The medial-pivot (MP) system for total knee arthroplasty (TKA) aims to restore more natural “ball and socket” knee kinematics compared to the traditional posterior-stabilized (PS) implants for TKA. The objective of this study was to determine if there was any difference in functional outcomes between patients undergoing MP-TKA versus PS-TKA.
This prospective randomized control trial consisted of 43 patients undergoing MP-TKA versus 45 patients receiving a single radius PS TKA design. The primary outcome was post-operative range of motion (ROM). Secondary outcomes included the Western Ontario and McMaster Universities Arthritis Index (WOMAC), Oxford Knee Score (OKS), Knee Society Score (KSS), and radiological outcomes. All study patients were followed-up for two years after surgery.
Patients undergoing MP-TKA had comparable ROM at one-year (114.6° ± 16.3° vs. 111.3° ± 17.8° respectively, p = 0.88) and two-years after surgery (114.9° ± 15.5° vs. 114.9° ± 16.4° respectively, p = 0.92) compared to PS-TKA. There were also no differences in WOMAC (26.8 ± 19.84 vs. 22.0 ± 12.03 respectively, p = 0.14), OKS (42.7 ± 8.1 vs. 42.3 ± 6.7 respectively, p = 0.18), and KSS clinical scores (82.9 ± 16.96 vs. 81.42 ± 10.45 respectively, p = 0.12) and KSS functional scores (76.2 ± 18.81 vs. 73.93 ± 8.53 respectively, p = 0.62) at two-years follow-up. There was no difference in post-operative limb alignment or complications.
This study demonstrated excellent results in both the single-radius PS-TKA design and MP-TKA design. No differences were identified at 2-year follow-up with respect to post-operative ROM and PROMs.