The Use of Medial Pivot Prostheses for the Treatment of Moderate and Severe Deformities.

BACKGROUND

Total knee arthroplasty is the standard treatment for advanced knee osteoarthritis. Medial pivot (MP) prostheses aim to better replicate native knee biomechanics, but their efficacy in moderate to severe deformities remains unclear compared to posterior-stabilized (PS) designs or more constrained implants.

METHODS

A retrospective cohort study was conducted, analyzing patients who had primary knee osteoarthritis and > 10° varus deformity who underwent total knee arthroplasty with either an MP or PS prosthesis between 2017 and 2020. A total of 164 patients (101 MP and 63 PS) met the inclusion criteria. There were no significant demographic differences found between groups, with 40-month follow-ups in both groups. Functional outcomes were assessed using the Knee Society Score (KSS) and visual analog scale for pain. Complications and implant survival were also evaluated. All surgeries were performed by the same surgical team, following a standardized technique to achieve adjusted mechanical alignment.

RESULTS

At 1 year, the functional KSS was similar between MP (90 [80.0 to 100]) and PS (90 [75.8 to 90.0]) (P < 0.01). The objective KSS was 85 (70.0 to 94.0) in the PS versus 84 (74.0 to 93.2) in the MP group, P = 0.57, with no clinically important difference. Improvement in KSS was significant in both groups, with 96.1% showing clinical improvement. There were no significant differences found in complications.

CONCLUSIONS

We observed that 90% of the series achieved clinically relevant improvement with both implants, showing that the use of MP designs could be considered an alternative for the treatment of moderate to severe varus deformities. When comparing both groups, although medians were equal (90), there was a significant difference in functional KSS evaluation in favor of the MP design, whereas the clinical objective KSS evaluation showed no significant difference.