MATERIAL and METHODS: 110 dry adult sacrums gathered from the bone collections of the Laboratory of the Anatomy Department of Dokuz Eylul University School of Medicine were examined. The parameters analysed were: 1) results of parameters related to the posterior sacral wall; 2) classification and rate of the closure defects; 3) classification of the top sacral vertebrae according to the shape of its superior surface; 4) presence of sacralisation and lumbalisation among sacrums with dorsal wall defects; 5) vertebral levels of apex of the sacral hiatus; and 6) vertebral levels of closure defects of the sacrums.

RESULTS: We determined 22/110 (20%) sacrums demonstrated spina bifida. Of these 22 sacrums, 4 (18.18%) showed complete and 18 (81.82%) showed incomplete spina bifida. We noted the coexistence of spina bifida with sacralisation (6/22 [27.27%]) and lumbalisation (5/22 [22.73%]). The types of defects were described and grouped as ?V? (Type 1), inverse ?V? (Type 2), window (Type 3), foramen (hole) (Type 4), sand watch (Type 5), narrow linear (Type 6), wide linear (Type 7), and bridged (Type 8). The shape of upper surfaces of the sacrums with spina bifida was grouped as: cavity (20/22, 90.9%), hump (1/22, 4.5%), and flat (1/22, 4.5%).

CONCLUSION: A precise definition of the anatomical variations of sacrums is essential for surgeons, particularly when operating using endoscopic techniques and for anaesthesiologists applying caudal epidural block. Keywords : Defect, Sacral hiatus, Sacrum, Spina bifida