The acetabulum (hip socket) is the part of your pelvis that connects your femur (thigh bone) to your pelvis. This "ball and socket" joint permits movement between your femoral head (top of thigh bone) and your pelvis, and lets you walk and your hip move. Your acetabulum is the cup that the ball of the top of your femur rests in. Both your femoral head and acetabulum have cartilage on the surface of the bone to allow smooth frictionless movement.
Mechanism and Epidemiology
In general, the bone of the pelvis and acetabulum is very strong and it takes a lot of force to create a fracture (break). This usually occurs after a car accident, a motorcycle crash, or a fall from height. In the elderly, the bone is not as strong as in younger people, and a fall from a standing position can cause an acetabular fracture. Depending on the severity of the accident and the position of the femoral head (top of the thigh bone), the acetabulum can break in just one or several different places.
Patients who have an acetabular fracture have usually been involved in some sort of bad accident, and are brought to an emergency room to be evaluated. A doctor will give you a full physical examination to identify all areas of injury and to make sure all the nerves of your leg and foot are working correctly. The healthcare team will take x-rays and a CT scan to provide the surgeon with information so he or she can decide what treatment is needed. Sometimes, the injury will cause the femoral head (top of thigh bone) to break through the acetabulum. Doctors call this a fracture dislocation, and it will require the physicians to relocate your femoral head back into the acetabulum. This is typically done in the emergency room. In addition, many injuries will require placement of a traction pin, which uses a wire placed into your bone above your knee to allow you to apply weight to your leg. This helps hold your femoral head in the appropriate place and prevents the cartilage of the femoral head from grinding on the fracture.
Acetabular fractures are complex injuries, and may be treated with or without surgery, depending on the type and location of the break. As soon as possible, you should consult with an orthopaedic surgeon who has experience treating acetabular fractures. If your injury is misdiagnosed, the femoral head (top of the thigh bone) can rub within the acetabulum (hip socket) and cause damage to your cartilage. If your cartilage is damaged too much, you may risk early onset arthritis in your hip. Depending on the location and severity of your fracture, patients who require surgery may need an incision in the front of the pelvis, the back or side of the thigh, or both. Some injuries can be treated with minimally invasive methods using just a few small incisions around the hip.
The purpose of the surgery is to realign your bones into the appropriate position and hold them there with plates and screws. This ensures your hip socket is round and smooth again and will heal in the correct position. Doing so protects the cartilage in your hip and gives you the best chance to avoid arthritis.
With or without surgery, there will be a period where you cannot put any significant weight on your injured leg. You will likely hear the terms "toe touch" or "touch down" weight bearing, in which you will be allowed to let your foot touch the floor but not stand on it. This will help you with balance while also allowing the acetabulum to heal appropriately. Your surgeon will advise you on how long you should limit weight bearing; generally from 6-12 weeks. During that time, you will need crutches or a walker to help you move around, and possibly a wheelchair for longer distances. Putting weight on your leg before you heal adequately can risk your plates and screws loosening and your bones moving out of alignment. This can put your hip socket at risk for pain and early arthritis. After enough time has passed, you will begin walking slowly. You will likely need to work with a physical therapist to help regain your muscle strength, endurance, and coordination. If you had injuries to both hips, or an additional injury so you cannot put weight on either leg, you will have to wait longer to put weight on your acetabular fracture repair.
The major concern after an acetabular fracture is hip arthritis. Arthritis is when the cartilage in your joint is damaged and wears out. Instead of having a smooth layer of cartilage to protect the bones of your joint, your bone will rub directly on bone, which causes pain and makes it difficult to move. There are many factors that can affect your chance of developing arthritis, including your age, the type and severity of your acetabulum fracture, quality of surgical repair, allowing adequate healing time before walking, and success regaining full strength and endurance. Many patients can return to full or near normal level of function and activities in 6-9 months. Patients often continue to improve for up to a year after surgery. For patients who do develop hip arthritis, it may happen quickly over months or very slowly over years. Your surgeon can help you with physical therapy, medications, and possibly injections. If your pain is very high and your function is severely impacted, you might be a candidate for a hip replacement, and should talk to your surgeon about it.
Jonathan G. Eastman, MD
Edited by the OTA Patient Education Committee
All x-rays and pictures taken from the personal collection of Dr. Eastman