Effect of Weight Change on Patient-Reported Outcomes Following Total Joint Arthroplasty

Increased body mass index (BMI) has been previously described as a risk factor for complications after total joint arthroplasty (TJA); however, its effect on patient-reported outcomes has not been thoroughly investigated. This study examines the effect of postoperative weight change on the Patient-Reported Outcomes Measurement Information System Physical Function (PROMIS-PF) scores for total knee arthroplasty (TKA) and total hip arthroplasty (THA) patients.

A retrospective review of 988 patients undergoing THA or TKA was performed. PROMIS-PF scores and BMI were recorded throughout the study duration. Patients were classified by a 5% change in BMI. A univariate analysis evaluated differences across groups. Mixed-effect models evaluated predictors of change in functional score over the postoperative follow-up time.

43.1% patients had a THA and 56.9% patients had a TKA. At 0 to 3 months, 92% of patients had no change in BMI, 3 to 6 months 82% had no change, and 6 to 12 months 80% had no change. There were no significant demographic or comorbidity differences across groups for both THA and TKA. Similar improvements in PROMIS-PF scores were observed across weight change groups. In the mixed-effect models, postoperative time was found to be a significant predictor of postoperative PF score. Both THA and TKA patients saw greater improvements in PROMIS-PF scores in patients with lower preoperative BMIs.

These results demonstrate most patients do not experience substantial changes in weight following TJA. However, lower BMIs at the time of surgery were associated with an increased functional improvement. Therefore, efforts to optimize BMI should be focused preoperatively to improve surgical outcomes.