Fracture Healing

Fracture Healing is mineralisation of mesenchymal tissue or new bone formation by the process of regeneration and repair.

Fracture healing is majorly of two types-

  • Primary union

When fracture can not be treated conservatively, it requires surgical approximation by application of compression clamps or metal plates. Such fracture units without haematoma formation. These are early ambulatory but slow healing fractures.

Fig- Surgical repair by ORIF with plates and Screws
  • Secondary union

It is a common type of fracture which heals by immobilization in plaster cast or in operation that is done without disturbing fracture haematoma.

It occurs in continuous series of stages-

  1. Stage of haematoma
  2. Stage of granulation tissue
  3. Stage of callus formation
  4. Stages of remodelling (consolidation)
  5. Stage of modelling (remodelling)

1.Stage of haematoma-

Due to sharp fractured edges nearby vessels and soft tissues get torned resulting in localised accumulation of blood and formation of haematoma which later develops in a meshwork for granulation tissue. Due to ischemic necrosis few osteocytes die whereas few convert to precursor cells.

2. Stage of granulation tissue-

In this stage precursor cells differentiate to form fibroblasts, new vessels and osteoblasts etc and proliferation of mesenchymal cells from periosteum and endosteum.

Clots are removed by proliferation of macrophages, giant cells and other cells.

3. Stage of callus formation-

The granulation tissue further differentiates to form an osteoid matrix. This undergoes calcification to form a “woven bone callus” that bridges the gap between featured ends.

Woven bone is First sign of bone formation that is visible on x-ray.

4. Stage of remodeling-

Woven bone is replaced by osteoclast, new vessels and osteoblasts which form lamellar bone by developing the Harvesian system around vessels. The bone regains its strength.

5.Stage of modelling-

The bone regains its original shape. The major stimulus to this process comes from local bone strains i.e., weight bearing stresses and muscle forces when the person resumes activity. The process generally continues for life time.

Reference-

  • Harsh Mohan ( Textbook of pathology)
  • J. Maheshwari and Vikram A. Mhaskar ( Essential orthopaedics)