SN3 SHORT NOTE 5M ★ High-yield

Describe the stages of fracture healing. Add a note on the factors affecting it and its complications.

Pathology · 2nd Professional — Para-Clinical

Definition

Fracture healing is the process by which a broken bone is restored, and is one of the few examples in the adult of true regeneration rather than repair by scar.

Stages

Stage	Timing	Events
1. Haematoma	Immediate to 48 hours	Blood from torn vessels clots between and around the fragments; provides a fibrin scaffold and a source of cytokines
2. Inflammation and granulation tissue	Days 2–7	Neutrophils then macrophages remove debris; capillaries and fibroblasts invade
3. Soft (provisional) callus	1–3 weeks	Fibrous tissue and cartilage bridge the gap; the fracture becomes "sticky" but is not yet strong; not visible on radiographs
4. Hard (bony) callus	3–6 weeks	Woven bone is laid down by endochondral and intramembranous ossification; callus is visible radiologically and clinical union occurs
5. Remodelling	Months to years	Woven bone is replaced by lamellar bone along lines of stress; the medullary cavity is restored; excess callus resorbed

CLINICAL PEARL

Bone is the one adult tissue that heals without a scar. Remodelling along Wolff's law — bone is laid down where it is needed and resorbed where it is not — can eventually make the healed site indistinguishable from the original. In a child the remodelling capacity is so great that considerable angulation corrects itself.

Primary and Secondary Bone Healing

Feature	Primary (direct)	Secondary (indirect)
Requires	Rigid internal fixation with the fragments in contact	Some movement; conservative treatment or flexible fixation
Callus	Absent or minimal	Abundant and visible
Mechanism	Osteons cross the fracture line directly (cutting cones)	Endochondral ossification through a cartilage intermediate
Speed	Slower to gain strength	Faster to gain bulk
Example	Compression plating	Plaster cast; intramedullary nail

Factors Affecting Fracture Healing

Local	Systemic
Inadequate immobilisation — the commonest cause of non-union	Age — children heal far faster
Infection	Nutrition — protein, calcium, vitamins C and D
Poor blood supply — scaphoid, neck of femur, talus	Corticosteroids; smoking; NSAIDs
Interposition of soft tissue between fragments	Diabetes; anaemia
Extensive comminution or bone loss	Osteoporosis; malignancy
Distraction of the fragments	Endocrine disease

Complications and Applied Aspects

Delayed union — healing takes longer than expected for the site
Non-union — healing has ceased; a false joint (pseudarthrosis) may form, and it requires bone grafting and stable fixation
Malunion — healing in a poor position, with deformity and altered function
Avascular necrosis — at sites where the blood supply enters distally: the proximal scaphoid, head of femur and talus
Fat embolism after fracture of a long bone; presents 24–72 hours later with dyspnoea, confusion and a petechial rash
Compartment syndrome — pain out of proportion and pain on passive stretch; requires urgent fasciotomy, and the pulse may still be present
Myositis ossificans — heterotopic bone in muscle after trauma, an example of metaplasia

All questions in Inflammation & Repair

Every Pathology chapter →