Sacral Arch Defect and Low Backache

SummaryThis paper presents the findings of a morphological and metrical study, based on 107 adult human columns, of the variations which occur in the last lumbar spinous process and laminae in association with upper or complete defect of the posterior wall of the sacral canal.When there is a defect of the upper sacral arches or complete defect of the posterior wall of the sacral canal, several types of variations may occur in the arch and the spinous process of the last lumbar vertebra. One such variation of clinical significance is a marked hyperplasia of the spinous process (spina magna) which occurred in 1.9% in the present series. It is suggested that in the differential diagnosis of low midline backache this condition should be considered as one of several possible causes of low midline backache. It is further suggested that appropriate radiological techniques should be developed to show the entire spinous process of the last lumbar vertebra and the extent of defect of the posterior wall of the sacral canal.