A hip dislocation occurs when the head of the thighbone (femur)
slips out of its socket in the hip bone (pelvis). In approximately
90% of patients, the thighbone is pushed out of its socket in a
backwards direction (posterior dislocation). This leaves the hip in
a fixed position, bent and twisted in toward the middle of the body.
The thighbone can also slip out of its socket in a forward direction
(anterior dislocation). If this occurs, the hip will be bent only
slightly, and the leg will twist out and away from the middle of the
body.
A hip dislocation is very painful. Patients are unable to
move the leg and, if there is nerve damage, may not have any feeling
in the foot or ankle area.
The hip is a ball-and-socket joint: the ball-shaped head of the
femur fits inside a cup-shaped socket in the pelvis. The structure
of a ball-and-socket joint gives it a great deal of stability and
allows it to move freely. A great amount of force is required to pop
the thighbone out of its socket, but that's just what happens in a
hip dislocation.
Motor vehicle accidents are the most common cause of hip
dislocations. (Wearing a seatbelt can greatly reduce your risk.)
Falls from a height (such as a fall from a ladder) or industrial
accidents can also generate enough force to dislocate a hip.
With hip dislocations, there are often other injuries, including
fractures in the pelvis and legs, back injuries, or head injuries.
A hip dislocation is an orthopaedic emergency. Call for help
immediately. Do not try to move the injured person, but keep him or
her warm with blankets.
Usually, a physician can diagnose a hip dislocation simply by
looking at the position of the leg. X-rays will show whether there
are any additional fractures in the hip or thighbone.
If the patient has no other complications, the physician will
administer an anesthetic or a sedative and manipulate the bones back
into their proper position (this is called a reduction).
In some cases the reduction must be done in the operating room
with anesthesia. A formal procedure with an incision may be required
to reduce the hip.
Following treatment, the surgeon will request another set of
X-rays and possibly a computed tomography (CT) scan to make sure
that the bones are in the proper position.
It takes time- sometimes 2 to 3 months - for the hip to heal after a
dislocation. The rehabilitation time may be longer if there are
additional fractures. An orthopaedic surgeon may recommend traction
for a short period of time, followed by controlled exercises using a
continuous passive motion machine.
Patients can probably begin walking with crutches when free of
pain. A walking aid, such as a cane, should be used until the limp
disappears.
A hip dislocation can have long-term consequences, particularly
if there are associated fractures. As the thighbone is pushed out of
its socket, it can disrupt blood vessels and nerves. When blood
supply to the bone is lost, the bone can die, resulting in avascular
necrosis or osteonecrosis. The protective cartilage covering the
bone may also be damaged, which increases the risk of developing
arthritis in the joint.
