Effect of Body Mass Index and Psychosocial Traits on Total Knee Replacement Costs in Patients with Osteoarthritis.

OBJECTIVE: Clinical and psychosocial attributes are associated with clinical outcomes after total knee replacement (TKR) surgery in patients with osteoarthritis (OA), but their relationship with TKR-related costs is less clear. Our objective was to evaluate the effect of clinical and psychosocial attributes on TKR costs. METHODS: We conducted a 6-month prospective cohort study of patients with knee OA who underwent TKR. We examined baseline demographic, clinical [body mass index (BMI) and comorbidities], and psychosocial attributes (social support, locus of control, coping, depression, anxiety, stress, and self-efficacy); baseline and 6-month OA clinical outcomes [Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and function]; and 6-month direct and indirect TKR-related costs. Multiple regression was performed to identify determinants of TKR-related costs. RESULTS: We included 212 patients; 66% were women, 71% were white, and the mean age was 65.2 years. The mean baseline WOMAC pain score was 55 (SD 19) and WOMAC function score was 54 (SD 20). Mean total TKR-related costs were US$30,831 (SD $9893). Multivariate regression analyses showed that increasing BMI and anxiety levels and decreasing levels of positive social interactions were associated with increased costs. A lower cost scenario with a lower range of normal BMI (19.5), highest positive social interaction, and no anxiety predicted TKR costs to be $22,247. Predicted costs in obese patients (BMI 36) with lowest positive social interaction and highest anxiety were $58,447. CONCLUSION: Increased baseline BMI, anxiety, and poor social support lead to higher TKR-related costs in patients with knee OA. Preoperative interventions targeting these factors may reduce TKR-related costs, and therefore be cost-effective.

Cost-effectiveness of total knee replacement: a prospective cohort study.

OBJECTIVE: Total knee replacement (TKR) rates have significantly increased in the past decade. While the procedure itself might be costly, the cost-effectiveness and potential offset costs from patient and societal benefits have not been clearly established. The objective of this study was to perform an economic evaluation of TKR in patients with knee osteoarthritis (OA). METHODS: We conducted a 6-month prospective cohort study of 212 patients with knee OA who underwent TKR at a single hospital in Houston, Texas. We included patient-level data from hospital billing databases and the patients' self-reported direct and indirect costs. The clinical outcome measure was pain and function measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire; we used the minimum clinically important difference (MCID; ≥20-point change) and the WOMAC 20% (WOMAC20), 50% (WOMAC50), and 70% (WOMAC70) relative improvement criteria. Incremental cost-effectiveness ratios were estimated using direct and indirect costs and WOMAC improvement. A societal perspective was used and multiple sensitivity analyses were performed to assess the robustness of the principal analysis. RESULTS: The total incremental cost per TKR was $20,133. The incremental cost-effectiveness ratios (ICERs) for improvement at 6 months were $33,345, $25,255, $35,274, and $56,908 for the MCID, WOMAC20, WOMAC50, and WOMAC70, respectively. Best- and worst-case scenario sensitivity analyses did not have a significant impact on the ICERs. Patient time lost was the most influential variable in the multiway sensitivity analysis. CONCLUSION: TKR is an effective intervention in reducing pain and improving functional status among patients with knee OA and is cost effective at both low and high levels of improvement.