Introduction & Perspective
Throughout the history of the chiropractic profession, there has been a sustained belief that a bone in the spine can become fixed in an abnormal position (subluxated). When the spine is properly adjusted, the bone is corrected to a normal position. Proving this has been the nemesis of scientific investigation and research for all these many years. Even to this day, few chiropractors and researchers are aware of the ability of (orthogonally based) upper cervical chiropractors to objectively measure misalignments of the cervical spine using angular (rotatory) relationships. Fewer still are aware of the ability of upper cervical chiropractors to apply the correction principle and not only return a subluxated bone to a defined normal position but to proportionately correct the entire spine and all of the spinal elements to the vertical axis, the normal position defined by gravity itself. In the standing position, this constitutes a minimal stress, minimal energy position for the entire body, thereby serving well as a defined and objectively measurable “normal”.
During early chiropractic investigations and education, the focus of care was on the upper cervical spine. Over time, this focus shifted to the entire spine creating a shift in belief systems between upper cervical and “full-spine” or “segmental” chiropractors. Few resources have been dedicated to research to test the upper cervical proposition that spinal misalignments (abnormal position) create mechanical distress that has a global affect on the nervous system, body posture, and normal physiology.
Chiropractic research has been focused on the effectiveness of spinal manipulation therapy regarding the outcomes of a wide range of symptoms, pain relief, and increasing the mechanical range of motion. This has been practiced to the near exclusion of determining what is biomechanically and neurologically normal. This also includes identifying what forces should be used to correct spinal misalignments and what forces produce common spinal misalignments. There are no studies showing the negative health effects of chronic spinal misalignments.
Research Goals
The Spinal Model project specifically addresses what is biomechanically normal. Once a biomechanical normal is established, then measurements become less relative, more absolute and scientifically acceptable. After biomechanical normal is established, we will assess the effects of misalignments/mal-position of both cervical vertebra and head-neck relationships, as well as the effect of forces the head-cervical spine and forces producing malposition of both cervical vertebra and head–neck relationships.
Modeling Technique
The stress strain relationships, material behavior, geometry, loads and constraints on any structural component can be represented by a set of equations. However, as the complexity of the geometry (i.e., the shape of the component), loading conditions and the constraints in an engineering problem increase, it becomes impossible to find an exact solution to this set of equations. Finite element analysis is a numerical technique that is used to find an approximate solution to this set of equations.
The engineering-problem in finite element analysis is represented by what is called a finite element model. In a finite element model, the geometry of the structural component is divided into small parts/mesh. Each of these small parts is called an “element” and the points where these small parts connect to each other is called a “node”. Appropriate material properties are assigned to each element. Therefore, intuitively, as the size of the element becomes smaller, the model more closely represents the actual material continuity that exists. As the mesh is refined, the model shape will match more closely to the actual shape.
The University of Toledo Spine Research Laboratory’s ABAQUS software is used for finite element analysis. Previously, 3-D finite element models have been made of the lumbar, thoracic, and cervical spinal segments. These models incorporated all the details of the segment including the ligaments, facet joints, the intervertebral discs, vertebral bodies, etc. The material properties of various tissues have been adapted from the literature and from in-house data.
Principal Investigators/Credentials
The principal investigator of this project is Dr. Vijay K. Goel, McMaster-Gardner Professor of Orthopedic Bioengineering, Co-Director Engineering Center for Orthopaedic Research Excellence (E-CORE) at the University of Toledo. Dr. Goel holds appoints in the Departments of Bioengineering and Orthopaedic Surgery in the Colleges of Engineering and Medicine. His specialty is in orthopedic and dental biomechanics, especially spine biomechanics and spinal discs. Dr. Goel is a recipient of the University of Toledo’s 2005-2006 Outstanding Faculty Researcher Award and is internationally renowned for his work on spinal implants. In 2003 he received the H.R. Lissner Award from the American Society of Mechanical Engineers for his work on spinal implants. Between 2000 and 2006 he has published 56 peer-reviewed manuscripts, several book chapters, and more than 130 abstracts.
Drs. Keith Denton, Teresa Palmer and Mr. Jim Palmer provided valuable support and guidance for this study.