1. General Principles & Basic Science MCQs

In the pathogenesis of periprosthetic joint infections, bacterial biofilm formation significantly complicates non-operative eradication. Which of the following mechanisms is the primary reason biofilm-associated bacteria are highly resistant to systemic beta-lactam antibiotics?

When applying an external fixator for a damage-control orthopedics approach, drilling through the diaphyseal cortical bone can generate significant heat, risking thermal necrosis and subsequent pin loosening or infection. To minimize peak intraosseous temperatures, which drilling parameters are most optimal?

A patient develops severe hypocalcemia following an inadvertent resection of the parathyroid glands during thyroidectomy. Normally, parathyroid hormone (PTH) regulates serum calcium by acting directly on bone and kidney. What is a primary direct action of PTH on the renal tubules?

The insertion site of a tendon or ligament into bone, known as an enthesis, typically consists of four distinct histological zones that transition mechanical stress. Which zone is immediately distal to the tidemark and provides a transitional gradient of stiffness?

Platelet-rich plasma (PRP) is extensively utilized in general orthopedics to theoretically enhance soft tissue healing. The alpha granules of platelets release numerous growth factors upon degranulation. Which of the following growth factors released from PRP is the primary molecular driver of angiogenesis?

Following a closed humerus fracture, a patient develops a complete radial nerve palsy. Electromyography (EMG) at 4 weeks shows fibrillations, but no voluntary motor unit action potentials. Pathologically, the injury involves complete disruption of the axon and myelin sheath, but the endoneurium, perineurium, and epineurium remain completely intact. According to the Seddon classification, what is this specific grade of nerve injury?

A 35-year-old male undergoes open reduction and internal fixation for a tibial shaft fracture. The surgeon utilizes a recombinant human bone morphogenetic protein (rhBMP-2) to augment healing. Which of the following best describes the intracellular signaling pathway directly activated by this biologic agent?

A surgeon uses a titanium alloy screw to secure a stainless steel plate in a fracture fixation. Over time, the implant site demonstrates significant corrosion and osteolysis. What specific type of corrosion is occurring due to the use of these two different metals?

A 30-year-old female is diagnosed with an unresectable giant cell tumor of the sacrum. She is started on denosumab therapy. What is the exact mechanism of action of this medication?

In the context of biomechanics of ligaments and tendons, which of the following terms describes the gradual increase in deformation of a viscoelastic material over time when subjected to a constant, sustained load?

A 28-year-old female presents with a destructive, eccentric, lytic lesion in the distal femur that extends to the subchondral bone. Biopsy confirms Giant Cell Tumor of bone. Medical management with denosumab is considered. What is the specific molecular mechanism of action of this medication?

According to Perren's strain theory, the type of bone healing that occurs depends on the mechanical environment at the fracture site. For absolute stability and primary (osteonal) bone healing to occur, the strain at the fracture gap must be maintained below what threshold?

Orthopedic implant infections are notoriously difficult to eradicate due to biofilm formation. Within a mature biofilm, bacteria coordinate their behavior, alter gene expression, and increase virulence based on local population density. What is the term for this cell-to-cell communication mechanism?

A 55-year-old female presents with diffuse bone pain and proximal muscle weakness. Laboratory evaluation reveals hypocalcemia, hypophosphatemia, elevated parathyroid hormone (PTH), and elevated alkaline phosphatase. Which of the following is the most likely diagnosis?

When comparing titanium alloy (Ti-6Al-4V) to 316L stainless steel for orthopedic implants, which of the following is a characteristic biomechanical property of titanium?

An infant presents with multiple fractures, hepatosplenomegaly, and cranial nerve palsies. Radiographs show a generalized "bone-in-bone" appearance. The primary cellular defect in this condition is characterized by a failure of which of the following processes?

A 65-year-old patient with a 15-year-old total hip arthroplasty presents with groin pain. Radiographs reveal extensive periprosthetic osteolysis. Which cytokine is primarily responsible for mediating osteoclast activation in response to polyethylene wear debris?

A 72-year-old male develops a chronic periprosthetic joint infection caused by Staphylococcus epidermidis. The pathogenesis of this infection relies heavily on bacterial adherence and biofilm formation. Which component is crucial for the initial irreversible attachment phase of this organism to the implant?