Determining Health-Related Quality-of-Life Outcomes Using the SF-6D Following Total Hip Arthroplasty

Background: Following total hip arthroplasty, patients’ perception of their postoperative improvement and health plays a large role in satisfaction with and success of the surgical procedure. The Short Form-6D (SF-6D) is a health-related quality-of-life measure that assigns numerical value to the perception of patients’ own health. The purpose was to determine SF-6D values of patients after total hip arthroplasty, to determine whether score changes were clinically relevant, and to compare these with postoperative functional improvements.

Methods: We evaluated 188 patients who underwent primary total hip arthroplasty at 7 institutions and who had a mean age of 69 years (range, 47 to 88 years) and a mean body mass index of 28.8 kg/m2 (range, 19.8 to 38.9 kg/m2). The SF-6D values were obtained from patients’ SF-36 scores, and clinical relevance of value changes was determined using effect size. Using previous research, effect sizes were considered small between 0.2 and 0.5, moderate between 0.6 to 0.8, and large at >0.8. Clinical correlation was assessed using the Lower-Extremity Activity Scale and Harris hip scores. Patients were assessed preoperatively and postoperatively at 6 months and 1, 2, 3, and 5 years.

Results: The SF-6D scores improved from preoperatively and achieved significance (p < 0.05) at all points. The effect size demonstrated good clinical relevance up to the latest follow-up: 1.27 at 6 months, 1.30 at 1 year, 1.07 at 2 years, 1.08 at 3 years, and 1.05 at 5 years. The Lower-Extremity Activity Scale improved at all follow-up points from preoperatively to 1.8 at 6 months, 2.0 at 1 year, 1.8 at 2 years, 1.5 at 3 years, and 1.6 points at 5 years. The Harris hip score improved to 38 points at 6 months, 40 points at 1 year, 38 points at 2 years, 39 points at 3 years, and 41 points at 5 years postoperatively. The improvements in the Lower-Extremity Activity Scale and the Harris hip score significantly positively correlated (p < 0.01) with the SF-6D scores at all time points.

Conclusions: SF-6D scores after total hip arthroplasty correlate with functional outcomes and have clinical relevance, as demonstrated by their effect size. Incorporating this straightforward and easy-to-use measurement tool when evaluating patients following total hip arthroplasty will facilitate future cost-utility analyses.

Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.