Activated nitinol compression staples are associated with favorable biomechanical properties for talonavicular...

Nitinol compression staple use in foot and ankle arthrodesis procedures, including for the talonavicular joint, has gained acceptance. A previous study provided evidence for using nitinol compression staples in talonavicular arthrodesis (TNA) based on functional biomechanical testing comparisons to "gold standard" lag screw fixation. This study aimed to further compare the functional biomechanical properties of nitinol compression staple fixation to lag screw fixation for arthrodesis of the talonavicular joint. Body-temperature incubation and ankle inversion and eversion loading sequences were added to previously reported biomechanical testing.

Robotic testing was performed on cadaveric feet (n = 10; 5 matched pairs) after TNA using either two nitinol compression staples or two fully threaded lag screws. TNA method was randomized, alternating between matched-pairs of left and right feet. After surgical stabilization, specimens were incubated at 38 °C for 24 h to simulate the initial postoperative period in a patient. After plantarflexion and dorsiflexion testing, the specimens underwent inversion and eversion testing, cycling from 20° inversion to 10° eversion for 10 cycles. Displacements were tracked using optical tracking markers. Significant (p < 0.05) differences between staple versus screw fixation cohorts were determined using paired t-Tests.

All specimens completed testing with none experiencing failure at the TNF. No statistically significant differences in functional biomechanical testing properties were noted between nitinol compression staple fixation and lag screw fixation for TNA.

The study findings provide additional support for nitinol compression staple fixation as an option for talonavicular arthrodesis fixation. Taken together, the results of functional biomechanical testing studies have provided sufficient evidence for initiation of a prospective clinical outcomes study using nitinol compression staples for talonavicular arthrodesis fixation at our institution.