BMI, Physical Function, Osteoarthritis Severity Associated With Total Knee Arthroplasty Outcomes

High presurgical body mass index (BMI) was associated with poor physical function after total knee arthroplasty (TKA), whereas better presurgical physical function and osteoarthritis (OA) severity were associated with better physical function, according to results from a systematic review and meta-analysis published in JAMA Network Open.

The investigators searched published studies using a prespecified, peer-reviewed protocol and preprint registered in the International Prospective Register of Systematic Reviews from January 1, 2000, to October 8, 2021. In order to satisfy eligibility criteria, prospective longitudinal observational studies and randomized clinical trials included adults diagnosed with OA scheduled for primary TKA, as well as estimates of association between preoperative or intraoperative factors and physical function at 3, 6, and 12 months after TKA. Retrospective studies and case-controlled studies were excluded from this analysis.

Of the 12,052 studies, 391 prospective longitudinal observational studies met the inclusion criteria for full-text examination, with only 20 studies (11,317 patients and 37 factors) meeting the criteria for qualitative analysis at 3, 6, and 12 months, and 17 studies met the criteria for quantitative analysis at 6 and 12 months.

Mean correlation with higher BMI was estimated to be -0.15 (95% CI, -0.24 to -0.05; P = .33; P score = 70.0%), while mean correlation with better physical function was estimated to be 0.14 (95% CI, 0.02 to 0.26; P = .03; P score = 65.6%). Mean correlation with more severe OA was estimated to be 0.10 (95% CI, 0.01 to 0.19; P = .17; P score 53.8%). In sensitivity analyses, mean correlation with better physical function was estimated to be 0.20 (95% CI, 0.04 to 0.36; P = .02).

Limitations of the study included the variety of factors that were measured using a range of methods, and the narrow inclusion criteria that may have excluded important evidence. Moreover, some studies had larger sample sizes than others, which may lead to discrepancies in I² statistics. The study may lack generalizability to individual patients considering the population level scope of the study.

“Importantly, our findings did not suggest that individual patients with a poor risk factor profile will not experience functional improvement if they undergo TKA,” the study authors concluded. “Our findings merely suggest that identified factors were correlated with poorer or better physical function in an absolute sense and may therefore be useful for guiding expectations about TKA outcomes.”

Reference

Olsen U, Lindberg MF, Rose C, et al. Factors correleated with physical function 1 year after total knee arthroplasty in patients with knee osteoarthritis. JAMA Netw Open. 2022;5(7):e2219636. doi:10.1001/jamanetworkopen.2022.19636