A Biomechanical Comparison of Short Segment Long Bone Fracture Fixation Techniques

Abstract

To determine whether using 2 small fragment plates (3.5 mm screw size) side by side is biomechanically superior to the use of 1 large fragment plate (4.5 mm screw size), in the fixation of "short segments" in long bone fractures. Fiber-filled epoxy bone surrogates were plated across 1-cm gaps with 3 different constructs. Six surrogates were fixed using 2 side-by-side 3.5-mm waisted compression plates and six 3.5-mm screws, 6 surrogates were fixed using one 4.5-mm waisted compression plate and two 4.5-mm screws, and 6 surrogates were fixed using one 3.5-mm waisted compression plate and three 3.5-mm screws. These constructs then underwent cyclic axial compression in 100-N increments until 500 N was reached. Then, they underwent cyclic cantilever bending at 2 Hz and at a 23.6 N·m moment until fatigue failure occurred. Also, a single load to failure test was performed in cantilever bending to evaluate plate strength. The cumulative gap length change after 500 cycles of loading up to 500 N was 3.4% ± 0.4% for the 3.5 mm double plate construct, 9.5% ± 1.4% for the 4.5 mm single plate construct, and 14.4% ± 0.9% for the 3.5 mm single plate construct. In cantilever bending, the 3.5 mm double plate construct failed after 15,345 ± 2493 cycles, the 4.5 mm single plate construct failed after 2713 ± 1811 cycles, and the 3.5 mm single plate construct failed in its first cycle. In single load to failure testing, the load at offset yield was higher in the 3.5 mm double plate construct than the 4.5 mm single plate construct. This study suggests that in situations where anatomy or other limitations limit the length of bone segments available for fixation, it may be preferable to use 2 small plates with more screws rather than 1 large plate with few screws.