[Biometric and biomechanic analysis of lumbar posterior facets based on a CT-scan database]. / Analyse biométrique et biomécanique des articulaires lombaires postérieures au sein d'une base de données scanographique.

AIM OF THE STUDY: Our knowledge on anatomy of lumbar spine is based on few cadaver's study with old and few subjects. CT-scan is very precise for lumbar facet's morphology. We have analysed 400 subjects. The aim of this study is to measure different distances, angles and circles to better understand the mechanical function of the lumbar facets. PATIENTS AND METHODS: We have analysed 720 CT-scan. We had 217 men and 183 women with 59 years of mean age. We used native slices of 1.25 mm thick from L1 to S1. We created transversal plan and we put different mark point. We took their coordinates and we have calculated different distances, angles and mechanical circles. We have compared different axis of rotation of the facets. RESULTS: From L1 to S1, the facets goes near to the posterior wall and far from themselves. Moreover, the posterior angle between both facets increase down to the sacrum. The radius of the left side circle and the right one are very closed in 50% of the cases but the three radius are close only in 10% of cases. CONCLUSION: This study based on 400 subjects shows that there is not a unique axis of rotation for both lumbar posterior facets. We have had only 50% of symmetry between both sides whatever the level studied.