Influence of Tibial Component Position on Altered Kinematics Following Total Ankle Arthroplasty During Simulated Gait.

Abstract

Ankle and hindfoot kinematics following total ankle arthroplasty (TAA) are poorly understood and it is unclear whether patients can replicate physiologic motion after TAA. Furthermore, the effect of implant position on TAA kinematics is unknown. The objective of this study was to compare ankle and hindfoot kinematics pre- and post-TAA during simulated gait and determine to what degree tibial component position correlated with variations in ankle kinematics. Eight midtibia cadaveric specimens were utilized in this institutional review board-approved study. The stance phase of gait was simulated both pre- and post-TAA in each specimen using a 6 degrees of freedom robotic platform. Ankle and hindfoot kinematics were measured from reflective markers attached to bones via surgical pins. The effect of tibial component position on absolute differences in ankle kinematics was assessed using linear regression. No differences were observed in ankle sagittal and coronal plane motion between the intact and TAA conditions. Differences in ankle joint kinematics were identified in the transverse plane, where internal talar rotation was significantly increased following TAA compared with the native condition. The medial-lateral position of the tibial component was found to correlate with the altered transverse plane motion observed after TAA (β = 1.861 degrees/mm, <i>R</i>² = 0.72, <i>P</i> = .008). No significant differences in subtalar and talonavicular joint kinematics in any plane were observed comparing the pre- and post-TAA condition. This study demonstrated an increased internal rotation of the ankle in the transverse plane following TAA. This increase was correlated with the medial-lateral position of the tibial implant. This finding could have clinical implications for how tibial components are positioned during the operative procedure, and how implant design and position may affect ankle kinematics following TAA.