1. General Principles & Basic Science MCQs

When performing a direct anterior approach for total hip arthroplasty, the superficial internervous plane utilizes the interval between which two muscles?

A 32-year-old woman presents with knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion in the proximal tibia. Biopsy shows multinucleated giant cells in a background of mononuclear stromal cells. Denosumab therapy is considered for this patient. What is the mechanism of action of this drug?

A 10-year-old boy presents with a pathologic fracture through a central, lytic, expansile lesion in the proximal humerus metaphyseal-diaphyseal junction. A 'fallen leaf' sign is noted on the radiograph. If the lesion had been aspirated prior to fracture, the fluid obtained would typically show high levels of which of the following compared to serum?

A 25-year-old man presents with anterior tibial pain. Radiographs show a multilocular, eccentric, diaphyseal lytic lesion with cortical thickening. Histology reveals nests of epithelial-appearing cells in a fibrous stroma. Which immunohistochemical marker will best differentiate this lesion from osteofibrous dysplasia?

A 70-year-old man presents with anterior bowing of the tibia and progressive hearing loss. Labs show an elevated alkaline phosphatase with normal calcium and phosphorus. Biopsy of the tibia shows a mosaic pattern of lamellar bone. The primary cellular defect in this disease is located in which cell type?

A 30-year-old postpartum woman presents with a firm mass in her abdominal wall. Excisional biopsy reveals a poorly circumscribed proliferation of bland spindle cells surrounded by dense collagen, lacking significant pleomorphism or atypical mitoses. Which of the following signaling pathways is characteristically altered in this lesion?

A 25-year-old woman is evaluated for multiple bony deformities and soft tissue nodules. Imaging shows numerous enchondromas and multiple phleboliths in the soft tissues, indicative of hemangiomas. Which of the following mutations is most strongly associated with her underlying syndrome?

A 65-year-old female presents with generalized bone pain, fatigue, and weight loss. Radiographs demonstrate multiple "punched-out" lytic skull lesions. Laboratory workup reveals hypercalcemia and an elevated creatinine level. The profound bone destruction in this condition is primarily mediated by which cytokine profile in the bone marrow microenvironment?

A 70-year-old male presents with progressive hearing loss, increasing hat size, and anterolateral bowing of his tibiae. Serum alkaline phosphatase is markedly elevated, while calcium and phosphorus are normal. Familial forms of this highly active bone remodeling disorder are most strongly associated with mutations in which of the following genes?

A 12-year-old boy presents with multiple painless, bony protuberances around his knees and ankles pointing away from the joint. His father has similar lesions. The genetic mutation responsible for this condition directly causes a defect in which of the following cellular processes?

An 80-year-old man presents with increasing hat size and dull, aching pain in his right femur. Laboratory studies show markedly elevated serum alkaline phosphatase with normal calcium and phosphorus levels. Which of the following gene mutations is most strongly implicated in the familial form of this disease?

What antithrombotic agent is a selective factor Xa inhibitor?

What is the difference between annealed (below the melting temperature) and remelted highly crossedlinked polyethelyne?

A 72-year-old man with previous total hip arthroplasty developed hip pain of 1 month’s duration. He underwent dental work 6 weeks ago. Aspiration showed a white blood cell count of > 6000 cells/µL (reference range, 4500-11000/µL) and presence of gram-positive cocci in clusters on gram stain. The orthopaedic surgeon recommended urgent debridement and irrigation. The components were judged to be stable with regard to fixation, and the surgeon elected to retain the implants. The patient had a final culture that revealed methicillin-resistant Staphylococcus aureus (MRSA). If the attending physician recommended the 2-stage protocol including the use of an antibiotic-cement spacer, what is the most likely prognosis for this patient?

Viscosupplementation (hyaluronan) achieves what effect in treatment of osteoarthritis pain of the knee?

A 72-year-old man was scheduled for left total knee replacement. He has a history of hypertension and deep venous thrombosis (DVT) in his right lower extremity after an ankle fracture 2 years ago that was treated nonsurgically. The patient asked about the recommended types of DVT prophylaxis or investigations. Based on the 2011 AAOS Clinical Practice Guideline, Preventing Venous Thromboembolic Disease in Patients Undergoing Elective Hip and Knee Arthroplasty, what is an acceptable option?

A 72-year-old woman returns 3 weeks after a right total knee replacement. She has been experiencing increasing pain, swelling, and decreasing range of motion during the last 10 days. Examination shows the knee to be more swollen and warm than what is typical at 3 weeks after surgery. The knee feels stable, but she has diffuse tenderness and range of motion is between 15 and 85 degrees. What is the most appropriate investigation(s) to diagnose the etiology of her current problem?

These are the anteroposterior and lateral radiographs taken 8 months after revision of an aseptically loose acetabular component of an 81-year-old man who has mild cognitive impairment but is medically healthy. A 32-mm femoral head with metal-on-polyethylene was used at the time of revision. He has a history of numerous subluxation events and 2 dislocations requiring closed reduction since the cup revision. An abduction brace was prescribed after the first dislocation. The hip functions well apart from the episodes of instability. Erythrocyte sedimentation rate and C-reactive protein values are within defined limits. What is the most appropriate treatment for his recurrent instability?

The pharmacokinetics of which deep venous thrombosis (DVT) prophylactic agent are affected by liver function and dietary intake?

What infection-control measure has been shown to have the most notable impact in reducing surgical-site infections?