Healing: How do fractures heal?
The process that occurs after injury
that restores continuity and function of the tissues. There is a gradual replacement of
the injured and necrotic tissue by living tissue which then differentiates into bone,
muscle, tendon etc. The process will be described in detail elsewhere. Basically there are
- Inflammation: The damage to the bone
and muscle, as well as the bleeding sets off an inflammatory reaction. The bleeding from
the injury stops when the blood coagulates forming a blood clot. The early clot stimulates
the growth of small capillary blood vessels from the surrounding normal tissue into the
damaged area. As the blood supply increases the area swells and hurts. The vessels bring
with them cells which lay down collagen fibres. (0-7 days)
- Soft Callus: The
volume which was originally blood clot and dead tissue is replaced by scar tissue,
collagen fibres laid down in a random fashion with a rich blood supply and nerve supply. Cartilage
tissue may develop in soft callus. The rubbery tissue is strong enough to
keep the bone fragments together as long as it isn't stressed too much.
(7 days to 6 weeks)
- Hard Callus: Some of
the cells in the soft callus differentiate into bone forming cells which
produce bone mineral. This is laid down in the scar tissue to stiffen it.
The result is "woven bone" bridging across from one fragment to
another. It is 80% as strong as normal bone. (6 to 12 weeks)
- Consolidation: The
woven bone is gradually remodelled into compact bone
around the circumference of the bone and a medullary cavity is reformed. As a result the
bone recovers almost all of its pre-injury strength. Remodelling is
stimulated by stressing the bone moderately. (3 months to 18 months)
From: Myles Clough
Why does it take so long?