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Fracture healing and non-union
A fracture heals when the right biology (blood supply and cells) meets the right mechanics (suitable stability); hypertrophic non-union comes from instability and is treated by stabilisation, while atrophic non-union comes from poor biology and is treated by stabilisation plus bone graft.
Why it matters in the exam
Questions in this area present a fracture that has not healed after months and ask for the type and treatment, or for a risk factor. Healing passes through four stages: haematoma and inflammation, soft callus, hard callus and remodelling. There are two healing paths: primary healing without callus, with absolute stability and compression between the fragments (a compression plate in a simple or intra-articular fracture); and secondary healing through callus, with relative stability and some movement (cast, intramedullary nail, external fixator). Non-union is defined as a fracture that has not healed and shows no healing progress over several consecutive months, usually after 6–9 months from injury; delayed union is slower healing than expected that is still progressing. Risk factors: smoking, diabetes, malnutrition and vitamin D deficiency, open or high-energy fractures, infection, unsuitable fixation and damage to the blood supply. Areas with a marginal blood supply are especially prone to non-union: the scaphoid, the femoral neck, the distal tibia and the base of the fifth metatarsal (Jones fracture). Before any non-union surgery, infection must be excluded, because an infected non-union needs debridement before reconstruction. Another common question concerns malunion, in which the fracture has healed with angular or rotational deformity or shortening.
Key points
- Healing needs good biology and suitable stability.
- Primary healing with absolute stability; secondary through callus with relative stability.
- Hypertrophic — a stability problem; atrophic — a biology problem.
- Areas at risk: scaphoid, femoral neck, distal tibia and Jones fracture.
- Exclude infection and treat risk factors such as smoking.
Summary table
| Type | Radiographic appearance | Main cause | Treatment |
|---|---|---|---|
| Hypertrophic non-union | Abundant callus, elephant foot, open fracture line | Instability; biology is good | Stabilisation (for example nail or plate), no graft needed |
| Atrophic non-union | Thin, rounded ends, no callus | Poor biology, poor blood supply | Stabilisation, freshening of the ends and autologous bone graft |
| Oligotrophic non-union | Little callus | Displacement or poor contact between fragments | Improve contact and stability, sometimes graft |
| Infected non-union | Sometimes with dead bone and a sinus | Infection | Debridement, antibiotics, then reconstruction |
| Delayed union | Slow healing that is still progressing | General risk factors | Treat risk factors and observe |
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Sources
- Rockwood and Green's Fractures in Adults, 9th ed. (2019) — Bone and Cartilage Healing; Nonunions
- AO Principles of Fracture Management, 3rd ed. (2017) — Biology and Biomechanics of Fracture Healing
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.