Biomechanical Comparison of Nitinol Compression Staples vs Fully Threaded Lag Screws for Talonavicular Arthrodesis

Abstract

Category: Hindfoot; Other Introduction/Purpose: The talonavicular joint is a crucial component of the hindfoot complex. Talonavicular arthrodesis has significant effects on foot biomechanics and motion. Current techniques for talonavicular arthrodesis vary and include a variety of constructs. Despite favorable clinical results, there is a lack of data regarding the biomechanical performance of second-generation nitinol compression staples compared to screw fixation for talonavicular arthrodesis. The objective of this study was to compare nitinol compression staples with fully threaded lag screws in talonavicular fusion with respect to their clinically relevant biomechanical properties during functional testing. Methods: A single orthopaedic surgeon used either two nitinol compression staples (Arthrex, Naples, FL) or two fully threaded lag screws (Arthrex, Naples, FL) on cadaveric feet (n=12; 6 matched pairs) to perform surgical arthrodesis of the talonavicular joint; each pair undergoing each procedure in random order and alternating between left and right feet. Optical tracking markers were attached to the talus and navicular bone to track displacements. Specimens were loaded at 89N/sec from 30N to 445N for 1 minute. A continuous compressive load of 445N was applied while cycling from 30° plantarflexion to 15° dorsiflexion for 10 cycles. Translation data were recorded along the X, Y, Z planes. Rotation data were recorded for roll, pitch, and yaw. Significant (p < 0.05) differences were determined using paired t-Tests, comparing staple fixation versus screw fixation for each measured variable. Results: There were no statistically significant differences between staples and screws between translation in the X, Y, and 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 only (p=0.009). Conclusion: Based on clinically relevant biomechanical properties measured during functional robotic testing of the hindfoot, nitinol compression staples are a viable option for use in talonavicular arthrodesis.