According to the old children’s song, the thigh bone is connected to the hip bone. However, genetics and traumatic events sometimes conspire to make that connection rather tenuous. Hip dislocation occurs when your thigh bone or femur slips out of your hip bone socket or acetabulum. Treat a hip dislocation in an adult or child after a trauma as a medical emergency. Your physician likely will consult with an orthopedist, a doctor who specializes in the musculoskeletal system. Hip dislocation cuts across all age groups, including children. It can cause severe pain. Treatment varies depending on the severity of your injury and the cause.
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Types of Dislocation
Doctors recognize two subcategories of hip dislocation: Native and total joint. In adults, native hip dislocation usually results from high-energy trauma, such as a car accident, as opposed to low-energy trauma (ex: fall from standing). Most traumatic hip dislocations occur when the top of your thigh bone pushes backward in what doctors refer to as a posterior dislocation. Dislocations also can occur when the bone is pushed forward, called an anterior dislocation, or when the hip socket fractures and the femoral head displaces into the fracture. Total joint dislocation happens when the femoral ball, located at the top of your thigh bone, dislodges and moves outside your prosthetic hip socket.
In children, developmental problems or neuromuscular disorders can cause native hip dislocation. Developmental dysplasia of the hip refers to a condition that causes abnormal formation of the femoral head, the top of your thigh bone, and/or the acetabulum, hip socket. The condition leads to improper hip positioning and possible chronic dislocations that can start before birth. Neuromuscular disorders can also cause abnormally shaped hip joints that can dislocate chronically. These patients often require muscle or bone surgeries to help correct or prevent the dislocation from occurring.
Developmental dysplasia patients generally receive a brace known as a Pavlik harness. If the harness fails, patients get a cast after the hip is relocated, usually in an operating room. If casting fails, the surgeon may perform a procedure such as tendon releases, in which the tendons are stretched and lengthened. Some patients may even require pelvic or femoral osteotomies, procedures that surgically realign the bone.
If you seek hip dislocation treatment in an emergency room for a native or total hip after a traumatic event, doctors first attempt a reduction replacing the bone or total hip into the socket, generally performed with the patient under sedation. The hip is then put through a range of motion to test stability. Leg lengths are checked to make sure they are even. If the procedure is unsuccessful, the patient may require an operation.
Some patients have to be placed into a knee immobilizer or brace to limit their range of motion to prevent another dislocation. Patients with acetabulum fractures, where the femoral head dislocates into the fractured acetabulum, also may require skeletal traction, or the use of weights pulling against the dislocation or fracture to help improve alignment prior to having the acetabulum repaired in the operating room.
Recurrent dislocation or signs of failure in prosthetic components of the total hip often require a revision surgery, replacement of worn previously implanted parts.
If a native hip dislocation is not relocated, blood supply to your thigh bone may be compromised, resulting in cell death and possible long-term health consequences such as osteonecrosis and osteoarthritis of the hip.
Traumatic hip dislocations can cause sciatic nerve injuries or result in fractures of the femoral head, femoral neck or acetabulum. Other associated injuries from high speed trauma include ligament injuries in the knee.
About 1 to 4 percent of total hip arthroplasty patients -- those who have had joint replacement surgery -- suffer a dislocation, the majority of which are posterior dislocations. Up to 16 percent of revision total hip arthroplasty patients will have a dislocation.