Article

3D geometrical assessment of femoral curvature: A reverse engineering technique

Department of Aerospace Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand.
Journal of the Medical Association of Thailand = Chotmaihet thangphaet 10/2008; 91(9):1377-81.
Source: PubMed

ABSTRACT

Investigate the 2D/3D geometry of femoral curvature and femoral length using the advanced technique of computerized tomography combined with reverse engineering techniques.
The present study was performed using reverse engineering technique based on CT data of 99 cadaveric femora. The femur was divided into three segments, proximal, mid-shaft, and distal regions by defining 35% and 65% of the femoral total length as a boundary of each region. The intramedullary canal in the mid-shaft region was mainly extracted to determine the set of circular center, which could consequence to approximate the 3D femoral radius of curvature using the 3D least square best fit. The 3D femoral curvature was then projected into A-P and M-L directions to investigate the correlation of 2D/3D femoral curvature as normal radiographic images.
It was found that the average 3D Thai femoral curvature was 895.46-mm (SD = 238.06) and the average femoral total length is 421.96-mm (SD = 27.61). In addition, the 2D femoral curvature derived from sagittal radiographic image can be used to determine the 3D femoral curvature with this equation: R3D = RSagittal + 3.67 with r = 0.987.
This described technique is a non-destructive method that can effectively assess the internal/ external 3D geometric data of the femur The obtained data is useful to develop a proper design of prosthesis that required inserting into the intramedullary canal. From the present study, it can be concluded that the 2DSagittal femoral curvature derived from standard radiographic image can be represented for the 3D femoral curvature.

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    • "Thus, neither the anterior curvature nor the lateral bow can provide an accurate description and detailed knowledge of the femoral curvature in 3D space. For the first time, Chantarapanich et al. reconstructed and calculated the femoral curvature in 3D space and concluded that the femoral 3D curvature was closely correlated with the curvature on the sagittal plane, irrespective of that on the coronal plane [24]. "
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    • "Thus, neither the anterior curvature nor the lateral bow can provide an accurate description and detailed knowledge of the femoral curvature in 3D space. For the first time, Chantarapanich et al. reconstructed and calculated the femoral curvature in 3D space and concluded that the femoral 3D curvature was closely correlated with the curvature on the sagittal plane, irrespective of that on the coronal plane [24]. "
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    • "Other important parameters are the bowing angle and the anterior bowing, which is vital in prosthesis design [22]. Extreme bowing femora influence the stability of the implant especially with the cementless hip stem at distal diaphysis leading to overreaming, which risks more bone loss during surgery to prevent femora fracture [40, 41]. "
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