Hormone replacement therapy (HRT) taken regularly for 6 months after a knee or hip replacement was associated with a 40% reduced risk of needing repeat surgery, a study found.
A population-based study based on national data for England and Wales found that more than 2% of procedures typically have to be repeated within 3 years, primarily because of osteolysis (75% of cases).
Researchers assessed the likelihood of repeat joint replacement surgery among women who required a first knee or hip replacement between 1986 and 2006. Matched samples were created of 2,700 HRT users and 8,100 women who had not used HRT to compare the risk of repeat surgery over a period of 3 years.
Results appeared online first Jan. 22 in the Annals of the Rheumatic Diseases.
Failure incidence was 2.61/1,000 person-years-at-risk (95% CI, 1.79 to 3.61) in HRT users, and 4.25 (95% CI, 3.81 to 5.02) among HRT non-users. Those who had taken HRT regularly for 6 months or more after their surgery were 38% less likely to require repeat surgery than were those who had not done so (95% CI, 0.41 to 0.94; P=0.023). Those who regularly took HRT for 12 months or more after their procedure were 52% less likely to need further surgery during the 3-year monitoring period (95% CI, 0.29 to 0.78).
Higher adherence and therapy duration were associated with further reductions in revision rates. Taking HRT before surgery, however, made no difference to the risk of implant failure, the findings showed (hazard ratio [HR], 1.06; 95% CI, 0.66 to 1.70; P=0.80), but a strong protective effect was present for those with a first prescription after surgery (HR, 0.24; 95% CI, 0.10 to 0.55; P=0.001). The findings held true even after taking account of other influential factors, including use of drugs that can impair bone turnover (HR, 0.61; 0.40 to 0.92; P=0.019).
Low estrogen levels have been implicated in bone thinning and loss, while HRT is thought to help conserve bone thickness. But this is the first study to show that it can help prevent repeat surgery in women who have undergone hip/knee replacement, noted the authors.
“As the rate of revision at 7 years is under 5%, it is likely that any antiresorptive drugs would be used in a targeted manner to patients identified as being at high risk of failure,” they wrote. “Given the risk of venous thromboembolic events with HRT, HRT should be stopped 6 weeks before and after surgery. This is supported by our observation that the protective effect of HRT was only evident when started after and not before the primary arthroplasty.”