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Biomedical subjects

H W Staudte

Publications and source records attributed to H W Staudte.

At least 19 recordsLinked to original sources
PubMed2000

[Planning and performance of orthopedic surgery with the help of individual templates].

Operational interventions can be planned and simulated accurately with the help of a three-dimensional reconstruction of the anatomical bone structures, created from the tomographic data of a patient. Computer-assisted navigation systems or robotic systems can assist the intraoperative realization of the planned intervention and may support the spatial orientation within the operational field. As an inexpensive alternative without the high excessive technical workload on the physicians or the surgical personnel, individual templates were developed in the Helmholtz Institute Aachen. In this approach the negative three-dimensional bone surface, known exactly from the 3D-reconstruction of the patient's bone by the planning system DISOS, is milled into a small cubic block of polycarbonate. During the intervention, the template serves as a reference for the spatial orientation and as a tool-guide for cutting or milling of the bone according to the previous planning. Clinical and experimental studies have shown that operation times as well as intraoperative X-ray times can be shortened by the use of individual templates, while preserving the task sequence of the conventional operation procedures.

Arthroplasty, Replacement, Hip↗
PubMed2000

[CRIGOS: development of a compact robot for image-guided orthopedic surgery].

In this paper, we present a medical robot system dedicated to support the surgeon during challenging tasks within orthopedic interventions. The main goal of this work is to develop a system as technically simple as the surgical requirements allow to keep its cost and complexity to a minimum. Therefore, we primarily focus on calibrated X-ray imaging for image acquisition, an easy registration procedure and robotic execution using a positioning device with simple parallel kinematics. Examples of different orthopedic interventions using the compact robot system for image-guided orthopedic surgery (CRIGOS) are presented, as well as various modes of execution of the device.

Arthroplasty, Replacement, Knee↗
PubMed1999

CRIGOS: a compact robot for image-guided orthopedic surgery.

The CRIGOS (compact robot for image-guided orthopedic surgery) project was set up for the development of a compact surgical robot system for image-guided orthopedic surgery based on user requirements. The modular system comprises a compact parallel robot and a software system for planning of the surgical interventions and for supervision of the robotic device. Because it is not sufficient to consider only technical aspects in order to improve in clinical routine the therapeutic outcome of conventional interventions, a user-centered and task-oriented design process has been developed which also takes human factors into account. The design process for the CRIGOS system was started from requirement analysis of various orthopedic interventions using information gathered from literature, questionnaires, and workshops with domain experts. This resulted in identification of conventional interventions for which the robotic system would improve the medical and procedural quality. A system design concept has been elaborated which includes definitions of components, functionalities, and interfaces. Approaches to the acquisition of calibrated X-rays will be presented in the paper together with design and evaluation of a first human-computer interface. Finally, the first labtype parallel robot based on low-cost standard components is presented together with the first evaluation results concerning positioning accuracy.

Humans↗
PubMed1998

Computer assisted orthopaedic surgery with image based individual templates.

Recent developments in computer assisted surgery offer promising solutions for the translation of the high accuracy of the preoperative imaging and planning into precise intraoperative surgery. Broad clinical application is hindered by high costs, additional time during intervention, problems of intraoperative man and machine interaction, and the spatially constrained arrangement of additional equipment within the operating theater. An alternative technique for computerized tomographic image based preoperative three-dimensional planning and precise surgery on bone structures using individual templates has been developed. For the preoperative customization of these mechanical tool guides, a desktop computer controlled milling device is used as a three-dimensional printer to mold the shape of small reference areas of the bone surface automatically into the body of the template. Thus, the planned position and orientation of the tool guide in spatial relation to bone is stored in a structural way and can be reproduced intraoperatively by adjusting the position of the customized contact faces of the template until the location of exact fit to the bone is found. No additional computerized equipment or time is needed during surgery. The feasibility of this approach has been shown in spine, hip, and knee surgery, and it has been applied clinically for pelvic repositioning osteotomies in acetabular dysplasia therapy.

Acetabulum↗
PubMed1996

A desktop image processing system for computer-assisted orthopedic surgery (DISOS).

Within the framework of our research activities in orthopedic surgery a PC-based imageprocessing system for the processing of x-ray computer-tomographic data has been developed. The system is used as a work platform for the investigations concerning interaction modalities, strategies and techniques for an efficient planning and execution of surgical interventions in orthopedic surgery by means of individual templates. The method of individual templates has been presented in /1,2/ and will not be subject of this paper.

Computer Peripherals↗
PubMed1996

Using human factor analysis and VR simulation techniques for the optimization of the surgical worksystem.

The introduction of minimal invasive operating techniques into the conventional surgical worksystem, requires a fundamental analysis of the resulting problems. Based on ergonomic investigations, concerning working postures, static holding work and task sequence analysis, bottlenecks of workplace design can be demonstrated. As a contribution to the optimization of workplace design, the development of a CAD-based VR simulation environment with an integrated anthropometric man-model, as a very useful tool for anthropometric system design is presented.

Computer Simulation↗
PubMed1994

Age- and sex-dependent force-related function of the cervical spine.

A total of 272 normal persons (109 men, 163 women) between the age of 14 and 84 years was studied for age, body weight, height, neck circumference and neck length. For evaluation of performance, a lifting test and an isometric extension force test showed sex- and age-specific differences in this group. A reliability test with two independent observers showed a good correlation of two consecutive measurements. The lifting test (PILE) and the isometric neck extension force test (IMPET) have been shown to be easy to administer, inexpensive and reliable. The data presented can be used as a data base for European persons for clinical research.

Adolescent↗
PubMed1983

Assessment of motor blockade during epidural anesthesia.

Motor blockade during epidural anesthesia was assessed using dynamometry to measure the maximum force of plantar flexion, and the Bromage score method. In a randomized double-blind study, 40 orthopedic patients received one of the following four local anesthetics epidurally: 0.5% bupivacaine-HCl (n = 10), 0.5% bupivacaine-CO2 (n = 10), 1.0% etidocaine (n = 10), and 1.5% etidocaine (n = 10), all without addition of a vasoconstrictor. The decrease of force, measured by dynamometry, followed an e function. This function permits the description of motor blockade development using one single number, its half-life. This finding corresponds to the increase of motor nerve fiber blockade due to diffusion of the local anesthetic into the nerve. Dynamometry was more precise than the Bromage score in describing motor blockade. Both the Bromage score and dynamometry produced roughly comparable results of onset, rate of development, and maximum intensity of motor blockade. These parameters of motor blockade were superior after both etidocaine solutions compared to both bupivacaine solutions. Neither carbonization of bupivacaine nor increased concentration of etidocaine significantly improved motor blockade produced by these drugs. Dynamometry is a time consuming and costly method for accurate quantification of motor blockade during epidural anesthesia; the Bromage score is more practical under clinical considerations and provides useful information.

Adolescent↗
PubMed1981

[Internal mechanics of the musculature, theoretical study of normal and atrophic muscles (author's transl)].

The article demonstrates, taking muscles of feathery structure as an example, that loss of contractile muscular mass by one-half would correspond to one-half of the power at the tendon if the muscle fibres are arranged in parallel. In the force-distance profile changes after the muscular mass has been reduced to one-half; the muscles with a more pronounced feathery structure will possess a little more than one-half of the original force in the state of greater muscle fibre length. On the other hand, if an atrophic muscle of this type, i.e. of feathery structure, is shortened, there is a considerable loss of power which goes far beyond the loss of muscular mass. This change in the force-distance profile of atrophic feathery muscles can be ascribed to the change in the geometric arrangement of the individual fibres, and to the maximum capacity of extension of the muscle fibres to twice their original length. This performance will explain at least in part the inhibition of the final stretching of the knee joint in case of atrophy of the vastus muscles, the feathery structure of which differs individually.

Biomechanical Phenomena↗
PubMed1981

[Cervical osteoplastic laminectomy for an intramedullary astrocytoma in an eight-year-old child (author's transl)].

In view of the hazards of extensive laminectomy in children, an osteoplastic laminectomy was used in an eight-year-old child suffering from an intramedullary astrocytoma extending from C4 to C7. The laminae were first of all divided bilaterally about 2 mm medial to their origin, with a fine spherical cutter. After dividing the ligamenta flava and the interspinous ligaments the dorsal wall of the spinal canal from C4 to C7 was removed en bloc. The dura was opened and the spinal cord split in the midline after which the microsurgical excision of a spindle-shaped cystic astrocytoma was carried out. After closing the dura drill holes were made bilaterally in the stumps of the pedicles and in the ends of the resected laminae. The entire piece, consisting of laminae and ligaments was replaced and fixed to the stumps of the pedicles with four pairs of wire sutures. Included in the sutures was a small block of bone measuring 2 x 3 x 5 mm, which replaced the bone lost in the saw-cuts and thus prevented any narrowing of the spinal canal. The ligaments were sutured and the wound closed in layers, with drainage. Immobilization in a Minerva plaster for three months.

Astrocytoma↗
PubMed1979

[A contribution to the differential indication of endoprosthetic knee-joint substitution (author's transl)].

The article describes a few guiding points for indicating the need for a knee-joint endoprosthesis, basing on experience with 253 cases, followed up for 2--48 months. Following the application of prostheses according to Walldius-Debeyre and Guepar, several complications were seen which we tried to reduce by introducing four prostheses of different sizes, since the choice of the implantates could be adapted to the prevailing anatomical conditions. A hinged-joint prosthesis of the St. George type is indicated in cases of most severe axial deviation, severe flexion contraction, extensive loss of bone substance, and instability of the ligaments. Sheeban's prosthesis is indicated in severe damage involving both compartments, limited frontal axial deviation, and flexion contraction of not more than 25 degrees with intact lateral ligaments. In younger patients with rheumatoid arthritis we implant the Geomedic prosthesis. If only one knee-joint compartment is involved, and after the possibility of readjustment osteotomy has been excluded, we consider a sliding prosthesis to be the prosthesis of choice.

Age Factors↗
PubMed1976

Studies on the fine structure of invertebrate blood vessels. II. The valves of the lateral sinus of the leech, Hirudo medicinalis L.

The position, structure and function of the valves within the lateral sinus of the medical leech, Hirudo medicinalis, are described on the basis of vital, light- and electron microscopy. In this species the valvular apparatus consists of multiple elongated fir cone-shaped fibrous villi surrounding the orifices of the latero-lateral and latero-dorsal vessel like a tentacular crest. Each villus is covered by a thin sheet of a continuous endothelium. The valves prevent the backflow of hemolymph during systolic contraction of the lateral sinus. The endothelium contains many small mitochondria and polyribosomes in the perinuclear cytoplasm and it develops deep projections into the underlying connective tissue. Each of these consists of a multilayered system of closely interwoven thin endothelial membranes. The endothelium is anchored to its basement membrane by means of a great number of poorly defined hemidesmosomes. The fibrous tissue of the villi consists mainly of a homogeneous vitreous matrix in which few cellular components and very fine filaments are dispersed. Close to the endothelium this matrix appears to be condensed to form a multilayered framework made out of a basement membrane-like material. Though the valves themselves are devoid of muscle cells, those situated at their base and thus belonging to the vascular wall proper, display some specific morphological features: in particular the nuclei of these cells show a distinct fibrous lamina. Moreover, these muscle cells seem to be innervated only by one type of axon, containing both small, lucent synaptic vesicles as well as some of the dense-core variety. These findings are compared with data from earlier works and are discussed in relation to the hemodynamic functions of this valvular apparatus.

Animals↗