The problem of evaluating in situ pinning of slipped capital femoral epiphysis: an experimental model and a review of 63 consecutive cases.

Over a 3-year follow-up period, 63 hips (in 49 patients) that were pinned as treatment for slipped capital femoral epiphysis were examined and evaluated. A 36.8% incidence of unsuspected pin penetration was discovered. Four types of experimental models representing different degrees of severity of slipped capital femoral epiphysis were designed and manufactured in the bioengineering laboratory. In situ pinning was performed on each model. An extensive series of controlled test films on the models indicated the difficulty of accurately determining the true position of the pins with conventional roentgenographic views. Subsequent fluoroscopic analysis revealed a verifiable correlation between the limited visualization of conventional X-ray analysis following the pinning of a slipped capital femoral epiphysis and unrecognized pin penetration.