Biomechanical analysis of screw fixation vs. K-wire fixation of a slipped capital femoral epiphysis model

Previous data have shown that due to the technical ease, low-morbidity, and lower complication rates, the single-implant fixation is the current standard for stabilization of slipped capital femoral epiphysis (SCFE) fixation. Multiple-implant fixation is thought to be combined with a higher incidence of serious complications. The purpose of the current study was to evaluate single- vs. multiple-implant fixation regarding strength and stiffness. Furthermore, different screw designs, including telescopic screw, were evaluated regarding the stiffness, strength, and especially fixation failure. Forty porcine proximal femurs were sectioned through the physeal line using a gigli saw and stabilized with a 7.3-mm stainless steel AO screw, a dynamic telescopic screw, three 1.6-mm Kirschner wires (K-wires), and three 2.0-mm K-wires. The femurs were biomechanically tested to determine failure load (N) and stiffness (N/mm). No significant differences were found regarding failure load and stiffness between the two screw groups. The 2.0-mm K-wire construct was significantly the strongest and stiffest fixation. The 1.6-mm K-wire fixation had the lowest values, but not statistically significant. Regarding the fixation failure, no femoral shaft fracture occurred. SCFE stabilization with three 2.0-mm K-wires leads to increased stability over single-screw fixation and 1.6-mm K-wire fixation. However, none of the two screws seemed to be superior in fixation stability and fixation failure.