Comparison of in vivo ankle joint kinematics after total ankle replacement with different types of talar components

Implant loosening and sinking are the primary reasons for revision surgery following total ankle arthroplasty (TAA). Utilizing a custom-made artificial talar prosthesis in conjunction with TAA (combined TAA) is anticipated to address these issues. However, few studies have investigated in vivo ankle joint kinematics after TAA with an artificial talar prosthesis, and there is a need to evaluate and compare this newer approach with conventional talar implants, which only replace the articular surface of the talus (standard TAA). This study aimed to compare postoperative ankle joint kinematics in vivo between standard TAA and combined TAA. Twenty-six orthopedic patients who underwent TAA participated in this study (standard TAA: 9; combined TAA: 17). Computed tomography (CT) of the ankle was performed in non-weight-bearing maximal dorsiflexion and plantarflexion. In vivo ankle joint kinematics during these movements were calculated using three-dimensional implant models created from CT images and registered with the iterative closest point algorithm. The transitional motion from dorsiflexion to plantarflexion and the implant position and posture at each ankle position were assessed. There was no significant difference in the transition angles from dorsiflexion to plantarflexion between the standard and combined TAA groups. After combined TAA, the ankle joints exhibited a posture of more inclined inversion and abduction, and the implant position and posture did not significantly impact the postoperative range of motion. Although the sample size was insufficient for statistical analysis because of the rarity of the surgery, these findings offer insights for future implant design and surgical techniques.