Background: Talonavicular arthrodesis (TNA) is indicated for treatment of disorders that require immobilization of the hindfoot. Lag screw fixation is considered the reference standard technique for TNA. Despite consistently favorable clinical results using lag screw fixation, it is still associated with higher than desired complication and failure rates. Nitinol compression staples have been used for TNA based on potential advantages over lag screw fixation. However, functional biomechanical data comparing lag screw and nitinol compression staples for TNA are lacking. Therefore, the objective of this study was to compare nitinol compression staples to fully threaded lag screws for use in TNA with respect to their biomechanical properties during functional robotic testing., Methods: TNA was performed on cadaveric feet (n = 12; 6 matched pairs) using either two nitinol compression staples (Arthrex, Naples, FL) or two fully threaded lag screws (Arthrex, Naples, FL) in random order, alternating between paired left and right feet. After instrumentation, specimens were mounting in a robotic testing system and loaded at 89 N/sec from 30 N to 445 N for 1 min. Then, continuous compressive load of 445 N was applied while cycling from 30° plantarflexion to 15° dorsiflexion for 10 cycles. Optical tracking markers attached to the talus and navicular bone tracked displacements. Translation data were recorded along the X, Y, Z planes. Rotation data were recorded for roll, pitch, and yaw. Significant (p < 0.05) differences between fixation methods were determined using paired t-Tests for each measured variable., Results: There were no statistically significant differences between staples and screws for translation in X, Y, or Z planes. When comparing rotation (roll, pitch, and yaw), there were no statistically significant differences with the exception of increased roll rotation for staple fixation versus lag screw fixation during static compression testing (p = 0.009)., Conclusion: Based on comparison to the reference standard lag screw fixation for clinically relevant biomechanical properties measured during functional robotic testing of the hindfoot, nitinol compression staples are a viable option for talonavicular arthrodesis., Competing Interests: James L. Cook receives research support from AO Trauma; receives IP royalties, paid consultant, receives research support from Arthrex, Inc; receives research support from Collagen Matrix Inc; receives research support from DePuy, A Johnson & Johnson Company; receives editorial or governing board from Journal of Knee Surgery; is a board or committee member for Midwest Transplant Network; is a board or committee member, receives IP royalties and receives research support from Musculoskeletal Transplant Foundation; receives research support from National Institutes of Health (NIAMS & NICHD); receives research support from Orthopaedic Trauma Association; receives research support from Purina; receives research support Regenosine; receives research support from SITES Medical; receives publishing royalties, financial or material support Thieme; receives paid consultant Trupanion; and receives research support from the U.S. Department of Defense. Kyle M. Schweser is a board or committee member AAOS; is a board or committee member for AAOS: Board or committee member; is a board or committee member for AO North America; is paid consultant for ODI; is a board or committee member for Orthopaedic Trauma Association; and receives research support Synthes. Prati Jahnu Reddy, Blaine Manning, Will Bezold, and Ashwin Garlapaty have no conflicts of interest to disclose., (© 2023 Professor P K Surendran Memorial Education Foundation. Published by Elsevier B.V. All rights reserved.)