In VitroBiomechanical Comparison of 3.5 mm LC‐DCP/Intramedullary Rod and 5 mm Clamp‐Rod Internal Fixator (CRIF)/Intramedullary Rod Fixation in a Canine Femoral Gap Model

ObjectiveTo compare the biomechanical properties of clamp rod internal fixation (CRIF)/rod and LC‐DCP/rod constructs in a canine femoral gap model.Study DesignCadaveric biomechanical study.Sample PopulationCanine femora (n = 10 pair).MethodsFemora with 40 mm ostectomies were assigned to LC‐DCP/rod or CRIF/rod treatment groups. Five construct pairs had 4‐point bending and 5 pairs had torsional loading. Construct stiffness, strength, and bending angle at failure or permanent angular deformation (torsional loading) were determined. Statistical comparisons were performed using Studentttests; significance was set atP ≤ .05.ResultsThere was significantly greater permanent angular deformation, or residual twist, in the CRIF/rod constructs (23.1 ± 0.89°) compared with LC‐DCP/rod constructs (7.47 ± 2.08°). Whereas there was no significant difference in torsional stiffness of these constructs at torsional loads <4.92 N m (P = .819), LC‐DCP/rod constructs had significantly greater torsional stiffness (0.303 ± 0.079 N m/°) and strength (11.546 ± 2.79 N m) than CRIF/rod construct stiffness (0.06 ± 0.013 N m/°) and strength (6.078 ± 0.527 N m) at torsional loads >4.92 N m. Differences in stiffness and strength in 4‐point bending were not statistically significant.ConclusionsLC‐DCP/rod constructs had significantly less permanent angular deformation than CRIF/rod constructs. CRIF/rod constructs became less stiff as torsional load was increased, thus the LC‐DCP/rod constructs had significantly greater torsional stiffness and strength under high torsional loads. LC‐DCP/rod and CRIF/rod constructs performed similarly under 4‐point bend loading conditions.