The locking attachment plate for proximal fixation of periprosthetic femur fractures - A biomechanical comparison of two techniques

摘要

Purpose Mechanical properties of a locking attachment plate construct (LAP-LCP), allowing bicortical screw placement laterally to the prosthesis stem, are compared to a cerclage-LCP construct. Methods Eight right synthetic femora with implanted uncemented hip endoprosthesis were cut distally and fixed with LCP, monocortical locking screws and either LAP (n04) or cerclage (n04). Cyclic testing was performed with monotonically increasing sinusoidal load until failure. Relative movements at the plate-femur interface were registered by motion tracking. Statistical differences were detected by unpaired t-test and general linear model repeated measures. Results Stiffness of the LAP-LCP was significantly higher at the beginning (875.4 N/mm ± 29.8) and after 5000 cycles (1213.0 N/mm ± 101.1) compared to the cerclage-LCP (644.96 N/mm ± 50.1 and 851.9 N/mm ± 81.9), with P=0.013. Relative movements for AP-bending (B) and axial translation (T) of the LAP-LCP at the beginning (0.07°± 0.02, 0.20 mm ± 0.08), after 500 cycles (0.16°±0.10, 0.26 mm ± 0.07) and after 5000 cycles (0.26°±0.11, 0.31 mm ± 0.07) differed significantly from the cerclage- LCP (beg.: 0.26°±0.04, 0.28 mm ± 0.05; 500 cyc: 0.47°± 0.03, 0.53 mm ± 0.07; 5000 cyc.: 0.63°±0.18, 0.79 mm ± 0.13), with B: P=0.02, T: P=0.04. Relative movements for medial bending were not significantly different between the two constructs. Cycles to failure (criterion 1 mm axial translation) differed significantly between LAP-LCP (19,519± 1,758) and cerclage-LCP (11,265±2,472), with P=0.035. Conclusions Biomechanically, the LAP-LCP construct improves proximal fixation of periprosthetic fractures compared to the cerclage-LCP construct.