Three-dimensional reconstruction and reverse-engineering used to establish lower-extremity mechanical axes in healthy adults

Abstract

Objective To present a method to establish lower-extremity mechanical axes by means of three-dimensional (3D) reconstruction and reverse-engineering.Methods Twenty healthy adult volunteers of Han ethnic group were enrolled in the present study.They were 10 men and 10 women,18 to 22 years of age (average,19.3 years).Continuous spiral CT scans were conducted on their both lower extremities.The original scan data in the.dicom format were imported into the Mimics Innovation Suite 14.0 software for 3D reconstruction of models of lower extremity bones which were saved in the.stl format.Next,the 3D models were imported into Geomagic Studio 2012 software before centers of the femoral head,the knee,the tibia and the ankle were defined and the mechanical axes of the tibia and femur were determined on the 3D reconstruction models.Results The average lower-extremity mechanical axis at the coronal view was 178.6° ± 2.4° for the male and 177.1°± 2.5° for the female; the included angles between the femoral and tibial mechanical axes averaged 2.1° ± 1.8° for the male and 2.2° ± 1.9° for the female; the average lower-extremity mechanical axis at the sagittal view was 178.5° ± 2.2° for the male and 177.6° ± 2.3° for the female.There were no significant differences between male and female or between the left and the right sides of the lower limb regarding the lower-extremity mechanical axis.Conclusion 3D reconstruction and reverse-engineering is a digital and individualized method that can be used to determine lower-extremity mechanical axes. Key words: Imaging, three-dimensional; Reverse-engineering; Mechanical axis