1086
U N I T 1 2
Musculoskeletal Function
U N D E R S T A N D I N G
Fracture Healing
A fracture, which is any break in a bone, undergoes a healing process to reestablish
bone continuity and strength.The repair of simple fractures is commonly divided
into four phases: (1) hematoma formation, (2) fibrocartilaginous callus formation,
(3) bony callus formation, and (4) remodeling.
Hematoma
Medullary
cavity
Compact
bone
Fibrin
meshwork
Capillary
buds
Blood
clot
Hematoma Formation.
When
a bone breaks, blood vessels in the
bone and surrounding tissues are
torn and bleed into and around the
fragments of the fractured bone,
forming a blood clot, or hematoma.
The hematoma facilitates the for-
mation of the fibrin meshwork that
seals off the fracture site and serves
as a framework for the influx of
inflammatory cells, the ingrowth
of fibroblasts, and the development
of new capillary buds (vessels).
It is also the source of signaling
molecules that initiate the cellular
events that are critical to the healing
process.
1
Fibrocartilaginous
Callus
Formation.
As new capillaries
infiltrate the hematoma at the frac-
ture site, it becomes organized into
a form of granulation tissue, called
procallus
. Fibroblasts from the peri-
osteum, endosteum, and red bone
marrow proliferate and invade the
procallus. The fibroblasts produce a
fibrocartilaginous soft callus bridge
that connects the bone fragments.
Although this repair tissue usually
reaches its maximum girth at the
end of the 2nd or 3rd week, it is not
strong enough for weight bearing.
2
New blood
vessels
Fibrocartilaginous
callus
Fibroblasts
Collagen
Dead bone
