The change of whole lumbar segmental motion according to the mobility of degenerated disc in the lower lumbar spine: a kinetic MRI study

Purpose: To analyze the effects of mobility of degenerated disc in the lower lumbar discs (L4–5 and L5–S1) on both whole lumbar motion and adjacent segment ROM. Methods: The kMRIs with disc degeneration at L4–5 or L5–S1 were classified into three groups: the normal group, the motion-preserved (MP) group and the motion-lost (ML) group based on range of motion (ROM) of 5° in the degenerated segment. Each segmental ROM, whole lumbar motion, and the contribution % of the upper lumbar spine (ULS: L1–2–3) and the lower lumbar spine (LLS: L4–5–S1) motion to whole lumbar motion were measured and compared with each of the other groups. Results: There were 94, 99 and 66 patients in the normal group, MP group and ML group, respectively. The normal group showed no significant difference compared to the MP group in all ROM parameters. The ML group showed significantly less whole lumbar motion, more contribution % in the ULS and less in the LLS than the normal and the MP groups. The ROM in the superior adjacent segment in the ML group was not significantly different between that in the normal and MP group. Conclusions: Degenerated lumbar discs did not show hypermobility within functional ROM. Loss of segmental ROM from advanced disc degeneration did not cause an increase in the ROM of the superior adjacent segment in vivo. When the LLS had motion-lost, advanced disc degeneration, whole lumbar motion was significantly decreased and compensatory increase in ROM was accomplished by the ULS.