Quantifying degree of difficulty in hip - resurfacing of pistol-grip deformity.

This study used computer simulation to endeavor to quantify the relative degree of difficulty of resurfacing femora with pistol-grip deformities compared to relatively normal femora. Computer models of five pistol-grip femora and one relatively normal femur were computed from computed tomography (CT) scans of patients who had undergone computer-assisted hip resurfacing. A computer simulation of positioning the femoral resurfacing component on the femur was performed to count the number of acceptable configurations of the component on the femur. A high number of acceptable configurations implies that the surgeon has greater freedom, or greater margin for error, in implanting the component compared to a femur with a smaller number of acceptable configurations. We found that pistol-grip deformities dramatically reduce the number of acceptable configurations for valgus alignment, and that such configurations result in decreased femoral offset and increased depth of reaming.