIP) joints, distinguishing it from rheumatoid arthritis which typically spares them. The classic "pencil-in-cup" deformity is due to concurrent periarticular bone erosion and new bone formation.

Question 2

A 52-year-old male with severe psoriatic arthritis on adalimumab (Humira) is scheduled for an elective total knee arthroplasty. According to current ACR/AAHKS guidelines, how should his biologic therapy be managed perioperatively?

Explanation

The ACR/AAHKS guidelines recommend withholding biologic agents for exactly one dosing cycle prior to elective arthroplasty to minimize infection risk. The medication can generally be resumed 14 days postoperatively once the surgical wound shows signs of appropriate healing.

Question 3

Which of the following radiographic findings is most characteristic of psoriatic arthritis as opposed to rheumatoid arthritis?

Explanation

Psoriatic arthritis is characterized by a combination of bone destruction (osteolysis) and new bone formation (periostitis, ankylosis). It characteristically lacks the profound periarticular osteopenia typically seen in rheumatoid arthritis.

Question 4

A patient with a long-standing history of psoriasis presents with severe, deforming joint destruction of the hands resulting in "telescoping" fingers. Which severe subtype of psoriatic arthritis does this clinical picture represent?

Explanation

Arthritis mutilans is a severe, destructive form of psoriatic arthritis causing extensive bone resorption (osteolysis). This severe shortening leads to redundant skin folds and the classic "telescoping" phenomenon of the digits.

Question 5

A 35-year-old male with known psoriatic arthritis develops severe, progressive axial spine pain and asymmetric sacroiliitis. Which human leukocyte antigen (HLA) is most strongly associated with this specific axial presentation?

Explanation

Spinal and sacroiliac involvement in psoriatic arthritis is strongly associated with the HLA-B27 genotype. In contrast, HLA-DR4 is typically associated with rheumatoid arthritis.

Question 6

A 40-year-old male complains of a chronic, painless, swollen right knee. MRI demonstrates a frond-like synovial mass.

What is the characteristic MRI finding that confirms this diagnosis?

Explanation

Lipoma arborescens consists of mature fat expanding the subsynovial tissue. Therefore, it follows the signal intensity of subcutaneous fat on all MRI sequences, displaying high signal on T1/T2 and suppressing on fat-saturated (STIR) images.

Question 7

Which histologic description best characterizes the lesion known as lipoma arborescens?

Explanation

Histologically, lipoma arborescens is identified by the massive replacement of subsynovial connective tissue by mature adipocytes. It presents as a villous or frond-like proliferation without cellular atypia or malignancy.

Question 8

A 38-year-old female presents with mechanical catching and recurrent effusions in her knee. Imaging and gross pathology are shown.

What is the definitive treatment for this symptomatic primary lesion?

Explanation

The treatment of choice for symptomatic lipoma arborescens is arthroscopic or open synovectomy. Recurrence after thorough surgical excision is exceptionally rare.

Question 9

When attempting to differentiate lipoma arborescens from pigmented villonodular synovitis (PVNS) on MRI, which feature is highly specific for PVNS?

Explanation

PVNS is characterized by hemosiderin deposition, which appears as low signal on T2-weighted images and causes "blooming" artifact on gradient-echo (GRE) sequences. Lipoma arborescens lacks hemosiderin and follows fat signal.

Question 10

Which of the following joint conditions is most commonly associated with the development of secondary lipoma arborescens?

Explanation

While lipoma arborescens can be primary, it is most often a secondary, reactive process resulting from chronic synovial irritation. It is most frequently associated with underlying degenerative joint disease (osteoarthritis) or prior trauma.

Question 11

An 8-year-old boy with Down syndrome presents with hyperreflexia, a new wide-based gait, and neck pain.

Dynamic flexion-extension radiographs reveal an atlanto-dens interval (ADI) of 11 mm. What is the most appropriate management?

Explanation

The patient has symptomatic atlantoaxial instability (AAI) with an ADI greater than 10 mm and myelopathic signs. The gold standard treatment is a posterior C1-C2 arthrodesis to stabilize the joint and decompress the spinal cord.

Question 12

A 45-year-old male with a history of psoriasis presents with asymmetric oligoarthritis and dactylitis. Radiographs of the hands reveal periarticular erosions and bone proliferation at the distal interphalangeal (DIP) joints. According to the CASPAR criteria, which of the following clinical findings is most specific to the diagnosis of Psoriatic Arthritis?

Explanation

Nail dystrophy, including pitting and onycholysis, is a hallmark of Psoriatic Arthritis (PsA) and a key component of the CASPAR criteria. Subcutaneous nodules and positive RF are characteristic of Rheumatoid Arthritis, not PsA.

Question 13

A 50-year-old female with severe psoriatic arthritis is scheduled for a total knee arthroplasty (TKA). She is currently managed with secukinumab. What is the mechanism of action of this biologic agent?

Explanation

Secukinumab is a human monoclonal antibody that selectively targets and inhibits Interleukin-17A (IL-17A), a key cytokine involved in the pathogenesis of psoriatic arthritis.

Question 14

A patient with advanced psoriatic arthritis presents with a 'telescoping' digit resulting from severe osteolysis of the phalanges. Which of the following terms correctly describes this classic deformity?

Explanation

Main en lorgnette, or opera-glass hand, is a consequence of arthritis mutilans in severe psoriatic arthritis. It is caused by severe osteolysis leading to a telescoping, flail digit.

Question 15

When comparing outcomes of total joint arthroplasty in patients with psoriatic arthritis to those with primary osteoarthritis, patients with psoriatic arthritis are at an increased risk for which of the following complications?

Explanation

Patients with psoriatic arthritis have a higher risk of periprosthetic joint infection following total joint arthroplasty compared to osteoarthritis patients. This is likely due to systemic immunosuppressive medications and skin flora colonizing psoriatic plaques.

Question 16

A 38-year-old male presents with characteristic 'pencil-in-cup' deformities on hand radiographs. Which pathophysiologic process best explains this radiographic appearance in psoriatic arthritis?

Explanation

The 'pencil-in-cup' deformity is formed by concurrent periarticular marginal erosions (osteolysis) and new bone proliferation at the entheses. This concurrent destruction and formation is classic for psoriatic arthritis.

Question 17

A 45-year-old male presents with chronic, painless, boggy swelling of the left knee. An MRI is obtained. Based on the likely diagnosis of Lipoma Arborescens, what is the classic MRI finding?

Explanation

Lipoma arborescens follows fat signal on all MRI sequences, showing high signal on T1 and T2, and complete signal loss on fat-suppressed (STIR or Fat-Sat) sequences. Blooming artifact would suggest Pigmented Villonodular Synovitis (PVNS).

Question 18

Which of the following histological descriptions is diagnostic for Lipoma Arborescens?

Explanation

Lipoma arborescens is characterized by a villous or frond-like proliferation of the synovium, where the subsynovial connective tissue is entirely replaced by mature adipocytes without atypia.

Question 19

Lipoma arborescens is most frequently associated with which of the following underlying conditions?

Explanation

While lipoma arborescens can be idiopathic, it is most commonly a reactive process associated with degenerative joint disease (osteoarthritis) or chronic mechanical irritation.

Question 20

A 52-year-old female diagnosed with Lipoma Arborescens of the suprapatellar pouch continues to have mechanical symptoms and massive effusions despite intra-articular corticosteroid injections. What is the recommended treatment?

Explanation

The treatment of choice for symptomatic lipoma arborescens that fails conservative management is arthroscopic or open synovectomy. This typically yields excellent results with a low recurrence rate.

Question 21

Which anatomic location is most commonly affected by Lipoma Arborescens?

Explanation

Lipoma arborescens predominantly affects the knee joint, with the suprapatellar pouch being the most frequent and characteristic site of involvement.

Question 22

A 7-year-old boy with Down syndrome presents for cervical spine screening. Radiographs demonstrate an atlanto-dens interval (ADI) of 6 mm and a Space Available for Cord (SAC) of 16 mm. He is neurologically intact. According to AAOS guidelines, what is the most appropriate management?

Explanation

In asymptomatic children with Down syndrome and an ADI of 5-9 mm (with SAC > 14 mm), the recommended management is restriction from high-risk or contact sports and regular monitoring. Surgical stabilization is indicated for ADI > 10 mm, SAC < 14 mm, or the presence of neurologic symptoms.

Question 23

What is the critical Space Available for the Cord (SAC) threshold at the C1-C2 level that signifies an absolute indication for surgical stabilization in a patient with Down syndrome, regardless of symptoms?

Explanation

A Space Available for the Cord (SAC) of less than 14 mm at the atlantoaxial junction represents a critical threshold for impending neurologic compromise and is an absolute indication for fusion.

Question 24

A 12-year-old girl with Down syndrome presents with habitual bilateral patellar dislocations. Which underlying anatomic abnormalities primarily drive patellofemoral instability in this population?

Explanation

Patellar instability in Down syndrome is extremely common and is driven by generalized ligamentous laxity combined with osseous dysplasia, most notably a flattened (hypoplastic) femoral trochlea.

Question 25

A newborn with Down syndrome undergoes a pelvic radiograph for hip screening. Which of the following classic radiographic findings is typically seen in the pelvis of infants with Trisomy 21?

Explanation

The classic pelvic radiographic appearance in Down syndrome includes flared iliac wings and flattened acetabular roofs, resulting in a decreased iliac index. This contrasts with developmental dysplasia of the hip (DDH), which shows an increased acetabular index.

Question 26

When performing an atlantoaxial fusion for severe instability in a patient with Down syndrome, what is the most commonly reported significant postoperative complication?

Explanation

Patients with Down syndrome have inherently poor bone quality, ligamentous laxity, and immunologic deficiencies, resulting in a significantly higher risk of pseudoarthrosis (nonunion) following cervical spine fusion compared to the general population.

Question 27

In an adolescent with idiopathic scoliosis, which of the following combinations of congenital vertebral anomalies carries the highest risk for rapid curve progression and often requires early surgical intervention?

Explanation

A unilateral unsegmented bar combined with a contralateral hemivertebra at the same level provides maximal asymmetric growth potential. This combination carries the highest risk of rapid curve progression in congenital scoliosis.

Question 28

A 13-year-old female is 5 days post-operative from a posterior spinal fusion for adolescent idiopathic scoliosis. She complains of postprandial bilious vomiting and epigastric pain. An upper GI series shows delayed gastric emptying and an abrupt cut-off of contrast in the duodenum. What anatomic structure is responsible for compressing the duodenum?

Explanation

This patient is presenting with Superior Mesenteric Artery (SMA) syndrome (Cast syndrome). Lengthening of the spine alters the aortomesenteric angle, causing the SMA to compress the third portion of the duodenum.

Question 29

According to the Lenke Classification system for Adolescent Idiopathic Scoliosis, what defines a structural proximal thoracic (PT) curve?

Explanation

In the Lenke classification, a minor curve is considered structural if it does not correct to less than 25 degrees on side-bending radiographs, or if there is a regional kyphosis of at least 20 degrees.

Question 30

A 14-year-old male with severe spastic cerebral palsy (GMFCS Level V) is undergoing posterior spinal fusion for a 75-degree neuromuscular scoliosis. He has a pelvic obliquity of 25 degrees. What is the primary functional indication for extending the fusion to the pelvis in this patient?

Explanation

In non-ambulatory patients with severe neuromuscular scoliosis and significant pelvic obliquity, extending the fusion to the pelvis (e.g., via iliac screws or Galveston technique) is critical to restoring a level pelvis, ensuring stable sitting balance, and preventing ischial pressure ulcers.

Question 31

Which of the following Sanders skeletal maturity stages correlates most closely with the peak height velocity (PHV) and the highest risk of curve progression in Adolescent Idiopathic Scoliosis?

Explanation

Sanders Stage 3 (adolescent rapid growth phase) correlates strongly with peak height velocity (PHV). This stage indicates the period of maximal skeletal growth and the highest risk for scoliosis curve progression.

Question 32

A 45-year-old female with a history of scaly plaques on her extensor surfaces presents with chronic hand pain. Radiographs demonstrate erosive changes at the distal interphalangeal (DIP) joints, characterized by proximal phalanx tapering and distal phalanx base expansion. Which of the following is the most likely diagnosis?

Explanation

The classic "pencil-in-cup" deformity at the DIP joints is highly characteristic of psoriatic arthritis. Rheumatoid arthritis typically spares the DIP joints and involves the MCP and PIP joints.

Question 33

A 52-year-old male with psoriatic arthritis is scheduled for a total hip arthroplasty. He is currently well-controlled on adalimumab (a TNF-alpha inhibitor). According to current ACR/AAHKS guidelines, what is the most appropriate perioperative management of his biologic medication?

Explanation

Current ACR/AAHKS guidelines recommend withholding biologic therapies, such as adalimumab, for one dosing cycle prior to elective arthroplasty to minimize infection risk. It can be restarted once the surgical wound is fully healed (typically 14 days).

Question 34

Which of the following clinical or radiographic features most reliably distinguishes psoriatic arthritis from rheumatoid arthritis?

Explanation

Psoriatic arthritis frequently causes dactylitis ("sausage digits") and primarily targets the DIP joints. In contrast, rheumatoid arthritis classically involves the MCP/PIP joints and features significant periarticular osteopenia without dactylitis.

Question 35

What is the primary early pathologic target of inflammation in psoriatic arthritis that leads to joint destruction, differentiating it from the primary target in rheumatoid arthritis?

Explanation

Psoriatic arthritis is a seronegative spondyloarthropathy characterized primarily by enthesitis (inflammation at tendon/ligament insertions). Rheumatoid arthritis is primarily driven by primary synovial inflammation (synovitis).

Question 36

Compared to patients with primary osteoarthritis, patients with psoriatic arthritis undergoing primary total knee arthroplasty have a significantly higher risk of which of the following postoperative complications?

Explanation

Patients with psoriatic arthritis have an elevated risk of periprosthetic joint infection following arthroplasty. This is attributed to compromised skin integrity (psoriatic plaques), systemic immune dysregulation, and the use of immunomodulatory medications.

Question 37

A 35-year-old male presents with chronic, painless swelling of the right knee. MRI demonstrates a frond-like mass in the suprapatellar pouch.

Which of the following MRI characteristics is pathognomonic for this condition?

Explanation

Lipoma arborescens is characterized by a frond-like synovial mass that follows fat signal on all MRI sequences. It appears hyperintense on T1 and T2 and suppresses completely on fat-saturated (STIR) images.

Question 38

Which of the following is the most definitive surgical management for symptomatic lipoma arborescens of the knee that has failed conservative treatment?

Explanation

The definitive treatment for symptomatic lipoma arborescens is an open or arthroscopic synovectomy. The condition is benign, and recurrence after adequate synovectomy is extremely rare.

Question 39

Histologic examination of a specimen retrieved from a patient with lipoma arborescens will classically demonstrate which of the following?

Explanation

Lipoma arborescens is not a true neoplasm but a reactive condition. Histology shows the replacement of the normal subsynovial stroma by mature adipocytes underlying a hypertrophic synovial lining.

Question 40

In which anatomic location is lipoma arborescens most frequently identified?

Explanation

Lipoma arborescens most commonly affects the knee, particularly the suprapatellar pouch. It frequently presents as a painless, chronic, and boggy effusion.

Question 41

Which of the following underlying conditions is most frequently associated with the development of secondary lipoma arborescens?

Explanation

While lipoma arborescens can be idiopathic, it is most commonly a secondary reactive process associated with underlying chronic synovial irritation, most notably degenerative joint disease (osteoarthritis) or prior trauma.

Question 42

An 8-year-old child with Down syndrome presents for clearance to participate in the Special Olympics.

They are completely asymptomatic. Flexion-extension cervical radiographs reveal an atlantodens interval (ADI) of 6 mm. What is the most appropriate next step in management?

Explanation

In Down syndrome, an ADI between 5 mm and 10 mm in an asymptomatic patient indicates atlantoaxial instability but does not require surgery. The standard of care is restriction from high-risk/collision sports and regular observation.

Question 43

The myriad of orthopedic manifestations seen in Down syndrome, including patellofemoral instability, pes planus, and hip subluxation, are primarily attributed to which underlying pathophysiology?

Explanation

The primary orthopedic issues in Down syndrome stem from generalized ligamentous laxity (due to an underlying collagen defect) combined with significant muscular hypotonia. This leads to joint hypermobility and instability.

Question 44

A 10-year-old male with Down syndrome presents with a 3-week history of a limp and poorly localized knee pain. Radiographs confirm a slipped capital femoral epiphysis (SCFE). Compared to an idiopathic SCFE in a neurotypical child, this patient is at an increased risk for which of the following?

Explanation

Patients with Down syndrome have a higher incidence of SCFE and a significantly higher rate of bilateral involvement compared to the idiopathic population. They often present younger and require careful evaluation of the contralateral hip.

Question 45

A child with Down syndrome presents with a characteristic hand anomaly.

What is the specific anatomic basis of the clinodactyly commonly observed in these patients?

Explanation

Clinodactyly in Down syndrome is classically caused by a hypoplastic and wedged (delta) middle phalanx of the fifth digit, causing radial deviation of the distal phalanx. It rarely causes functional impairment.

Question 46

An adult with Down syndrome presents with progressive clumsiness, hyperreflexia, and a positive Babinski sign. Cervical radiographs are obtained. Which radiographic measurement is the strongest indicator of neurologic compromise and risk of spinal cord compression?

Explanation

While an elevated ADI indicates instability, the Space Available for the Cord (SAC) is the most reliable predictor of neurologic deficit. A SAC of less than 14 mm correlates strongly with an increased risk of spinal cord compression.

Question 47

A 12-year-old female presents with a 32-degree right thoracic curve. She has not reached menarche. Radiographs demonstrate open triradiate cartilages and a Risser stage of 0. What is the most appropriate management?

Explanation

TLSO bracing is indicated for patients with Adolescent Idiopathic Scoliosis (AIS) who have a curve between 25 and 45 degrees and significant remaining growth (Risser 0-2, premenarchal, open triradiate cartilages).

Question 48

In a 9-month-old infant diagnosed with infantile idiopathic scoliosis, which of the following radiographic parameters is the most reliable predictor of curve progression requiring intervention?

Explanation

The Rib-Vertebral Angle Difference (RVAD), or Mehta's angle, is the most important prognostic factor in infantile scoliosis. An RVAD > 20 degrees strongly predicts curve progression and typically warrants serial Mehta casting.

Question 49

A 13-year-old boy presents for school scoliosis screening. Radiographs demonstrate a 38-degree left-sided thoracic scoliosis. His neurologic examination is entirely normal. What is the most appropriate next step in his evaluation?

Explanation

A left-sided thoracic curve in a patient with presumed adolescent idiopathic scoliosis is considered "atypical" and carries a high risk of an underlying neural axis abnormality, such as a syrinx or Arnold-Chiari malformation. An MRI of the entire spine is required.

Question 50

In a patient with Adolescent Idiopathic Scoliosis, which of the following clinical milestones corresponds with the period of greatest risk for rapid curve progression?

Explanation

The highest risk of curve progression in AIS occurs during the adolescent growth spurt, specifically at the time of peak height velocity. This typically occurs just prior to menarche and Risser 1, while triradiate cartilages are still open.

Question 51

During a posterior spinal fusion for a 55-degree thoracic scoliosis, the neuromonitoring technician reports a sudden, bilateral 60% decrease in amplitude and a 15% increase in latency of the somatosensory evoked potentials (SSEPs). Which of the following is the best initial step?

Explanation

A significant change in SSEPs (amplitude drop >50%, latency increase >10%) indicates potential spinal cord compromise. The initial response includes alerting the surgical team, raising MAP to maximize cord perfusion, assessing for anemia/blood loss, and reversing any recent corrective forces.

Question 52

A 45-year-old female with a history of scaly plaques on her extensor surfaces and nail pitting presents with hand pain. Radiographs demonstrate a "pencil-in-cup" deformity of the distal interphalangeal joints. Which of the following is the most likely diagnosis?

Explanation

Psoriatic arthritis often presents with asymmetric oligoarthritis, DIP joint involvement, and nail changes. The classic radiographic finding is the "pencil-in-cup" deformity due to periarticular erosions and bone resorption.

Question 53

A 45-year-old male presents with worsening pain and stiffness in his fingers. Exam shows nail pitting and dactylitis. Radiographs reveal osteolysis of the proximal phalanx with bony proliferation of the distal phalanx base. What is the most likely diagnosis?

Explanation

Psoriatic arthritis often presents with nail pitting, dactylitis, and involves the DIP joints. Radiographs characteristically show a "pencil-in-cup" deformity due to simultaneous periarticular erosion and bone proliferation.

Question 54

Which of the following immunogenetic markers is most strongly associated with the axial spine manifestations of psoriatic arthritis?

Explanation

Psoriatic arthritis is a seronegative spondyloarthropathy. Axial spine involvement is strongly associated with the HLA-B27 haplotype, similar to ankylosing spondylitis.

Question 55

A patient with severe psoriatic arthritis is started on secukinumab after failing methotrexate therapy. What is the precise mechanism of action of this biological medication?

Explanation

Secukinumab is a monoclonal antibody that specifically targets and inhibits interleukin-17A. IL-17A plays a key role in the pathogenesis of both psoriasis and psoriatic arthritis.

Question 56

When planning total knee arthroplasty for a patient with advanced psoriatic arthritis, the surgeon must counsel the patient on which of the following elevated post-operative risks compared to primary osteoarthritis?

Explanation

Patients with psoriatic arthritis undergoing total joint arthroplasty have an increased risk of post-operative stiffness and infection. Skin flora alterations and immunosuppressive medications contribute to the elevated infection risk.

Question 57

Which radiographic feature in the hand is characteristic of psoriatic arthritis and helps distinguish it from rheumatoid arthritis?

Explanation

Unlike rheumatoid arthritis, psoriatic arthritis typically features bone proliferation, periostitis, and enthesitis. Periarticular osteopenia is classically present in RA but absent in PsA.

Question 58

A 50-year-old male presents with a painless, slowly enlarging, boggy swelling of the left knee. MRI demonstrates a frond-like synovial mass with signal intensity identical to subcutaneous fat on all sequences.

What is the best initial definitive surgical treatment for a highly symptomatic patient?

Explanation

The clinical and MRI findings represent lipoma arborescens, characterized by villous lipomatous proliferation of the synovium. The definitive treatment for symptomatic cases is complete open or arthroscopic synovectomy.

Question 59

Lipoma arborescens is a rare, benign intra-articular lesion. Which of the following underlying joint conditions is most frequently associated with its development?

Explanation

Lipoma arborescens is generally considered a reactive process rather than a true neoplasm. It is most commonly associated with chronic joint irritation, particularly secondary to degenerative osteoarthritis.

Question 60

A 45-year-old woman presents with recurrent knee effusions. MRI reveals a villous, lipomatous synovial proliferation.

Which MRI sequence change will confirm the diagnosis of lipoma arborescens by extinguishing the high signal of the lesion?

Explanation

The lesion is composed of mature adipose tissue. Therefore, its signal will follow fat on all sequences and will suppress (appear dark) on fat-suppressed sequences like STIR or T1-fat sat.

Question 61

Histological examination of a specimen retrieved from a knee synovectomy in a patient with suspected lipoma arborescens will most likely demonstrate which of the following?

Explanation

Lipoma arborescens is characterized histologically by the diffuse replacement of the sub-synovial connective tissue with mature adipocytes forming villous projections. Hemosiderin deposition would indicate PVNS.

Question 62

What is the most common anatomical location for the development of lipoma arborescens?

Explanation

Lipoma arborescens most frequently affects the knee, specifically localizing to the suprapatellar pouch. It typically presents as a slow-growing, painless effusion.

Question 63

A 7-year-old child with Down syndrome presents for routine orthopedic evaluation.

Cervical spine flexion-extension radiographs are obtained. Which of the following radiographic measurements is the most reliable indicator of impending neurologic compromise and an absolute indication for posterior cervical fusion?

Explanation

In patients with Down syndrome, a Space Available for the Cord (SAC) of less than 14 mm is the most reliable predictor of neurologic risk. This finding warrants consideration of posterior C1-C2 fusion.

Question 64

A 10-year-old boy with Down syndrome presents with a 2-month history of a limp and poorly localized thigh pain. Exam reveals obligate external rotation of the hip during passive flexion. Which of the following is the most likely diagnosis?

Explanation

Children with Down syndrome are at increased risk for SCFE, frequently due to underlying endocrine issues (e.g., hypothyroidism). Obligate external rotation with hip flexion is the classic physical exam finding for SCFE.

Question 65

Which of the following lower extremity orthopedic conditions is most prevalent in the Down syndrome population due to underlying collagen defects and generalized ligamentous laxity?

Explanation

Generalized ligamentous laxity and hypotonia in Down syndrome frequently lead to patellofemoral instability. Recurrent subluxation or dislocation often requires surgical soft tissue realignment if symptomatic.

Question 66

According to the American Academy of Pediatrics (AAP), what is the current recommendation regarding routine cervical spine radiographic screening for asymptomatic children with Down syndrome prior to participation in sports?

Explanation

The AAP has retired its recommendation for routine cervical spine radiographic screening in asymptomatic children with Down syndrome. Emphasis is now placed on a thorough clinical history and targeted neurologic examination.

Question 67

A 12-year-old girl with Down syndrome presents with a 45-degree thoracic scoliotic curve.

Compared to adolescent idiopathic scoliosis (AIS), how does the management and prognosis of scoliosis in patients with Down syndrome typically differ?

Explanation

Scoliosis in Down syndrome has a higher incidence and progression rate than standard AIS. Furthermore, orthotic bracing is often poorly tolerated and less effective due to the patient's underlying hypotonia and body habitus.

Question 68

In a 13-year-old female with adolescent idiopathic scoliosis, which of the following combinations of factors represents the highest risk for curve progression?

Explanation

The risk of curve progression in AIS is highest in patients with significant skeletal immaturity (Risser 0, open triradiate cartilage, pre-menarchal) combined with a larger initial curve magnitude (>25 degrees).

Question 69

In the Lenke classification system for adolescent idiopathic scoliosis, a proximal thoracic curve is considered "structural" and must be included in the fusion construct if the curve bends out to what minimum Cobb angle on side-bending radiographs?

Explanation

According to the Lenke classification, minor curves are considered structural if they do not bend out to less than 25 degrees (i.e., remain ≥25 degrees) on side-bending radiographs, or if there is kyphosis ≥ +20 degrees.

Question 70

A 6-month-old infant is diagnosed with infantile idiopathic scoliosis. The rib-vertebral angle difference (RVAD) is calculated at the apical vertebra. An RVAD greater than what threshold suggests a high probability of curve progression?

Explanation

An RVAD (Mehta's angle) greater than 20 degrees in infantile scoliosis is highly predictive of a progressive curve. An RVAD less than 20 degrees typically indicates an resolving curve that may only require observation.

Question 71

When evaluating the spinal radiographic manifestations of a patient with psoriatic arthritis compared to ankylosing spondylitis, psoriatic arthritis is more characteristically associated with which of the following findings?

Explanation

Psoriatic arthritis often presents with bulky, asymmetric, non-marginal syndesmophytes (paramarginal ossification). This clearly distinguishes it from the thin, symmetric, marginal syndesmophytes typically seen in ankylosing spondylitis.

Question 72

A 55-year-old male with long-standing psoriatic arthritis is planning to undergo a total knee arthroplasty (TKA). Compared to a patient with primary osteoarthritis, this patient is at a significantly higher risk for which of the following postoperative complications?

Explanation

Patients with psoriatic arthritis have a higher risk of periprosthetic joint infection following TKA compared to osteoarthritis patients. This is attributed to skin colonization from psoriatic plaques, underlying immunosuppression from biologic therapies, and chronic systemic inflammation.

Question 73

A 42-year-old male presents with a chronic, slowly enlarging, painless knee effusion. An MRI is obtained.

Based on the most likely diagnosis, what is the definitive treatment of choice?

Explanation

The image demonstrates lipoma arborescens, characterized by frond-like fat accumulations in the synovium. The definitive and curative treatment is an open or arthroscopic synovectomy.

Question 74

A 7-year-old child with Down syndrome wishes to participate in the Special Olympics. Cervical spine flexion-extension radiographs reveal an anterior atlantodens interval (ADI) of 6 mm. The patient has no neurologic symptoms. What is the most appropriate management according to current guidelines?

Explanation

In children with Down syndrome, an ADI between 4.5 mm and 10 mm without neurologic symptoms indicates atlantoaxial instability requiring restriction from collision sports and gymnastics. Surgery is generally reserved for patients with an ADI >10 mm or those with neurologic deficits.

Question 75

A 2-year-old female is diagnosed with congenital scoliosis secondary to a fully segmented hemivertebra at T8. Which of the following is the most appropriate routine screening protocol to order upon making this diagnosis?

Explanation

Congenital scoliosis is frequently associated with other VACTERL anomalies. Up to 30% of patients have genitourinary anomalies and 10% have cardiac anomalies, making renal ultrasound and echocardiography mandatory screening tools.

Question 76

The pathophysiology of psoriatic arthritis distinguishes it from rheumatoid arthritis by the primary anatomic site of initial inflammation. Which of the following structures is the earliest and primary target of the inflammatory process in psoriatic arthritis?

Explanation

Unlike rheumatoid arthritis, which is primarily a synovitis, the primary inflammatory lesion in psoriatic arthritis and other spondyloarthropathies is enthesitis (inflammation at the site of tendon or ligament attachment to bone). This leads to characteristic bone proliferation and erosions.

Question 77

Which of the following histological findings is pathognomonic for lipoma arborescens?

Explanation

Lipoma arborescens is a rare, benign intra-articular lesion characterized histologically by the villous proliferation of the synovium and the replacement of the subsynovial connective tissue by mature fat cells.

Question 78

A 10-year-old boy with Down syndrome presents with a painless limp.

What is the primary underlying cause of recurrent hip instability and subluxation in this specific patient population?

Explanation

Hip instability in Down syndrome is relatively common and is primarily driven by generalized ligamentous laxity and muscular hypotonia, rather than a primary bony dysplastic event. Over time, this chronic subluxation can lead to secondary acetabular dysplasia.

Question 79

A 12-year-old female with Adolescent Idiopathic Scoliosis (AIS) presents with a right thoracic curve. Which of the following combinations of factors indicates the highest risk for curve progression?

Explanation

The risk of progression in AIS is highest during peak growth velocity. A curve of 25 degrees in a pre-menarchal patient with a Risser 0 score carries an approximately 68-100% risk of progression, according to Lonstein and Carlson criteria.

Question 80

A 50-year-old patient with long-standing psoriatic arthritis develops profound osteolysis of the phalanges, resulting in redundant overlying skin and telescoping digits (arthritis mutilans). What is the primary molecular driver of the massive bone resorption seen in this condition?

Explanation

Arthritis mutilans is a severe, destructive form of psoriatic arthritis. The profound osteolysis is driven by the marked upregulation of Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL), which massively stimulates osteoclast differentiation and activity.

Question 81

Lipoma arborescens is most frequently observed in which of the following anatomic locations?

Explanation

Lipoma arborescens predominantly affects the knee joint, specifically localizing most often in the suprapatellar pouch. It presents as a painless, boggy swelling of the joint.

Question 82

In evaluating a patient with Down syndrome for cervical spine instability, which radiographic measurement is the most reliable predictor of impending neurologic compromise?

Explanation

While the ADI is used for screening, the Space Available for the Cord (SAC), also known as the posterior atlantodens interval (PADI), is the most reliable predictor of neurologic risk. A SAC of less than 14 mm is a critical threshold for neurologic compromise.

Question 83

In a 65-year-old female undergoing spinal deformity correction for adult degenerative scoliosis, achieving which of the following spinopelvic parameters is most strongly correlated with favorable postoperative health-related quality of life (HRQOL) outcomes?

Explanation

In adult spinal deformity, sagittal balance is the primary driver of patient-reported outcomes. Restoring the lumbar lordosis to within 10 degrees of the patient's fixed pelvic incidence (PI-LL < 10 degrees) is critical for optimal clinical results.

Question 84

Which of the following physical examination findings in the hand is highly characteristic of psoriatic arthritis but is exceptionally rare in rheumatoid arthritis?

Explanation

Psoriatic arthritis classically involves the DIP joints and can present with dactylitis (sausage digits) and nail pitting. Rheumatoid arthritis typically spares the DIP joints and instead affects the MCP and PIP joints.

Question 85

A 50-year-old female has a chronically swollen knee. MRI is obtained.

Which specific MRI sequence characteristic most definitively establishes the diagnosis of lipoma arborescens?

Explanation

The defining MRI feature of lipoma arborescens is a villous, frond-like synovial mass that follows the signal intensity of subcutaneous fat on all sequences (high on T1/T2) and completely suppresses on fat-saturated sequences.

Question 86

A 14-year-old girl with Down syndrome presents with recurrent, habitual patellar dislocations. Nonoperative management has failed. Operative intervention in this population is challenging due to generalized ligamentous laxity. Which approach is most often required for successful stabilization?

Explanation

Patellofemoral instability in Down syndrome is multifactorial, involving generalized laxity, hypoplastic trochleas, and valgus alignment. Isolated soft tissue procedures have a high failure rate, usually necessitating combined bony (e.g., tibial tubercle transfer, distal femoral osteotomy) and soft-tissue reconstruction.

Question 87

A 14-year-old non-ambulatory male with spastic quadriplegic cerebral palsy presents with a 75-degree neuromuscular scoliosis. What is the primary indication for extending the posterior spinal fusion construct to the pelvis in this patient?

Explanation

In non-ambulatory patients with severe neuromuscular scoliosis, extending the fusion to the pelvis is primarily indicated to correct and maintain pelvic obliquity. This restores a level pelvis, preventing ischial pressure ulcers and improving sitting balance and head control.

Question 88

A 35-year-old male with psoriatic arthritis has predominantly axial disease (spondylitis and sacroiliitis) that has remained highly active despite maximum doses of NSAIDs. According to current treatment guidelines, what is the preferred next step in pharmacologic management?

Explanation

While traditional DMARDs like methotrexate are used for peripheral psoriatic arthritis, they are generally ineffective for axial disease. The standard next step for NSAID-refractory axial psoriatic arthritis is initiation of a biologic, typically a TNF inhibitor.

Question 89

While lipoma arborescens is generally considered a benign, slow-growing neoplastic condition, it is most frequently encountered in patients with a history of which of the following underlying joint pathologies?

Explanation

Lipoma arborescens can occur as a primary condition but is most commonly considered a reactive process secondary to chronic synovial irritation. It is most frequently associated with underlying degenerative joint disease (osteoarthritis) or prior joint trauma.

Question 90

A 4-year-old child with Down syndrome presents with severe, symptomatic, flexible pes planovalgus that causes frequent tripping. Which of the following is the most appropriate initial management?

Explanation

Symptomatic, flexible pes planovalgus in children with Down syndrome is initially managed non-operatively. Supramalleolar orthoses (SMOs) provide medial arch and hindfoot support, significantly improving postural stability and walking mechanics in these hypotonic patients.

Question 91

A 4-year-old boy presents with a 65-degree progressive early-onset scoliosis (EOS). He undergoes surgical treatment with distraction-based growth-friendly implants (growing rods). What is the most common long-term complication associated with this surgical strategy?

Explanation

Growing rods require repetitive lengthening, leading to a high cumulative risk of complications over time (the 'law of diminishing returns'). Implant-related complications, specifically rod breakage and anchor pull-out, are the most common adverse events encountered.

Question 92

A 6-year-old boy with Down syndrome presents for a routine orthopedic evaluation prior to participating in the Special Olympics. Lateral flexion-extension cervical radiographs are obtained.

At what Atlanto-Dens Interval (ADI) threshold is surgical stabilization typically recommended in an entirely asymptomatic child with Down syndrome?

Explanation

In Down syndrome, an ADI greater than 5 mm indicates atlantoaxial instability. However, prophylactic surgical fusion is generally recommended for asymptomatic patients only when the ADI approaches or exceeds 10 mm, or if the Space Available for the Cord (SAC) is less than 14 mm.

Question 93

A 45-year-old male presents with chronic, painless swelling of the right knee without prior trauma. A sagittal T1-weighted MRI is shown below.

Which of the following is the most definitive and appropriate treatment for this condition?

Explanation

The MRI demonstrates lipoma arborescens, characterized by a frond-like, villous proliferation of hyperplastic synovium replaced by mature fat, classically in the suprapatellar pouch. The definitive treatment for symptomatic patients is arthroscopic or open complete synovectomy.

Question 94

A 50-year-old male with a long-standing history of generalized psoriasis develops progressive foreshortening of his digits, resulting in a "telescoping" phenomenon. Which of the following cytokines is most directly responsible for driving the extensive osteoclastogenesis and bone resorption seen in this specific presentation?

Explanation

Arthritis mutilans is a severe form of psoriatic arthritis characterized by massive osteolysis and "telescoping" digits. This aggressive bone resorption is driven primarily by an immense upregulation of RANKL, which strongly stimulates osteoclastogenesis and bone destruction.

Question 95

A 4-year-old girl with Down syndrome presents with a painless limp.

Radiographs demonstrate bilateral hip subluxation with an increased acetabular index. Which of the following underlying pathophysiologic factors most significantly contributes to the high rate of joint instability in this population?

Explanation

Down syndrome (Trisomy 21) is strongly associated with generalized hypotonia and severe ligamentous capsular laxity. This inherent tissue laxity heavily contributes to characteristic orthopedic manifestations like hip dysplasia, patellar instability, and atlantoaxial instability.

Question 96

A 12-year-old female with Down syndrome presents with a progressive 55-degree thoracic scoliotic curve. If posterior spinal fusion is performed, which of the following postoperative complications is significantly more common in this patient population compared to age-matched patients with adolescent idiopathic scoliosis?

Explanation

Patients with Down syndrome undergoing spinal fusion for scoliosis have a significantly higher risk of complications compared to idiopathic cohorts. Postoperative surgical site infections and implant-related complications are markedly elevated, often attributed to altered cellular immunity and poor tissue healing.

Question 97

A 38-year-old female presents with a slowly enlarging, boggy right knee effusion. MRI reveals a large, villous synovial mass in the suprapatellar pouch.

To reliably differentiate lipoma arborescens from Pigmented Villonodular Synovitis (PVNS) on MRI, which of the following imaging characteristics is most uniquely diagnostic of lipoma arborescens?

Explanation

Lipoma arborescens consists of mature adipose tissue, so it follows fat signal on all sequences (high on T1/T2) and completely suppresses on fat-saturated images. In contrast, PVNS exhibits low signal on T1/T2 and distinct blooming artifact on GRE sequences due to hemosiderin deposition.

Question 98

A 55-year-old male with long-standing psoriatic arthritis is evaluated for progressive cervical neck pain. He is HLA-B27 positive. Which of the following cervical spine manifestations is most characteristic of his disease compared to classical Rheumatoid Arthritis?

Explanation

While cervical spine involvement in psoriatic arthritis can manifest with atlantoaxial instability similar to Rheumatoid Arthritis, it is distinguished by osteoproliferative changes. These include bulky anterior syndesmophytes, paravertebral ossification, and facet autofusion, reflecting its nature as a spondyloarthropathy.

Question 99

A 6-year-old boy with Down syndrome is diagnosed with a 35-degree right thoracic scoliosis. There is no evidence of atlantoaxial instability. Regarding the non-operative management of his spinal deformity, what is the expected efficacy of TLSO bracing?

Explanation

In patients with Down syndrome and other neuromuscular or syndromic conditions, conservative management with bracing is often poorly tolerated. Furthermore, it has a significantly higher failure rate in halting curve progression compared to adolescent idiopathic scoliosis, frequently necessitating surgical intervention.

Question 100

A 42-year-old female with severe psoriatic arthritis presents with incapacitating pain, instability, and a 40-degree flexion deformity of her dominant index finger distal interphalangeal (DIP) joint. Radiographs show a classic "pencil-in-cup" deformity. If surgery is planned, which of the following is the most reliable procedure?

Explanation

For advanced, symptomatic DIP joint destruction in psoriatic arthritis, such as a "pencil-in-cup" deformity, DIP joint arthrodesis is the gold standard treatment. It provides stable, pain-free pinch function and is typically positioned in 0 to 10 degrees of flexion for the index finger.

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

ABOS Orthopedic Board Review: Psoriatic Arthritis, Lipoma Arborescens, Down Syndrome, Scoliosis | Part 30

Key Takeaway

ABOS Orthopedic Board Review: Psoriatic Arthritis, Lipoma Arborescens, Down Syndrome, Scoliosis | Part 30

Chapter Index