Hip > Hip Dislocation

What is a Hip Dislocation?

A hip dislocation is a severe injury in which the upper, ball–shaped portion (head) of the thighbone (femur) is completely displaced from the rounded socket (acetabulum) portion of the outer pelvis where the head is normally located within the acetabulum. In some cases, the head only partially displaces from the acetabulum (subluxation) and returns to its normal location within the acetabulum (reduction). There are three major types of hip dislocations:

   Posterior hip dislocations: The femoral head is forced out of the acetabulum and rests behind the acetabulum. This is the most common type of hip dislocation. A posterior hip dislocation can damage the sciatic nerve, which is a major nerve of the lower extremity located just behind the hip joint, and is often associated with fractures of the posterior lip of the acetabulum.

   Anterior hip dislocations: The femoral head is forced out of the acetabulum and rests in front of the acetabulum. An anterior hip dislocation can cause damage to neurovascular structures in front of the acetabulum.

   Central fracture–dislocations: In some types of fractures of the acetabulum, the femoral head displaces past the confines of the pelvis into the lower abdomen. This injury can also result in damage to neurovascular structures and requires special techniques and implants to fix operatively.

Hip dislocations are an orthopedic emergency. If you suspect you have suffered a hip dislocation, an ambulance should be called immediately.

Hip dislocations are usually the result of high-energy trauma, such as automobile and motorcycle accidents and falls, in which a hard, direct blow is delivered to the knee or hip. Athletes who take part in contact sports, such as football, rugby, or hockey, are also at risk. Children under six years of age, whose bones are not fully formed, can be susceptible to hip dislocations from less severe trauma, such as falling while walking or doing splits.

Several other serious injuries can be associated with, or develop as a consequence of, a hip dislocation, despite appropriate care. These include:

   Injury to the sciatic and femoral nerves in the leg

   Fractures of the acetabulum, femoral head, and upper portion of the femur

   Blockage of the femoral artery and vein, known as vascular thrombosis

   Torn muscles, ligaments, and soft–tissue structures of the hip and thigh

   Damage to the joint surfaces of the hip

   Osteonecrosis (also called avascular necrosis), a deficiency of the blood supply to the femoral head that causes the bone to die and collapse

   Post–traumatic arthritis. This would depend on numerous factors, such as the amount of damage to the cartilage of the joint surface at the time of injury, the presence of fractures of the femoral head or acetabulum, and, potentially, the length of time before the hip is reduced.

There are usually three parts to an orthopedic evaluation: medical history, physical examination, and tests your physician may order.

To help achieve an accurate diagnosis, your physician will ask you to describe your present problem, as well as the location, severity, and duration of your symptoms. You will be asked when and how your symptoms began, what aggravates and relieves your symptoms, and any history of previous trauma or treatment. You may also be asked about your other medical conditions, such as diabetes and allergies, previous surgeries, medications you are taking, and your social history including profession, hobbies, tobacco use, alcohol consumption, and living situation. Your physician may also ask you about physical and athletic goals. This information may help your physician decide what treatment option might be best for you.

Since a hip dislocation usually is the result of high–energy trauma, your physician may conduct a head–to–toe (multi–system) evaluation to look for associated injuries. In particular, your physician will concentrate on the affected hip and lower extremity. Your physician will look for lacerations and bruises, weakness, and abnormal pulses, sensation, and reflexes. The position of your hip and lower extremity also provides your physician with valuable information regarding the direction of your possible hip dislocation. If your hip is extended and is rotated to the outside, you may have an anterior dislocation. If your hip is flexed and rotated to the inside, you may have a posterior dislocation.

Your physician may use the following tests:

   X–rays, to look for fractures and dislocations of the bones and joints.

   After reduction of a dislocated hip, a CT scan, commonly referred to as a CAT scan, is usually obtained to look for the presence of bone fragments trapped within the joint and to make sure that the head is completely reduced within the hip socket (acetabulum). If there is a fracture associated with the dislocation, then the CT is useful in characterizing the nature of the fracture.

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