the logotype for the biomechanics of the spine
By Janis Savlovskis, MD

This section aims to demonstrate and argue the range of motion implemented in our spine model. So anyone who uses our website and application for fun, for curiosity, or professionally – might be sure – there is a solid scientific basis behind every illustration.

Screenshot of the Application demonstrating the maximum axial rotation of the spine
Neutral spine. Screenshot of the app The Biomechanics of the Spine The maximum axial rotation to the right. Screenshot of the app The Biomechanics of the Spine

The screenshots of the application, highlighting the geometrical plasticity of the spine coupled with the complexity of any motion. Click an image to see the transition between the neutral spine and the maximum axial rotation.

Those who are familiar with the topic know that the spine's biomechanics is complicated and sometimes counterintuitive. The scientific evidence collected during the last 50 years has demonstrated that the only possible path to the knowledge in this field lies in the continuous critical analysis. No authority statement could be trusted without checking the methods and statistics backing it. We've made an effort to keep things as simple as possible and present a kind of literature meta-analysis about the different aspects of the spine motion.

We disclose the evidence-based logic behind our spine biomechanical model in the following chapters:

You might ask – why we didn't take a well-known and respected textbook and didn't animate our 3D model according to the angles indicated in one trustworthy source? It may sound overconfident, but the answer is – the lack of reliability. Many textbooks contain detailed information about the angles of ROM of the spine, but usually no or very little information about the source of evidence for those numbers. Unfortunately, the credibility of these numbers outside of the context with literature data is very low. To demonstrate that, we have selected three textbooks of the highest authority.

  • ‣ White AA, Panjabi MM. Clinical Biomechanics of the Spine. Lippincott Williams & Wilkins; 1990.
  • ‣ Neumann DA. Kinesiology of the Musculoskeletal System. 2nd ed. Mosby; 2010.
  • ‣ Kapandji A. The Physiology of the Joints. Vol 3. 2nd ed. Churchill Livingstone. 1974.

, and included the reported ROM data, when appropriate, in the graphs summarizing ROMs in different planes so that anyone can visualize the magnitude of an issue.

We should also mention the considerable variability of the results caused by the differences in study design, selected population, and methods chosen to measure the spine's biomechanical properties. To minimize this variability, we have applied the following selection criteria to the data included in the analysis:

  • ‣ When the appropriate evidence from the in vivo studies was available, the ex vivo studies were excluded
  • ‣ Only the healthy/asymptomatic group from case-control studies was included
  • ‣ The female cohort results (when possible) were excluded from the analysis
  • ‣ The analysis (when possible) includes data only from young individuals, preferably of the 3rd decade of life
First published: Jan/2022