Hormone Replacement Therapy Cuts Hip Revision Rates

Hormone replacement therapy (HRT), taken by a patient after a total knee or hip arthroplasty, was associated with almost a 40% decrease in the rate of revision surgery, according to Med Page Today senior staff writer, Nancy Walsh. Walsh reported on a study funded by the National Institute for Health Research and conducted at the Nufield Orthopedic Center, University of Oxford, United Kingdom.

The most common reason joint replacements fail after the first year, according to Walsh, is aseptic loosening, resulting from osteolysis in the neighboring bone. The study authors wrote, “The mechanisms underlying loosening are still obscure, but it is widely accepted that periprosthetic bone loss secondary to chronic inflammation and osteoclastic activity is the main pathway. Strategies aimed at reducing periprosthetic osteolysis and the consequent bone loss and migration would seem a logical way to reduce arthroplasty failure and hence the need for revision.”

Researchers looked at the rate of revision of 224, 733 women following hip or knee joint replacement from 1986 to 2006. Two thousand seven hundred of the women had been HRT users and 8, 100 had not. The later group was the control subjects. The mean age was 65 and 56% of the women had had a hip replaced.
The results, according to Walsh: the use of HRT for six months or longer was associated with a failure rate of 2.61 per 1, 000 person-years-at-risk which compared with a failure rate of 4.25 per 1, 000 for non-HRT users.

The timing of the HRT use also proved to be significant. There appeared to be little or no benefit if it began before the arthroplasty but there was a “strong protective effect” observed when it was taken following the surgery. The subject’s adherence to the treatment and the size of the HRT dose also influenced the outcome. Those with high adherence had a decreased hazard ratio of 0.22.

Walsh quoted the study authors who wrote, “Animal studies have suggested that estrogen deficiency exerts a negative influence on bone tissue around knee implants, while HRT minimizes periprosthetic bone loss and improves bone ingrowth around the implant.”