Waseem Amir Bashir MBChB, Presenter: Nothing to Disclose

Tetsuya Torio MD, Abstract Co-Author: Nothing to Disclose

Francis William Smith MD, Abstract Co-Author: Nothing to Disclose

Keisuke Takahashi, Abstract Co-Author: Nothing to Disclose

Malcolm Pope PhD, Abstract Co-Author: Nothing to Disclose

To define the optimal sitting posture by investigating variable seated positions using positional MRI. Normal lumbar spine position during sitting has long been debated. In 1953, Keegan hypothesised a relationship between lordosis and trunk-thigh angle using plain radiography of only 4 individuals. No one has ever replicated his original study.

Measurements of lumbar lordosis angles, intervertebral disc (IVD) heights and translation of the nucleus pulposus (NP) were made on 22 normal subjects with no history of back pain or surgery using a 0.6 Tesla whole-body positional MRI scanner. We then determined which sitting position showed the least biomechanical stress on the lumbar spine. This study would not have been possible on a regular fixed ‘tunnel’ recumbent scanner.

We found IVD height showed a tendency to decrease as lumbar lordosis decreased in variable sitting positions from reclining to forward flexion. The NP showed movement within a limited range in normal IVDs without change of its overall area. The optimal sitting position was with a trunk-thigh angle of 135 degrees. This position was shown to cause least 'strain' on the lumbar spine, most significantly when compared with an upright 90 degree sitting posture.

We have adapted a small plain radiography study from 53 years ago and shown the best biomechanically and anatomically 'neutral' sitting postion using positional MRI. It is well known that a relationship exists between seating posture and back pain and therefore this study has provided data that will help to reduce the incidence of chronic back problems from bad sitting positions.

We have shown that positional MRI is of value in the evaluation of future seating design and as a result help to reduce chronic back problems from bad seating posture.

Bashir, W, Torio, T, Smith, F, Takahashi, K, Pope, M, The Way You Sit Will Never Be the Same! Alterations of Lumbosacral Curvature and Intervertebral Disc Morphology in Normal Subjects in Variable Sitting Positions Using Whole-body Positional MRI.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4435870.html