Kinematic analysis of diseased and adjacent segments in degenerative lumbar spondylolisthesis

Background contextDegenerative spondylolisthesis is a common pathologic condition that leads to lumbar instability and significant clinical symptoms. The effect of this pathology on adjacent lumbar motion segments, however, has not yet been studied.PurposeTo characterize the motion characteristics of lumbar degenerative spondylolisthesis at both the diseased and adjacent levels in patients with low-grade, single-level lumbar degenerative spondylolisthesis using kinetic magnetic resonance imaging (kMRI).Study designRetrospective study of patient kMRIs.Patient sampleOne-hundred twelve patient MRIs with low-grade, single-level lumbar spondylolisthesis were included.Outcome measuresAngular and translational motion.MethodsThis study compared 112 patients diagnosed with low-grade (Grade 1 or 2), single-level lumbar degenerative spondylolisthesis at L3–L4, L4–L5, or L5–S1 with 296 control patients without spondylolisthesis. Angular and translational motion were measured using patient kMRIs. The level of slip was graded according to the Meyerding classification system, and disc degeneration was classified according to the Pfirrmann system. Instability was defined as translational motion greater than 4 mm.ResultsLumbar hypomobility was often present regardless of the level of degenerative spondylolisthesis. A slip at L3–L4 resulted in the largest decrease in lumbar range of motion. Instability at the diseased level was most common at L3–L4 (36%), followed by L5–S1 (31%) and L4–L5 (30%). Instability at the adjacent segments was most frequent at L4–L5 (49%), followed by L5–S1 (34%) and L3–L4 (23%). Patients with stable spondylolisthesis generally had decreased angular motion at all lumbar levels. Translational motion at the diseased level was consistently increased. Disc degeneration was significantly greater at the level of slip for the L3–L4 and L4–L5 spondylolisthesis groups and equal to the control group in the L5–S1 group. There was no significant difference in disc degeneration at adjacent segments in L3–L4 and L4–L5 degenerative spondylolisthesis patients, but there was a significant decrease with an L5–S1 slip.ConclusionsThere were a similar percentage of patients in each degenerative spondylolisthesis group with lumbar instability. Angular motion decreased at the diseased level with L3–L4 and L5–S1 spondylolisthesis, but increased with L4–L5 spondylolisthesis. Translational motion, however, increased at the diseased level in all three groups. There was compensatory hypermobility at adjacent levels in patients with unstable spondylolisthesis at L3–L4 and L4–L5, but not at L5–S1.