Biomedical subjects

L-P Nolte

Publications and source records attributed to L-P Nolte.

7 recordsLinked to original sources

PubMed2006

[The foundations of computer assisted surgery].

Using navigation systems in general orthopaedic surgery and, in particular, knee replacement is becoming more and more accepted. This paper describes the basic technological concepts of modern computer assisted surgical systems. It explains the variation in currently available systems and outlines research activities that will potentially influence future products. In general, each navigation system is defined by three components: (1) the therapeutic object is the anatomical structure that is operated on using the navigation system, (2) the virtual object represents an image of the therapeutic object, with radiological images or computer generated models potentially being used, and (3) last but not least, the navigator acquires the spatial position and orientation of instruments and anatomy thus providing the necessary data to replay surgical action in real-time on the navigation system's screen.

Computer Graphics↗

PubMed2006

Computer-assisted, fluoroscopy-based ventral spondylodesis of thoracolumbar fractures.

OBJECTIVE: To design and evaluate a novel computer-assisted, fluoroscopy-based planning and navigation system for minimally invasive ventral spondylodesis of thoracolumbar fractures. MATERIALS AND METHODS: Instruments and an image intensifier are tracked with the SurgiGATE navigation system (Praxim-Medivision). Two fluoroscopic images, one acquired from anterior-posterior (AP) direction and the other from lateral-medial (LM) direction, are used for the complete procedure of planning and navigation. Both of them are calibrated with a custom-made software to recover their projection geometry and to co-register them to a common patient reference coordinate system, which is established by attaching an opto-electronically trackable dynamic reference base (DRB) on the operated vertebra. A bi-planar landmark reconstruction method is used to acquire deep-seated anatomical landmarks such that an intraoperative planning of graft bed can be interactively done. Finally, surgical actions such as the placement of the stabilization devices and the formation of the graft bed using a custom-made chisel are visualized to the surgeon by superimposing virtual instrument representations onto the acquired images. The distance between the instrument tip and each wall of the planned graft bed are calculated on the fly and presented to the surgeon so that the surgeon could formalize the graft bed exactly according to his/her plan. RESULTS: Laboratory studies on phantom and on 27 plastic vertebras demonstrate the high precision of the proposed navigation system. Compared with CT-based measurement, a mean error of 1.0 mm with a standard deviation of 0.1 mm was found. CONCLUSIONS: The proposed computer assisted, fluoroscopy-based planning and navigation system promises to increase the accuracy and reliability of minimally invasive ventral spondylodesis of thoracolumbar fractures.

Algorithms↗

PubMed2004

Kinematic response of lumbar functional spinal units to axial torsion with and without superimposed compression and flexion/extension.

Experimental data suggest that lumbar torsion contributes to lumbar disc degenerative changes, such as instability, spondylolisthesis and spinal canal stenosis. However, some basic mechanical characteristics of the lumbar spine under torsional loading have not yet been reported in detail. For example, the function of the facet joints under combined mechanical loads such as torsion with superimposed flexion or extension postures is an area of interest about which little biomechanical data have been reported. In this study, the kinematic response to axial torsion with superimposed axial compression (200 N), compression-flexion (3 and 6 Nm) and compression-extension (3 and 6 Nm) was investigated in 10 cadaveric lumbar functional spinal units. Range of motion (ROM), and helical axes of motion (HAM), were analyzed. There was no difference in ROM between no preload, pure compressive and flexion-compression preload conditions. The ROM was significantly reduced by both extension-compression preload conditions (11% reduction for 3 Nm and 19% reduction for 6 Nm of extension) compared to the pure compressive preload. For no preload, the average HAM position in the transverse plane of the intervertebral disc was near the posteriormost part of the disc and located laterally on the side contralateral to the applied torsional moment. In the transverse plane, the HAM position showed a discrete trend towards the posterior part of the specimens during extension. Kinematic data were visualized using computer animation techniques and CT-based reconstructions of the respective specimens. This information may be used for identifying and characterizing physiologic and pathologic motion and for specifying conservative and surgical treatment concepts and, thus, may find application to identifying indications for spinal fusion or in evaluating the effect of future semi-flexible instrumentation.

Adult↗

PubMed2004

[Intraoperative three-dimensional navigation for pedicle screw placement].

The mobile SIREMOBIL Iso-C(3D) C-arm (Siemens, Erlangen, Germany) is the first device permitting intraoperative, three-dimensional representation of bone structures. A high-resolution, isotropic 3D data cube in the isocenter with sides of approximately 12 cm is calculated simultaneously. The SIREMOBIL Iso-C(3D) is linked to the navigation system. This makes it possible to transfer the generated 3D data directly to the linked navigation system without the need for surgeon-dependent registration. In this prospective clinical trial, we evaluated the accuracy of pedicle screw placement using this device. In 61 patients, a total of 302 pedicle screws were placed. Only in five cases (1.7%) were misplacements of > or =2 mm shown in postoperative control CT. The average fluoroscopy time was 1.28+/-0.56 min, and the average operative duration was 103.26+/-23.3 min. There were no postoperative neurological complications in any of the 30 patients. From these data, we conclude that Iso-C(3D) navigation is a very accurate method for the placement of pedicle screws.

Adolescent↗

PubMed2002

Computer assisted screw insertion into real 3D rapid prototyping pelvis models.

OBJECTIVE: Show the use of computer navigation in exact screw positioning in the different pelvic bones. BACKGROUND: Computer assisted pedicle screw insertion in the spine is an established procedure. Screw fixation is also used in highly difficult pelvic and hip surgery (arthroplasty revision surgery and tumor surgery). DESIGN: Insert as long screws as possible with computer navigation into the different bones of the pelvis and compare these results with a non-computer controlled method. METHODS: The computer navigation was done with the system of Medivision (Oberdorf, Switzerland), the software was SurgiGATE 2.1. Optically controlled spine instruments and a special calibrated drill were used. The screw insertion with and without computer navigation took place in seven real rapid prototyping pelvis models matched by pairs. Three screws were inserted into the Os ileum, one into the Os pubis and one into the Os ischium. The length of the inserted screws were measured and compared using routine statistic methods. RESULTS: The mean screw length with vs. without computer navigation was 8.9 vs. 5.7 cm in the Os ileum (P=0.0001), 6.0 vs. 4.2 cm in the Os pubis (P=0.01) and 4.3 vs. 3.9 cm in the Os ischium (not significant). CONCLUSIONS: The use of computer navigation allows for the insertion of longer screws into the bones of the pelvis (more exact positioning), which requires a more precise original point of entry and direction of the drill (vector). RELEVANCE: The insertion of fixation screws in highly difficult pelvic and hip surgery (revision arthroplasty, tumor surgery) are another field for the use of computer navigation.

Arthroplasty, Replacement, Hip↗

PubMed1995

Clinical evaluation of a system for precision enhancement in spine surgery.

Most techniques in segmental spinal fixation surgery rely on the identification of predefined targets with the help of anatomical landmarks and on intraoperative use of image intensifiers. However, because there is no direct link between the image information, the accessible spinal anatomy, and the action of surgical instruments several potential problems and possible complications are still involved. A novel system for spinal surgery has been designed allowing for the real-time, intraoperative localization of surgical instruments in medical images. In practice this was achieved by combining image-guided stereotaxis with advanced optoelectronic position sensing techniques. Modules were developed for image data processing, surgical planning and simulation, and various intraoperative procedures. A detailed validation of the system was performed indicating an overall accuracy to be better than the slice distance of the spinal image used. In an in-vitro setting 20 pilot holes for pedicle screws were prepared in human cadaveric lumbar spines. An analysis in 77 histological cuts showed an ideal location in 70 and only minor cortex engagement in seven sections. In vivo the system has been successfully applied in three posterior low lumbar stabilizations with overall 15 transpedicular screws. RELEVANCE--:This article focuses on the clinical evaluation of a computer-assisted surgery system and its application to the operating theatre for transpedicular fixation of the spine. The given approach effectively keeps the surgeon 'in the loop' and requires only minor modifications of the established surgical techniques and associated instruments. The results of this study indicate that advanced computer-assisted techniques may significantly improve the accuracy and safety of surgical interventions of the spine. The proposed technique may in future be adapted to other applications in orthopaedic surgery.

Journal Article↗

PubMedDate not supplied

New orthopaedic implant management tool for computer-assisted planning, navigation, and simulation: from implant CAD files to a standardized XML-based implant database.

Computer-Assisted Orthopaedic Surgery (CAOS) has made much progress over the last 10 years. Navigation systems have been recognized as important tools that help surgeons, and various such systems have been developed. A disadvantage of these systems is that they use non-standard formalisms and techniques. As a result, there are no standard concepts for implant and tool management or data formats to store information for use in 3D planning and navigation. We addressed these limitations and developed a practical and generic solution that offers benefits for surgeons, implant manufacturers, and CAS application developers. We developed a virtual implant database containing geometrical as well as calibration information for orthopedic implants and instruments, with a focus on trauma. This database has been successfully tested for various applications in the client/server mode. The implant information is not static, however, because manufacturers periodically revise their implants, resulting in the deletion of some implants and the introduction of new ones. Tracking these continuous changes and keeping CAS systems up to date is a tedious task if done manually. This leads to additional costs for system development, and some errors are inevitably generated due to the huge amount of information that has to be processed. To ease management with respect to implant life cycle, we developed a tool to assist end-users (surgeons, hospitals, CAS system providers, and implant manufacturers) in managing their implants. Our system can be used for pre-operative planning and intra-operative navigation, and also for any surgical simulation involving orthopedic implants. Currently, this tool allows addition of new implants, modification of existing ones, deletion of obsolete implants, export of a given implant, and also creation of backups. Our implant management system has been successfully tested in the laboratory with very promising results. It makes it possible to fill the current gap that exists between the CAS system and implant manufacturers, hospitals, and surgeons.

Computer-Aided Design↗