Medial-stabilized TKA has better flexion and early recovery than single-radius TKA

Good range of motion is essential to patient satisfaction after TKA. Both the single-radius (SR) and medial-stabilized (MS) devices were engineered with the focus of enhancing knee joint flexion.

Brett K. Jones et al conducted a study to determine whether two year outcomes differ between these two implant groups. The study has been published in 'The knee' journal.

210 patients took part in this retrospective cohort single center study. The SR patients (n = 109) were enrolled in one randomized trial, and the MS knees (n = 101) in another. All surgeries were performed by the same surgeon (DFS), using a fully custom manual instrumentation set for the SR implants, and the off-the-shelf manual KA instruments for the MS implants, allowing for an identical unrestricted calliper verified kinematic alignment surgical technique. The PC L was sacrificed in all cases. All patients were assessed post-operatively at six weeks, six months, one year and two years. Outcomes that were tracked throughout this study include the Knee Society Scores (KSS) and range of motion (ROM) of the knee as measured by the senior surgeon using a large goniometer in all cases. Surgical data and adverse events were recorded. Participants had full extremity standing anteroposterior radiographs taken preoperatively, at six weeks, and one year postoperative.

Key findings of the study were:

• There were no statistically significant differences between treatment groups in terms of preoperative demographic characteristics.

• The MS group had significantly better knee flexion starting at six months postoperative through two years postoperatively (p < 0.05 – p < 0.001).

• The Knee Society Pain/Motion score was better in the MS group at one year (95.41 vs 90.86, p < 0.002).

• The Knee Society Pain score was also better in the MS group starting at six weeks through one year (six weeks: 35.3 vs 30, p = 0.007; one year: 46.4 vs 42.4, p = 0.005, respectively).

The authors concluded that – “The MS group had better clinical outcomes than the SR group, with significantly greater knee flexion from six months through two years, better Knee Society Pain scores at six weeks through one year, and higher Knee Society Pain/Motion scores at six weeks and one year postoperatively.”

Level of Evidence: I.

Further reading:

Better flexion and early recovery with medial-stabilized vs single-radius total knee arthroplasty with kinematic alignment: Two-year clinical results, Brett K. Jones, Brian J. Carlson et al, The Knee 43 (2023) 217–223 https://doi.org/10.1016/j.knee.2023.06.010