Biomechanical Comparison of Locking Compression Plate and Limited Contact Dynamic Compression Plate Combined with an Intramedullary Rod in a Canine Femoral Fracture-Gap Model.

ObjectiveTo compare the biomechanical properties of locking compression plate (LCP) and a limited contact dynamic compression plate combined with an intramedullary rod (LC-DCP-R) in a cadaveric, canine, femoral fracture-gap model. Study DesignIn vitro biomechanical study; nonrandomized, complete block (dog). Sample PopulationPaired cadaveric canine femora (n=10 dogs). MethodsPaired femurs with a mid-diaphyseal 20mm gap were stabilized with either LCP or LC-DCP-R. Nondestructive testing up to 60% of body weight (BW) was followed by a continuous destructive test. Comparative structural properties, 3-dimensional (3D) interfragmentary motion, and plate linear strain were evaluated. Paired comparisons were made between LCP and LC-DCP-R. ResultsStiffness after nondestructive testing was significantly lower for LCP with a mean (95% confidence interval [CI]) of 61N/mm (46-76) versus 89N/mm (67-110) for LC-DCP-R (P=.0072). Ultimate load to failure was significantly lower for LCP with a median (interquartile range [IQR]) of 270N (247-286) versus 371.5 (353-385) for LC-DCP-R (P=.002). Axial motion at 60% BW was significantly higher for LCP with a median (IQR) of 1.01mm (0.71-1.26) versus 0.36mm (0.20-0.49) for LC-DCP-R (P=.002). Shear motion was significantly higher for LCP with a median (IQR) of 1.18 (0.78-1.58) versus 0.72mm (0.45-1.00) for LC-DCP-R (P=.018). Strain was significantly higher for mid-LCP surface with a mean (95%CI) at 60% BW of 979def (579-1378) versus 583def (365-801) at mid-LC-DCP-R surface (P=.0153). The elastic limit strain of the plates was not different and was reached at a mean (95%CI) load of 241N (190-292) for LCP versus 290N (245-336) for LC-DCP-R (P=.12). ConclusionThe LC-DCP-R showed higher stiffness and resistance to failure, lower interfragmentary motion, and lower plate strain and stress compared to LCP.