1. General Principles & Basic Science MCQs

A 72-year-old female on chronic alendronate therapy presents with groin pain and sustains a low-energy subtrochanteric femur fracture. X-rays show a transverse fracture with lateral cortical thickening and a medial spike. What is the fundamental mechanism driving this specific fracture pattern?

A patient undergoing total hip arthroplasty has a history of heparin-induced thrombocytopenia (HIT). The surgeon elects to use a direct thrombin inhibitor for postoperative DVT prophylaxis. Which of the following medications fits this description?

Low-intensity pulsed ultrasound (LIPUS) is sometimes used to accelerate bone healing in delayed unions. By which cellular mechanism does LIPUS primarily stimulate osteogenesis?

In implant-related orthopedic infections, bacteria such as Staphylococcus epidermidis evade host immune responses and antibiotic penetration by producing a biofilm. What is the primary structural component of this biofilm matrix?

A 55-year-old male presents with acute knee swelling. A joint aspiration yields synovial fluid with a white blood cell count of 45,000 cells/mm3 (85% polymorphonuclear leukocytes). Polarized light microscopy reveals negatively birefringent, needle-shaped crystals. What is the primary biochemical defect associated with this condition?

Articular cartilage is highly resilient due to its specialized extracellular matrix. Which of the following represents the most abundant solid component of the articular cartilage matrix by dry weight?

Recombinant human parathyroid hormone (Teriparatide) is used for the treatment of severe osteoporosis. While continuous high levels of PTH cause bone resorption, how does intermittent daily administration of teriparatide primarily affect bone?

A 76-year-old female with osteoporosis suffers a T12 compression fracture. She has been treated conservatively with bracing, analgesics, and activity modification. Six weeks later, she still requires narcotic pain medication to ambulate. MRI is ordered to evaluate for percutaneous vertebroplasty. Which MRI sequence finding most strongly correlates with successful pain relief following vertebroplasty?

A 32-year-old female undergoes curettage and cementing of a giant cell tumor of the proximal tibia. Recurrence occurs 18 months later, with massive joint destruction precluding joint salvage. Neoadjuvant treatment is planned prior to an intra-articular resection. What is the mechanism of action of the targeted medical therapy typically used in this scenario?

A 68-year-old female presents with severe back pain. Radiographs show multiple 'punched-out' lytic lesions in the skull and vertebral bodies. Laboratory testing reveals hypercalcemia and an M-spike on serum protein electrophoresis. The extensive osteolysis in this disease is primarily mediated by the interaction between myeloma cells and the bone microenvironment. Which specific mechanism is responsible for osteoclast overactivation in this condition?

A 70-year-old male with a history of advanced prostate cancer presents with severe low back pain. Radiographs demonstrate widespread blastic metastases in the lumbar spine and pelvis. The osteoblastic nature of prostate cancer bone metastases is primarily driven by the secretion of which of the following factors by the tumor cells?

A patient with an unresectable sacral giant cell tumor of bone (GCTB) is treated with denosumab. Denosumab exerts its therapeutic effect in this condition by binding to which of the following?

A 65-year-old man presents with severe back pain and multiple lytic lesions in the axial skeleton on plain films. A technetium-99m bone scan shows no increased radiotracer uptake in these areas. What is the primary cellular mechanism driving bone destruction in this condition?

A 28-year-old male sustains a closed mid-shaft humeral fracture resulting in an immediate complete radial nerve palsy. He is treated non-operatively with a functional brace. At 12 weeks post-injury, the fracture shows early signs of union, but there is no clinical or electromyographic (EMG) evidence of radial nerve recovery. What is the most appropriate next step in management?

A 28-year-old male bodybuilder presents with severe pain and ecchymosis over his anterior axillary fold after bench pressing a heavy weight. Examination reveals loss of the anterior axillary fold contour and weakness in internal rotation. In this demographic, the most common site of a pectoralis major rupture occurs:

During a lateral deltoid-splitting approach for open reduction and internal fixation of a proximal humerus fracture, the surgeon must identify and protect the axillary nerve. At what average distance distal to the lateral edge of the acromion does the axillary nerve cross the humerus?

A patient presents with a brachial plexus injury resulting in Horner syndrome. Which root is most likely avulsed, and what is the prognosis for spontaneous recovery?

A 25-year-old male sustains a closed midshaft humeral fracture with an immediate radial nerve palsy. Closed reduction is performed, and post-reduction examination reveals a worsening of the radial nerve palsy. What is the most appropriate next step?