Hormone Therapy May Benefit New Joints

Women who underwent total knee or hip replacements were significantly less likely to have implant failure if they began taking hormone replacement therapy (HRT) after the procedure, a large observational study has found.

Over a period of about three years, women who used HRT post-surgically for at least six months had about a 40 percent reduction in the rate of revision surgery (HR 0.62, 95 percent CI 0.41-0.94, P=0.023), according to Nigel K. Arden, M.D., from the University of Oxford, and colleagues.

Those who continued on HRT for one year experienced a further reduction in risk — by about half (HR 0.48, 95 percent CI 0.29-0.78, P=0.003), the researchers reported online in Annals of the Rheumatic Diseases.

Loss of the implant after a year post-surgery most commonly results from chronic inflammation, osteolysis near the joint, and aseptic loosening.

“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 noted.

Some studies have looked at the effects of antiresorptive agents such as bisphosphonates, with their antiosteoclastic properties, but results have been mixed.

HRT also has antiresorptive effects on bone, and the U.K. General Practice Research Database includes information about the large population of women who used these agents in decades past, as well as all those who underwent total hip or knee replacement between 1986 and 2006.

Of the 24,733 women who had the joint surgery, the researchers selected 2,700 who had used HRT for at least 6 months after having knee or hip replacement surgery, propensity matching them with 8,100 nonusers.

Median age was 65, and body mass index averaged 29. In 56 percent, the joint replaced was the hip, and in the remainder it was the knee.

A total of 6 percent were taking bisphosphonates, 1.4 percent were receiving calcium and Vitamin D supplements, and 0.35 percent were on oral corticosteroids.

The revision rate in the entire group by three years post-surgery was 0.76 percent (95 percent CI 0.53-10.5) for knees and 0.97 percent (95 percent CI 0.74-12.5) for hips.

The rate among those who had used HRT for at least 6 months after the joint replacement was 2.61 per 1,000 person-years at risk (95 percent CI 1.79-3.61), compared with 4.25 (95 percent CI 3.81-5.02) for nonusers.

After adjustment for use of other drugs with effects on bone, protective effects again were seen for HRT (HR 0.61, 95 percent CI 0.40-0.92, P=0.019).

Unlike post-surgical use, no benefit was seen for HRT before the joint arthroplasty (HR 1.06, 95 percent CI 0.66-1.70, P=0.80). A possible explanation for this was that the decrease in bone resorption associated with HRT could interfere with implant integration in the post-surgical period, according to the researchers.

The rate of joint failure by 7 years is low, below 5 percent, according to the National Joint Registry of England, Wales, and Northern Ireland.

Therefore, Arden and colleagues recommended that consideration be given to the use of antiresorptive treatment following joint replacement in a targeted way for those at greatest risk of failure, also keeping in mind the chance of venous thromboembolism with HRT.

A strength of the study was its large and representative population, while a limitation was its observational design, although the researchers sought to avoid confounding by indication through propensity score matching of cases and controls.

There also may have been residual confounding by factors such as type of implant and fixation, since this information wasn’t available in the database.