Poor relationship between frontal tibiofemoral and trochlear anatomic parameters: Implications for designing a trochlea for kinematic alignment.

Abstract

The kinematic alignment (KA) technique for total knee arthroplasty (TKA) is an emerging implant positioning philosophy that aims to restore constitutional knee anatomy to improve knee kinematics. At present, the KA technique aims to reconstruct native femorotibial (FT) joint alignment, however there is still insufficient consideration towards the inter-individual trochlear anatomy variability. Poor trochlear restoration may compromise clinical outcomes. Our study aimed at assessing the anatomical relationship between the native trochlea and other FT anatomical parameters. Fifty-eight preoperative CT scans of low-grade knee arthritic patients were segmented to create 3D bone models. The FT and the PF anatomical parameters were measured using in-house software. Values were compared between different groups of lower limb and FT joint line (JL) orientation, and correlations between FT and PF anatomical parameters were assessed. We were unable to detect any significant correlation between groove orientation (frontal and axial) or groove radius and either the hip-knee-ankle (HKA), or the lateral distal femoral (LDFA), or the medial proximal tibial (MPTA), or the FTJL-mechanical axis (FTJLMAA) Angles. When considering the correlation within sub-groups of limb or JL orientation, we only found a positive correlation (r = 0.464, p = 0.022) in the varus lower limb (HKA ≤ 180°) sub-group between groove frontal orientation and LDFA. Our study shows that the determination of several limb, knee, and JL parameters is of poor value to predict individual trochlea anatomy. This raises the issue of how to improve femoral component design to achieve individualised FT and PF anatomical restoration with KATKA. Level 1 - computational study.