Basic Science
Core concepts
Basic science underpins every clinical answer. Master bone biology: osteoblast/osteoclast coupling, RANK-RANKL-OPG signaling, and the phases of fracture healing (inflammatory, reparative, remodeling). Understand biomechanics: moment arms, bending vs torsional stiffness, the neutral axis, and how implant modulus mismatch causes stress shielding. Know the structure and healing of tendon, ligament, and cartilage, including the limited intrinsic healing of articular cartilage and the role of the tidemark. Study biomaterials: titanium vs cobalt-chrome vs polyethylene wear, corrosion, and the host response to particulate debris. Microbiology matters: biofilm formation, the rationale for antibiotic-loaded cement, and the mechanisms of resistance. Also review statistics for exam questions: sensitivity, specificity, positive predictive value, and study design (Level I evidence, RCTs, cohort studies).
Traps
Examiners test the difference between sensitivity and PPV (PPV depends on prevalence). They also probe whether you understand that stress shielding is a modulus mismatch phenomenon, not simply a size issue, and that cartilage has essentially no intrinsic repair capacity once the tidemark is breached.
Rule of thumb
When an implant is much stiffer than bone, expect stress shielding; when wear debris is present, expect an inflammatory osteolytic response mediated by macrophages and cytokines.
Worked example
A question asks which factor most increases PPV of a diagnostic test: the answer is higher disease prevalence in the population tested, not higher sensitivity alone.