Association of the 36-Item Short Form Health Survey Physical Component Summary Score With Patient Satisfaction and Improvement 2 Years After Total Knee Arthroplasty

Abstract

Increases in total knee arthroplasty (TKA) utilization rates suggest that its indications have been expanded to include patients with less severe symptoms. A recent study challenged the cost-effectiveness of TKA in this group of patients. To determine the association of the 36-Item Short Form Health Survey physical component summary score (SF-36 PCS) with patient satisfaction 2 years after TKA. This cohort study reviewed registry data from 2 years of follow-up of patients who underwent unilateral TKA from January 1, 2010, to December 31, 2014, at a single-center tertiary institution in Singapore. Data were acquired on April 27, 2017, and analyzed from August 15, 2017, to December 22, 2017. Patient satisfaction and SF-36 PCS. Preoperative disability and postoperative function as measured by the SF-36 PCS were correlated with Δ (2-year end point score minus baseline score) and patient satisfaction, scored on a 6-point Likert scale, with lower scores indicating greater satisfaction. Of the 6659 patients, 5234 (78.6%) were female and 5753 (86.4%) were of Chinese ethnicity. Mean (SD) age was 67.0 (7.7) years, and mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 27.7 (4.6). At 2-year follow-up, the mean (SD) SF-36 PCS score improved from 32.2 (10.1) to 48.2 (9.5) (P < .001). There were 1680 patients (25.2%) who described their satisfaction as excellent, 2574 (38.7%) very good, 1879 (28.2%) good, 382 (5.7%) fair, 96 (1.4%) poor, and 48 (0.7%) terrible. The minimal clinically important difference (change in SF-36 PCS of 10 from baseline) was met in 4515 patients (67.8%), and overall satisfaction was 97.8% (6515 patients). Covariance analysis showed significantly higher satisfaction in patients with preoperative scores of 40 to less than 50. Patients who were unlikely to meet the minimal clinically important difference compared with those who were likely to meet it (SF-36 PCS of ≥42.1 vs <42.1) had significantly higher 2-year satisfaction (mean [SD], 2.15 [0.9] vs 2.23 [1.0]; P = .009). The findings suggest that a general health score, such as SF-36, is not associated with patient satisfaction 2 years after TKA. Functional assessment, preoperative counseling, and modification of expectations appear to remain vital before TKA.