Spinous process morphology: the effect of ageing through adulthood on spinous process size and relationship to sagittal alignment

Study designBlinded radiographic analysis of CT scans reformatted for precise lumbar spinous process (LSP) measurement.ObjectiveTo investigate the effect of ageing on LSP morphology and influence of LSP morphology on lumbar spine sagittal alignment.Summary of background dataThere is little data reporting the influence of ageing on spinous process size. There is data describing the increase in size of other body parts with age, such as the femur, ears, vertebral body, and nose. Several old cadaveric and radiographic studies have reported the formation of osseous spurs within the supraspinous and interspinous ligaments.Method200 abdominal CT scans taken for trauma and vascular investigation were reformatted to allow precise bony measurement of the lumbar spine. Two observers were blinded from the age and demographics of the patients. Sagittal and coronal plane projections were used to measure the height and width of the spinous processes (L1–L5), respectively. The relationship between spinous process size, age, and supine lordosis was investigated.ResultsLSP height increases by 0.03–0.07 mm/year (p < 10−3 to 10−8) and width by 0.05–0.06 mm/year (p < 10−11 to 10−15). Lumbar lordosis decreases with increasing LSP height (p < 0.0004) but is not related to increasing LSP width (p = 0.195). Supine lordosis increases by 0.1°/year (p = 0.004).ConclusionsThis study demonstrates that the dimensions of the LSP change with age. Increases in LSP height and even more impressive increases in LSP width occur with advancing age. There is an inverse relationship between lumbar lordosis and LSP height.