Fracture Healing
Definition and biological basis
Fracture healing is the restoration of continuity, mechanical strength and function of a broken bone by a coordinated biological process involving inflammation, cellular proliferation, angiogenesis, matrix formation, mineralisation and remodelling. Unlike soft tissues, bone can heal with restoration of near-normal architecture, although the final result depends upon stability, vascularity, fracture pattern, soft-tissue injury and the biological environment.
Healing is influenced by two interrelated requirements: biological competence, meaning viable osteogenic cells and adequate blood supply, and mechanical competence, meaning an appropriate strain environment at the fracture site. Excessive motion produces fibrous tissue or non-union, whereas controlled interfragmentary motion may stimulate callus formation. Excessive rigidity can suppress external callus but may permit direct healing when anatomical reduction and intimate stability are achieved.
Types of fracture healing
| Type | Essential conditions | Main features | Clinical implication |
|---|---|---|---|
| Secondary, indirect or callus healing | Relative stability with controlled interfragmentary movement | Haematoma, inflammation, soft callus, hard callus and remodelling; periosteal and endosteal callus are prominent | Typical of cast treatment, functional bracing and bridge plating |
| Primary, direct or osteonal healing | Absolute stability, minimal gap and usually anatomical reduction | Direct osteonal remodelling across the fracture; little or no external callus | Seen with compression… |