BONE HEALING/FRACTURE HEALING:-
- Healing of the bone fracture & attaining its original architecture & strength- takes months to years to complete
- Three Major Phases:– I. Reactive Phase, II. Reparative Phase & III. Remodelling Phase
- I. Reactive Phase: 3 stages- 1) Haematoma formation- within hours; 2) Stage of Inflammation- within 48 hours; 3) Stage of Granulation tissue formation- 2 to 12 days.
- II. Reparative Phase: 4) Stage of Callus formation- Soft callus & Hard callus ( 1 wk to several months); 5) Lamellar bone deposition.
- III. Remodelling Phase: Remodelling to original bone contour- continues for several months to years.
- Factors affecting fracture healing:
- 1. FRACTURE MOVEMENT- Surgical stabilisation, Dynamisation, Distraction Histiogenesis(DO)
- 2. ANGIOGENESIS- Healthy soft tissue, Biological Fixation, Grafting Technique
- 3. BONE REGENERATION- Grafting technique, Cells, Growth Factors, Osteoconductive Agents
- BIOLOGY OF FRACTURE HEALING
(A) Unstable Fracture:- formation of an intermediate callus prior to bone formation (3 overlapping phases – Inflammation/Repair/Remodelling)—> Indirect/Secondary Bone healing.
Amount of callus formed depends upon stability of fracture & increases with greater instability
I) Healing under uncontrolled motion:-Bone formation only in a stable biochemical environment with an inter-fragmentary strain < 2%(INTER-FRAGMENTARY STRAIN THEORY OF PERREN).
Inter-fragmentary strain– defined as deformation occurring at the fracture site relative to the size of fracture-gap.
a)Inflammatory Phase:- Haematoma formation
>Resorption of fragmented ends —->Lower inter-fragmentary strain —->Minimize deformation of local tissue
b)Repair Phase:- When haematoma matures into connective tissue, interfragmentary strain decreases.
—>Granulation tissue >Conn. tissue formation —->Cartilage formation —->Cartilage mineralisation —->Woven bone formation
Outcome of facture-healing: i)Compromise Vascularity + Excessive Instability
—->Fibrous tissue formation —>Atrophic Non-union
ii) Adequate Vascularity + High Inter-fragmentary Motion
—>Cartilaginous callus —>Hypertrophic Non-union/Pseudoarthrosis
iii) Stable fracture + Adequate Vascularity
—–>Mineralised Callus Formation
II) Healing under Restricted motion:- intermediate between biological immobilisation by a callus formed in spontaneous healing & callus-free repair formed after absolute stabilisation;
-depends upon use of type of Plate, I/M nailing, External fixator etc.
(B) Stable Fracture:
> PRIMARY HEALING:-direct filling of fracture-site with bone, without formation of mechanically relevant periosteal/endosteal callus(No callus),No resorption of fracture ends; e.g. Rigid nongliding implants like Compression Plate, Lag Screws etc.
Two types of Primary healing:- a) CONTACT HEALING– When defect ≤0.01mm & Inter-fragmentary strain <2%
>Primary Osteonal Reconstruction by CUTTING CONE FORMATION (1st Osteoclasts, then Osteoblasts & Angiogenesis + Remodelling) >cutting cones progress @ 50-100µm/day
– In contact healing, bone union & remodelling occurs simultaneously.
b) GAP HEALING– Gaps <800µm-1mm; Strain <2%
–Sequential bony union & remodelling
-Fracture sites fill directly by INTRAMEMBRANOUS BONE FORMATION; the newly formed lamellar bone is perpendicular to the long bone axis
BIOLOGICAL STIMULATION OF FRACTURE HEALING- Bone grafts & substitutes; Growth factors; BMPs etc
BIOPHYSICAL STIMULATION OF FRACTURE HEALING-
~LIPUS(low intensity pulsed ultrasound)
~PEMF(pulsed electromagnetic field)
~LPDC(low power direct current)
~ECSWS(extracorporeal shockwave stimulation)
~LIHFV(low intensity high frequency vibration)
CHAO-Classification of Bone union mechanism:
3.Oppositional New Bone Formation
4.Osteonal Migration (Creeping Substitution)