Fixation of transverse midshaft clavicle fractures with nitinol staples vs. superior locked plating: a biomechanical study

Background: Nitinol staples have been used effectively for stabilization and compression at fracture sites. This study compared yield load, fracture displacement, and load to failure between nitinol staples and superior plating for midshaft clavicle fractures. Methods: Ten pairs of cadaveric clavicles underwent midshaft osteotomy. Each specimen in each pair was randomly assigned to fixation with superiorly placed nitinol staples or with superior plating. Specimens were loaded cyclically with increasing loads to a maximum of 1200 cycles and 60 N. Fracture displacement and construct stiffness were compared at each load. Load to failure was performed at the conclusion of testing. Results: The staple group demonstrated lower yield load and higher median fracture displacement at all levels of force compared to the plate group. Median displacement at physiologic load was 15.3 (IQR 12.8-16.5) mm for the staple construct and 2.9 (IQR 2.5-3.6) mm for plated constructs (P=2.04E-07). Median stiffness of plated constructs was significantly higher than staple constructs at all levels (P<0.05). Median cycles to failure for staple constructs was significantly lower compared to plated constructs (P=0.004). Median load to failure was significantly higher for plated constructs compared to staple constructs (P=2.8E-06). Conclusions: Nitinol staple fixation of midshaft clavicle fractures demonstrated lower yield load, stiffness, increased displacement, and lower load to failure compared to superior plate fixation. However, staple constructs provided adequate stability to maintain reduction of the fracture at physiologic levels of repetitive stress, indicating a potential role for nitinol staples in clavicle fracture fixation.