Biomechanical evaluation of proximally placed femoral less-invasive stabilization system plates

Loss of fixation of the Synthes 13-hole femoral Less-Invasive Stabilization System (LISS) plate has been noted. The biomechanical stability of this plate may be affected by improper proximal placement. We conducted a study to determine if there is any difference in fixation failure, deformation, or stiffness based on proximal placement. Using synthetic composite bones, we created a comminuted supracondylar distal femur fracture, AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) 33-A3. Three groups of 9 femurs each were created: 1 correctly positioned group and 2 incorrectly positioned groups, 1 with the proximal aspect of the plate 1 cm anterior and 1 with the proximal aspect of the plate 1 cm posterior. The constructs were tested in axial, torsional, and cyclical axial modes to assess plastic and total deformation and stiffness. Under axial loading, the posteriorly placed plate showed a 16.4% increase in stiffness. There was a significant increase of 12% in torsional stiffness in the anteriorly placed plate. Under cyclical axial loading, there was a significant increase of 14% in total deformation in the anteriorly placed plate. No fixation failure was observed. One-centimeter variation in proximal placement of a 13-hole LISS plate in a synthetic composite fracture model had little effect on the overall construct.