Biomedical subjects

H Visarius

Publications and source records attributed to H Visarius.

7 recordsLinked to original sources

PubMed1997

Improved accuracy of pedicle screw insertion with computer-assisted surgery. A prospective clinical trial of 30 patients.

STUDY DESIGN: A prospective clinical trial was done to study the accuracy of pedicle screw placement in 30 consecutive computer-assisted orthopedic surgeries. OBJECTIVES: To determine the accuracy and clinical applicability of this new method for pedicle screw insertion. SUMMARY OF BACKGROUND DATA: Conventional screw insertion techniques have been associated with high pedicle screw malplacement rates in cadaver studies and clinical studies with postoperative computed tomography evaluation. METHODS: Thirty transpedicular, low-back, titanium instrumentations were performed with computer-assisted orthopedic surgery. The accuracy of screw placement was evaluated using a sophisticated computed tomography protocol. RESULTS: The total number of pedicle screws was 174. Of these, 139 (79.9%) could be inserted with computer-assisted orthopedic surgery. The malplacement rate of computer-assisted orthopedic surgery screws was 4.3%. In screws that were not inserted by computer-assisted orthopedic surgery, the malplacement rate was 14.3%. One malplaced screw that had not been inserted with computer-assisted orthopedic surgery caused L4 root paresis. CONCLUSIONS: The accuracy of pedicle screw placement using computer-assisted surgery proved to be superior to the accuracy obtained when using conventional techniques.

Bone Screws↗

PubMed1997

Accuracy of computer-assisted pedicle screw placement. An in vivo computed tomography analysis.

STUDY DESIGN: A computer-assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. OBJECTIVES: To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. SUMMARY OF BACKGROUND DATA: Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. METHODS: The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. RESULTS: The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. CONCLUSIONS: The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.

Bone Screws↗

PubMed1997

Man-machine interfaces in computer assisted surgery.

The clinical potential of computer assisted surgery (CAS) has been more and more widely acknowledged since CAS systems have been introduced into the operating room (OR) theater. Especially the improvements in safety and accuracy are remarkable and strengthen the ties between surgeons and engineers. Tumor stereotaxis was introduced to neurological surgery in the early 1980s, and currently systems with and without robotic navigation are in use for specific medical indications. Recently, solutions for computer assisted orthopedic surgery were developed and applied to various anatomical regions. However, with the establishment of CAS in vivo, a new complex of problems, which was not present in the laboratory setup, was introduced: the man-machine interface. Currently, the complexity of available CAS systems requires the presence of at least one system engineer (often called the "operator") in the OR. As a consequence, there is no possibility for direct communication between the surgeon and the machine or software. Most of the program steps involved in CAS and choices to be made intraoperatively have to be transferred to the software by means of communication of the surgeon with the operator. Particularly, the establishment of a relation between the virtual object (i.e., a medical image) and the surgical object (i.e., the patient), often denoted as "matching" or "skeletal registration," requires intensive interaction of the surgeon with the computer. A literature survey revealed that no CAS system in clinical use exists without a system engineer or a comparable person, and our clinical experience indicated that the matching process is a weak point in most systems. Because it appears to be contradictory to cost-reduction efforts in health care to have a highly paid specialist in the OR, this research evaluates strategies to facilitate the man-machine interface with the final goal of establishing a direct control of the system by the surgeon or the medical personnel traditionally present at surgery. Options to be investigated include 1) a CAS control panel (virtual keyboard) as an integrated component of the existing navigation system and 2) introduction of a commercial voice-recognition system. The implementation of these strategies into the existing CAS setup at the Department of Orthopaedic Surgery at the Inselspital (University of Bern) and clinical experience gained are reported.

Biomedical Engineering↗

PubMed1996

Image-guided computer-assisted spine surgery: a pilot study on pedicle screw fixation.

As the pedicle offers a strong point of attachment to the spine, several instrumentation systems using screws that go through the pedicle into the vertebral body have been developed to provide internal stability. All pedicle screw systems share the risk of damage to adjacent neural structures as a result of improper screw placement. A computer-assisted system allowing precise preoperative planning and real-time intraoperative interactive image localization has been implemented for spine instrumentation to optimize transpedicular spine fixation. A validation study was performed in an in vitro set-up drilling 20 pedicle pilot holes in lumbar vertebrae. An analysis in 77 histological cuts showed an ideal location in 70 with no case of injury to the pedicle cortex. We discuss initial clinical experience on cases of posterior lumbar stabilization. Interactive computer-assisted spine surgery provides an accurate and safe approach for transpedicular screw fixation and may provide a useful tool for optimization of spine surgery.

Bone Screws↗

PubMed1995

Computer-aided fixation of spinal implants.

Medical imaging provides an important basis for modern diagnosis as well as for preoperative planning of surgical procedures. However, information gained cannot be transferred directly into the operating room. Furthermore, the safety and accuracy of the surgical intervention would be improved by interactive navigation of surgical instruments. These features are provided by the system for computer-aided fixation of spinal implants described in this paper.

Computer Simulation↗

PubMed1993

A biomechanical comparison of cervical laminaplasty and cervical laminectomy with progressive facetectomy.

The effects of multilevel cervical laminaplasty and laminectomy with increasing amounts of facetectomy on stability of the cervical spine were tested with physiologic loading in nine cadaveric specimens. Cervical spines, levels C2-C7, were tested with physiologic loading in a constraint-free test system, the motion of each body being tracked in a three-dimensional coordinate system. Cervical laminectomy with 25% or more facetectomy resulted in a highly significant increase in cervical motion compared to the intact specimens for the dominant motions of flexion/extension (P < 0.003), axial torsion (P < 0.001), and lateral bending (P < 0.001). Cervical laminaplasty was not significantly different from the intact control, except for a marginal increase in axial torsion. Coupled motion did not change with laminaplasty or laminectomy with progressive facetectomy. As little as 25% facetectomy adversely affects stability after multilevel cervical laminectomy. Cervical laminaplasty avoids this problem, while still affording multilevel decompression. Therefore in patients undergoing cervical laminectomy accompanied by more than 25% bilateral facetectomy, concurrent arthrodesis should be performed.

Absorptiometry, Photon↗

PubMedDate not supplied

[Comparative biomechanical studies following automated percutaneous nucleotomy and diskotomy].

APLD is considered as the last step of conservative treatment for lumbar disc herniation assuming that a negative biomechanical effect of APLD is not expected. Biomechanical effects of APLD were investigated in comparison to open discectomy. APLD decreased disc height less than open discectomy and increased instability and flexibility less. The position of the center of rotation was not significantly altered.

Adult↗