Goh CS, Santoni BG, Puttlitz CM, Palmer RH. Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523. AJVR 2009 Jan 70 1 23-9 Objective-To compare the mechanical behaviors of a semicontoured, locking compression plate-rod (LCP-rod) construct and an anatomically contoured, limited-contact dynamic compression plate-rod (LC-DCP-rod) construct applied to experimentally induced gap fractures in canine femora. Sample Population-16 femora from 8 cadaveric dogs. Procedures-8 limbs from 8 dogs were assigned to the LCP-rod construct group or the LC-DCP-rod construct group. In each femur, a 39-mm mid-diaphyseal ostectomy was performed at the same plate location and the assigned construct was applied. Construct stiffness and ostectomy gap subsidence were determined before and after cyclic axial loading (6,000 cycles at 20%, 40%, and 60% of live body weight [total, 18,000 cycles]). Three constructs from each group further underwent 45,000 cycles at 60% of body weight (total, 63,000 cycles). Following cyclic loading, mode of failure during loading to failure at 5 mm/min was recorded for all constructs. Results-After 18,000 or 63,000 cycles, construct stiffness did not differ significantly between construct groups. No implant failure occurred in any construct that underwent 63,000 cycles. In both construct groups, ostectomy gap subsidence similarly increased as axial load increased but did not change after 18,000 cycles. Mean +/- SEM loads at failure in the LCP-rod (1,493.83 +/- 200.12 N) and LC-DCP-rod (1,276.05 +/- 156.11 N) construct groups were not significantly different. The primary failure event in all constructs occurred at the screw hole immediately distal to the ostectomy. Conclusions and Clinical Relevance-Biomechanically, the semicontoured LCP-rod construct is similar to the anatomically contoured LC-DCP-rod system.