Invasiveness of decompression surgery affects modeled lumbar spine kinetics in patients with degenerative spondylolisthesis.

Introduction: The surgical treatment of degenerative spondylolisthesis with accompanying spinal stenosis focuses mainly on decompression of the spinal canal with or without additional fusion by means of a dorsal spondylodesis. Currently, one main decision criterion for additional fusion is the presence of instability in flexion and extension X-rays. In cases of mild and stable spondylolisthesis, the optimal treatment remains a subject of ongoing debate. There exist different opinions on whether performing a fusion directly together with decompression has a potential benefit for patients or constitutes overtreatment. As X-ray images do not provide any information about internal biomechanical forces, computer simulation of individual patients might be a tool to gain a set of new decision criteria for those cases. Methods: To evaluate the biomechanical effects resulting from different decompression techniques, we developed a lumbar spine model using forward dynamic-based multibody simulation (FD_MBS). Preoperative CT data of 15 patients with degenerative spondylolisthesis at the level L4/L5 who underwent spinal decompression were identified retrospectively. Based on the segmented vertebrae, 15 individualized models were built. To establish a reference for comparison, we simulated a standardized flexion movement (intact) for each model. Subsequently, we performed virtual unilateral and bilateral interlaminar fenestration (uILF, bILF) and laminectomy (LAM) by removing the respective ligaments in each model. Afterward, the standardized flexion movement was simulated again for each case and decompression method, allowing us to compare the outcomes with the reference. This comprehensive approach enables us to assess the biomechanical implications of different surgical approaches and gain valuable insights into their effects on lumbar spine functionality. Results: Our findings reveal significant changes in the biomechanics of vertebrae and intervertebral discs (IVDs) as a result of different decompression techniques. As the invasiveness of decompression increases, the moment transmitted on the vertebrae significantly rises, following the sequence intact ➝ uILF ➝ bILF ➝ LAM. Conversely, we observed a reduction in anterior-posterior shear forces within the IVDs at the levels L3/L4 and L4/L5 following LAM. Conclusion: Our findings showed that it was feasible to forecast lumbar spine kinematics after three distinct decompression methods, which might be helpful in future clinical applications.

Tentorial Incision vs. Retraction of the Tentorial Edge during the Subtemporal Approach: Anatomical Comparison in Cadaveric Dissections and Retrospective Clinical Case Series.

Objective The aim of this study was to compare tentorial incision (group A) versus retraction and tack up suture (group B) of the tentorial edge during the subtemporal approach for surgery in the high basilar region. Design 24 cadaveric dissections and 4 clinical cases of aneurysms of the high basilar region are presented. Assessment included visibility and operability afforded by either tentorial incision creating a dural flap (group A) or retraction of the tentorial edge and tethering with a suture (group B). Four patients, two with superior cerebellar artery aneurysms and two with proximal posterior cerebral artery aneurysms were treated with each approach. Results In the quantitative evaluations, we found no significant difference in the exposure of the posterior cerebral, superior cerebellar, and perforant arteries as well as surgical working area provided by either approach. However, tentorial incision allowed a significantly greater exposure of the basilar artery and the fourth cranial nerve (both p < 0.001). Concerning operability, tentorial incision provided no objective advantage for direct clipping of the high basilar region (groups A vs. B, p > 0.05). Subjectively, clipping of the high basilar segment was feasible using tentorial tethering only. Conclusion Retraction of the free edge of the tentorium downward by tethering with a suture is simple and fast method for exposure of aneurysms in the high basilar region when the pathology does not require a proximal control. In our data the rather more invasive and time consuming tentorial incision provided an additional objectified advantage only for placement of a proximal temporary clip.

Computer simulation and image guidance for individualised dynamic spinal stabilization.

PURPOSE: Dynamic implants for the human spine are used to re-establish regular segmental motion. However, the results have often been unsatisfactory and complications such as screw loosening are common. Individualisation of appliances and precision implantation are needed to improve the outcome of this procedure. Computer simulation, virtual implant optimisation and image guidance were used to improve the technique. METHODS: A human lumbar spine computer model was developed using multi-body simulation software. The model simulates spinal motion under load and degenerative changes. After virtual degeneration of a L4/5 segment, virtual pedicle screw-based implants were introduced. The implants' positions and properties were iteratively optimised. The resulting implant positions were used as operative plan for image guidance and finally implemented in a physical spine model. RESULTS: In the simulation, the introduction and optimisation of virtually designed dynamic implants could partly compensate for the effects of virtual lumbar segment degeneration. The optimised operative plan was exported to two different image-guidance systems for transfer to a physical spine model. CONCLUSION: Three-dimensional computer graphic simulation is a feasible means to develop operative plans for dynamic spinal stabilization. These operative plans can be transferred to commercially available image-guidance systems for use in implantation of physical implants in a spine model. This concept has important potential in the design of operative plans and implants for individualised dynamic spine stabilization surgery.

Automatic scanning of large tissue areas in neurosurgery using optical coherence tomography.

BACKGROUND: With its high spatial and temporal resolution, optical coherence tomography (OCT) is an ideal modality for intra-operative imaging. One possible application is to detect tumour invaded tissue in neurosurgery, e.g. during complete resection of glioblastoma. Ideally, the whole resection cavity is scanned. However, OCT is limited to a small field of view (FOV) and scanning perpendicular to the tissue surface. METHODS: We present a new method to use OCT for scanning of the resection cavity during neurosurgical resection of brain tumours. The main challenges are creating a map of the cavity, scanning perpendicular to the surface and merging the three-dimensional (3D) data for intra-operative visualization and detection of residual tumour cells. RESULTS: Our results indicate that the proposed method enables creating high-resolution maps of the resection cavity. An overlay of these maps with the microscope images provides the surgeon with important information on the location of residual tumour tissue underneath the surface. CONCLUSION: We demonstrated that it is possible to automatically acquire an OCT image of the complete resection cavity. Overlaying microscopy images with depth information from OCT could lead to improved detection of residual tumour cells.

Implementation of a critical incident reporting system in a neurosurgical department.

BACKGROUND: Critical incident monitoring is an important tool for quality improvement and the maintenance of high safety standards. It was developed for aviation safety and is now widely accepted as a useful tool to reduce medical care-related morbidity and mortality. Despite this widespread acceptance, the literature has no reports on any neurosurgical applications of critical incident monitoring. We describe the introduction of a mono-institutional critical incident reporting system in a neurosurgical department. Furthermore, we have developed a formula to assess possible counterstrategies. METHODS: All staff members of a neurosurgical department were advised to report critical incidents. The anonymous reporting form contained a box for the description of the incident, several multiple-choice questions on specific risk factors, place and reason for occurrence of the incident, severity of the consequences and suggested counterstrategies. The incident data was entered into an online documentation system (ADKA DokuPik) and evaluated by an external specialist. For data analysis we applied a modified assessment scheme initially designed for flight safety. RESULTS: Data collection was started in September 2008. The average number of reported incidents was 18 per month (currently 216 in total). Most incidents occurred on the neurosurgical ward (64%). Human error was involved in 86% of the reported incidents. The largest group of incidents consisted of medication-related problems. Accordingly, counterstrategies were developed, resulting in a decrease in the relative number of reported medication-related incidents from 42% (March 09) to 30% (September 09). CONCLUSIONS: Implementation of the critical incident reporting system presented no technical problems. The reporting rate was high compared to that reported in the current literature. The formulation, evaluation and introduction of specific counterstrategies to guard against selected groups of incidents may improve patient safety in neurosurgical departments.

Risk management in the treatment of malignant gliomas with BCNU wafer implants.

Implantation of BCNU wafers (Gliadel®) into the resection cavity has demonstrated a survival benefit for patients with newly diagnosed malignant gliomas. The follow-up of two phase III trails has further shown that the number of long-term survivors was significantly increased by BCNU wafer treatment. BCNU wafer implantation may be integrated into current multimodal first line strategies. In the setting of recurrent disease BCNU wafer implantation has also shown a survival benefit and now extends the treatment options in a patient population that typically has undergone extensive pretreatment. An analysis of the literature has helped to clearly identify the risks associated with topic BCNU treatment. Here we summarize the incidence and time course of adverse events associated with local chemotherapy and propose solutions. The growing body of experience with BCNU wafer implantation may serve as a basis to develop adequate risk management strategies with regard to patient selection, surgical techniques, and follow-up schedules.

A non-midline spheno-orbital encephalocele in a newborn.

Basal encephaloceles in western countries occur in 1 of every 35 000-40 000 live births; with an incidence of less than 10% they are the least common of all encephaloceles. Certain subtypes such as transsphenoidal variants may be as rare as 1 in 700 000 live births. These rare encephaloceles are classified into five anatomic types: spheno-ethmodial, transsphenoidal, spheno-orbital, transethmoidal, and spheno-maxillary. Here we present an exceedingly rare variant of a non-midline basal encephalocele of the spheno-orbital type, which was treated by resection of the encephalocele, which contained dysplastic central nervous system tissue, on day four post partum. The patient had no neurological deficits and a six year follow-up showed a normal intellect and a good cosmetic result.

Brain-mapping using robotized TMS.

We present first results of brain-mapping using robotic Transcranial Magnetic Stimulation. This non-invasive procedure enables the reliable detection of the representation of individual muscles or muscle groups in the motor-cortex. The accuracy is only exceeded by direct electrical stimulation of the brain during surgery. Brain-mapping using robotic TMS can also be used to detect displacements of brain regions caused by tumors. The advantage of TMS is that it is non-invasive. In this study, we compare results from statistical mapping with robotic TMS to results achieved from direct stimulation done during tumor surgery. To our knowledge this is the first study of this type. We mapped the representation of three muscle groups (forearm, pinky and thumb) in tumor patients with the robot-aided TMS protocol and with direct stimulation. The resulting maps agree within 5mm.