Bone and Fractures

6 Stages of Fractures Healing  

1. Fracture 

2. Hematoma  

3. Inflammation  

4. Fibrovascular (after primary heatoma) 

5. Bone Formation  

6. Remodelling  

Stage 1 Fracture

Increased nociceptor activity

Pain from free nerve endings

Healing starts with anabolic growth phase

Stage 2: Hematoma

Mass of usually blood clot within fracture space

Inflammatory response initiated

Forming template for matrixed callus clot formation

Stage 3: Inflammation

Secretion of proin-inflammatory molecules

Peaks within 24h, lasts 7 days

Promotes angiogenesis and vascular endothelial growth factor

Stage 4: Fibrovascular (soft callus formation)

Fibrin rich granulation, cartilaginous callus

mesenchymal stem cells recruited and proliferate into osteogenic cells

Stage 5: Bone formation (hard callus)

Revascularization through angiogenesis results in dynamic blood flow alterations

Cartilage replaced with woven bone, callus becomes more solid and rigid

Stage 6: Remodeling

Hard callus remodels into lamellar bone structure with central medullary

Granulated load re-introduction is crucial for effective remodeling

Common causes of Fractures

Trauma (falls, MVA, sports injuries) and diseases that result in weakened bone structure (osteoporosis)

Simplified Sequence of Fracture Healing

Clot Formation (0-5) Blood vessels are torn, leading to blood clotting and inflammation

Callus Formation (5-28) A soft callus replaces the blood clot (around 5-11 days), holding the bone together but lacking strength

Remodeling (day 18-months) The bony callus undergoes remodeling, restoring the normal bone structure

Direct Fracture Healing

Occurs when bony fragments are perfectly reduced, aligned, and fixed, under compression) with no motion at the fracture site. Can be achieved by ORIF under compression