3D Vertebrae Measurements: Assessing Vertebral Dimensions in Human Spine Mesh Models Using Local Anatomical Vertebral Axes

TL;DR

The paper addresses the need for efficient vertebral morphometrics by introducing a fully automated pipeline that measures vertebral body dimensions on 3D spine meshes using local vertebral axes. It segments vertebral bodies, extracts endplates, and derives landmark-based dimensions, implemented as a 3D Slicer plugin for lumbar and thoracic spines. The authors validate the approach on VerSe and synthetic Sawbone datasets, reporting mean absolute errors around $1.32$ mm for lumbar vertebrae on VerSe and an overall $MAE$ of about $0.7$ mm on Sawbone, with ICCs indicating substantial agreement with expert measurements. Qualitative results show reprojection of mesh-derived measurements onto CT images, suggesting potential for efficient longitudinal studies and preoperative planning, with plans to extend to rotational metrics and cervical vertebrae.

Abstract

Vertebral morphological measurements are important across various disciplines, including spinal biomechanics and clinical applications, pre- and post-operatively. These measurements also play a crucial role in anthropological longitudinal studies, where spinal metrics are repeatedly documented over extended periods. Traditionally, such measurements have been manually conducted, a process that is time-consuming. In this study, we introduce a novel, fully automated method for measuring vertebral morphology using 3D meshes of lumbar and thoracic spine models.Our experimental results demonstrate the method's capability to accurately measure low-resolution patient-specific vertebral meshes with mean absolute error (MAE) of 1.09 mm and those derived from artificially created lumbar spines, where the average MAE value was 0.7 mm. Our qualitative analysis indicates that measurements obtained using our method on 3D spine models can be accurately reprojected back onto the original medical images if these images are available.

Figures (3)

• Figure 1: Sample measurements of established dimensional parameters of the vertebral body shown on a 3D model of L2
• Figure 2: Overview of the proposed approach: the local vertebrae orientations are calculated first((a)-(c)). Subsequently, cutting planes in the frontal view (d) are established based on the Center of Mass (CoM) and a normal vector derived from step (c). This procedure precisely segments the vertebral geometry into focused region of interest, i.e. vertebral body. In the next step, the upper and lower endplates are extracted from the vertebral body ((e)). In final steps, the intersection points are calculated after cutting the vertebral body with the local frontal and sagittal planes. The landmarks (marked red and green in (i-j)) for the dimensional measurements then derived from the these intersections and are used to identify the vertebral dimensions.
• Figure 3: Back-projection of vertebral measurements into its corresponding sagittal CT scan of VerSe2020 dataset. Six landmarks in the local sagittal plane define the outer distances as well as the vertebral body height in the center.