Influence of Isolated Talonavicular and Subtalar Joint Arthrodesis on Hindfoot Kinematics and Range of Motion During Cadaveric Gait Simulation.

Background: Isolated subtalar and talonavicular joint arthrodeses have been associated with adjacent joint arthritis and altered hindfoot kinematics during simplified loading scenarios. However, the effect on kinematics during dynamic activity is unknown. This study assessed changes in subtalar and talonavicular kinematics after isolated talonavicular (TN _iso ) and subtalar (ST _iso ) arthrodesis, respectively, during stance simulations.
Methods: Fourteen midtibia specimens received either a TN _iso or ST _iso arthrodesis, with 7 randomized to each group. A 6-degree-of-freedom robot sequentially simulated the stance phase for the intact and arthrodesis conditions. Bootstrapped bias-corrected 95% CIs of the talonavicular and subtalar joint kinematics were calculated and compared between conditions.
Results: The TN _iso decreased subtalar inversion, adduction, and plantarflexion in late stance ( P  < .05). The subtalar range of motion in the sagittal and coronal planes decreased by 40% ( P  = .009) and 46% ( P  = .002), respectively. No significant changes in talonavicular joint kinematics were observed after isolated subtalar arthrodesis; however, the range of motion was reduced by 61% ( P  = .007) and 50% ( P  = .003) in the coronal and axial planes, respectively.
Conclusion: In this model for arthrodesis, changes in subtalar kinematics and motion restriction were observed after isolated talonavicular arthrodesis, and motion restriction was observed after isolated subtalar arthrodesis. Surprisingly, talonavicular kinematics did not appear to change after isolated subtalar arthrodesis.
Clinical Relevance: Both joint fusions substantially decrease the motion of the reciprocal adjacent joint. Surgeons should be aware that the collateral costs with talonavicular fusion appear higher, and it has a significant effect on subtalar kinematics during the toe-off phase of gait.
Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: The authors report support for the present manuscript from a Paragon 28 research grant contract; Paragon 28 provided screws to perform the arthrodesis conditions and complete the original study that this short report expands on. Disclosure forms for all authors are available online.