The Sagittal Angle and Orientation of Superior Articular Facets of the Zygapophyseal Joints at Lumbosacral Junction

Abstract

The study of geometric properties of lumbosacral junction which include sagittal angle and orientation of articular facets may reveal vital information on its mechanical function in stability and mobility. Vertebral columns of 45 male human cadavers had their angle of the superior articular facets of fourth and fifth lumbar and first sacral vertebrae in relation to the sagittal plane measured with a modified protractor. The difference of orientation of right and left superior articular facets 0 0 were noted. The angular values of L4SAL and L4SAR are 37.7^o and 36.2^o respectively. L5SAL and L5SAR are 47.0^o and 48.5^o respectively. Also, the mean values of the S1SAL and S1SAR are 52.5^o and 54.7^o respectively. Tropism of more than 20 existed in 58% of sagittal angle for both fourth, fifth lumbar and 62% for first sacral vertebra. The orientation of superior articular facets of L4, L5 and S1 region was posteromedial. The changes in orientation and sagittal angle of superior articular facets from fourth lumbar to first sacral joints was characterized by increase in sagittal plane angulation.