An in vitro biomechanical comparison of a 5.5 mm limited-contact dynamic compression plate fixation with a 4.5 mm limited-contact dynamic compression plate fixation of osteotomized equine third metacarpal bones |
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| Authors: | Sod Gary A Mitchell Colin F Hubert Jeremy D Martin George S Gill Marjorie S |
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| Institution: | Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA |
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| Abstract: | Objectives— To compare monotonic biomechanical properties and fatigue life of a 5.5 mm broad limited‐contact dynamic compression plate (5.5‐LC‐DCP) fixation with a 4.5 mm broad LC‐DCP (4.5‐LC‐DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. Study Design— In vitro biomechanical testing of paired cadaveric equine MC3 with a mid‐diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. Sample Population— Adult equine cadaveric MC3 bones (n=18 pair). Methods— MC3 were divided into 3 test groups (6 pairs each) for: (1) 4‐point bending single cycle to failure testing; (2) 4‐point bending cyclic fatigue testing; and (3) torsional single cycle to failure testing. The 8‐hole, 5.5 mm broad LC‐DCP (5.5‐LC‐DCP) was applied to the dorsal surface of 1 randomly selected bone from each pair. One 8‐hole, 4.5 mm broad LC‐DCP (4.5‐LC‐DCP) was applied dorsally to the contralateral bone from each pair. Plates and screws were applied using standard ASIF techniques. All MC3 bones had mid‐diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t–test within each group. Significance was set at P<.05. Results— Mean yield load, yield bending moment, composite rigidity, failure load and failure bending moment under 4‐point bending, single cycle to failure, of the 5.5‐LC‐DCP fixation were significantly greater (P<.024) than those of the 4.5‐LC‐DCP fixation. Mean cycles to failure for 4‐point bending was significantly (P<.05) greater for the 4.5‐LC‐DCP fixation compared with the 5.5‐LC‐DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion for the 5.5‐LC‐DCP fixation was not significantly different (P>.05) than those with the 4.5‐LC‐DCP fixation. Conclusion— 5.5‐LC‐DCP fixation was superior to 4.5‐LC‐DCP fixation in resisting the static overload forces under palmarodorsal 4‐point bending. There was no significant difference between 5.5‐LC‐DCP fixation and 4.5‐LC‐DCP fixation in resisting static overload forces under torsion; however, the 5.5‐LC‐DCP offers significantly less stability (80% of that of the 4.5‐LC‐DCP) in cyclic fatigue testing. Clinical Relevance— The results of this in vitro study may provide information to aid in the selection of a biological plate for long bone fracture repair in horses. |
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