Associations between lumbosacral transitional anatomy types and degeneration at the transitional and adjacent segments

Background contextThe relation between specific types of lumbosacral transitional vertebra and the degree of degeneration at and adjacent to the transitional level is unclear. It is also unknown whether the adjacent cephalad segment to a transitional vertebra is prone to greater degeneration than a normal L5-S1 level.PurposeThe purpose of this study was to evaluate the relation between specific lumbosacral transitional vertebra subtypes according to the Castellvi classification, and to determine the severity of degeneration at the transitional level and the adjacent cephalad segment.Study designThis study was a retrospective review.Patient samplesNinety-two subjects with lumbosacral transitional vertebra grade 2 or higher and 94 control subjects without were retrieved from a picture archiving and communication system (PACS) search.Outcome measuresDisc degeneration parameters at the transitional and at the adjacent cephalad level were measured.MethodsAfter institutional review board approval, 92 subjects (42 men; mean age, 57±16 years) with lumbosacral transitional vertebra grade 2 or higher and 94 control subjects (41 men; mean age, 51±16 years) without were retrieved from a PACS search. Degeneration of the last two segments of the lumbar spine was quantified using the Pfirrmann and Modic classifications, along with documentation of annular tears, disc herniations, and disc height, and were compared between the two groups. Furthermore, L5-S1 levels in the control subjects were compared with the adjacent cephalad segments of the transitional vertebrae for the same parameters.ResultsAlthough the control subjects, at L5-S1, had moderate to severe degeneration by Pfirrmann grades (31%) and Modic changes ([MC] 20%), in comparison, the discs at the transitional level of the lumbosacral transitional vertebra group demonstrated significant less degeneration (3% and 1%, respectively; each p<.05). The adjacent cephalad segments of the lumbosacral transitional vertebra group showed significantly greater degeneration (Pfirrmann grade 5, 39%; MC, 30%) compared with the L4-L5 level in control subjects (16% and 11%, respectively; each p<.05). The severity of disc degeneration using all parameters correlated with the type of lumbosacral transitional vertebra. The degree of degeneration of L5-S1 in control subjects was similar to the adjacent cephalad segment in lumbosacral transitional vertebrae.ConclusionIncreasing the mechanical connection of a lumbosacral transitional vertebra protects the disc at the transitional level and predisposes the adjacent cephalad segment to greater degeneration. The adjacent cephalad segment had a comparable degree of degeneration as the L5-S1 level in control subjects.