Determination of Femoral Neck Angle and Torsion Angle Utilizing a Novel Three-Dimensional Modeling and Analytical Technology Based on CT Datasets

Abstract

IntroductionExact knowledge of femoral neck inclination and torsion angles is important in recognizing, understanding and treating pathologic conditions in the hip joint. However, published results vary widely between different studies, which indicates that there are persistent difficulties in carrying out exact measurements.MethodsA three dimensional modeling and analytical technology was used for the analysis of 1070 CT datasets of skeletally mature femurs. Individual femoral neck angles and torsion angles were precisely computed, in order to establish whether gender, age, body mass index and ethnicity influence femoral neck angles and torsion angles.ResultsThe median femoral neck angle was 122.2° (range 100.1–146.2°, IQR 117.9–125.6°). There are significant gender (female 123.0° vs. male 121.5°; p = 0.007) and ethnic (Asian 123.2° vs. Caucasian 121.9°; p = 0.0009) differences. The median femoral torsion angle was 14.2° (-23.6–48.7°, IQR 7.4–20.4°). There are significant gender differences (female 16.4° vs. male 12.1°; p = 0.0001). Femoral retroversion was found in 7.8% of the subjects.ConclusionPrecise femoral neck and torsion angles were obtained in over one thousand cases. Systematic deviations in measurement due to human error were eliminated by using automated high accuracy morphometric analysis. Small but significant gender and ethnic differences were found in femoral neck and torsion angles.

Automated femoral version estimation without the distal femur

“…The median femoral neck angle, also referred to as inclination, was 129.4° (range 100.8–147.9°, IQR 125.4–133.3°). IQR inclination ranges from 117.9 to 125.6° . This version and inclination data indicate the subjects included in this study reflect measures comparable with the population at large as presented in a study of over 1,000 individuals .…”

“…The median version angle, often referred to as femoral torsion, was 15.5° (range −20.1–52.3°, IQR 9.1–21.9°). Literature indicates IQR version ranges from 7.4 to 20.4° . The median femoral neck angle, also referred to as inclination, was 129.4° (range 100.8–147.9°, IQR 125.4–133.3°).…”

“…Two important relationships for this orientation are femoral inclination and femoral version. Femoral inclination, or angle of inclination, is the angle formed between the femoral neck axis and the axis of the femoral shaft in the frontal plane and averages between 120° and 125° in the normal adult hip . Femoral version is the anterior deviation of the femoral neck axis from the posterior condylar line and averages 14.0 ± 6.0° in the normal population, indicating that the femoral head is normally anteverted or oriented anteriorly.…”

“…When viewing axial slices with CT, the orientation of the femoral neck axis changes with respect to the slice level . A 2D view does not accurately capture the 3D nature of version as the 3D femoral neck axis presents differently from both superior and inferior aspects . CT or MR imaging would permit more accurate measurements by creating 3D models of the femur, however manually selecting the 3D femoral neck axis is challenging.…”

New Design Process for Anatomically Enhanced Osteosynthesis Plates

“…SOMA was based on a correspondence mapping algorithm implemented by Gottschling et al and Schröder et al which allowed for virtual morphometric measurement of individual bone properties (length, width, perimeter, curvature, etc. ) and for quantifying the conformity of plate models and bone shapes . SOMA was applied on 3D bone models of 115 individual MC5 bones.…”