Comparative strength measurements of five different fixation systems applied on an in vitro model of femoral midshaft osteotomy.

Oblique midshaft fractures of long bones can be stabilized using either plates and screws, lag screws, wires, cerclages, or a combination of these methods. Fractures at the distal tip of a well-fixed femoral prosthesis are difficult to stabilize with plates and screws because of the underlying intramedullary stem, polymethylmetacrylate (PMMA) cement, and thin periprosthetic femoral cortex. In this study we compared in vitro the mechanical performance of five different osteosynthesis techniques applied on an oak femoral model obliquely oscillated to mimic a short oblique fracture: (a) Double stainless steel wiring; (b) two 4.5 mm lag screws; (c) combination of one 4.5 mm cortical screw and one stainless steel wire; (d) one titanium compression cerclage Gundolf (CCG) combined with one 4.5 mm screw; and (e) double CCG. The five fixation constructs were subjected to a noncyclic destructive axial compression and torsional loading. The highest torque stiffness proved to be the double CCG and the double screw constructs, followed by and combination of CCG-screw and double screw constructs. The mode of failure in torque was a longitudinal crack close to the screw tip and loosening of the CCG and wire. The double screw, double CCG, and screw-CCG constructs provided the highest stiffness in axial compressive forces. The mode of failure in compression was loosening of the CCG and wire and bending of the screw. This comparative study showed that double CCG can theoretically replace the conventional methods of "minimal" osteosynthesis in the midshaft of long bones, and thus shows promise in the treatment of difficult short-oblique type femoral fracture at the distal tip of a well-fixed femoral prosthesis. The advantages of using the CCG is simplicity of technique, biocompatibility of titanium, no interference in modern imaging techniques, and avoidance of stripping of muscles and degloving of bone surfaces, as often happens in platting.