1. General Principles & Basic Science MCQs

Primary (direct) bone healing circumvents the formation of a provisional cartilaginous callus.

Which of the following mechanical conditions is an absolute requirement for contact healing to occur across a fracture site?

At a direct ligament or tendon insertion site (enthesis) into bone, the tissue transitions through four distinct histological zones. The transition from unmineralized fibrocartilage to mineralized fibrocartilage is demarcated by which of the following structures?

Galvanic corrosion can occur when two dissimilar metals are placed in physical contact within the electrolytic environment of the human body. If a 316L stainless steel screw is placed into a Ti-6Al-4V titanium plate, which of the following reactions is most likely to occur?

Bone morphogenetic proteins (BMPs) are potent osteoinductive factors utilized in orthopedic surgery to stimulate bone formation. The intracellular signaling cascade triggered by BMP binding to its cell-surface serine/threonine kinase receptor is primarily mediated by which of the following molecules?

Osteoinductive bone grafts such as demineralized bone matrix (DBM) rely on Bone Morphogenetic Proteins (BMPs) to stimulate bone formation. BMP-2 initiates intracellular signaling by directly binding to which of the following types of receptors on osteoprogenitor cells?

Articular cartilage relies on specific mechanisms for lubrication depending on the applied load and sliding speed. Under high-load, low-speed conditions, boundary lubrication is primarily mediated by which of the following molecules synthesized by superficial zone chondrocytes?

According to Perren's strain theory, the mechanical environment at a fracture site dictates the mode of biological healing. What is the maximum interfragmentary strain threshold that allows for primary bone healing (direct lamellar bone formation) without an intermediate fibrocartilage callus?

A patient sustains a closed midshaft humerus fracture and immediately develops a complete radial nerve palsy. The surgeon elects for nonoperative management and orders an electromyogram (EMG). At what minimum time point after the injury will fibrillation potentials characteristic of axonal denervation first be reliably detected?

Continuous systemic administration of parathyroid hormone (PTH) leads to net bone resorption, a process requiring osteoclast activation. However, osteoclasts lack receptors for PTH. The catabolic effect of PTH is mediated primarily through its direct binding to receptors on which of the following cell types?

A surgeon plans to use a titanium locking plate with 316L stainless steel screws to fix a complex periarticular fracture. This combination is generally avoided due to the risk of galvanic corrosion. In this mixed-metal construct, which of the following accurately describes the electrochemical reaction?

Understanding joint reaction forces is critical for orthopedic implant design. During a normal gait cycle, the peak joint reaction force across the hip occurs during which phase, and is approximately what multiple of body weight?

A surgeon reams the femoral medullary canal to insert a larger diameter solid intramedullary nail. If the radius of the selected solid titanium nail is increased by a factor of 2, the theoretical torsional rigidity (polar moment of inertia) of the nail increases by a factor of:

When preparing antibiotic-loaded polymethylmethacrylate (PMMA) bone cement for an articulating spacer in a two-stage revision for periprosthetic joint infection, which of the following antibiotic properties is most critical for ensuring its effective local elution?

During post-operative rehabilitation following an Achilles tendon repair, the physical therapist applies different types of muscle contractions to safely load the musculotendinous unit. Which of the following types of muscle contraction physiologically generates the highest maximal force?

During in vitro tensile testing of an intact anterior cruciate ligament (ACL), the initial portion of the stress-strain curve is non-linear and exhibits high compliance, a region known as the "toe region". This biomechanical behavior is primarily due to which of the following microstructural phenomena?

Sclerostin regulates bone mass by inhibiting osteoblastogenesis and bone formation. This molecule exerts its primary effect by blocking which of the following intracellular signaling pathways?

According to the principles of orthopedic screw biomechanics, which of the following variables has the most significant mathematical influence on the pull-out strength of a cortical screw?

A surgeon plans to use a 316L stainless steel plate for a femur fracture but only has titanium screws available. Which type of corrosion is most likely to occur at the screw-plate interface?