Curvature of the femur and the proximal entry point for an intramedullary rod.

The degree of anterior curvature of 14 human femurs and four currently marketed intramedullary rods was analyzed with the use of an interactive graphic computer program. The radius of curvature of the femurs ranged from 188.5 to 68.9 cm (average, 114.4 cm). The radius of curvature of three of the four rods analyzed fell beyond the spectrum of radii found in the human femurs. A concomitant investigation of the most appropriate proximal entry site for an intramedullary rod was done based on the patterns of exit sites for both flexible guide wires and two intramedullary rods introduced in a retrograde fashion from the intercondylar notch in 14 matched pairs of human femora. The most appropriate area for proximal access into the medullary canal for these devices would appear to be at the junction of the femoral neck and the greater trochanter slightly anterior to or in the pyriformis recess.