A Review of Applicable Materials for 3D Printing a Biomechanically Accurate Cervical Spine Model for Surgical Education & Case Preparation

Objectives: The authors review the literature to compare biomechanical properties of the human cervical spine as determined by cadaveric and finite elemental model (FEM) studies, with commercially available three-dimensional (3D) printing materials to aid in the development of 3D-printed cervical spines that can be used as biomechanically accurate educational tools. Specifically, 3D printing materials for fused deposition modeling (FDM) printers were explored. Methods: A literature review of biomechanical specifications such as Young’s Modulus and Poisson’s ratio of certain anatomical aspects of the cervical spine was performed by searching the databases PubMed, MEDLINE via Ovid, Wolters Kluwer, ClinicalKey, and EMBASE via Elsevier for keywords. The anatomical features that were investigated included cortical and cancellous bone, facet joints, intervertebral discs, and ligaments. Additionally, datasheets from companies Stratasys, Fillamentum, NinjaTek, SD3D, Polymakers, Lubrizol and BASF were compiled to review the specifications and mechanical properties of their 3D printing materials. Results: Suggested FDM 3D printing materials were assigned to anatomical features of the cervical spine according to their respective biomechanical properties, namely: cortical and cancellous bone, facet joint articular cartilage and the synovial membrane, both the ground substance and fibers of the annulus fibrosus, nucleus pulposus, anterior and posterior longitudinal ligaments, ligamenta flava, interspinous ligaments, and capsular ligaments. Conclusions: FDM 3D printing can improve development of cervical spine models for educational use and surgical case preparation. Commercially available materials and techniques exist to simulate all of the major anatomical components of the cervical spine

A pain in the neck: Articular process joint osteochondrosis and intervertebral disc degeneration in warmblood horses

Cervical vertebral stenotic myelopathy (CVM) is a well-known syndrome in horses in which compression of the spinal cord and nerves in the neck leads to nervous signs. In warmblood horses, osteoarthrosis of the articular process joints is the most common underlying pathology resulting in CVM. The cause for the osteoarthrosis is unknown. In this thesis, first the possible role of osteochondrosis, a defect in the development of bone, in the development of articular process joint arthrosis is explored. Non-clinical osteochondrosis was found to be common, however without preference for the predilection site of osteoarthrosis. Therefore osteochondrosis does not seem a likely main cause. Yet, a significant variation in the shape of the articular surfaces of the process joints was seen and some of these shapes were correlated with the presence of osteochondrosis. Next, the possible role of intervertebral disc degeneration (IVDD) in the development of articular process joint osteoarthrosis was explored, because a correlation between the two is seen in dogs and people. Equine IVDD has been considered clinically insignificant even though research confirming this has not been published. In contrast to literature, we found that the intervertebral disc of horses does have a nucleus pulposus and that IVDD is common with a predilection site concurrent with that of osteoarthrosis. Biochemical changes, important for biomechanical characteristics, associated with equine IVDD differed from those in dogs and people. However, the changes that were found, have in human discs and in equine tendons been associated with stiffness, loss of strength and brittleness. It is likely that these biomechanical changes are also present in the degenerated equine intervertebral disc. This could lead to changes in loading of the articular process joints and therefore it is possible that equine IVDD can lead to articular process joint osteoarthrosis and CVM