227COCCYGEAL SACRALISATION – A STUDYThe coccyges are a series of rudimentary vertebrae forming the caudal termination of the vertebral column. At the cranial end of the sacrum when L5 fuses with S1, it is termed as Lumbar sacralisation. At the caudal end of sacrum, when first coccygeal vertebra fuses with the S5 it is termed as Coccygeal sacralisation. Hence when sacrum comprises of six vertebrae, it is always due to the loss of a vertebra from the lumbar region or coccygeal region. There is hardly any literature available related to the coccygeal region. It is important to study the variations at the caudal end of the sacrum not only to enhance the data base of anatomical variants of sacrum but also from the clinical point of view. Hence the study is aimed at identifying the prevalence of coccygeal sacralisation, classifying them and analysing details of the same. Materials and Methods: Total fifty adult dry human sacra with attached coccyx were examined in the Department of Anatomy of K. J. Somaiya Medical College with respect to five pairs of sacral foramina. Those vertebrae which exhibited lumbar sacralisation were excluded. They were grouped as follows: Type I Coccygeal sacralisation was formed by complete fusion of coccygeal vertebra with S5 vertebra. Type II Coccygeal sacralisation was formed by fusion of body with the apex of sacrum; and transverse process of Co1vertebra with inferior lateral angle of sacrum but coccygeal cornua did not fuse with sacral cornua. Hence fusion was incomplete medially.Type III Coccygeal sacralisation was formed by fusion of body with apex of sacrum; and sacral cornua with cornua of coccygeal vertebra. The transverse process of Co1 vertebra does not fuse with inferior lateral angle of sacrum. Hence fusion was incomplete laterally.Observations: Eight sacra showed coccygeal sacralisation (16%) of which 4 (8%) were Type I showing complete fusion, 2 (4%) was of Type II showing incomplete fusion medially and 2 (4%) was of Type III showing incomplete fusion laterally.Conclusion: The classifications in the present study range from complete fusion of vertebrae to incomplete fusion of parts of the vertebrae. This is essential for diagnosis of sacralisation related diseases to understand the degree of ossification and the extent of fusion. Sacralisation of coccygeal vertebra may cause coccygodynia, caudal block failure, difficult second stage of labour, a difficult forceps delivery and perineal tear. Thus knowledge of sacralisation of lumbar and coccygeal vertebra is of utmost importance to anatomist, orthopaedicians, physicians, surgeons and obstetricians.sharad@somaiya.eduResearch1112021Sacrum,Coccyx,Coccygeal Sacralisation,Complete Fusion,Incomplete Fusion,Ossification,Coccygodynia,Caudal Block,Labour,Forceps DeliveryDr. Shaheen Rizvi,Dr. Sharadkumar Pralhad SawantDepartment of Anatomy, K. J. Somaiya Medical College, Somaiya Ayurvihar, Eastern Express Highway, Sion, Mumbai-400 022.,Professor and Head Maharashtra University of Health Sciences, Nashik, Maharashtra.