A 3D Shape Reconstruction of Ligament from Arthroscopic Images

In vivo data on the biomechanics of knee ligaments and their behavior under stress are necessary to understand and treat knee injuries. To obtain this data, accurate measurement of strains on and in the ligament is necessary. Technical and ethical considerations make such in vivo measurements of a human knee difficult or impossible. To overcome these problems, we planned to combine two techniques to measure stress/strain distributions; One is an arthroscopic measurement of ligament’s deformation. The other is to introduce stress/strain distributions using the deformation data through the FEM analysis. The objective of this study was to establish the method to obtain the 3D deformations from the arthroscopic images. The endoscopic photos were converted into grey scale images, and the shape from shading method was used to generate the objects' 3D shape from the images. Once the system was calibrated, a swine femur and tibia were set in a special fixture, and the industrial endoscope was used to pictures of the anterior cruciate ligament (ACL) at various angles of knee flexion. Three-dimensional coordinates were obtained by the level set method from the brightness data on the processed image and the three-dimensional shape of the ACL surface was generated.

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