Critical-sized bone defects: essential concepts for the higher orthopaedic examination

To provide a practical review of the assessment and management of critical-sized bone defects (CSDs) for candidates preparing for higher orthopaedic examinations.

This narrative review considers definitions and classification, clinical assessment, acute management, reconstructive techniques and salvage options.

A critical-sized bone defect (CSD) is unlikely to heal without intervention because of its size and location, although no numerical threshold defines criticality. Assessment should consider skeletal stability, infection, vascularity, soft tissues, host factors and likely function. After resuscitation, priorities include debridement, skeletal stabilisation and soft-tissue cover. Definitive bone loss should be assessed after debridement, which may require multiple operations. Reconstruction may be single-stage or staged. Options include bone grafting or acute shortening in selected cases, bone transport, the induced-membrane technique and vascularised bone transfer. Patient-specific implants show promise, but long-term evidence is limited. Planning should involve an orthoplastic team, with microbiology input if infection is suspected. Amputation should be considered if reconstruction is unlikely to yield a functional limb.

Successful management requires infection control, stable fixation and reliable soft-tissue cover. The reconstructive approach should reflect the defect and the patient's circumstances, balancing likely functional benefit against the burden of treatment.