From Jonathan Cluett, M.D.,
Your Guide to Orthopedics.
FREE Newsletter. Sign Up Now!

About.com Health's Disease and Condition content is reviewed by Kate Grossman, MD

The acetabulum is the socket of the ball-and-socket hip joint. The top of the thigh bone (femur) forms the ball, and the socket (acetabulum) is part of the pelvic bone.

Is the acetabulum the same as the pelvis?
The acetabulum is part of the pelvis. The part of the pelvis that forms the hip socket is the acetabulum. The acetabulum is round in shape, and covered inside with smooth cartilage. This cartilage forms the smooth surface of the hip joint.

What is an acetabular fracture?
An acetabular fracture occurs when the socket of the hip joint is broken. This is much less common than most hip fractures, where the ball of the ball-and-socket joint is broken.

How does an acetabular fracture occur?
Acetabular fractures either occur with high-energy trauma (e.g. auto collisions, falls, etc.) or as an insufficiency fracture. In younger patients, there is almost always significant trauma, and commonly associated injuries, when an acetabular fracture occurs. In elderly patients, acetabular fractures can occur due to bone weakened from osteoporosis.

What is the treatment of an acetabular fracture?
In patients who have a traumatic acetabular fracture, the treatment depends on the extent of cartilage displacement, and hip instability. The hip joint should be stable (the ball held tightly within the socket) and the cartilage should be smoothly contoured. Surgery is often recommended for:

• Aligning the cartilage surface

• Removing debris (bone) from within the hip joint

• Restoring stability of the hip

Elderly patients have surgery less frequently, and fractures may be allowed to heal even if the alignment is not perfect.

Whether or not surgery is performed, patients must minimize the weight they place on the affected extremity, often for up to three months. Patients are usually allowed to place their foot on the ground (touch-down weight-bearing), but no more force is allowed on the leg. Walking on the extremity too soon risks further displacement of the broken fragments of bone.

What are the complications associated with acetabular fractures?
Unfortunately, the long-term prognosis of acetabular fractures has many potential complications. In the early period, patients who have acetabular fractures often have associated injuries including head injuries, abdominal injuries, urologic injuries, and other musculoskeletal injuries (spine and knee are most common). These patients are at high risk of developing blood clots in the legs and pelvis. Patients who have surgery risk infection, nerve and blood vessel injury, and wound healing problems.

In the longer-term, the common problem is the development of hip arthritis. Patients often eventually need a hip replacement surgery. Other possible problems include hip osteonecrosis, heterotopic bone (excess bone) formation.

References:

• Baumgaertner MR, "Fractures of the posterior wall of the acetabulum" J. Am. Acad. Ortho. Surg., Jan 1999; 7: 54 - 65.