IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 14, Issue 12 Ver. II (Dec. 2015), PP 106-108 www.iosrjournals.org DOI: 10.9790/0853-14122106108 www.iosrjournals.org 106 | Page Variation in the number of sacral pieces Dr. Irungbam Deven Singh 1 , Dr. Rajkumari Ajita 2 , Dr. Th. Naranbabu Singh 3 1. Assistant Professor, 2. Associate Professor & 3. Professor, Department of Anatomy, Regional Institute of Medical Sciences, Imphal, Manipur, India __________________________________________________________________________________________ Abstract: Sacrum consists of 4 to 7 pieces. Variation in the number of sacral pieces may be produced by sacralization or lumbarization. A sacralized L5 vertebra will give rise to a sacrum with 6 pieces whereas a completely lumbarized S1 will reduce the number of sacral pieces to 4. The first coccygeal piece may also be incorporated into the sacrum to produce a sacrum with 6 pieces. Lumbarization and sacralization are arise because of abnormal development of the vertebrae in this region and are usually associated with low back pain. The aim of the study was to study variation in the number of sacral pieces. Thirty dry human sacra were taken up for the study. The number of sacral pieces varied from 4 to 6. The incidences of sacra with 4, 5 and 6 pieces were 6.7%, 66.7% and 20% respectively. Four (13.3%) of the sacra with 6 segments resulted from incorporation of the first coccyx. Two (6.7%) of the sacra with 6 segments had sacralization of L5 vertebra. Two sacra (6.7%) had complete lumbarization of the S1 vertebra. Morphological or numerical variations of sacrum is common. Knowledge of these variations may help in the better management of low back pain. Key words: Numerical variation, lumbarization, sacralization, lumbosacral transistional vertebra, low back pain I. Introduction Sacrum is a triangular bone formed by the fusion of five sacral vertebrae. It forms the posterosuperior wall of the pelvis. It is normally formed by the fusion of 5 sacral vertebrae. The function of the sacrum is to transmit the weight of the body to the hip bones. The numerical variations of the sacrum include partial or complete separation of the S1 segment from the sacrum (lumbarization), partial or complete fusion of the fifth lumbar vertebra with the first sacral vertebra (sacralization), the last two conditions may respectively increase or reduce the number of sacral pieces. The number of fused sacral pieces varies from 4 to 7 pieces. [1] The variations consist of sacralization of L5 vertebra or lumbarization of the S1 vertebra or incorporation of first piece of coccyx to sacrum. A lumbosacral transition vertebra (LSTV) is an abnormal vertebra with a feature intermediate between lumbar and sacral vertebrae. Its transverse process may articulate or fuse with the sacrum or ilium of hip bone. LSTVs include lumbarization and sacralization. The LSTVs are associated with altered biomechanics of the spine and low back pain. [2] II. Materials & methods The study was done on 30 human adult dry sacra at the Department of Anatomy, Regional Institute of Medical Sciences, Imphal. The number of segments or evidence of sacralisation or lumbarisation was noted. III. Results The number of sacral segments varied from 4 to 6. Eight sacra (26.6%) showed abnormal number of pieces [Table 1]. Table 1. Incidence of Sacra with Abnormal Number of Pieces Sacrum with 4 pieces Sacrum with 6 pieces Lumbarisation Sacralisation Incorporation of coccyx to sacrum Complete & Bilateral Complete & Unilateral Complete & Bilateral Total Unilateral Bilateral Total 2 (6.7%) 1 (3.3%) 1 (3.3%) 2 (6.7%) 1 (3.3%) 3 (10.0%) 4 (13.3%) Six (20.0%) sacra had 6 pieces. Most (66.7%) of them had had 5 pieces. Six (20.0%) sacra had 6 pieces. Two (6.7%) of the sacra with 6 segments had sacralization of L5 vertebra. One (3.3%) of these two had complete unilateral sacralization of L5 vertebra on the left side [Fig. 1]. Another one (3.3%) had bilateral complete sacralization of L5 vertebra [Fig. 2]. Four (13.3%) of these sacra with 6 segments resulted from incorporation of the first piece of coccyx [Fig. 3]. Out of these 4, one (3.3%) was unilateral (right-sided) and the other 3 (10%) were bilateral. Two (6.7%) sacra were found to have complete bilateral lumbarization and had only 4 pieces [Fig. 4].