The association between body mass index and patient‐reported outcome measures before and after primary total hip or knee arthroplasty: a registry

Abstract

AbstractBackgroundThe objective is to determine whether body mass index is associated with patient‐reported expectations and well‐being before primary total hip or total knee arthroplasty, and patient‐reported outcomes 6 months after surgery.MethodsData were obtained from the Australian Orthopaedic Association National Joint Replacement Registry. Outcome measures included pre‐operative expectations for post‐operative mobility, joint pain and health, pre‐ and post‐operative EQ‐5D‐5L, EQ‐VAS, Oxford Hip/Knee Scores and joint pain scales, and post‐operative perceived change and perceived satisfaction. Associations with BMI were assessed using chi‐square tests, analysis of variance and Linear Mixed Models equations.ResultsData were available for 12 816 primary THA patients and 20 253 primary TKA patients. Pre‐operatively, patients in higher BMI categories were significantly more likely to expect ongoing problems with mobility, more joint pain and poorer health following surgery (P<0.01 for all analyses). For arthroplasty patients, higher BMI was associated with poorer pre‐operative and post‐operative scores for all measures. BMI was positively associated with improvements in EQ‐5D, OHS/KS and joint pain. While between‐group differences were statistically significant, many were small in magnitude. There was no association between BMI and patient‐perceived change or satisfaction after arthroplasty.ConclusionPatients undergoing THA/TKA, higher BMI was associated with lower pre‐operative expectations, poorer well‐being before surgery, and worse scores after surgery. Patients who were obese demonstrated comparable satisfaction with their operated joint, compared with non‐obese patients. BMI was associated with greater pre‐ to post‐operative improvements in outcome scores for EQ‐5D, VAS knee, OHS/OKS and joint pain but these differences may not be clinically important.