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A Study on Anatomical Variations of Sacral Foramina and its Clinical Relevance

Introduction: The Sacrum is a large, triangular, shield-shaped bony structure, formed by the fusion of five individual sacral vertebrae. Ventral surface of sacrum bears four pelvic sacral foramina allowing the passage of ventral rami of upper four sacral spinal nerves and the lateral sacral arteries. The posterior surface of sacrum bears four dorsal sacral foramina, lateral to the articular tubercles. The dorsal sacral foramina allow passage of dorsal rami of upper four sacral spinal nerves. Aim: The present study was carried out to evaluate the numerical variations of pelvic and dorsal sacral foramina of dry human sacrum. Materials and Methods: A descriptive osteological study was done to look for numerical variations in the number of pelvic and dorsal sacral foramina. Hundred dry adult human sacrum were collected from the Department of Anatomy of Nilratan Sircar Medical College, Kolkata over a period of 2011-2013. Any variations in the number of segments of sacrum were examined. Identification of six segmented sacrum with five pairs of sacral foramina and four segmented sacrum with three pairs of sacral foramina was performed. The data was collected and statistical analysis was done in simple percentage form. Results: Hundred dry adult human sacra were examined for the number of pelvic and dorsal sacral foramina. Three sacra (3%) were found with three pairs of sacral foramina and two sacra (2%) with five pairs of sacral foramina. In one (1%) of the sacrum, lumbosacral transitional vertebra was seen with five foramina on left side and four foramina on the right side of median sacral crest. All other sacra have normal four pairs of sacral foramina. Conclusion: Variation in segmental composition of sacrum results in lumbarisation or sacralisation with altered number of sacral foramina. Persons with these variations may often presents with low back pain. This knowledge of lumbarisation and sacralisation must be kept in mind while doing surgical and anaesthetic procedures in this region. Information of segmental variations of sacrum is important for anaesthetists, surgeons, obstetricians, radiologists and forensic experts.