Basic Sciences of Orthopedics: Anatomy, Biomechanics, Pathology, Physiology
What you must understand
Candidates are expected to link structure to function: physeal and apophyseal anatomy, blood supply of the femoral head and scaphoid, nerve root myotomes and dermatomes, compartment pressures, and the biomechanics of levers, moments, and load transfer. Know the stress–strain curve (elastic region, yield point, ultimate strength, fatigue failure), viscoelasticity of tendon and cartilage, and the mechanostat principle governing bone remodeling. Understand fracture healing biology: hematoma and inflammatory phase, soft and hard callus, remodeling; primary versus secondary healing; and the effects of smoking, NSAIDs, and diabetes.
Traps in questions
- Confusing anatomic snuffbox contents with the blood supply of the scaphoid (retrograde, distal-to-proximal, hence proximal pole nonunion risk).
- Mixing up myotomes (C5 deltoid, C6 wrist extensors, C7 elbow extensors, C8 finger flexors, L4 tibialis anterior, L5 extensor hallucis longus, S1 gastrocnemius).
- Assuming cartilage heals like bone - it is avascular and has poor intrinsic repair.
- Forgetting that compartment syndrome can occur with open fractures and in the presence of palpable pulses.
Worked rule of thumb
For any nerve-injury question, localize by the first motor deficit and sensory level, then ask whether the lesion is pre- or post-ganglionic. A high radial nerve palsy spares the triceps if the lesion is at the spiral groove; a posterior interosseous nerve lesion spares wrist extension but loses finger and thumb extension.
Exam strategy
Anchor basic-science answers in clinical consequences - the examiner rewards the candidate who explains why the anatomy matters.