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Biomedical subjects

F Gebhard

Publications and source records attributed to F Gebhard.

At least 19 recordsLinked to original sources
PubMed2001

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 destabilization 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.

Adult↗
PubMed2001

[New methods in polytrauma surgery. Results of a Study Congress at castle Reisenburg 27/28 February 2000].

Recently, in Germany the academic environment has changed and an upheaval occurred that directly do affect academic research activities. Increasingly, the funding of scientific projects is not provided anymore by the universities themselves or the government, but has to be acquired as grants. While in the past, research was conducted by single departments, nowadays and more and more in the future scientific networks have to be established by combining 'local' and even 'distant' knowledge. With this changing background in mind representatives of different scientific institutions met at the Reisensburg castle to discuss the current state and future trends in four major research fields: "Epidemiology of Severe Trauma", "Head Injury", "Pathophysiology of Damage to the Chest", and "Posttraumatic Soft Tissue Injury".

Germany↗
PubMed2001

[Influence of prosthesis design on intramedullary pressure formation in femur shaft implants of cemented hip endoprostheses].

The increase of intramedullary femoral pressure can lead to the intravasation of bone marrow and fat cells into the blood stream of the femoral vein and consequently into the pulmonary circulation. This effect is the same in intramedullary nailing and in the implantation of femoral stem prostheses. In a prospective study we evaluated the intraoperative, intramedullary pressure in the distal femur during the implantation of femoral stem prostheses with two different designs. In eight patients we implanted Müller straight stems and in another eight we implanted stem type Option 3000. Intramedullary pressure was recorded continuously by the implantation of a microtip pressure probe (piezoresistive principle, 50 Hz) in the distal femur. We found markedly higher pressure in Müller straight stem prostheses: range: 590-2,570 mmHg (median = 1,293, SD = 627 mmHg). Intramedullary pressure in stem prosthesis type Option 3000 was much lower: range: 59-574 mmHg (median = 289, SD = 219 mmHg). The differences were statistically significant (p = 0.0008). By changing the designs of femoral stem prostheses, the intramedullary pressure can be markedly reduced. In the case of elderly patients or those with pulmonary illness we recommend femoral stem prosthesis designs, which induce little increase in the intramedullary pressure, in order to reduce cardiopulmonary complications.

Bone Cements↗
PubMed2001

[Precision in standardized Iso-C-Arm based navigated boring of the proximal femur].

C-arm navigation is a new tool in computer assisted surgery. The aim of this study is to evaluate the accuracy of Iso-C-arm based drill holes in the proximal femur. In nine artificial proximal femura, two holes with an angle of 135 degrees and 100 degrees in relation to the shaft axis were drilled in the direction of the femoral head. The defined target of the 3.2 mm drillings was a 4 mm steel ball, which had previously been placed and fixed at the cranial center of the femoral head. All the drillings were standardized with a navigated drilling machine fixed to a frame which only allowed movement of the system in the direction of the drill. During navigation the positions of the drill before commencement and at the deepest point of the canal were recorded. After drilling all specimens were evaluated by CT, and the coordinates of the center of the start and the end of the drilled hole and the center of the ball were determined. Using vector calculation, the smallest distance between the straight line, defined by the center of the starting point and the end point of the drill hole, and the center of the ball was calculated. Additionally, the coordinates of the intersection between the perpendicular to the center of the ball and the straight line were determined (xv, yv, zv), to evaluate the direction of misplacement of the drilled canal in relation to the target. For the 135 degrees drill holes, a median of 2.5 mm for the smallest distance between the straight line, given by the center of the start and the end of the hole, and the center of the ball was investigated (range 1.6-3.7 mm). For the 100 degrees holes the median was 3.1 mm (range 1.8-4.2 mm). The main plane of deviation in all of the 135 degrees holes was posteriorly, whereas in the 100 degrees holes posterior deviation occurred in four cases, cranial in three cases, and in one case each caudal and anterior deviation occurred. In our opinion, the accuracy of fluoroscopy based navigation applied in the region of the proximal femur is sufficient and reproducible. This technique can be used for implant placement at the proximal femur in the future.

Equipment Design↗
PubMed2001

[Precision analysis of navigation-assisted implanted thoracic and lumbar pedicled screws. A prospective clinical study].

A prospective clinical trial was performed to study the accuracy of pedicle screw placement of consecutive computer-aided and conventional techniques. Concerning the clinical performance of the navigation system, the average time of matching has been 8.4 minutes per vertebrae. For evaluation of the results, only complete intraosseous placement of the pedicle screw has been defined as correct position. Any medial or lateral perforation of the cortical structure of the pedicle was recorded as malplacement. In the CT-controlled patients complete intrapedicular placement of the screw was obtained in 36 of 45 thoracic (80%) and in 22 of 27 navigated lumbar (81%) pedicles. In the conventional cohort group 27 of 34 (79%) thoracal and 43 of 52 (83%) lumbar screws were completely in. No radicular neurologic damage, caused by a malplaced transpedicular screw has been observed in both groups. In the presented study is shown, that the application of the computer-assisted freehand navigation can improve results concerning the precision of spinal screw placement. Although, the spinal navigator has to consider a learning curve for the clinical inauguration of the system and the qualification of the implant system for computer-assisted application.

Bone Plates↗
PubMed2001

[Computer-assisted surgery: developments and prospects in 2001. Results of a workshop at Schloss Reisenburg, 23-24 November 2000].

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

Arthroplasty, Replacement, Knee↗
PubMed2001

[Computer assisted surgery, 2001 development and prospects. Results of a congress at Reisensburg Castle, 23-24 November 2000]].

The progress in computer assisted surgery (CAS) is influenced by new technologies in imaging as well as by the input of the users. At present, CAS procedures are established in dorsal spine instrumentation, prosthetics and long bone surgery. Present status and future of CAS was a topic of an expert meeting at the Reisensburg castle. Imaging will speed up in the future using multi-detector techniques. C-arm navigation will gain more information using the 3D technology intraoperatively. CT based navigation procedures are standard in spine and will be established in pelvic surgery. CAS in robotics at the moment means the use of robot-assistance. A new concept is the modality-based navigated surgery, which can be used at various skeletal locations. Visualization of patient data will improve using 3D semi-transparencies with real time update. In the future it will be mandatory to find algorithms to fuse the different possibilities and techniques. A new concept of surgical training is necessary to teach CAS procedures. Therefore discussion must go on to improve these systems.

Forecasting↗
PubMed2001

Early inflammatory mediator response following isolated traumatic brain injury and other major trauma in humans.

The inflammatory response following isolated traumatic brain injury (TBI) is characterised by the release of pro- and anti-inflammatory mediators. In order to determine the important mediators regarding survival and outcome of patients with severe traumatic isolated head injuries, we performed this prospective preclinical and clinical study starting upon arrival at the site of the accident. After approval by the local ethics board committee, 94 multiple-injury patients were enrolled. Of these, 72 patients suffered from major injuries; the other 22 patients had a severe isolated brain injury and were allotted to subsets of survival or nonsurvival. Of the pro- and anti-inflammatory mediators (cytokines, arachidonic acid metabolites and soluble adhesion molecules), interleukin-6 (IL-6), IL-12 and malone dialdehyde (MDA) appeared to be of specific importance; maximum IL-6 plasma levels were eightfold higher in cases of nonsurvival than in those of survival. Patients that did not survive TBI were the only ones to express an IL-12 increase, whereas survivors and patients with other major trauma did not show any increase within the first 24 h. An early distinct decrease of MDA showed in patients who did not survive TBI, in contrast to survivor patients who exposed almost constant levels during the first 24 h.

Adult↗
PubMed2001

Reduced serum total reductive capacity in lethal severe trauma.

BACKGROUND: Risk assessment is a prerequisite for effective treatment and triage in severe injury. A novel substrate-based assay to measure total reductive capacity (TORC) in serum was used to stratify risk of lethal outcome in severe trauma in a clinical trial. METHODS: Serum of patients with severe trauma (Injury Severity Score > 19) was obtained at the accident site, at admission, and at regular intervals thereafter. TORC was determined and correlated to outcome. The TORC assay uses thiol-labeled arachidonic acid as substrate from which free thiols are released by reductive amino acids and the specific activity of phospholipase A2. Free thiols are coupled to monochrombimone, and the resulting fluorescence is proportional to TORC. RESULTS: Eighteen patients with lethal severe trauma and 16 patients who survived were studied. Injury Severity Scores (lethal, 33 (29--43); survival, 31 (25--42); p = NS) and Polytrauma Scores (lethal, 25 [18--32]; survival, 26 [23--31], p = NS) were not significantly different. At the accident site, patients with a lethal course had significantly lower TORC than nonlethal cases (59.2 +/- 5.1 ng/mL vs. 89.5 +/- 6.7 ng/mL; p < 0.001). Values at admission were similar (lethal, 51.2 +/- 7 ng/mL; survival, 73.8 +/- 9 ng/mL; p < 0.01). At the accident site and at admission, TORC < 82.3 ng/mL was prognostic of lethal outcome (sensitivity, 88%; specificity, 65%/73% and 69%, respectively, for admission). CONCLUSION: Serum reductive potential at the site of accident or at admission allows the stratification of trauma patients with respect to lethal outcome in severe trauma when severity scores fail to do so.

Adolescent↗
PubMed2001

Trauma severity-dependent changes in AT III activity.

Trauma may cause a relevant reduction in antithrombin (AT) III activity, which is associated with adverse events. The very early changes in AT III activity after accident trauma are still unclear and possible relations with Interleukin (IL)-6, which is known to interact with AT III, have not been investigated so far. Upon approval of the IRB/IEC, 30 patients were enrolled with multiple injuries (ISS 9-75). Groups were performed according to injury severity, IL-6 concentration, and survivors versus non-survivors. Blood samples were collected at the scene of accident then at 2, 4, 6, 12, and 24 h and at day 3, 5, 10 and 15. No patient received AT III concentrates. In all groups a reduction in AT III activity occurred, which was most pronounced in very severe injuries. The activity re-increased spontaneously and steadily in all groups regardless of the IL-6 concentration. There was no clear impact of the AT III activity on survival.

Adolescent↗
PubMed2001

Computer assisted treatment of pelvis fractures.

The presented approach is the realization of a minimal invasive treatment of pelvis fractures using the computer aided surgery (CAS). Main problem of tracking of major bone fragments after reposition is solved by implementing of 3D ultrasound to obtain intraoperative bone surfaces. Preoperative and intraoperative data sets are matched. Major fragments are tracked. The real time navigation is possible.

Feasibility Studies↗
PubMed2000

Optical conductivity of the half-filled hubbard chain

We combine well-controlled analytical and numerical methods to determine the optical conductivity of the one-dimensional Mott-Hubbard insulator at zero temperature. A dynamical density-matrix renormalization group method provides the entire absorption spectrum for all but very small coupling strengths. In this limit we calculate the conductivity analytically using exact field-theoretical methods. Above the Lieb-Wu gap the conductivity exhibits a characteristic square-root increase. For small to moderate interactions, a sharp maximum occurs just above the gap. For larger interactions, another weak feature becomes visible around the middle of the absorption band.

Journal Article↗
PubMed2000

Is interleukin 6 an early marker of injury severity following major trauma in humans?

HYPOTHESIS: Interleukin 6 (IL-6), a multifunctional cytokine, is expressed by various cells after many stimuli and underlies complex regulatory control mechanisms. Following major trauma, IL-6 release correlates with injury severity, complications, and mortality. The IL-6 response to injury is supposed to be uniquely consistent and related to injury severity. Therefore, we designed a prospective study starting as early as at the scene of the unintentional injury, to determine the trauma-related release of plasma IL-6 in multiple injured patients. PATIENTS AND METHODS: On approval of the local ethics committee, 94 patients were enrolled with different injuries following trauma (Injury Severity Score [ISS] median, 19; range, 3-75). The patients were rescued by a medical helicopter. Subsets were performed according to the severity of trauma--4 groups (ISS, <9, 9-17, 18-30, and >32)-and survival vs nonsurvival. The first blood sample was collected at the scene of the unintentional injury before cardiopulmonary resuscitation, when appropriate. Then, blood samples were collected in hourly to daily intervals. Interleukin 6 plasma levels were determined using a commercial enzyme-linked immunosorbent assay test. The short-term phase protein, C-reactive protein, was measured to characterize the extent of trauma and to relate these results to IL-6 release. RESULTS: As early as immediately after trauma, elevated IL-6 plasma levels occurred. This phenomenon was pronounced in patients with major trauma (ISS, >32). Patients with minor injury had elevated concentrations as well but to a far lesser extent. In surviving patients, IL-6 release correlated with the ISS values best during the first 6 hours after hospital admission. All patients revealed increased C-reactive protein levels within 12 hours following trauma, reflecting the individual injury severity. This was most pronounced in patients with the most severe (ISS, >32) trauma. CONCLUSIONS: To our knowledge, this is the first study that elucidates the changes in the IL-6 concentrations following major trauma in humans as early as at the scene of the unintentional injury. The results reveal an early increase of IL-6 immediately after trauma. Moreover, patients with the most severe injuries had the highest IL-6 plasma levels. There is strong evidence that systemic IL-6 plasma concentrations correlate with ISS values at hospital admission. Therefore, IL-6 release can be used to evaluate the impact of injury early regardless of the injury pattern.

Adolescent↗
PubMed2000

[Computer-assisted surgery].

The term "computer-assisted surgery" (CAS) contains a variety of different applications. Priorities in trauma surgery have navigation systems. In fact, two basically different developments can be distinguished: on one hand, the possibility of navigation, based on preoperative CT data sets; and on the other hand navigation in intraoperative C-arm images. With the present available navigation technology, it can be assumed that intraoperative CT-based tracking in the field of spinal surgery can be performed accurately, regardless of whether active or passive markers are used. Another navigation option is C-arm-based osteosynthesis of the proximal femur. An application of navigation assistance in the field of pelvic surgery is osteotomy and placement of iliosacral screws. Future developments will have to concentrate on the technical characteristics of each navigation system. Advantageous concepts of visualization may generate required information to the surgeon in a way that unconstrained interaction at the operation table is combined with simultaneous integration of virtual and computer-aided visual information. New tracking systems will allow the reconstruction of data sets after reposition of segmented bone fragments, so that also in complex pelvic fractures the implantation of screws after reposition will be possible. Computer-aided surgery is able to improve the precision of operations in trauma surgery. In future, further developments of navigation systems can be expected. This fact is supported by the establishment of faster and cheaper hardware, as well as more intelligent and user-friendly software.

Bone Screws↗
PubMed2000

[Cost analysis of the treatment of patients with multiple trauma].

Current clinical management after multiple trauma is expensive. The aim of the present study was to quantify the actual costs of inpatient treatment after multiple trauma in a German university hospital, to compare the actual costs with the reimbursement rates, and to identify important determinants of costs. Routine documentation of hospital costs at a patient level was not available. Therefore a method for calculating the costs of resource utilization during clinical treatment of patients was developed. The concept was based on financial and utilization data provided by the hospital administration and patient-specific data. The average costs per case in the study group (mean ISS = 37) were 73.613 DM, maximal costs were up to 292.490 DM. The most costly components were intensive care, accounting for 60%, followed by procedures in the operating room (24%). A comparison with the reimbursement rates resulted in an average loss of 23.211 DM per case. Factors significantly associated with the costs of acute care hospitalization were outcome, injury severity, pattern of injury, blood volume replacement, length of mechanical ventilation, and number of operations. Whereas patient age, CNS state, mechanism of injury, pre-hospital care, and time between accident and hospital admission revealed no effect. Given the current reimbursement rates, multiple trauma care clearly belongs to those categories of care which have to be subsidized within the hospital. Any challenge to the optimal level of care resulting from this should be avoided.

Acute Disease↗
PubMed2000

[Limits of CT-based computer navigation in spinal surgery].

Computer-assisted and navigation-based therapeutic tools have found their first application in the field of spinal surgery. Meanwhile, the basic principles have been extended to other procedures, such as screw osteosynthesis of the pelvis and navigation of long bones. Commonly, all procedures except C-arm navigation are based on three-dimensional data sets. Data acquisition and processing as well as planning require specific steps, which should guarantee adequate accuracy and successful navigation. All steps up to intraoperative navigation and potential pitfalls in every part of the interaction are demonstrated, with reasons of undesired results presented.

Bone Screws↗