Cadaveric Gait Simulation of the Effect of Subtalar Arthrodesis on Total Ankle Replacement Kinematics

Abstract

Background: Patients undergoing total ankle replacement (TAR) often have symptomatic adjacent joint arthritis and deformity. Subtalar arthrodesis can effectively address a degenerative and/or malaligned hindfoot, but there is concern that it places abnormal stresses on the TAR and adjacent joints of the foot, potentially leading to early TAR failure. This study hypothesized that ankle and talonavicular joint kinematics would be altered after subtalar arthrodesis in the setting of TAR. Methods: Thirteen mid-tibia cadaveric specimens with neutral alignment were tested in a robotic gait simulator. To simulate gait, each specimen was secured to a static mounting fixture about a 6-degree of freedom robotic platform, and a force plate moves relative to the stationary specimen based on standardized gait parameters. Specimens were tested sequentially in TAR and TAR with subtalar arthrodesis (TAR-STfuse). Kinematics and range of motion of the ankle and talonavicular joint were compared between TAR and TAR-STfuse. Results: There were significant differences in kinematics and range of motion between TAR and TAR-STfuse groups. At the ankle joint, TAR-STfuse had less internal rotation in early-mid stance ( P < .05), with decreased range of motion in the sagittal (–2.7 degrees, P = .008) and axial (–1.8 degrees, P = .002) planes in early stance, and increased range of motion in the coronal plane in middle (+1.2 degrees, P < .001) and late (+2.5 degrees, P = .012) stance. At the talonavicular joint, there were significant differences in axial and coronal kinematics in early and late stance ( P < .05). Subtalar arthrodesis resulted in significantly decreased talonavicular range of motion in all planes in early and late stance ( P < .003). Conclusion: In ankles implanted with the TAR design used in this study, kinematics of the ankle and talonavicular joint were found to be altered after subtalar arthrodesis. Aberrant motion may reflect altered contact mechanics at the prosthesis and increased stress at the bone-implant interface, and affect the progression of adjacent joint arthritis in the talonavicular joint. Clinical Relevance: These findings may provide a correlate to clinical studies that have cited hindfoot arthrodesis as a risk factor for TAR failure.

Hindfoot Arthrodeses and the Order of Joint Fixation Influence Tibiotalar Kinematics During Simulated Stance

“…18 The use of 14 specimens was based on previous studies reporting joint kinematics. 3,12 The sample size was chosen to have sufficient power to compare the single and double arthrodeses conditions to intact (repeated measures), to compare single to double hindfoot arthrodeses (repeated measures), and to assess the differences between the ST double and TN double arthrodesis groups (2 independent groups).…”

“…Furthermore, our results align with previous biomechanical evidence indicating that a subsequent subtalar arthrodesis after TAA can alter tibiotalar motion. 1,12 One study assessing the impact on post-TAA kinematics of subtalar arthrodesis observed increased tibiotalar internal rotation during the late stance. 12 Our results also showed an increased internal tibiotalar joint rotation following double hindfoot arthrodesis.…”

“…18 The use of 14 specimens was based on previous studies reporting joint kinematics. 3,12 The sample size was chosen to have sufficient power to compare the single and double arthrodeses conditions to intact (repeated measures), to compare single to double hindfoot arthrodeses (repeated measures), and to assess the differences between the ST double and TN double arthrodesis groups (2 independent groups). Power analyses were made assuming a paired t test and independent samples t test with means and 95% CI data average across the stance phase and a significance level of .05 for the 2 types of analyses, respectively.…”

Robotic Technology in Foot and Ankle Surgery: A Comprehensive Review

“…The UMS was a robot with six degrees of freedom, four linear tendon actuators, and a rotatory Achilles actuator to simulate muscle engagement during walking. Lastly, a 2022 study used a robotic gait simulator to measure osseous kinematics after subtalar arthrodesis in cadavers with TAA implants, ultimately finding that ankle kinematics at the talonavicular joint were significantly altered after subtalar arthrodesis, correlating to clinical observations that have indicated that subtalar arthrodesis may be a risk factor for TAA failure [ 21 ]. Multiple other studies have also performed similar in vitro studies of foot bone and ligamentous kinematics with custom cadaveric gait simulators [ 22 , 23 , 24 ], with recent studies utilizing them to examine progressive collapsing foot deformities to best simulate stance phase and characterize the foot pathology [ 21 ].…”

“…Lastly, a 2022 study used a robotic gait simulator to measure osseous kinematics after subtalar arthrodesis in cadavers with TAA implants, ultimately finding that ankle kinematics at the talonavicular joint were significantly altered after subtalar arthrodesis, correlating to clinical observations that have indicated that subtalar arthrodesis may be a risk factor for TAA failure [ 21 ]. Multiple other studies have also performed similar in vitro studies of foot bone and ligamentous kinematics with custom cadaveric gait simulators [ 22 , 23 , 24 ], with recent studies utilizing them to examine progressive collapsing foot deformities to best simulate stance phase and characterize the foot pathology [ 21 ]. When comparing the range of motion of joint rotations and translations with the gold standard for in vivo kinematics, each of these studies demonstrated replicability and correspondence with in vivo values, suggesting the advantage of robotic gait simulators for providing exceptionally realistic descriptions of bony and ligamentous motion.…”