Single versus double screw fixation for treatment of slipped capital femoral epiphysis: a biomechanical analysis.

Slipped capital femoral epiphyses (SCFE) were created in 10 pair of bovine femurs. Each pair was pinned with a single screw on one side and two screws contralaterally. The specimens were reloaded to failure. Double pin fixation yielded only a 33% increase in stiffness as compared with single pin fixation. Resistance to further slip was not proportional to screw number. The stiffness of neither double nor single screw fixation approximated that of the intact physis. Single screw fixation in slipped epiphyses is recommended because the small gains in stiffness with a second screw do not offset the risk of complications.