Redefining lumbosacral transitional vertebrae (LSTV) classification: integrating the full spectrum of morphological alterations in a biomechanical continuum.

In light of advancements in imaging techniques and basic science studies, this study proposes modifications in the existing Castellvi's classification for better clinical and biomechanical correlation of LSTV subtypes. LSTVs are commonly occurring variations of the lower spine. The current system does not include functionally important structural variations of the neural arch components and sacral auricular surfaces induced by LSTV afflictions within the classification. This study is an attempt to integrate vital biomechanical correlates into the proposed modification. Emerging diagnostic and clinical evidence also point out the need of understating subdivisions within LSTV anomalies as distinctly stratified entities to get a better correlation with the biomechanical continuum involved with LSTV associated low back pain. Important neural arch element and sacral auricular surface alterations associated with each LSTV subtypes were studied from a large number of osseous samples and data available from published LSTV related clinical and morphological studies. Sacralisation and lumbarisation were designated separate stratifications in the proposed revision, with arrangement of the LSTV subtypes as members of a LSTV anatomical 'array' extending cranio-caudally at the lumbo-sacral junction. The proposed modification is capable of identifying LSTV associated structural defects (in anterior and posterior elements), their exact level of occurrence and status of facet and auricular surface morphologies. Coding for the inclusion of biomechanically important alterations associated with LSTV types within the proposed new classification would probably be helpful in better clinical correlation of LSTV.