The Anatomic Investigation For Direct Reparative And Reconstructive Surgery Of Spondylolysis

Study DesignThis study evaluated the dimensions of transverse process, lamina and pars interarticularis of L4, 5 segments of vertebral column and its spatial relationship with the nearby anterior branch of spinal nerve, using normal adult spine specimens. ObjectivesTo provide a set of data to facilitate the reparative and reconstructive surgery of spondylolysis. Summary of Background dataThe technique of direct reparative and reconstructive surgery of spondylolysis has abtained rapid development in recent years thanks to its retaining of spinal motion to the greatest extent. However, the relavent anatomic data needed unfortunately remains largely unkown, thus surgeons have to rely on their experience when performing this kind of operation, which is actually quite dangerous . MethodsSpinal vertebrae of L4 and L5 segments from Thirty one normal adult corpuses were directly measured for this study. The values measured included(1) the length of transverse process, the width of transverse process at the starting point, the width of transverse process at the interior quarter point, the width of transverse process at midpoint, the thickness of transverse process at the starting point, the thickness of transverse process at the midpoint, the thickness of transverse process at the midpoint. (2)the height of lamina at the midpoint, the thickness of the superior border of lamina at the midpoint, the thickness of the inferior border of lamina at the midpoint, the thickness of the midline of lamina at the midpoint, the distance from the midpoint of the borderline between the spinous process and the lamina to the point right in front of the starting point of superior articular process on the other side, the distance from the midpoint of the borderline between the spinous process and the lamina to the point right in front of the starting point of the transverse process on the other side, the distance from the midpoint of the borderline between the spinous process and the lamina to the point right in front of the starting point of inferior articular process on the other side, the angle between the screw's passway and the sagittal plane from superior view, the angle between the screw's passway and the sagittal plane from posterior view, (3)the height of isthmus at the midpoint, the thickness of isthmus at the intersection point between its superior border and the superior articular process, the thickness of isthmus at the intersection point between its inferior border and the inferior articular process. All the values were measured on both sides.Twenty two normal adult spines with intact vertebrae, spinal cords and spinal nerves were measured. The values under measurement included the distance from the starting point of transverse process on its superior border tothe anterior branch of spinal nerve in front of it, the distance from the interior quarter point of transverse process on its superior border to the anterior branch of spinal nerve in front of it, the distance from the midpoint of transverse process on its superior border to the anterior branch of spinal nerve in front of it, the distance from the starting point of transverse process on its inferior border to the anterior branch of spinal nerve in front of it, the distance from the interior quarter point of transverse process on its inferior border to the anterior branch of spinal nerve in front of it, the distance from the midpoint of transverse process on its inferior border to the anterior branch of spinal nerve in front of it, the proportion accounted by the length of shadow projected by anterior branch of spinal nerve on the superior border of transverse process in the total length of superior border of transverse process, the proportion accounted by the length of shadow projected by anterior branch of spinal nerve on the inferior border of transverse process in the total length of inferior border of transverse process. All the values were also measured on both sides.The structure of bone trabecula in the transverse process of L4 and L5 segments of human vertebrae were observed under optic microscope. ResultsGenerally speaking, the situation in L5 is significantly different from that in L4. The vertebra of L5 has larger transverse process, higher lamina, thicker inferior border of lamina, longer articular screw passway, a greater entry angle of screw, and closer contact with the ajacent spinal nerve. The vertebra of L4 has thicker superior border of lamina.ConclusionsThe transverse process of L5 has a better tensile strength against the tensile band. But the close contact with nearby nerve fibers imposes a greater challenge on surgeons. As for laminar screws, there is a longer screw pathway and wider entry angle from inferior view for L5. Forthermore, one should be fully clear about the precise definition of each value when trying to put them to use.