Abstract
The Lumbar Spinous Processes (LSP) have an important anatomical and biomechanical function protecting the neural structures in the spinal canal, and as an anchor for the inter and supraspinous ligaments, and the inter-segmental paraspinal muscles. They also influence access to the spinal canal for neural decompressive surgical procedures. More recently the LSPs have attracted increased interest as a site for surgical device attachment in an attempt to both decrease the symptoms of spinal stenosis, and as a site for intersegmental stabilization without formal fusion. There is evidence that various anatomical structures have altered morphology with ageing, and there is anecdotal evidence of changing LSP morphology with age. This study aims to clarify the influence of age on LSP morphology, and on lumbar spine alignment.
200 CT scans of the abdomen were reformatted with bone windows in sagittal and coronal planes allowing precise measurement of LSP dimensions, and Lumbar Lordosis. Observers were blinded to patient demographics. Inter-observer reliability was examined. Data was analysed by an independent statistician.
The smallest LSP is at L5. The male LSP is on average 2–3mm higher and 1mm wider than the female LSP. LSP height increases significantly with age at every level in the lumbar spine (p< 10-5 at L2). The LSPs increase in height by 2–5mm between 20–85 years of age (p< 10-6), which was as much as 31% at L5 (p< 10-8). Width increases proportionally more, by 3–4mm or greater than 50% at each lumbar level (p< 10–11). Lumbar lordosis decreases in relation to increasing LSP height (p< 10-4) but is independent of increasing LSP width (p=0.2).
This study demonstrates that the dimensions of the LSP change with age. Increases in LSP height occur with age. More impressive increases in LSP width occur with advancing age. This study suggests that loss of lumbar lordosis is correlated with changing LSP morphology.
The increased width of the LSP with age influences access to the spinal canal, particularly if midline-preserving approaches are attempted in the ageing population. There is increased bone volume for bone grafting procedures with increasing age. The reduced distance between LSPs with age may influence design of implants that stabilize this region of the spine, and occur not only as a result of disc space narrowing, but also as a consequence of increased LSP dimensions.
Correspondence should be addressed to: Associate Professor N. Susan Stott, Orthopaedic Department, Starship Children’s Hospital, Private Bag 92024, Auckland, New Zealand.
