fracture healing mechanism

1. Fracture Healing

2. Terminology
Osteoblast – Osteocytes – forms
and destroys bone;
on-going remodeling
of bone

3. Osteoclasts – Intercambium
layer serves as a
foundation for blood
vessels and provides
a place for muscular
attachment

4. Exudate – fluid with a high protein
content and containing cellular debris
that comes from blood vessels and
accumulates in the are of injury.

5. Hematoma Formation (1st)
~ 4 days (acute inflammation)
Hematoma forms in medullary canal
and surrounding soft tissue in first 48-
72 hours

6. Hematoma Form. continues
Dead bone and
tissue =
inflammatory
reaction including
vasodilation, plasma
exudate, and
inflammatory cells

7. Cellular Formation Phase(2nd)
Acidic environment but
turning neutral

8. Cellular form. continued
Influx of endosteal cells from cambium
layer produce a fibrous callus
(environment has high oxygen tension)
then cartilage (has a low oxygen
tension environment) and

9. Callus Formation Phase (3rd)
Fibroblast deposit collagen in the
granulation tissue
Soft Callus is formed (Unorganized
network of woven bone);

10. Internal callus
(grows quickly to
create rigid
immobilization)

11. Callus Phase continued
The hard callus lasts 3-4 months.
Hard callus – a gradual connection of
bone filament to the woven bone (Acts
like a temporary splint)
Bone is beginning to strengthen and
immobilize
If proper immobilization does not occur;
cartilage will form instead of bone

12. Ossification Phase (4th)
will occur with adequate immobilization
Bone ends become crossed with a new
Haversian system that will eventually
lead to the laying down of primary bone

13. Fracture is bridged
and united

14. Remodeling Phase (5th)
Remodeling hard callus to compact
bone
May take a few years
Completed when the fractured bone has
been restored to its original form or
shape or when it can withstand the
imposed stresses placed on it

15. Conditions that interfere with
fracture healing
Poor blood supply to the fractured area;
could lead to avascular or aseptic
necrosis
Poor immobilization of fracture site may
cause misalignment or deformity
Infection – more common with open
fractures