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Biomedical subjects

Lutz-Peter Nolte

Publications and source records attributed to Lutz-Peter Nolte.

15 recordsLinked to original sources
PubMed2006

Assessment of spline-based 2D-3D registration for image-guided spine surgery.

2D-3D registration of pre-operative 3D volumetric data with a series of calibrated and undistorted intra-operative 2D projection images has shown great potential in CT-based surgical navigation because it obviates the invasive procedure of the conventional registration methods. In this study, a recently introduced spline-based multi-resolution 2D-3D image registration algorithm has been adapted together with a novel least-squares normalized pattern intensity (LSNPI) similarity measure for image guided minimally invasive spine surgery. A phantom and a cadaver together with their respective ground truths were specially designed to experimentally assess possible factors that may affect the robustness, accuracy, or efficiency of the registration. Our experiments have shown that it is feasible for the assessed 2D-3D registration algorithm to achieve sub-millimeter accuracy in a realistic setup in less than one minute.

Algorithms↗
PubMed2005

Implementation, accuracy evaluation, and preliminary clinical trial of a CT-free navigation system for high tibial opening wedge osteotomy.

OBJECTIVE: The objectives of this study are to design and evaluate a CT-free intra-operative planning and navigation system for high tibial opening wedge osteotomy. This is a widely accepted treatment for medial compartment osteoarthritis and other lower extremity deformities, particularly in young and active patients for whom total knee replacement is not advised. However, it is a technically demanding procedure. Conventional preoperative planning and surgical techniques have so far been inaccurate, and often resulting in postoperative malalignment representing either under- or over-correction, which is the main reason for poor long-term results. In addition, conventional techniques have the potential to damage the lateral hinge cortex and tibial neurovascular structures, which may cause fixation failure, loss of correction, or peroneal nerve paralysis. All these common problems can be addressed by the use of a surgical navigation system. MATERIALS AND METHODS: Surgical instruments are tracked optically with the SurgiGATE((R)) navigation system (PRAXIM MediVision, La Tronche, France). Following exposure, dynamical reference bases are attached to the femur, tibia, and proximal fragment of the tibia. A patient-specific coordinate system is then established, on the basis of registered anatomical landmarks. After intra-operative deformity measurement and correction planning, the osteotomy is performed under navigational guidance. The deformities are corrected by realigning the mechanical axis of the affected limb from the diseased medial compartment to the healthy lateral side. The wedge size, joint line orientation, and tibial plateau slope are monitored during correction. Besides correcting uni-planar varus deformities, the system provides the functionality to correct complex multi-planar deformities with a single cut. Furthermore, with on-the-fly visualization of surgical instruments on multiple fluoroscopic images, penetration of the hinge cortex and damage to the neurovascular structures due to an inappropriate osteotomy can be avoided. RESULTS: The laboratory evaluation with a plastic bone model (Synbone AG, Davos, Switzerland) shows that the error of deformity correction is <1.7 degrees (95% confidence interval) in the frontal plane and <2.3 degrees (95% confidence interval) in the sagittal plane. The preliminary clinical trial confirms these results. CONCLUSION: A novel CT-free navigation system for high tibial osteotomy has been developed and evaluated, which holds the promise of improved accuracy, reliability, and safety of this procedure.

Arthroscopy↗
PubMed2005

A fluoroscopy-based surgical navigation system for high tibial osteotomy.

High tibial osteotomy is a widely accepted treatment for unicompartmental osteoarthritis of the knee and other lower extremity deformities, particularly in young and active patients. However, it is generally recognized as a technically demanding procedure. The lack of intraoperative control of the mechanical axis of the affected limb often results in postoperative malalignments, which is one of the main reasons for poor long-term results. Moreover, inaccurate osteotomies, such as insufficient or excessive bone cut, or incorrect orientation of the chisel or saw blade, have been observed. A computer assisted intraoperative planning and navigation system is therefore proposed in order to address these technical problems. During operation, fluoroscopic images are acquired and anatomical landmarks are digitized; a patient-specific coordinate system is established accordingly. After the three-dimensional measurement of the deformity and interactive planning of the osteotomy plane, the deformity is corrected under navigational guidance. The proposed system has been successfully introduced into the clinical practice of surgery after encouraging laboratory evaluations, with results affirming that it is safe and accurate.

Fluoroscopy↗
PubMed2004

Computer aided high tibial open wedge osteotomy.

High tibial osteotomy is a widely accepted treatment of medial compartment osteoarthritis as well as other lower extremity deformities. However, it is a technically demanding procedure. The lack of exact intraoperative real time control of the mechanical axis often results in postoperative malalignments, which is one reason for poor long term results. These problems can be addressed with the use of a surgical navigation system. Following exposure, dynamic reference bases (DRBs) are attached to the femur, and the proximal and the distal part of the tibia. After intraoperative measurement of the deformities and correction planning, the osteotomy is performed under navigational guidance. The wedge size, joint line orientation, and tibial plateau slope are monitored during correction. The in vitro evaluation with a plastic bone model suggests that the error of deformity correction is less than 1.7 degrees (95% confidence limits) in the frontal, and less than 2.3 degrees (95% confidence limits) in the sagittal plane, respectively. On a cadaver study of 13 legs, the mechanical axis intersected the Fujisawa line in 80.7% (range 77.5-85.8%). The preliminary clinical experience confirms these results. A novel computer tomography free navigation system for high tibial osteotomy has been developed that holds the promise of improving the accuracy, reliability, and safety of this kind of approach.

Adult↗
PubMed2003

Three-dimensional stabilization provided by the external spinal fixator compared to two internal fixation devices: a biomechanical in vitro flexibility study.

We performed an in vitro study to investigate the stabilization (i.e. motion reduction) provided by the external spinal fixator (ESF), and to compare the three configurations of the ESF with two internal fixation techniques. Six human cadaveric lumbar spine specimens (L3-S1) were subjected to multidirectional flexibility testing in six configurations: (1) intact, (2) ESF in neutral, (3) ESF in distraction, (4) ESF in compression, (5) translaminar facet screw fixation, and (6) internal transpedicular fixation. Both the ESF and the internal fixation systems stabilized the specimens from L4 to S1. In each testing configuration, pure bending moments of flexion-extension, bilateral axial rotation, and bilateral lateral bending were applied to the uppermost vertebra stepwise to a maximum of 10 Nm. The rigid body motion between the vertebrae was measured using an optoelectronic camera system, and custom software was used to calculate the intervertebral rotations. For each applied motion in all testing configurations, the total range of motion (ROM) of L4-S1 is reported. All three ESF configurations stabilized the spine significantly when compared to the intact specimen. The ESF in compression provided significantly more stabilization in flexion-extension than the two other ESF configurations, but no other significant differences were found between the three ESF modes. In flexion-extension the ESF stabilized the spine significantly when compared with the two internal fixation devices. Only in bilateral lateral bending was the ESF inferior to internal transpedicular fixation in providing stabilization. The results of the present study suggest that the ESF provides a high degree of stabilization for preoperative assessment of selected low back pain patients. Whether other non-mechanical factors affect the pain relief experienced by the patients remains unknown.

Adult↗
PubMed2003

A-mode ultrasound-based registration in computer-aided surgery of the skull.

OBJECTIVE: To evaluate the integration and accuracy of A (amplitude)-mode ultrasound-based surface matching for noninvasive registration of the head into a frameless computer-aided surgery system for otorhinology and skull base surgery. DESIGN: Experimental study and case series. SETTING: Academic medical center. PATIENTS: Twelve patients underwent anterior and paranasal skull base surgery with the routine use of a computer-aided surgery system. INTERVENTIONS: A computer-aided surgery system, based on an optoelectronic localizer, was used to track the skull and the surgical tools, including the A-mode ultrasound probe. The A-mode probe was a 10-MHz immersion transducer. An acoustic lens attached to the transducer focused the ultrasonic beam to a depth of 1 to 10 mm. Accuracy tests were performed for the ultrasound setup. Different surface point distributions were evaluated with respect to matching accuracy on a human cadaver skull specimen equipped with fiducial markers. The matching comparison was based on the fiducial registration error. For the clinical evaluation, the laboratory setup was transferred to the operating room. MAIN OUTCOME MEASURES: Noninvasive registration of the skull by using A-mode ultrasound in computer-aided surgery (practical and clinical measurements). RESULTS: The accuracy tests on the human skull specimen revealed that the mean +/- SD fiducial registration error was 1.00 +/- 0.19 mm in the best series for A-mode ultrasound surface matchings and was robust with respect to different sets of surface points. The mean +/- SD root mean square error from the 12 A-mode ultrasound matchings in the patient study was 0.49 +/- 0.20 mm. CONCLUSION: A-mode ultrasound surface matching can be used as a noninvasive and accurate registration procedure in computer-aided surgery of the head.

Bias↗
PubMed2003

Evaluation of 3D correspondence methods for model building.

The correspondence problem is of high relevance in the construction and use of statistical models. Statistical models are used for a variety of medical application, e.g. segmentation, registration and shape analysis. In this paper, we present comparative studies in three anatomical structures of four different correspondence establishing methods. The goal in all of the presented studies is a model-based application. We have analyzed both the direct correspondence via manually selected landmarks as well as the properties of the model implied by the correspondences, in regard to compactness, generalization and specificity. The studied methods include a manually initialized subdivision surface (MSS) method and three automatic methods that optimize the object parameterization: SPHARM, MDL and the covariance determinant (DetCov) method. In all studies, DetCov and MDL showed very similar results. The model properties of DetCov and MDL were better than SPHARM and MSS. The results suggest that for modeling purposes the best of the studied correspondence method are MDL and DetCov.

Algorithms↗
PubMed2003

Neck dissection shoulder syndrome: quantification and three-dimensional evaluation with an optoelectronic tracking system.

Objective 3-dimensional biomechanical changes of the shoulder at rest or during arm elevation were measured by means of a new specific method using an optoelectronic detection system that was developed for computer-aided surgery. Additionally, the shoulder syndrome following neck dissection was evaluated by the recognized orthopedic shoulder Constant score. The statistical evaluation encompassed 12 patients with unilateral radical neck dissection (RND), 12 patients with unilateral modified radical neck dissection (MRND) with preservation of the accessory nerve, and 10 healthy subjects. The healthy shoulders showed normal kinematic behavior, the so-called "scapulohumeral rhythm" (SHR). After MRND, the static scapular position and SHR showed no significant 3-dimensional variations. In contrast, RND produced a highly significant scapular displacement at rest (p < .01) and a near-total abolition of SHR. The Constant scores were significantly lower after RND than after MRND (p < .01). Three-dimensional evaluation of the shoulder syndrome supports the Constant score, quantifying what can be measured objectively.

Accessory Nerve↗
PubMed2003

Valuable use of computer-aided surgery in congenital bony aural atresia.

Congenital aural atresia repair is difficult owing to unpredictable anatomy. Benefits may be gained from computer-aided surgery (CAS), but its exact role has yet to be clearly defined. This is a retrospective study of 18 patients with bony type C (Schuknecht classification) congenital atresia. In the first group (n = 9), repair was performed with CAS while in the second group (n = 9), similar intervention was applied without CAS. Intra- and post-operative clinical and audiological findings were compared. CAS computed tomography (CT) images correlated well with intra-operative findings giving the surgeon more security and reducing operative time by 25 minutes. In our estimation, CAS is valuable for type C congenital aural atresia repair. It serves as an educational tool and as a guide for the experienced surgeon in critical situations where anatomical landmarks are distorted and where access is limited.

Abnormalities, Multiple↗
PubMed2003

A transcutaneous bone digitizer for minimally invasive registration in orthopedics: a real-time focused ultrasound beam approach.

Computer-guided navigation of surgical tool position in computer-assisted orthopedic systems requires the registration of computer tomographic (CT) images with underlying bone. This process is presently performed by manually digitizing points on bone with a pointer and aligning them to a preoperative CT scan. We propose the use of ultrasound to obtain points on bone transcutaneously. A custom-made A-mode probe features a modular lens focusing system and a one-step calibration method. A stable and precise echo detection algorithm is also implemented. The accuracies of three signal detection algorithms--standard deviation, cross-correlation (XCORR) and short-time Fourier transform--were compared using a known reflected signal. XCORR showed the most accurate and stable operation. To test our method of obtaining bone surface points, a plastic model of the fourth human lumbar vertebra was CT scanned and then immersed in a water bath. Six surface registrations of the vertebra using an accurate pointing device were compared to ten registrations obtained using the US probe (using the XCORR algorithm). Student's T-test showed no significant difference in error between the two methods, proving that ultrasound registration, using our method, is equivalent to the more conventional pointer method.

Algorithms↗
PubMed2002

A hybrid CT-free navigation system for total hip arthroplasty.

OBJECTIVE: To design and evaluate a novel CT-free image-guided surgical navigation system for assisting placement of both acetabular and femoral components in total hip arthroplasty (THA). MATERIALS AND METHODS: The methodology in this paper is conceptually based on our previous work on CT-free cup placement. For femoral component placement, two patient-specific reference coordinate systems are first defined: One for the pelvis, based on the so-called anterior pelvic plane (APP) concept, and one for the femur, using the center of the femoral head, the posterior condylar tangential line, and the medullary canal axis of the proximal femur. A hybrid method is used for the associated landmark acquisition, which involves percutaneous point-based digitization and bi-planar landmark reconstruction using multiple registered fluoroscopy images. The following clinical parameters are computed in real time: cup inclination and anteversion, antetorsion and varus/valgus of the stem, lateralization, and change in leg length for complete THA. In addition, instrument actions such as reaming, impaction, and rasping are visualized for the surgeon by superimposing virtual instrument representations onto the fluoroscopic images. RESULTS: A laboratory study of computer-assisted measurement of antetorsion and varus/valgus, change in leg length, and lateralization for femoral stem placement demonstrated the high precision of the proposed navigation system. Compared with CT-based measurement, mean deviations of 1.0 degrees, 0.6 degrees, 0.7 mm, and 1.7 mm were found for antetorsion, varus/valgus, change in leg length, and lateralization, respectively, with standard deviations of 0.5 degrees, 0.5 degrees, 0.6 mm, and 0.7 mm, respectively. A pilot clinical evaluation showed that THA could benefit from this newly developed CT-free hybrid system. CONCLUSIONS: The proposed CT-free hybrid system promises to increase the accuracy and reliability of THA surgery.

Aged↗
PubMed2002

Present state and future perspectives of computer aided surgery in the field of ENT and skull base.

BACKGROUND: CAS technology has emerged in the last 10 years and is more and more used for surgery of the anterior and lateral skull base. Endoscopic and microscopic CAS systems are available. The endoscopic key hole or minimal invasive procedure is used increasingly not only for treatment of inflammatory disease, but also for tumour surgery. The integration of CAS systems into these procedures raises the level of their safety and efficiency. In addition, they allow the distance to the bone border on the CT slices to be previewed and measured. OBJECTIVE: Review of the present state of CAS systems, our own experience as a research centre and as users of the systems, demonstration of new navigational devices, microscope integration and a new registration procedure developed for the "Bernese" frameless optical navigation system (SurgiGATE ORL@1000, medivision, [Synthes, Stratec-medical], CH-4436 Oberdorf). MATERIAL AND METHODS: The optical CAS system with microscope integration (VM 900@1000, Möller-Wedel, Germany), new devices and new matching procedure; accuracy tests on a cadaver skull and on the patient's head. RESULTS: The practical accuracy on the cadaver skull with the pointer system has a mean average error of 0.79 mm, and the clinical accuracy is between 0.5 mm and 2 mm. CONCLUSION: CAS-microscope integration, new CAS technical devices and new noninvasive CAS-registration procedures support the surgeon in more minimally invasive surgical procedures of the paranasal sinuses and the skull base. Future perspectives will be discussed.

Humans↗
PubMedDate not supplied

A comparison study assessing the feasibility of ultrasound-initialized deformable bone models.

This article presents a feasibility and evaluation study for using 2D ultrasound in conjunction with our statistical deformable bone model within the scope of computer-assisted surgery. The final aim is to provide the surgeon with enhanced 3D visualization for surgical navigation in orthopedic surgery without the need for preoperative CT or MRI scans. We unified our earlier work to combine several automatic methods for statistical bone shape prediction and ultrasound segmentation and calibration to provide the intended rapid and accurate visualization. We compared the use of a tracked digitizing pointer and ultrasound for acquiring landmarks and bone surface points for the estimation of two cast proximal femurs.

Bone and Bones↗
PubMedDate not supplied

Endoscope-based hybrid navigation system for minimally invasive ventral spine surgeries.

The availability of high-resolution, magnified, and relatively noise-free endoscopic images in a small workspace, 4-10 cm from the endoscope tip, opens up the possibility of using the endoscope as a tracking tool. We are developing a hybrid navigation system in which image-analysis-based 2D-3D tracking is combined with optoelectronic tracking (Optotrak) for computer-assisted navigation in laparoscopic ventral spine surgeries. Initial results are encouraging and confirm the ability of the endoscope to serve as a tracking tool in surgical navigation where sub-millimetric accuracy is mandatory.

Endoscopes↗