Implications of three-dimensional modeling of the proximal femur for cephalomedullary nailing: An Asian cadaver study

Purpose To determine the variability in the ideal entry point of cephalomedullary (CM) nail around the greater trochanter (GT) and the consequent conformity with the proximal femur by analyzing three-dimensional (3D) modeling and virtual implantation Materials and methods A total of 105 cadaveric femurs (50 males and 55 females) underwent continuous 1.0 mm slice computed tomography (CT) scans. CT images imported into Mimics^® software to reconstruct the 3D model of the proximal femur and medullary canal. PFNA-II^® was processed into a 3D model using a 3D-sensor at the actual size and optimally implanted in the proximal femur model using Mimics^® software. The ideal entry point, nail conformity with the proximal femur, and the relationship between the entry point and adjacent structures were assessed. Results The ideal entry point was located a mean of 2.38 mm (SD, 3.53 mm) medial to the tip of GT. No lateral cortex impingement of the proximal femur occurred in the coronal plane based on the recommended point. However, a disparity in the sagittal plane between the proximal shaft and nail curvature was found in 47 models (44.8%). Rotation and magnification of the 3D model exposed all nails above the surface of the medial side of the GT. The proximal nail end was contained entirely within bone and circumferential endosteal cortical contact was present at the nail-bone interface.