OBJECTIVETo observe morphological changes of lumbar intervertebral foramen and pathologic changes around the nerve root and to explore the main evaluation index for lumbar foraminal stenosis (LPS) in parasaggital MRI finding.

METHODSFrom Jan. 2007 to Aug. 2009, MRI finding in 35 patients with the LPS that were confirmed by surgery was retrospectively analyzed. This group including 27 males, 8 females; aged from 35 to 82 years with the mean of 54.5 years; the course was from 4 months to 8 years with the mean of 32 months. At the same time compared with another group including 37 cases whose MRI finding of foramen were normal. To find out the differences between two groups in effective foraminal height, effective superior foraminal width, the effective ratio of nerve root cross-sectional area and foramen cross-sectional area by analyzing the parasaggital MRI finding of L4.5 or L5S1 foramen. To analyze the main factors that included LPS.

RESULTSEffective foraminal height and effective superior foraminal width in L(4,5) or L5S1 foramen in LPS group was smaller than that of control group (P < 0.01). The effective ratio in LPS group was larger than that of control group (P < 0.01). A variety of interacting factor were included LPS. Degeneration of the vertebral disk and hypertrophic ligamentum flavum were the main factors of soft tissue. Hypertrophy of the articular process and osteophyte on border of the vertebral body were the main factors of bone tissue. The edema and adhesion of nerve root with adjacent tissue were the main factors of nerve root.

CONCLUSIONThe compound factors of soft tissue, bone tissue and nerve root resulted in LPS. MRI can adequately demonstrate anatomic structure of the foramen and pathologic changes of LPS. Effective foraminal height, effective superior foraminal width and the effective ratio can regard as the main evaluation index for LPS in parasaggital MRI finding.