Complexity of neutral zones, lumbar stability and subsystem adaptations: Probable alterations in lumbosacral transitional vertebrae (LSTV) subtypes

Physiological and anatomical ranges of movements at lumbar and lumbo-sacral motion segments are influenced by passive (bones and ligaments) and active (muscles) elements. The movements are visualized in terms of intrinsically unopposed (Neutral Zones) or opposed (Transitional Zones) movement zones. These two zones constitute the absolute ranges of motion for different regions of the spine. Though values of these ranges for flexion, extension, lateral bending and axial rotation at different spinal segments may demonstrate similarities across matched population, these parameters are most likely to show different values in lumbar spines affected with lumbo-sacral transitional vertebrae (LSTV). LSTV is a common variation of the lumbo-sacral junction and present well documented structural changes at the lower spine and L5/S1 vertebrae. This study attempts to (i) delineate and hypothesize relationships between changes in active and passive elements, (ii) understand the possibilities of restriction or augmentation in the values of these ‘zones’, and (iii) to predict overall LSTV induced physiological lumbar motion changes, in association with these variations.