1. General Principles & Basic Science MCQs

Bone morphogenetic proteins (BMPs) play a critical role in osteoinduction and fracture healing.

Upon BMP binding to its serine/threonine kinase cell surface receptors, which downstream intracellular signaling molecules are directly phosphorylated to translocate to the nucleus?

A 38-year-old female sustains a coronal shear fracture of the capitellum and lateral trochlea. Operative fixation via an extensile lateral approach (Kocher interval) is planned.

During distal extension of this approach, the surgeon must be careful to protect which nerve within the substance of the supinator muscle?

Articular cartilage is functionally divided into multiple distinct structural zones. Which of the following accurately describes the composition of the deep zone of articular cartilage compared to the other zones?

A 26-year-old overhead athlete undergoes shoulder arthroscopy for chronic pain. A Type II Superior Labrum Anterior to Posterior (SLAP) tear is identified. The surgeon places a suture anchor at the 12 o'clock position on the superior glenoid rim. If the drill or anchor is placed too deeply and medially into the glenoid neck, which neurological structure is at greatest risk of injury?

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is utilized in orthopedic surgery for its potent osteoinductive properties. Upon binding to its specific transmembrane serine/threonine kinase receptors, rhBMP-2 induces bone formation via phosphorylation of which of the following intracellular signaling molecules?

You are reviewing basic science concepts regarding articular cartilage.

Which structural zone of articular cartilage contains the highest concentration of water and features collagen fibers oriented parallel to the articular surface to resist shear forces?

In orthopedic surgery, preoperative antibiotics are routinely administered. Which of the following prophylactic antibiotics functions primarily by inhibiting bacterial cell wall synthesis via binding to the D-alanyl-D-alanine termini of the peptidoglycan precursor?

Receptor Activator of Nuclear factor Kappa-B Ligand (RANKL) is critical for osteoclast differentiation, activation, and survival. Which cell type is the primary endogenous source of RANKL in the bone microenvironment?

A 35-year-old man is involved in a high-speed motor vehicle collision. Judet views demonstrate a both-column acetabular fracture. Based on the fracture characteristics, which of the following features most strongly indicates the need for an anterior ilioinguinal approach rather than a posterior Kocher-Langenbeck approach?

A 28-year-old carpenter sustains a laceration to the volar aspect of his index finger, resulting in a Zone II flexor digitorum profundus (FDP) transection. He undergoes an immediate primary 4-strand core repair with an epitendinous suture. During his postoperative rehabilitation, at what time point is the healing tendon repair biomechanically at its weakest?

Bone graft substitutes are frequently used in orthopedic surgery to augment fusion masses and treat osseous defects. Which of the following bone graft substitutes functions primarily as an osteoinductive agent rather than being purely osteoconductive?

A 30-year-old female presents with knee pain. Radiographs reveal an eccentric, lytic lesion in the distal femoral epiphysis without a sclerotic margin. Biopsy shows multinucleated giant cells in a background of mononuclear stromal cells. The patient is treated with Denosumab prior to curettage. What is the mechanism of action of this medication?

Articular cartilage relies on the precise biochemical composition and structural orientation of its extracellular matrix for compressive and tensile strength. Which histological zone of articular cartilage is characterized by the highest concentration of water and the lowest concentration of proteoglycans?

Absolute stability constructs (e.g., lag screws and compression plates) in fracture fixation bypass the formation of a soft callus. Which of the following cell types plays the leading role in the 'cutting cone' phase of this specific type of bone healing?

The remarkable ability of articular cartilage to resist compressive loads is primarily attributed to the osmotic swelling pressure created by which of the following molecular components?

A 35-year-old recreational boxer presents with pain over the third metacarpophalangeal (MCP) joint. On physical examination, when he makes a fist, the extensor digitorum communis (EDC) tendon visibly subluxates into the ulnar gutter.

Which stabilizing structure is most likely disrupted?

According to Perren's Strain Theory of bone healing, different tissues tolerate different amounts of interfragmentary strain before mechanical failure. Which of the following tissues can tolerate the highest percentage of strain?

A 28-year-old carpenter amputates his index finger with a table saw. The digit is recovered at the scene but is inadvertently kept at room temperature instead of being cooled. What is the maximum generally accepted warm ischemia time beyond which replantation of a digit is contraindicated?

A 19-year-old overhead athlete with multidirectional instability (MDI) of the shoulder has failed a 6-month trial of physical therapy. He undergoes an open inferior capsular shift procedure. During the release of the inferior capsule from the humeral neck, which neurological structure is at greatest risk of iatrogenic injury?