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Shallow Hip Socket Linked to Osteoarthritis

A recent study from the Mayo Clinic has some new information for doctors who operate on hips. The results show the need to look for a bony abnormality called acetabular retroversion. The acetabulum is the hip socket. Retroversion means the back half of the socket is shallow. The socket doesn't fully cover the round head at the top of the thighbone.

Any hip operation must take this lack of coverage into account. Retroversion is linked to osteoarthritis (OA) of the hip. In this study researchers looked at X-rays of 82 hips with hip OA of unknown cause. They compared them to 99 X-rays taken for some other problem. Most of the patients in the second group had bladder surgery or a hysterectomy.

The authors report that 20 percent of the patients with hip OA also had acetabular retroversion. Only five percent of the nonorthopedic cases had this deformity. They think the lack of the back wall of the acetabulum is the simplest way to explain why patients with retroversion get OA. Contact pressures from movement may put extra stress on the cartilage of the hip where the back wall is missing. Every time someone stands up from a chair, reaction forces push up and back into the hip socket. Over time, hip OA occurs where the bone ends, leaving the head of the femur uncovered.

The authors say it's important to look for this problem whenever treating the hip. If the doctor is putting in a new hip replacement, the implant must be positioned just right to get the best coverage. The wrong angle in the new socket can lead to pinching of the tissues. Tissue tension and even hip dislocation are also possible.

X-rays can show acetabular retroversion. The doctor must look at X-rays carefully before a total hip replacement or other hip surgery is done. The presence of this acetabular retroversion will alert the surgeon to possible problems. The operation can be planned with this in mind.

References: Nicholas J. Giori, MD, PhD, and Robert T. Trousdale, MD. Acetabular Retroversion is Associated with Osteoarthritis of the Hip. In Clinical Orthopaedics and Related Research. December 2003. Vol. 417. Pp. 263-269.

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