Lumbosacral Transitional Vertebrae: A Cadaveric Investigation of Prevalence and Relation to Lumbar Degenerative Disease

STUDY DESIGN: This is a retrospective cohort study. OBJECTIVE: The objective of this study was to verify the prevalence of lumbosacral transitional vertebrae (LSTV) in the general population and measure the resulting spinal arthritic changes. SUMMARY OF BACKGROUND: LSTV are a morphologic variation within the lumbar spine that has potentially significant clinical implications. LSTV prevalence has been investigated using nonrandom volunteer samples and patient populations presenting with medical complaints such as abdominal or lumbar pain warranting computed tomography and magnetic resonance imaging scans. The examination of LSTV prevalence and variations using a true random population to our knowledge has yet to be conducted, and the relation between LSTV and spinal arthritis has not been rigorously examined. MATERIALS AND METHODS: A total of 560 cadaveric skeletons were obtained from the Hamann-Todd osteological collection. The transverse processes of the terminal lumbar vertebrae were examined and measured, since the classification at times is based on examination and at times is based on measurement. The lumbar degenerative disease was graded on each specimen. RESULTS: Our search revealed 489 (87.3%) nontransitional vertebrae and 71 (12.7%) transitional vertebrae, with the majority of these Castellvi type IA (N=28), type IB (N=19), and type IIA (N=11). Transitional vertebrae as a whole (standardized β=0.090, P=0.015), and in particular type Ia showed a correlation to osteoarthritis in the L4-L5 vertebral level (standardized β=0.089, P=0.015). CONCLUSIONS: This cadaveric study aids in establishing the prevalence of LSTV (12.7%) in a random population and the frequency of the various Castellvi LSTV morphologies. An association was found between type Ia morphology and L4-L5 osteoarthritis which has not been reported in the past, suggesting that mild LSTV may carry more significance to lumbar pathology than previously considered.