Originally published by Harvard Health.
What Is It?
In a normal hip joint, the rounded top of the thigh bone (femur) fits into a cup-shaped socket in the pelvis called the acetabulum. This type of joint is called a ball-and-socket joint. When the top of the femur moves out of its normal position in the socket, the hip is said to be disclocated.
A hip can become dislocated during many kinds of accidents, including falls from high places and motorcycle or car accidents. When this injury occurs in a head-on car crash, it is often nicknamed a “dashboard dislocation,” because it happens when the knee strikes the dashboard.
A traumatic hip dislocation is a medical emergency and needs to be treated immediately, ideally within 6 hours. That is because the injury stops blood from reaching the top of the femur, depriving the bone of its vital oxygen supply. Unless the dislocated hip is replaced in its socket promptly and normal circulation is restored within the hip joint, the top part of the femur can be permanently damaged. This permanent damage is called avascular necrosis.
Because traumatic hip dislocations often occur during serious high-impact accidents, up to 50% of patients also have a fractured bone in some part of the body, particularly in the upper part of the femur.
In an accident victim, a traumatic hip dislocation can cause the following symptoms:
- There is severe hip pain, especially when the leg is moved.
- The injured leg is shorter than the uninjured leg.
- The injured leg lies in an abnormal position. In most cases, the leg is bent at the hip, turned inward and pulled toward the middle of the body.
Doctors usually diagnose a traumatic hip dislocation by examining the hip joint. X-rays will be done to confirm the diagnosis, to see where the head of the femur is located and to check for fractures in the hip area. In some cases, a computed tomography (CT) or magnetic resonance imaging (MRI) scan may be helpful to provide additional details about the nature of the injury and to help determine the best treatment.
The hip will improve after initial treatment, and pain should subside. It is common, however, for a person to require crutches for a short time after treatment and to have a limp that continues for weeks. Complete healing of the hip and surrounding tissue can take two or three months. Your doctor may prescribe a strengthening program to strengthen muscles and ligaments around the hip and reduce the chance that the hip will become dislocated again.
A person with significant pain after a hip dislocation may have developed the complication avascular necrosis from injury to the hip’s blood supply. Avascular necrosis may require surgery and can make the recovery period much longer.
Wear a seat belt while driving or riding in a car, and take advantage of recommended safety equipment at work or during recreation.
If you have a traumatic hip dislocation, and there is no X-ray evidence of a fractured femur, the doctor probably will treat the dislocation in the emergency room without surgery. To accomplish this, the doctor will give you medications to ease your pain and relax your hip muscles. Once your hip muscles are relaxed, the doctor will move the head of your femur back into its socket. X-rays will confirm that its position is correct.
If you have a fractured femur in addition to your hip dislocation, your doctor will correct both injuries surgically.
When To Call a Professional
Call your doctor immediately if you cannot move your hip joint after a fall or other traumatic injury or if your affected hip is painful, swollen, tender or deformed.
Although the outlook depends on many factors, the timing of treatment is particularly important. For example, one study showed that 88% of patients had good or excellent results if a dislocated hip was restored to its normal position in its socket within 6 hours after injury. After 6 hours, the risk of permanent damage increased significantly, and it was highest when treatment was delayed for 24 hours or more.
About 20% of people who do not develop avascular necrosis eventually suffer from early arthritis in the affected hip.
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