1. General Principles & Basic Science MCQs

A newborn is evaluated for absent clavicles, open cranial sutures, and delayed fontanelle closure. This condition is associated with a mutation in a master transcription factor essential for osteoblast differentiation. Which of the following genes is most likely mutated?

A surgeon revises a failed stainless steel dynamic compression plate for a femur fracture by applying a titanium plate over the existing stainless steel screws. Several months later, rapid localized corrosion is noted at the screw-plate interfaces. Which of the following best explains this phenomenon?

Bone morphogenetic proteins (BMPs) are commonly used in spinal fusion surgery to promote osteoinduction. Following the binding of BMP to its cell surface receptor, which intracellular signaling molecules are directly phosphorylated to translocate to the nucleus and regulate gene transcription?

During the incorporation of a structural cortical bone allograft, the process involves concurrent osteoclastic resorption of the graft and osteoblastic bone formation. Which of the following best describes this biologic process?

Articular cartilage exhibits unique biomechanical properties to resist both compressive and tensile forces. Which component of the extracellular matrix is primarily responsible for the compressive stiffness of articular cartilage?

A 4-year-old boy presents with diffuse bone pain, gingival bleeding, and metaphyseal radiolucent bands on radiographs. The underlying nutritional deficiency impairs the function of an enzyme essential for collagen synthesis. Which step in collagen synthesis is primarily affected?

Intermittent administration of parathyroid hormone (PTH) analogues, such as teriparatide, is used to treat severe osteoporosis. What is the primary cellular mechanism by which intermittent PTH therapy increases bone mineral density?

Ligaments and tendons exhibit viscoelastic behavior, meaning their mechanical properties change depending on how quickly a force is applied. If a ligament is subjected to a rapid loading rate (high strain rate), how does its biomechanical response change compared to a slow loading rate?

The mechanical properties of cortical bone vary depending on the direction of the applied load. Cortical bone is strongest in compression along its longitudinal axis and weakest in tension transversally. This biomechanical characteristic is best termed:

According to Perren's strain theory, what level of tissue strain optimally promotes the formation of woven bone during secondary fracture healing?

In articular cartilage, which zone is characterized by the highest concentration of water and collagen fibers oriented parallel to the joint surface?

During skeletal muscle contraction, maximum isometric tension is generated at optimal resting length. This length corresponds physiologically to which of the following states?

On a load-elongation (stress-strain) curve of a normal ligament, what structural change is responsible for the initial "toe region"?

Combining a 316L stainless steel plate with a titanium alloy screw in a fracture construct is most likely to result in which type of corrosion?

A patient sustains a closed midshaft humerus fracture and presents with a radial nerve palsy. An EMG at 4 weeks shows fibrillation potentials in the brachioradialis, but an MRI demonstrates an intact epineurium. Which Seddon classification describes this injury?

Which of the following bone graft substitutes is considered exclusively osteoconductive and lacks both osteoinductive and osteogenic properties?

Rigid plate fixation of a transverse diaphyseal fracture leading to absolute stability primarily heals via which biological process?

During the early stages of osteoarthritis, which of the following enzymes is primarily responsible for the aggressive cleavage of Type II collagen in the extracellular matrix?

The pullout strength of a cortical screw is most directly proportional to which of the following geometric parameters?

In myelinated peripheral nerves, saltatory conduction occurs rapidly due to the high concentration of which specific ion channels at the Nodes of Ranvier?