Changes in sagittal component alignment alters patellar kinematics in TKA: an in vitro study

Patellar maltracking due to incorrect component alignment is considered as a main reason for anterior knee pain after total knee arthroplasty (TKA). In contrast to coronal and axial component placement, the influence of sagittal component alignment on patellar kinematics has not been investigated so far. In ten lower cadaveric limbs, TKAs were implanted using a commercial computer navigation system. In six knees, the femoral component was aligned in 5A degrees and in four knees in 0A degrees of flexion, respectively. Patellar kinematics were registered by means of a computer navigation system using an additional patella tracking array and correlated with femoral and tibial sagittal component alignment. Sagittal component alignment significantly altered patellar mediolateral shift (p < 0.05). In contrast, patellar epicondylar distance, rotation and tilt were not significantly influenced. Sagittal component alignment in TKA has a major impact on patellar kinematics and should therefore be considered while addressing tibiofemoral kinematics intraoperatively.