Temporal patterns of commonly used clinical outcome scales during a 5-year period after total knee arthroplasty

Abstract

Background It is not established beyond doubt whether improvements in functional outcome after total knee arthroplasty (TKA) are maintained in the long term. We therefore investigated the temporal patterns of functional outcome [using range of motion (ROM), American Knee Society (AKS) score, Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and 36-Item Short Form Health Survey (SF-36) score] over a 5-year period after uncomplicated TKA, and whether these patterns differed by implant type and patient age.

Materials and methods This prospective study evaluated 138 patients who underwent unilateral TKA with either a mobile-bearing (MB) or fixed-bearing (FB) posterior-stabilized prosthesis. An independent investigator evaluated the functional outcome at five time points: preoperatively and at 6-month, 1-year, 2-year, and 5-year follow-up. Differences in functional outcomes between adjacent time points were evaluated by mixed-effect model repeat measurement (MMRM).

Results The different functional outcome scores showed improvement till 6months–2years, followed by a variable decline. In patients aged ≥ 68years with an MB implant, most of the functional outcome scores declined between 2 and 5years after variable initial improvement till 6months–2years, whereas the parameters plateaued after 2years in those aged < 68years and in older patients with an FB implant.

Conclusions A decline in function and pain relief occurs 2years after TKA. This decline is more evident in older patients with an MB prosthesis. Based on these findings, we believe that use of MB implants in older patients (≥ 68years) requires further investigation.

Level of evidence Level3.