Role of lumbar interspinous distraction on the neural elements.

The interspinous distraction devices are used to treat variable pathologies ranging from facet syndrome, diskogenic low back pain, degenerative spinal stenosis, diskopathy, spondylolisthesis, and instability. The insertion of a posterior element with an interspinous device (ISD) is commonly judged responsive to a relative kyphosis of a lumbar segment with a moderate but persistent increase of the spinal canal and of the foraminal width and area, and without influence on low-grade spondylolisthesis. The consequence is the need of shared specific biomechanical concepts to give for each degenerative problem the right indication through a critical analysis of all available experimental and clinical biomechanical data. We reviewed systematically the available clinical and experimental data about kyphosis, enlargement of the spinal canal, distraction of the interspinous distance, increase of the neural foramina, ligamentous structures, load of the posterior annulus, intradiskal pressure, strength of the spinous processes, degeneration of the adjacent segment, complications, and cost-effectiveness of the ISD. The existing literature does not provide actual scientific evidence over the superiority of the ISD strategy, but most of the experimental and clinical data show a challenging potential. These considerations are applicable with different types of ISD with only few differences between the different categories. Despite--or because of--the low invasiveness of the surgical implantation of the ISD, this technique promises to play a major role in the future degenerative lumbar microsurgery. The main indications for ISD remain lumbar spinal stenoses and painful facet arthroses. A clear documented contraindication is the presence of an anterolisthesis. Nevertheless, the existing literature does not provide evidence of superiority of outcome and cost-effectiveness of the ISD strategy over laminectomy or other surgical procedures. At this time, the devices should be used in clinical randomized independent trials in order to obtain more information concerning the most advantageous optimal indication or, in selected cases, to treat tailored indications.

A new mechatronic assistance system for the neurosurgical operating theatre: implementation, assessment of accuracy and application concepts.

OBJECTIVE: To introduce a new robotic system to the field of neurosurgery and report on a preliminary assessment of accuracy as well as on envisioned application concepts. Based on experience with another system (Evolution 1, URS Inc., Schwerin, Germany), technical advancements are discussed. MATERIAL/METHODS: The basic module is an industrial 6 degrees of freedom robotic arm with a modified control element. The system combines frameless stereotaxy, robotics, and endoscopy. The robotic reproducibility error and the overall error were evaluated. For accuracy testing CT markers were placed on a cadaveric head and pinpointed with the robot's tool tip, both fully automated and telemanipulatory. Applicability in a clinical setting, user friendliness, safety and flexibility were assessed. RESULTS: The new system is suitable for use in the neurosurgical operating theatre. Hard- and software are user-friendly and flexible. The mean reproducibility error was 0.052-0.062 mm, the mean overall error was 0.816 mm. The system is less cumbersome and much easier to use than the Evolution 1. CONCLUSIONS: With its user-friendly interface and reliable safety features, its high application accuracy and flexibility, the new system is a versatile robotic platform for various neurosurgical applications. Adaptations for different applications are currently being realized.