SPINOUS PROCESS MORPHOLOGY AND ITS RELATIONSHIP TO THE SAGITTAL ALIGNMENT IN THE DEGENERATE SPINE

The purpose of this study was to establish the relationship between the anterior and posterior spinal elements and identify which morphological changes in the ageing spine has the greatest influence in determining the loss of lumbar lordosis. Method 224 patients9 (98 male, 126 female) erect plain lumbar radiographs were reviewed. Lateral plane projections were used to measure the lumbar angle (lordosis), spinous process (SP) height, the interspinous gap (ISG) height, the mid-vertebral body (MVB) height and the mid inter-vertebral disc (MIVD) height of vertebral bodies L1 to L5. The relationship between the heights of these structures and their relative influence and effect on the lumbar angle was investigated using a multiple linear regression model. Results SP, ISG, MVB and MIVD heights all had a statistically significant influence on determining the lumbar angle (p −3 ). All heights decreased with age except for the SP height (Graph 1). Age was associated with a decreasing lumbar angle (p 0.134) – (Graph 2). Increasing SP height had an inverse relationship on the lumbar angle. The increase in the SP height had the greatest influence on the lumbar angle (Beta coefficient of -0.71), whilst the MVB and MIVD heights had a lesser influence on determining the lumbar angle (Beta coefficients 0.29 and 0.53 respectively). Conclusion This study demonstrates that the changing morphology of the SP height in the ageing lumbar spine has the greatest influence on determining the lumbar angle of our measured variables. The relative cumulative effect of the increase in the height of the posterior spinal elements has a greater influence on the loss of the lumbar angle than the cumulative loss of height in the anterior spinal elements in the ageing lumbar spine.