Many patients take steroids for conditions such as chronic lung disease, rheumatologic problems, colitis, or autoimmune diseases. It is also not known what dose or length of steroid therapy causes harm. Steroid therapy – It is not clear why taking steroids causes osteonecrosis. Some of the common systemic causes include: It is not known if there is a single insult to the circulation or if the damage happens over a period of time. In this setting, it is common for both hips to be involved. Systemic causes of osteonecrosis are conditions which occur throughout the body. Even if a femoral neck fracture treated with pinning has healed, osteonecrosis can still be a secondary complication. When the capsule is damaged the fracture may not have enough blood supply to heal and osteonecrosis can develop. For this reason, displaced femoral neck fractures are often treated with hip replacement instead of fixing or pinning the break with screws. If the neck of the femur just below the femoral head is broken, and the fracture is out of place, it is likely that the capsule will be injured as well. The capsule of the hip joint can also be injured by fracture. Femoral head with osteonecrosis, outlined by arrows, notice the ball is no longer round. Restoring the blood supply quickly can help prevent osteonecrosisįigure 2. This can sometimes be done by closed manipulation under sedation or anesthesia. When there is a dislocation, it is important that the head be put back in the socket (reduced) as soon as possible. Posterior dislocations are commonly caused by high energy trauma such as an automobile accident or a fall from a height. Usually, the dislocation is posterior, that is out of the back side of the hip. The first is traumatic dislocation of the hip where the ball of the femur is forced out of the socket (acetabulum). Injury to the capsule can happen in two ways. When this happens there is no blood flow to a portion of the femoral head and the bone can die. If the capsule is injured, the blood supply may be disrupted. This is a balloon like structure that inserts on the neck of the femur and keeps joint fluid in the hip. Most of the blood supply to the femoral head comes through the lining of the hip joint called the capsule. When the disease is systemic, both hips and other joints such as the shoulders may be involved. When the disease results from injury, it is usually confined to the injured hip. Sometimes the cause is unknown and is said to be idiopathic. Osteonecrosis can result from direct trauma to the hip, a systemic disease, or unrelated factors such as radiation. Symptoms of osteonecrosis typically present 12 to 18 months after injury to the bone or blood supply.įigure 1. Over time, as the disease progresses, the joint surface of the femoral head may collapse (Figure 2) and lead to painful arthritis. At first, only the ball of the femur, the femoral head, is involved. Osteonecrosis literally means “bone death.” When the blood supply to the femoral head is damaged or disrupted, a portion of the bone dies. Osteonecrosis or avascular necrosis is a disease where the blood flow to the head (ball of your hip joint, Figure 1) of the femur is interrupted that results in a painful hip.
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