Enhanced Mid‐Flexion Stability in Cruciate‐Sacrificing Total Knee Replacement: Impact of Optimized Implant Designs Investigated Using Musculoskeletal Multibody Simulation

Total knee replacement (TKR) is a successful intervention for relieving pain and improving quality of life. In this context, mid-flexion instability and paradoxical anterior femoral movement remain challenging. However, the role of implant design in cruciate-sacrificing (CS) scenarios is unclear. Therefore, this study investigated the influence of newly developed CS TKR designs on mid-flexion stability and anterior-posterior (AP) translation using a musculoskeletal multibody simulation during squat motion. The multibody model of the lower extremity, which represented the knee joint with ligaments and muscle structures, was previously validated using instrumented knee data. It was used to analyze newly developed (oneKNEE® cruciate-retaining (CR)/CS and medial-stabilized (MS)) and clinically established (Columbus® ultra-congruent (UC) and P.F.C.™ Sigma® CR) TKR designs. For this purpose, the overall femoral AP translation and tibial internal-external rotation during squat motion (flexion from 0° to 90°) in the CS condition were evaluated. During mid-flexion, the P.F.C.™ Sigma® CR exhibited greater anterior femoral translation than the Columbus® UC, with posterior movement starting at 35.5° (3.4 mm anterior) versus 20° (2.1 mm). In contrast, the oneKNEE® CR/CS and MS designs showed continuous posterior femoral movement (reduced paradoxical translation), with anterior-to-posterior turning points at 9° (1.2 mm) and 13° (0.8 mm) during squat motion, respectively, without inhibiting internal-external rotation. The kinematics of the oneKNEE® designs were achieved by combining the single-radius femoral design and steep anterior ramp of the tibial components. These designs reduced paradoxical anterior femoral movement in mid-flexion in the CS condition, while not restricting tibial internal-external rotation.