Date Published: June 6, 2019
Publisher: Public Library of Science
Author(s): Thomas V. Perneger, Didier Hannouche, Hermès H. Miozzari, Anne Lübbeke, Yuanyuan Wang.
Patient-reported outcomes are increasingly used in evaluations of joint replacement surgery, but it is unclear if symptoms of osteoarthritis (i.e., pain and dysfunction) influence health perceptions similarly before and after surgery.
In this prospective study based on a hospital-based arthroplasty registry, patients with primary total hip or knee arthroplasty (THA, N = 990, and TKA, N = 907) completed the WOMAC Pain and Function scales, and the SF12 Physical and Mental Component Scores (PCS and MCS), before surgery and one year later. Associations between WOMAC and SF12 scales were examined using mixed linear regression models.
All patient-reported outcomes improved following total joint arthroplasty, but the associations between symptom scales and global health perceptions were altered. Mental health scores at a given level of pain or function were lower after surgery than before, by about 4–5 points, a clinically meaningful and statistically significant difference. In contrast, the associations between WOMAC scales and the PCS remained stable. These findings were observed in both cohorts of patients.
After total joint arthroplasty, mental health scores were lower than would have been expected given the symptomatic improvement. This suggests that relationships between patient-reported outcomes are context-dependent, and that care should be exerted when interpreting changes in patient-reported outcomes over time.
Patient-reported outcomes (PROs) such as pain and functional ability, perceptions of physical and mental health, and quality of life in a global sense, are increasingly used to assess the impact of joint replacement surgery [1–4]. PROs can be employed to guide clinical care decisions, monitor quality of care, perform between-hospital comparisons , or adjust reimbursement policies .
During the study period, 1969 THAs and 1834 TKAs were performed at the hospital (Fig 1), and 990 THAs in 935 patients and 907 TKAs in 842 patients completed both questionnaires and were included in this analysis.
This prospective study showed a substantial change in the relationships between symptoms (i.e., pain and function) and patients’ perceptions of mental health following total joint arthroplasty. Mental health scores were influenced to the same extent by pain and function after surgery as before (same slopes in the linear regression model), but their absolute level was lowered after surgery at a given level of pain and function (lower intercepts). For physical health, the absolute scores at mid-range values of pain and function were unchanged after surgery (same intercepts), but the associations became slightly stronger (steeper slopes). These results suggest that relationships between PROs are context-dependent, and that one should be careful when interpreting changes in PROs over time, especially if the changes are induced by surgery.
We found that perceptions of mental health were lower after total joint arthroplasty of the hip and knee than may have been expected based on symptom relief, whereas the perceptions of physical health were as predicted by symptom relief. The reasons for these phenomena should be explored, in order to facilitate the interpretation of post-intervention PRO scores.