Spinal Navigation Research Articles

A spine frame for intra-operative fixation to increase accuracy in spinal navigation and robotics

A spine frame for intra-operative fixation to increase accuracy in spinal navigation and robotics

A spine frame for intra-operative fixation to increase accuracy in spinal navigation and robotics

Objective: Intra-operative movements due to mechanical ventilation or manipulations are a limiting factor for accurate spinal navigation or robotic-assisted spinal surgery. The purpose of this study was to assess the accuracy of an intra-operative spinal fixation device in an experimental setup.Materials and Methods: We developed a fixation device, attached to the operating table, that combines soft tissue retraction with spinal process fixation. Using a lumbar spine cadaver, tightness of fixation was evaluated using two measurement systems. Accuracy measurements using changes in spatial co-ordinates of implanted reference markers were performed in three segments, following different manipulations of the spine. In addition, for intra-operative movements of the spine during mechanical ventilation, the range of motion was determined in 10 patients during lumbar interbody fusion.Results: The spine frame was easy to use and did not restrict screw insertion. Mean deviations of the markers' in all segments were measured at between 0.35 and 0.8 mm, following pedicle screw insertion and lateral traction. Intra-operative range of motion of the spine was measured with a mean value of 8.7 ± 3.3 mm.Conclusion: Using our spine frame, a rigid fixation following manipulation of the spine was demonstrated. By overcoming the intra-operative movement-dependent inaccuracy, safety in navigated spine surgery and robotic-assisted procedures might be improved.

Intraoperative Iso-C C-arm Navigation in Cervical Spinal Surgery

Fifty-two study participants underwent cervical spine surgery using intraoperative Iso-C imaging with or without spinal navigation. To evaluate prospectively the feasibility, advantages, limitations, and applications of Iso-C in cervical spine surgery. Existing stereotactic spinal navigational systems images must be acquired before surgery and typically require cumbersome point-to-point registration. Intraoperative computed tomography (CT) and magnetic resonance imaging (MRI) provide real-time information but can restrict access to the patient, preclude the use of traditional operating room tables, and are time-consuming. The Iso-C allows quick, CT-quality, real-time data acquisition without restricting access to the patient. The data acquired can be automatically transferred to navigational systems with the immediate ability to navigate for anterior or posterior cervical spine procedures. High-resolution isotropic three-dimensional data sets were acquired using the Iso-C intraoperative fluoroscopy in 52 cervical spine cases. In 30 cases, the data were imported automatically to the StealthStation Treon to support neuronavigation. In 22 cases, a postprocedural intraoperative CT was obtained with the Iso-C primarily to assess the extent of osseous decompression and/or the accuracy of implants or instrumentation. In most cases, a postoperative high-resolution CT image was obtained and compared with the Iso-C data. Successful automated registration suitable for navigation was attained for all anterior and posterior cervical spinal cases. The postprocedural intraoperative Iso-C data were 100% concordant with those of postoperative high-resolution CT as determined by a blinded neuroradiologist. Iso-C intraoperative fluoroscopy is an accurate and rapid way to perform CT-quality image-guided navigation in cervical spinal surgery. In most cases, it obviates the need for postoperative imaging.

Three-dimensional fluoroscopy-guided percutaneous thoracolumbar pedicle screw placement. Technical note.

The authors sought to evaluate the feasibility and accuracy of three-dimensional (3D) fluoroscopic guidance for percutaneous placement of thoracic and lumbar pedicle screws in three cadaveric specimens. After attaching a percutaneous dynamic reference array to the surgical anatomy, an isocentric C-arm fluoroscope was used to obtain images of the region of interest. Light-emitting diodes attached to the C-arm unit were tracked using an electrooptical camera. The image data set was transferred to the image-guided workstation, which performed an automated registration. Using the workstation display, pedicle screw trajectories were planned. An image-guided drill guide was passed through a stab incision, and this was followed by sequential image-guided pedicle drilling, tapping, and screw placement. Pedicle screws of various diameters (range 4-6.5 mm) were placed in all pedicles greater than 4 mm in diameter. Postoperatively, thin-cut computerized tomography scans were obtained to determine the accuracy of screw placement. Eighty-nine (94.7%) of 94 percutaneous screws were placed completely within the cortical pedicle margins, including all 30 lumbar screws (100%) and 59 (92%) of 64 thoracic screws. The mean diameter of all thoracic pedicles was 6 mm (range 2.9-11 mm); the mean diameter of the five pedicles in which wall violations occurred was 4.6 mm (range 4.1-6.3 mm). Two of the violations were less than 2 mm beyond the cortex; the others were between 2 and 3 mm. Coupled with an image guidance system, 3D fluoroscopy allows highly accurate spinal navigation. Results of this study suggest that this technology will facilitate the application of minimally invasive techniques to the field of spine surgery.

Computer-aided navigation in neurosurgery.

The article comprises three main parts: a historical review on navigation, the mathematical basics for calculation and the clinical applications of navigation devices. Main historical steps are described from the first idea till the realisation of the frame-based and frameless navigation devices including robots. In particular the idea of robots can be traced back to the Iliad of Homer, the first testimony of European literature over 2500 years ago. In the second part the mathematical calculation of the mapping between the navigation and the image space is demonstrated, including different registration modalities and error estimations. The error of the navigation has to be divided into the technical error of the device calculating its own position in space, the registration error due to inaccuracies in the calculation of the transformation matrix between the navigation and the image space, and the application error caused additionally by anatomical shift of the brain structures during operation. In the third part the main clinical fields of application in modern neurosurgery are demonstrated, such as localisation of small intracranial lesions, skull-base surgery, intracerebral biopsies, intracranial endoscopy, functional neurosurgery and spinal navigation. At the end of the article some possible objections to navigation-aided surgery are discussed.

Accuracy of Spinal Navigation for Magerl Screws

The influence of a protocol of preoperative computed tomography scanning and a special registration technique was assessed on the accuracy of navigation for implanting Magerl C1-C2-screws. The use of navigation systems for implanting Magerl screws could help to decrease the risk of complications and to reduce the required skin incision. Two parameters conceivably affecting the accuracy are the protocol of preoperative computed tomography scanning and the registration technique. Four cervical spine segments of human cadavers were scanned with two computed tomography protocols. Registration was done based on anatomic landmarks or using a specially designed percutaneous registration device. For the accuracy check, the pointer tip was placed exactly on the markers. The displayed distance on the monitor was referred as an estimate of accuracy. Varying the computed tomography protocol did not significantly affect the accuracy. The mean accuracy was improved from 3 mm after anatomic pair-point matching to 1.5 mm after matching using the percutaneous registration device. The accuracy obtainable seems to be sufficient for implanting Magerl screws by using frameless stereotactic navigation. Three-millimeter slice thickness and 2-mm table increment is a proper protocol for preoperative computed tomography scanning. Fiducial markers improve the accuracy significantly.

Spinal navigation in tumor surgery of the thoracic spine: first clinical results.

In this clinical study, the accuracy of computed tomography-based and computer-guided decompression and insertion of pedicle screws in patients who have had tumor-related posterior surgery of the thoracic spine was evaluated. Eight patients with advanced metastatic disease were treated surgically using a posterior approach with the assistance of an optoelectronic navigation system. Postoperative computed tomography scans were obtained for all patients and provided information regarding decompression and transpedicle implant localization. In all eight patients accurate decompression of the spinal canal was seen. Using the navigation system, 22 of 26 scheduled transpedicle screws were inserted using computer guidance. Eighty-six percent (19 of 22) of the navigated pedicle screws were positioned centrally in the bone. Initial results indicate that computer-aided frameless navigation in tumor surgery of the thoracic spine is a safe system to improve surgical performance during posterior decompression and transpedicle stabilization. Although computed tomography-based computer-assisted spinal navigation is important, the system is not 100% accurate. Therefore, application of the navigation system should be restricted to experienced surgeons who can continue the operation using a conventional approach. Finally, detailed knowledge of the principles of the tracking systems is necessary to prevent possible misinterpretation of information provided by the computer.

Image-guided spinal navigation: application to spinal metastases

Image-guided spinal navigation is an adjuvant surgical technology that has evolved over the past decade. It has been used as a replacement for conventional intraoperative imaging techniques to improve the spine surgeon's spatial orientation to nonvisualized anatomy. The author will review the principles of image-guided technology in spinal surgery and focus on its application to the management of spinal metastatic disease.

In vivo experiences with frameless stereotactically guided screw placement in the spine--results from 75 consecutive cases.

Whereas cranial neuronavigation is widely accepted as a helpful tool, larger series of the in vivo application of spinal neuronavigation do not exist. In the following we report our 4-year experience with spinal navigation in 75 consecutive cases for dorsal transpedicular screw placement. Seventy-five patients were planned for operation employing anatomical reference points defined on a 2-mm high resolution CT. We used single vertebra registration and surface matching. With the above methods, the mean registration deviation ranged from 0.18 mm (cervical spine) to 0.31 mm (lumbar spine). All our screws in the upper cervical spine were navigated correctly (17 patients), thus improving markedly the surgical outcome. The results were not as promising in the lumbar area. In only 84% was navigation reliable. The reason was the lack of a practicable tracking tool. Spinal neuronavigation based on anatomical reference points is able to improve the results in transpedicular screwing, especially in the cervical spine. The lack of a practicable tracking tool still hinders its use in routine clinical application.

Spinal Navigation in Cervical Fractures—A Preliminary Clinical Study on Judet-Osteosynthesis of the Axis

Objective: To evaluate the accuracy of CT-based and computer-aided screw insertion into the pedicles of the axis using the method of Judet.Materials and Methods: In two patients, four transpedicular implants of C2 were positioned using a computer-guided technique. One patient with iatrogenic destabüization of the posterior structures C3 and C4 and one patient with a hangman's fracture of the axis required pedicular fixation. In addition, intraoperative documentation of the additional time required for the navigation procedures was made. Finally, postoperative CTs of each patient provided further information about transpedicular implant localization.Results: Image-guided implantation of screws was possible in all scheduled pedicles of the axis. In the postoperative CT scans, none of the inserted screws perforated the medial or lateral pedicle. All screws were accurately positioned within the pedicles, and no anterior perforation of the screws into the vertebral foramen was observed.Conclusions: Our initial results using computer-aided implantation of Judet screws showed that these screws were inserted correctly. However, it is important to realize that movements can occur in the vertebral arch and lateral mass during the time between preoperative CT and surgery. This possibility for movement should be taken into account when procedures such as CT-based insertion of image-guided screws into patients with fractures of the isthmus C2 are performed, because damage to neurovascular structures can result. Therefore, this navigation system should only be used by experienced surgeons who can, if necessary, continue the intervention with more conventional techniques. In addition, it is essential that the surgeon have a complete understanding of the principles of the tracking systems to prevent possible misinterpretation of computer-generated information.

Incorporation of Intraoperative Computerized Tomography in a Newly Developed Spinal Navigation Technique

Objective: We report on the first successful incorporation of intraoperative computerized tomography in spinal navigation procedures.Materials and Methods: All operations were performed with the aid of a Tomoscan M mobile CT system (Philips Medical Systems, Eindhoven, The Netherlands). The system comprises a mobile gantry, a mobile patient examination table, and a mobile workstation. Three different navigation systems were used: the EasyGuide (Philips Medical Systems, Eindhoven, The Netherlands), the Surgical Tool Navigator (Zeiss, Oberkochen, Germany), and a prototype of an ultrasound navigation system developed by ourselves (TVS GbR, Chemnitz, Germany). All surgical operations were performed with the patient positioned on the mobile table of the CT system. Following dorsal preparation of the vertebral region, the surgeon implanted small titanium screws in the vertebrae to serve as fiducial markers. Image data acquisition and image-to-patient registration were performed after implantation of the marker screws. The pedicle screws were inserted using the navigation system, and the position of each implant was confirmed by intraoperative CT scans.Results: To date, 35 patients with various spine disorders have been operated upon using the technique described, and 161 pedicle screws have been inserted. There were no misplacements of pedicle screws. In three (1.9%) cases we observed lateral perforation (maximum 2 mm) of the lateral pedicle wall. We achieved a registration error of 0.85 mm (RMSE) ±0.42 mm (SD).Conclusions: The combination of intraoperative computerized tomography and spinal navigation allows easy navigation with a high application accuracy of 0.8 mm ± 0.4 mm (SD) at the target point (measured in experiments with a plastic spine model). The possibility of performing an intraoperative quality check on demand markedly improves the safety of these procedures.

Incorporation of intraoperative computerized tomography in a newly developed spinal navigation technique.

We report on the first successful incorporation of intraoperative computerized tomography in spinal navigation procedures. All operations were performed with the aid of a Tomoscan M mobile CT system (Philips Medical Systems, Eindhoven, The Netherlands). The system comprises a mobile gantry, a mobile patient examination table, and a mobile workstation. Three different navigation systems were used: the EasyGuide (Philips Medical Systems, Eindhoven, The Netherlands), the Surgical Tool Navigator (Zeiss, Oberkochen, Germany), and a prototype of an ultrasound navigation system developed by ourselves (IVS GbR, Chemnitz, Germany). All surgical operations were performed with the patient positioned on the mobile table of the CT system. Following dorsal preparation of the vertebral region, the surgeon implanted small titanium screws in the vertebrae to serve as fiducial markers. Image data acquisition and image-to-patient registration were performed after implantation of the marker screws. The pedicle screws were inserted using the navigation system, and the position of each implant was confirmed by intraoperative CT scans. To date, 35 patients with various spine disorders have been operated upon using the technique described, and 161 pedicle screws have been inserted. There were no misplacements of pedicle screws. In three (1. 9 %) cases we observed lateral perforation (maximum 2 mm) of the lateral pedicle wall. We achieved a registration error of 0.85 mm (RMSE) +/- 0.42 mm (SD). The combination of intraoperative computerized tomography and spinal navigation allows easy navigation with a high application accuracy of 0.8 mm +/- 0.4 mm (SD) at the target point (measured in experiments with a plastic spine model). The possibility of performing an intraoperative quality check on demand markedly improves the safety of these procedures.

Surgical treatment of lumbar spondylolisthesis.

This article provides an overview of studies that address the medical and surgical treatment of lumbar spondylolisthesis, both degenerative and isthmic. Although the efficacy of decompression for symptomatic lumbar stenosis recalcitrant to conservative treatment has been demonstrated, the addition of instrumentation to a fusion procedure remains controversial. The senior author's (VKHS) experience with pedicle screw fixation and fusion for lumbar spondylolisthesis, the addition of interbody fusion, and spinal navigation is reviewed.

Image-guided spinal surgery

Image-guided spinal surgery with the use of computer assistance enhances preoperative anatomic assessment as well as intraoperative spinal localization and navigation. This technology gives the surgeon an unprecedented ability to visualize and manipulate 3-dimensional imaging data along clinically relevant planes, enabling the surgeon to preoperatively assess the technical feasibility of a given procedure with respect to osseous navigation. Intraoperative registration of preoperative imaging data (computed tomography or magnetic resonance imaging) to the patient provides a more accurate means of localizing critical spinal structures than conventional methods. Tracking of surgical instruments in relation to patient-specific anatomy provides a view of structures hidden beneath the exposed spinal surface and a virtual view of proposed drill or screw trajectories. Image-guided spinal surgery can serve as a valuable tool for intraoperative navigation, particularly when dealing with complex or abnormal spinal anatomy. Considering the risks associated with certain operative procedures, such as C1–2 transarticular screw fixation, we believe that image-guided spinal surgery can offer a measure of safety exceeding that of conventional surgical approaches.

Incorporation of intraoperative computerized tomography in a newly developed spinal navigation technique

Incorporation of intraoperative computerized tomography in a newly developed spinal navigation technique

Spinal Markers: a New Method for Increasing Accuracy in Spinal Navigation

Spinal navigation opens up a completely new dimension in the planning and realization of neurosurgical and orthopedic procedures, and offers the possibility of simulating the operation preoperatively. There is currently only Limited experience with spinal navigation, and despite the development of advanced software, intraoperative difficulties include identification of characteristic and reproducible anatomical landmarks, localization of these points in the surgical field, referencing, and intraoperative control. We report the use of a new kind of implantable fiducial marker in a case of a 58-year-old female patient with spondylolisthesis. Percutaneously applied spinal markers were used as prominent anatomical landmarks and permitted much easier intraoperative handling. In our opinion, in the hands of an experienced neurosurgeon or orthopedist, the additional preoperative time required for placement of such spinal markers is negligible.

Image-Guided Spine Surgery

Conventional imaging techniques are of limited usefulness in spinal navigation, due to their lack of a "three-dimensional perspective." An interactive image-guided approach has been developed that provides a three-dimensional image-space representation of surgical space, using a specially designed referencing system and computer workstation. The system is described and results from laboratory tests and clinical cases are reported. It is concluded that interactive image-guided stereotaxis can be a valuable tool in spinal localization because of its degree of precision and the increased margin of safety it can offer.