A holistic parametric design attempt towards geometric modeling of the lumbar spine

摘要

Biomechanical studies based on anatomical meshes are often generated with various segmentation methods; hence they are fixed,preventing tuning of morphometrical parameters.The primary objective of this study was to develop a methodology that would allow construction of a robust and high-fidelity CAD model from the CT scans of an individual.In this framework,a holistic approach was adopted for the design of the lumbar spine.This involved the breaking-up of the design intent into three levels.From top-down,a master layout sketch of the vertebral curve was used to drive the entire model at the highest level.Secondly,each vertebra was divided into two parts in order to simplify the parameteriza-tion procedure.Thirdly,a spiral curve was introduced in order to facilitate the placement of the facet joints.This way,a statically-determinate vertebral stacking sequence during assembly was realized.Hausdorff distance between the CAD and CT meshes was used to evaluate the accuracy of the model.In addition,mean and standard deviation of the errors were also calculated.A new generic lumbar vertebral CAD model was successfully built and tested.This model could lead to dramatic reductions in both time and effort required to prepare patient-specific biomechanical models.