Conus medullaris level in vertebral columns with lumbosacral transitional vertebra

BACKGROUND: The estimated prevalence of lumbar or sacral transitional vertebrae (LSTV) in the population is 4% to 30%. Few small patient series have studied the normal level of the conus medullaris (CM) in individuals with LSTV. OBJECTIVE: To determine, by using a large cohort of patients, whether individuals of all ages with LSTV have different CM positions in the spinal canal in comparison with the rest of the population with normal vertebral columns. METHODS: We performed an institutional retrospective analysis of spinal magnetic resonance images on individuals with LSTV of all ages, sexes, and pathologies during a 10-year period. Fifty-seven percent of patients (n 467) had a lumbarized vertebra and 43% had sacralized vertebra (n 355). Mean age at the time of the study was 55 ± 19 years (range 1-97 years). Fifty-two percent were male and 48% were female. Sixty percent of subjects with a sacralized vertebra were female, and 54.5% of those with a lumbarized vertebra were male (P .001). RESULTS: The CM in individuals with a lumbarized vertebra was seen to be lower at L1-2 to L2s, than un those with a sacralized vertebra where most conuses were at T12-L1 to L1s (P ≤ 0.001). The CM level was similarly distributed among sexes and ages. CONCLUSION: In our series, the CM level, when lumbarization occurred, was lower, with a mean level at L1-L2, whereas a more superior mean level at T12-L1 was seen when sacralization occurred. CM level was not influenced by sex, age, or pathology other than tethered cords.