Abstract
Introduction
Primary mechanical fixation and secondary biologic fixation determine the fixation of an uncemented femoral component. An optimized adequacy between the implant design and the proximal femur morphology allows to secure primary fixation.
The femoral antetorsion has to be considered in order to reproduce the center of rotation.
A so-called «corrected coronal plane » including the center of the femoral head has therefore been defined. The goal of this study was to evaluate the proximal metaphysal volume and to design a straight femoral component adapted to this corrected coronal plane.
Materials and Methods
205 CT-scans (performed in 151 males and 54 females free of hip arthritis) have been analyzed with a three-dimensional reconstruction. The mean age was 68.5 years (35–93).
A corrected coronal plane has been defined including the center of the femoral head and the axis of the intramedullary canal. Five levels of sections (at a defined distance from the center of the femoral head) have been selected: 12.5mm, 50mm, 70mm, 90mm and 120mm. Three intramedullary criteria have been studied: volume between the 50mm and the 90mm sections (C1), the medial-lateral distance of the intramedullary canal (C2) at the 50mm, 70mm, and 90mm levels, and the A-P distance (C3) at the 50mm, 70mm, and 90mm levels (respectively C3–50, C3–70, and C3–90). The femoral head diameter, the femoral offset and the canal flare index (CT flare) have also been measured.
Results
The mean head diameter was 47.7mm (38–56). The mean femoral offset was 44mm. The mean canal flare index was 4.68 (2.71 to 7.86). Based on the different measurements a femoral component with a range of 10 different sizes has been designed.
Discussion
The morphological parameters of the studied population were comparable with published data. Radiological and CT-scan data have already been used in order to design femoral implants. However, these data did not consider the femoral antetorsion.
The use of the corrected coronal plane allowed for optimized measurements when compared with previous methods in order to design a femoral component.
Conclusion
The original method used in this study was to consider the corrected coronal plane in the design of a femoral component that respects the femoral antetorsion.
