Biomechanical analysis of screw fixation vs. K-wire fixation of a slipped capital femoral epiphysis model.
BACKGROUND
Previous data have shown that due to the technical ease, low-morbidity, and lower complication rates, the in situ 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.


METHODS
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).


RESULTS
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.


CONCLUSIONS
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.
Center for Musculoskeletal Surgery, Campus Virchow, Charité-University Medicine, Berlin, Germany. claudia.druschel@charite.de
Claudia
C
Druschel
Olga
O
Sawicki
Johannes
J
Cip
Werner
W
Schmölz
Julia F
JF
Funk
Richard
R
Placzek
D000818:Animals; D001863:Bone Screws; D001864:Bone Wires; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery; D016268:Internal Fixators; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery*; D008954:Models, Biological; D011474:Prosthesis Design; D060048:Slipped Capital Femoral Epiphyses / Q000503:physiopathology* / Q000601:surgery*; D013552:Swine; D016896:Treatment Outcome