Femoral curvature variability in modern humans using three-dimensional quadric surface fitting

Introduction This study analysed femoral curvature in a population from Belgium in conjunction with other morphological characteristics by the use of three-dimensional (3D) quadric surfaces (QS) modelled from the bone surface. Methods 3D models were created from computed tomography data of 75 femoral modern human bones. Anatomical landmarks (ALs) were palpated in specific bony areas of the femur (shaft, condyles, neck and head). QS were then created from the surface vertices which enclose these ALs. The diaphyseal shaft was divided into five QS shapes to analyse curvature in different parts of the shaft. Results Femoral bending differs in different parts of the diaphyseal shaft. The greatest degree of curvature was found in the distal shaft (mean 4.5° range 0.2°–10°) followed by the proximal (mean 4.4° range 1.5°–10.2°), proximal intermediate (mean 3.7° range 0.9°–7.9°) and distal intermediate (mean 1.8° range 0.2°–5.6°) shaft sections. The proximal and distal angles were significantly more bowed than the intermediate proximal and the intermediate distal angle. There was no significant difference between the proximal and distal angle. No significant correlations were found between morphological characteristics and femoral curvature. An extremely large variability of femoral curvature with several bones displaying very high or low degrees of femoral curvature was also found. Conclusion 3D QS fitting enables the creation of accurate models which can discriminate between different patterns in similar curvatures and demonstrates there is a clear difference between curvature in different parts of the shaft.