Biomechanical comparison of single- and double-pin fixation for acute slipped capital femoral epiphysis.

Biomechanics of pin fixation for acute slipped capital femoral epiphysis (SCFE) was studied in an in vitro immature canine model. Acute SCFE were created in 24 paired femurs. The paired specimens were pinned with either one or two pins and loaded to failure. Strength and stiffness of the paired limbs were expressed as percentages of the loads necessary to create the initial SCFE in the intact specimen. Strength and stiffness were equivalent statistically for the intact physis and the fractured physis fixed with two pins. Single pinning was only 83% as strong and 78% as stiff as the intact physeal plate. Double-pin fixation is recommended over single-pin fixation for acute SCFE. These data, however, should not be extrapolated to the clinical situation of fixation for chronic SCFE.