Änderung der Gesamtstatik der Wirbelsäule nach monosegmentaler Cage-Implantation im Rahmen von Transforaminal Lumbar Interbody Fusion- oder Posterior Lumbar Interbody Fusion- Operationen

The probability of suffering from low back pain and having to seek for diagnosis and treatment at least once in a lifetime is high. The causes thereof are mostly degenerative alterations of the lumbar spine. If conservative treatments are not successful, surgery is commonly considered a therapeutic option. Lumbar surgical procedures include the removal of disc protrusions or stenosis of the spinal canal as well as stabilization and fusion of vertebrae. Their goal is the restoration of physiological function. In order to achieve this, considering the sagittal profile of the spine is important. Physiologically, a perpendicular line in cervical vertebral body C7 reaches the back rim of the S1 upper plate. This leads to gravity centering between the feet and enables to keep the body upright easily. The lateral profile of the spine is maintained by the thoracic kyphosis and lumbar lordosis as well as the pelvis with its muscles and ligaments. Using minimal invasive procedures such as PLIF and TLIF, good fusion rates and long-term stability are achievable. For planning of the procedure usually a radiograph of the lumbar spine is performed while standing upright. Intraoperatively, the intervertebral disc space will be cleared, a cage will be introduced to correct the angles of the segment back to physiological levels and fixed thereafter using pedicle screws and a rod system. This thesis comprehensively and meticulously analyses the pre- and postoperatively performed x-ray images of the lumbar spine of 40 patients, using two different systems. This includes measuring several relevant angles and comparison of two measuring technologies. Additionally, 25 preexisting x-ray images of whole spines were analyzed with the aim of finding correlating parameters which can be reproduced by solely looking at the lumbar spine. Comparing the analysis systems Vertaplan® und RadiAnt®, a significant correlation in inter-, intra- and test – retest reliability can be shown. Vertaplan® offers the possibilty of simulating the impact of different cages on the spinal static, verifying this impact was not conducted in this study. Analysis shows, however, that even lordosing one segment during instrumented fusion has only little effect on the sagittal profile of the spine as a whole, with minor differences depending on the choice of the implant. 66 Harms cages, when implanted on the far anterior side of the motion segment which have a supposedly strong lordosing effect do not show significant changes in lordosis and whole profile of the spine. Unilateral “oblique” PLIF cages even lead to a slight decrease in lordosis. Potential reasons for this could be an actual decrease of the angle or the impression of the cage into the top and bottom plate of neighboring vertebral bodies. On the basis of the data presented it seems questionable how extensively a predictable and relevant change of lumbar lordosis and sagittal profile of the entire spine can be achieved by performing a single segment fusion. This might be due to segment dynamics under load and interplay of multiple links, muscles and ligaments which have formed an individual sagittal profile over the course of a patients live. This leads also to the conclusion that the usage of extensive planning software and linked angle adjustable cages should be critically scrutinized.