Global Spatiotemporal Gait Performance and Ambulation Capacity After Total Knee Arthroplasty: A Longitudinal Comparison of Fixed-Bearing and Mobile-Bearing Prostheses

Background: The choice between fixed-bearing (FB) and mobile-bearing (MB) prostheses in total knee arthroplasty (TKA) remains controversial, and longitudinal evidence based on objective instrumented assessment is limited. Objectives: To compare global spatiotemporal gait performance and ambulation capacity across three postoperative assessments in patients receiving FB versus MB/rotating-platform implants. Methods: In this retrospective, longitudinal, observational cohort study, patients who had undergone primary unilateral TKA were assessed at up to three postoperative visits approximately 12 months apart, the first at a median of 12 months after surgery. Gait speed, cadence, stride length, a step-time symmetry index and a gait quality index were obtained from a single lumbar-mounted inertial measurement unit during steady-state level walking, and ambulation capacity was measured with the 2-Minute Walk Test (2MWT). Linear mixed-effects models with a random intercept per patient, adjusted for age and sex, were fitted for all six outcomes, with time specified both as a linear term and, in a sensitivity analysis, as a categorical factor yielding estimated marginal means and between-group contrasts at each visit. Results: A total of 105 observations from 54 patients were analysed (29 FB, 25 MB/PS-RP). Groups were comparable at the first assessment on age, sex, body mass index, WOMAC score and all gait outcomes. No between-group difference reached statistical significance for any outcome, in either the linear or the categorical specification; all 18 visit-specific contrasts included the null value. Within the FB group, gait speed, stride length, the symmetry index, the gait quality index and 2MWT distance decreased significantly between the second and third assessments, a change based on six patients. Conclusions: Under the conditions of this study, no significant differences in global spatiotemporal gait performance or ambulation capacity were detected between FB and MB/rotating-platform prostheses. Because the study was not designed or powered as an equivalence trial, lacks preoperative and joint-level kinematic data, and cannot separate bearing design from the surgical approach with which it was collinear, these findings do not establish that the two designs perform equivalently.