Intraoperative Kinematics in Posterior Cruciate Ligament Retaining Total Knee Arthroplasty Using Different Inserts

We analyzed the intraoperative kinematics of total knee arthroplasty (TKA) using a navigation system to investigate the influence of different inserts on kinematics. This was a retrospective observational study. The Vanguard individualized design (33 patients, 33 knees) XP and anterior-stabilized (AS) inserts were used in TKA for osteoarthritis. Kinematic data were intraoperatively recorded. The range of motion, tibiofemoral rotational angle, anteroposterior translation of the femur, and varus-valgus laxity were compared between the two inserts (XP vs. AS). There was no significant difference in the range of motion (extension: XP, 3.7° ± 3.3° vs. AS, 3.8° ± 3.3°, p = 0.84; flexion: XP, 138.1° ± 10.2° vs. AS, 139.0° ± 13.3°, p = 0.73). With the AS insert, the tibia was gradually internally rotated as the knee was flexed. At maximum extension, the internal rotation was smallest with AS (XP 6.5° ± 4.0° vs. AS 5.1° ± 3.4°, p = 0.022), which was also associated with smaller anterior femoral translation (maximum extension: XP, 14.1 ± 4.8 mm vs. AS, 11.3 ± 4.7 mm, p = 0.00036; 30°: XP, 23.7 ± 5.6 mm vs. AS, 20.7 ± 5.1 mm, p = 0.000033; 45°: XP, 24.4 ± 4.9 mm vs. AS, 23.2 ± 4.5 mm, p = 0.0038). The AS was associated with a lower varus-valgus laxity (30° XP 4.1° ± 3.4 vs. AS 3.3° ± 2.7°, p = 0.036; 60°: XP, 3.2° ± 3.0° vs. AS, 2.4° ± 3.3°, p = 0.0089). The AS insert facilitated sequential tibiofemoral rotation with varus-valgus stability in mid-flexion without restricting the range of motion.