Evaluation of patellofemoral joint in ADVANCE® Medial-pivot total knee arthroplasty

Purpose ADVANCE (R) Medial Pivot (MP) (Wright Medical) total knee arthroplasty (TKA) was established to replicate normal tibio-femoral knee joint kinematics, however, its influence on the patello-femoral (PF) joint is unclear. The purpose in this study was to assess the PF joint conditions in Advance MP TKA, via radiography and three-dimensional image-matching software. Methods Ten subjects with osteoarthritis were treated with the ADVANCE MP TKA. Pre-operatively and one month after surgery, skyline views at 30, 60, and 90 degrees of flexion were taken, and patella shift and tilt were measured. With 2D-3D registration techniques using software, implant orientations were matched with the pre-operative CT and changes in the anterior part of the femoral prosthesis, condylar twist angle (CTA) for femoral rotation, and tibial rotation were evaluated. The relationships between morphological and rotational changes were evaluated. Results There were significant differences in patella tilt at 60 degrees and patella shift at all angles between pre- and post-operation (p<0.05). No correlation was found between morphological changes in the anterior femur with patella tilt and shift. A positive correlation between postoperative CTA and patella shift at 90 degrees was found (p<0.05); however, no correlation was found between rotational alignment of the tibial component and patella tilt and shift. Conclusions ADVANCE MP TKA changed patello-femoral joint kinematics, compared to that found before surgery. The kinematic features were mainly due to the design concepts for tibio-femoral joint motion, indicating the difficulty to reproduce normal patello-femoral joint kinematics after TKA.