Total joint arthroplasty is the most effective therapy for severe osteoarthritis of the lower limb. Increases in the numbers of elderly and obese individuals have driven up rates of primary arthroplasty. Revision surgery has a poorer clinical outcome than primary joint surgery and is more costly. The most common cause of revision is loosening, which occurs if the bone supporting the implant is resorbed. Bone remodelling at the bone-implant interface leads to localised bone lysis, which may also result in the need for revision. Efforts to identify patients at risk of revision and develop new treatments to improve implant survival are thus needed. Bisphosphonates, through their antiresorptive properties on osteoclast activity, have been suggested to possess potential protective effects on implant survival. Some RCTs have suggested such a benefit on implant survival after total arthroplasty of the knee or hip, by showing improvements in surrogate outcomes such as implant migration. However, none of the trials had used revision of the implant as the primary outcome. This retrospective observational study evaluated whether bisphosphonate use is associated with increased survival of implants in the lower limb after primary total arthroplasty.

Researchers examined data on all patients undergoing primary total arthroplasty of the knee (n=18,726) or hip (n=23,269) in 1986-2006 within the UK’s General Practice Research Database. Those with a history of hip fracture before surgery or rheumatoid arthritis, and individuals younger than 40 years at surgery were excluded. Bisphosphonate users were classified as patients with at least six prescriptions of bisphosphonates or at least six months of prescribed bisphosphonate treatment with more than 80% adherence before revision surgery. The outcome measure was revision arthroplasties occurring after surgery.

The following findings were reported for 41,995 patients undergoing primary hip or knee arthroplasty:

• 1912 bisphosphonate users had a lower rate of revision at five years than non-users (0.93% vs. 1.96%).

• Implant survival was longer in bisphosphonate users than in non-users in propensity adjusted models (hazard ratio 0.54; 0.29 to 0.99, p=0.047) and had an almost twofold increase in time to revision after hip or knee arthroplasty (time ratio 1.96 (1.01 to 3.82)

• Assuming 2% failure over five years, the number to treat to avoid one revision was estimated to be 107 for oral bisphosphonates.

The researchers conclude from this study that bisphosphonate use is associated with a lower rate of revision surgery of up to about 50% and a twofold greater median implant survival time after primary total arthroplasty of the lower limb in patients without a previous fracture. They add that these findings require replication and testing in experimental studies for confirmation.