HOW FRACTURES ARE DISPLACED
After a complete fracture the fragments usually become displaced, partly by the force of the injury, partly by gravity and partly by
the pull of muscles attached to them.
Displacement is usually described in terms of translation,
angulation, rotation and altered length:
· Translation (shift) – The fragments may be shifted sideways, backward or forward in relation to each other, such that the fracture surfaces lose contact. The fracture will usually unite as long as sufficient contact between surfaces is achieved; this may occur even if
reduction is imperfect, or indeed even if the fracture ends are off-ended but the bone segments come to lie side by side.
·
Angulation
(tilt) – The fragments may be tilted or angulated in relation to each other.
Malalignment, if uncorrected, may lead to
deformity of the limb.
· Rotation (twist) – One of the fragments may be twisted on its
longitudinal axis; the bone looks straight but the limb ends up with a
rotational deformity.
· Length – The fragments may be
distracted and separated, or they may
overlap, due to
muscle spasm, causing shortening of the bone.
HOW FRACTURES HEAL
It is commonly supposed that, in order to unite, a fracture must be
immobilized. This cannot be so since, with few exceptions, fractures unite whether they are
splinted
or not; indeed, without a
built-in mechanism
for bone union, land animals could
scarcely
have evolved. It is, however,
naive
to suppose that union would occur if a fracture were kept moving
indefinitely;
the bone ends must, at some stage, be
brought to rest relative to one another.
But it is not
mandatory
for the surgeon to impose this
immobility artificially
– nature can do it with
callus, and callus forms in response to movement, not to
splintage.
Most fractures are splinted, not to ensure union but to: (1)
alleviate pain; (2) ensure that union
takes place
in good position and (3) permit early movement of the limb and a return of function.
The process of fracture repair varies according to the type of bone involved and the amount of movement at the fracture site.
---from
《Apley’s System of Orthopaedics and Fractures》P689-690
