Abstract
Prospective match cohort study of disc degeneration progression over ten years with and without baseline discography
To compare progression of common degenerative findings between lumbar discs injected ten years earlier with those same disc levels in matched subjects not exposed to discography
Seventy-five subjects without serious low back pain illness underwent a protocol MRI and a L3/4, L4/5 and L5 S1 discography in 1997. A match group was enrolled at the same time and underwent the same protocol MRI examination. Subjects were followed for ten years. At 7 to 10 years after baseline assessment, eligible discography in controlled subjects underwent another protocol MRI. MRI graders, blind to group designation, scored both groups for qualitative findings.
Well matched cohorts, including 50 discography subjects and 52 control subjects met eligibility criteria for follow up evaluation. In all graded or measured parameters, discs that had been exposed to puncture and injection had greater progression of degenerative findings compared to control (non-injected) discs: progression of disc degeneration, 54 discs (35%) in the discography group compared to 21 (14%) in the control group (p=0.03); 55 new disc herniations in the discography group compared to 22 in the control group (p=0.0003). New disc herniations were disproportionately found on the side of the annular puncture (p=0.0006). The quantitative measures of disc height and disc signal also showed significantly greater loss of disc height (p=0.05) and signal intensity (p=0.001) in the discography disc compared to the control disc.
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 disk 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.
