Sagittal Stability and Implant Design Affect Patient Reported Outcomes After Total Knee Arthroplasty

Background: Joint stability is one of the goals of any joint replacement. The contribution of prosthesis design to sagittal stability in total knee arthroplasty (TKA) has emerged as an area of interest. The purpose of this study was to evaluate the sagittal stability of four prosthesis types and determine the effect on patient reported outcome measures (PROMs).

Methods: A matched-cohort cross-sectional study was performed on 60 patients after TKA at 1-year follow-up. Three surgeons performed 10 medially stabilized (MS) TKA and 10 non-MS TKA. Sagittal stability was assessed by a blinded observer using a KT-1000 arthrometer, Lachman's test, and the anterior drawer test. PROMs (Oxford, Knee Injury and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, Forgotten joint score) and visual analog scale assessed function and satisfaction.

Results: MS TKA had significantly decreased translation on KT-1000 and improved stability compared with non-MS TKA (P < .05). Increased PROMs were demonstrated in the MS TKA group compared with the non-MS TKA group (P < .05). When divided based on objective stability, regardless of the prosthesis type, patients with a stable knee had superior PROMs (P < .05), particularly in sport-related questions.

Conclusion: The MS TKA had significantly greater sagittal stability, improved PROMs, and satisfaction compared with non-MS TKA. Independent of prosthesis design, patients with greater sagittal stability demonstrated improved PROMs.