Postoperative Weight Loss After Antiobesity Medications and Revision Risk After Joint Replacement

The 2023 American College of Rheumatology and American Association of Hip and Knee Surgeons Clinical Practice Guideline concluded that obesity alone should not delay joint replacement. Therefore, a substantially increased utilization of joint replacement among patients with obesity could be expected. However, patients with obesity are at increased risk of revision, posing unique challenges as the surgery is complex and costly, and it remains unknown whether postoperative weight loss could decrease the risk of revision.

To examine the association of the proportion of postoperative weight loss following antiobesity medication use with the risk of revision among patients with obesity undergoing hip or knee replacement.

Using a target trial emulation, a causal inference framework, this retrospective cohort study investigated patients with obesity who underwent hip or knee replacement. Data were from the IQVIA Medical Research Database (2000-2023). Statistical analysis was performed from October 2023 to June 2024.

Emulated analyses of a hypothetical target trial were assessed for the association of small-to-moderate (2%-10%) or large (≥10%) weight loss after initiating antiobesity medications (orlistat, sibutramine, glucagon-like peptide-1 receptor agonists, and rimonabant) within 1 year with the risk of 5-year and 10-year revision after initiation of antiobesity medications.

Among 3691 qualified participants (mean [SD] age, 64.7 [9.3] years; 2322 [62.9%] women), the 5-year risks of revision were 5.6%, 4.4%, and 3.7% for weight gain or stable, small-to-moderate weight loss, and large weight loss groups, respectively. Compared with the weight gain or stable group, the hazard ratios (HRs) were 0.75 (95% CI, 0.55-1.04) for the small-to-moderate weight loss group and 0.57 (95% CI, 0.36-0.91) for the large weight loss group. Similar results were observed when the analyses were performed separately for hip or knee replacement. The HRs for revision were 0.55 (95% CI, 0.32-0.93) for small-to-moderate weight loss and 0.49 (95% CI, 0.25-0.97) for large weight loss groups compared with the weight gain or stable group in patients undergoing knee replacement; the corresponding HRs for revision were 0.82 (95% CI, 0.54-1.25) and 0.53 (95% CI, 0.30-0.93) in patients undergoing hip replacement. Consistent findings were obtained regarding the association of weight loss with the 10-year risks after initiating antiobesity medications.

In this cohort study using a target trial emulation, a higher proportion of weight loss after initiating antiobesity medications within 1 year was associated with a lower risk of 5-year and 10-year revision among patients with obesity undergoing joint replacement. These results suggest that antiobesity medication use, with relatively safe and sustainable weight loss, may be an effective strategy for improving implant survivorship of hip and knee replacements in the obese population.