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Background: The sacrum generally is composed of five vertebrae fused to form a triangular bony mass. Numerous anatomical variations of the sacrum have been reported including many reports of sacralization of the fifth lumbar in different race. There has never been reported among Thais.
Objective: To determine the incidence of sacralization of the fifth lumbar vertebra among Thais
Design: Descriptive study based on numerical survey.
Setting: Bone Collection Unit, Department of Anatomy, faculty of Medicine, Khon Kaen University, ThailandSubjects: Included were 206 sacra from Thai skeletons, 114 males and 92 females between 26 and 90 years of age at death.
Methods: An anatomical study was done on the sacrum. The sacra consisting of six vertebrae, by incorporation of the fifth lumbar, were selected. To confirm the lack of a fifth lumbar vertebra, we re-counted the lumbar vertebrae belonging to the same skeleton of the selected sacrum. The specimens were then carefully examined and recorded.Results: We found 9 (4.4%) specimens with the 5th lumbar vertebra fused to the first segment of the sacrum, representing sacralization; the incidence of which was 7 (6.1%) in males and 2 (2.1 %) in females. The degree of sacralization varied: complete in four out of seven of the males and incomplete in the remaining three out of seven males and in the two females. Conclusions: The present study shows that the incidence of sacralization of the 5th lumbar vertebra among Thai is about 4.4 %. The knowledge of this anatomical variation could be useful for the preliminary consideration in patient with low back problems.
Key words: Anatomic variation, Sacral foramina, Sacrum
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