FEMORAL ARTICULAR SHAPE AND GEOMETRY - A 3-DIMENSIONAL COMPUTERIZED ANALYSIS OF THE KNEE

An average, three-dimensional anatomic shape and geometry of the dista l femur were generated from x-ray computed tomography data of five fre sh asymptomatic cadaver knees using AutoCAD (AutoDesk, Sausalito, CA), a computer-aided design and drafting software. Each femur model was g raphically repositioned to a standardized orientation using a series o f alignment templates and scaled to a nominal size of 85 mm in mediola teral and 77 mm in anteroposterior dimensions. An average generic shap e of the distal femur was synthesized by combining these pseudosolid m odels and reslicing the composite structure at different elevations us ing clipping and smoothing techniques in interactive computer graphics . The resulting distal femoral geometry was imported into a computer-a ided manufacturing system, and anatomic prototypes of the distal femur were produced. Quantitative geometric analyses of the generic femur i n the coronal and transverse planes revealed definite condylar camber (3 degrees-6 degrees) and toe-in (8 degrees-10 degrees) with an obliqu e patellofemoral groove (15 degrees) with respect to the mechanical ax is of the femur. In the sagittal plane, each condyle could be approxim ated by three concatenated circular arcs (anterior, distal, and poster ior) with slope continuity and a single are for the patellofemoral gro ove. The results of this study may have important implications in futu re femoral prosthesis design and clinical applications.