1. General Principles & Basic Science MCQs

When comparing the biomechanical properties of cortical bone to cancellous bone on a stress-strain curve, which of the following statements is true?

According to Perren's strain theory, what is the maximum tissue strain allowable for primary (direct) bone healing to occur without the formation of a visible callus?

In cortical screw fixation, which of the following variables has the greatest direct influence on the pullout strength of the screw?

Bone Morphogenetic Proteins (BMPs) stimulate osteoblast differentiation and bone formation primarily by signaling through which of the following intracellular molecular pathways?

A surgeon removes a stainless steel plate that was previously placed adjacent to a titanium intramedullary nail. Significant corrosion is noted where the two metals were in contact. Which of the following principles best explains this phenomenon?

A new orthopedic implant is designed to minimize stress shielding in the adjacent host bone. To achieve this, the biomaterial should possess which of the following mechanical properties compared to traditional cobalt-chromium alloys?

On a load-deformation curve for a native human ligament, the initial "toe region" is characterized by low stiffness and high deformation with minimal applied force. This region corresponds physiologically to:

A pediatric patient treated with a dynamic orthosis experiences a progressive change in the shape of their limb over several weeks under a constant applied load. This biomechanical phenomenon is best described as:

Denosumab is used to treat osteoporosis and giant cell tumors of bone by inhibiting osteoclast maturation and activity. Which naturally occurring molecule does Denosumab mimic in its mechanism of action?

Cortical bone exhibits different mechanical properties depending on the direction of the applied load. For example, it is significantly stronger in longitudinal compression than in transverse tension. This fundamental material property is termed:

What strain environment, as described by Perren's strain theory, is required to dictate secondary bone healing via endochondral ossification?

A patient develops a painful mass over a plated clavicle fracture 2 years post-operatively. Surgery reveals black debris where a stainless steel screw was placed through a titanium plate. Which electrochemical process is primarily responsible?

During the remodeling phase of fracture healing, which enzyme is primarily responsible for creating the acidic microenvironment at the osteoclast ruffled border to dissolve bone mineral?

Which of the following molecules acts as a direct extracellular antagonist to the canonical Wnt signaling pathway, thereby inhibiting osteoblastogenesis and bone formation?

On a stress-strain curve, the total area under the curve before the point of material failure represents which mechanical property?

A patient with a tibia fracture is taking high-dose NSAIDs. This medication impairs fracture healing primarily by inhibiting the synthesis of which downstream mediator vital for endochondral ossification?

A bone graft incorporates through a slow process where osteoclasts resorb the donor bone and osteoblasts lay down new viable bone. This process, known as creeping substitution, is most characteristic of which graft type?

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

Fatigue failure of an orthopaedic implant is most likely to occur under which of the following conditions?