The Study: Standing sagittal alignment of the whole axial skeleton with reference to the gravity line in humans
- There is a lack of understanding of how the chain of balance of the boney structures from the feet to the head works because more information is needed regarding the three dimensional alignment of the boney structures relative to the gravity line (GL).
- The authors sought to study sagittal alignment in the standing position relative to the gravity line.
- They used an EOS 3D x-ray while the subjects stood on a force plate.
- They placed a mirror in the imaging room to help the subjects get a horizontal gaze.
- (This is important.) They defined the gravity line as “a vertical line drawn through the centre of vertical pressure measured by the force plate."
Please note: In this study "...the ankle joint was 4.8 cm posterior to the GL."
The subjects were 96 men and 40 women with a mean age of 39.7 years of age.
On average the following was found:
- The cervical and thoracic vertebrae were posterior to the GL.
- The apex of the thoracic kyphosis was at T7 and that point was "5 cm posterior to the GL."
- L4 was the apex of the lumbar lordosis and that was found to be anterior relative to the GL by 0.6 cm.
- "...the centre of the base of the sacrum (CBS) was just posterior to the GL."
- Subjects in their 40s, 50s and 60s the tended to exhibit L4, L5 and CBS which were significantly more posterior than these same areas for the subjects in their 20s.
Remember that these measurements were made relative to a gravity line determined by a force plate. This differs from a number of previous studies which have looked at a gravity or vertical axis line as drawn from some radiographic landmark. The mean age of the subjects was 39.7 years of age and it is interesting that there were changes in the findings as the subjects got older.
There are far too many findings to list in this review and you need to read the article to have a more complete understanding of all the results. Importantly, these authors found the gravity line by using a force plate and their gravity line does not pass through the ankle. It is an interesting but complex paper and it once again shows how much interest there is in boney alignment, this time relative to a gravity line determined by a force plate. We would like to thank our medical colleagues for their interest in boney alignment.
Reviewer: Roger Coleman DC
Editor: Mark R. Payne DC
Reference: Hasegawa K, Okamoto M, Hatsushikano S, Shimoda H, Ono M, Homma T, Watanabe K. Standing sagittal alignment of the whole axial skeleton with reference to the gravity line in humans. J Anat. See comment in PubMed Commons below2017 May;230(5):619-630. doi: 10.1111/joa.12586. Epub 2017 Jan 27.
Link to Abstract: https://www.ncbi.nlm.nih.gov/pubmed/28127750