Novel Tricortical Kirschner Wire vs Screw Fixation for Distal Chevron Osteotomy
Natalie Black, Dr. Jie Chen, Randal Morris, Dr. Vinod Panchbhavi
University of Texas Medical Branch School of Medicine
Introduction: Distal chevron osteotomies for hallux valgus correction are commonly fixed with screws. Kirschner wire fixation avoids permanent hardware and is cheaper, however traditional unicortical placement of kirschner wires can lead to loss of fixation. Tricortical kirschner wire fixation is a novel method used by the senior author which involves oblique wire placement such that three cortices are involved rather than one. This study biomechanically compares the fixation strength of tricortical kirschner wire fixation to traditional screw fixation. Methods: 4 matched pairs of first metatarsals were dissected out from cadaveric feet. Each metatarsal was loaded in the intact state, and a distal chevron osteotomy performed with use of a cutting guide. Each specimen per pair was treated with either 2mm tricortical kirschner wire or 2.7mm screw fixation and tested in 2 loading conditions in accordance with described methods: cantilever testing which simulates the anatomic position of the first metatarsal during standing and physiologic testing which simulates the combination of ground reaction and muscular forces acting upon the MTP joint. Initial stiffness ratios were calculated for both conditions and load to failure in the cantilever position. Results: The stiffness ratio was 44.16% for screw fixation in physiologic loading compared to 48.76% for tricortical wire fixation (p= 0.89). The stiffness ratio was 80.07% for screw fixation in cantilever loading compared to 78.49 (p=0.97). The load to failure was 239.81N for screw fixation compared to 184.90N for tricortical wire (p=0.59). Conclusion: The rigidity of tricortical kirschner wire fixation is not significantly different than screw fixation for distal chevron osteotomy, nor is the load to failure. This may be a cheaper alternative to screw fixation without the need for permanent hardware. We plan to test 5 more pairs.