Trauma & Orthopaedics

The ankle mortise is a ring of bone and ligament around the talus, so a fracture is only unstable if the ring has failed in more than one place, the principle underlying both the Weber classification and the Ottawa ankle rules.

Compression of the lumbosacral nerve roots below the spinal cord causes bilateral sciatica, saddle anaesthesia and bladder or bowel dysfunction together, because they share one anatomical compartment, and this is a time-critical surgical emergency.

Rising pressure within a closed fascial compartment collapses capillary perfusion long before it occludes major arteries, causing muscle and nerve ischaemia while pulses are still present, and demanding emergency fasciotomy.

The fracture line's relationship to the hip capsule decides whether the femoral head's blood supply survives, which in turn decides whether the head is fixed in place or replaced.

A fall onto an outstretched hand fractures the scaphoid across its waist, where retrograde blood supply makes the proximal fragment vulnerable to avascular necrosis and non-union, so clinical suspicion alone mandates immobilisation and repeat imaging.

The glenohumeral joint sacrifices bony stability for range of movement, so it dislocates more often than any other joint, typically anteriorly after a fall onto an abducted, externally rotated arm, putting the axillary nerve at risk.