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Biomedical subjects

E Hartwig

Publications and source records attributed to E Hartwig.

At least 19 recordsLinked to original sources
PubMed2005

Intramuscular pressure, tissue oxygenation and EMG fatigue measured during isometric fatigue-inducing contraction of the multifidus muscle.

Simultaneous measurement of intramuscular pressure (IMP), tissue oxygen partial pressure (pO(2)) and EMG fatigue parameters in the multifidus muscle during a fatigue-inducing sustained muscular contraction. The study investigated the following hypotheses: (1) Increases in IMP result in tissue hypoxia; (2) Tissue hypoxia is responsible for loss of function in the musculature. The nutrient supply to muscle during muscle contraction is still not fully understood. It is assumed that muscle contraction causes increased tissue pressure resulting in compromised perfusion and tissue hypoxia. This tissue hypoxia, in turn, leads to muscle fatigue and therefore to loss of function. To the authors' knowledge, no study has addressed IMP, pO(2) and EMG fatigue parameters in the same muscle to gain a deeper sight into muscle perfusion during contraction. As back muscles need to have a constant muscular tension to maintain trunk stability during stance and locomotion, muscle fatigue due to prolonged contraction-induced hypoxia could be an explanation for low back pain. Sixteen healthy subjects performed an isometric muscular contraction exercise at 60% of maximum force until the point of localized muscular fatigue. During this exercise, the individual changes of IMP, pO(2) and the median frequency (MF) of the surface EMG signal of the multifidus muscle were recorded simultaneously. In 12 subjects with a documented increase in intramuscular pressure, only five showed a decrease in tissue oxygen partial pressure, while this parameter remained unchanged in six other subjects and even increased in one. A fall in tissue pO(2) was associated with a drop in MF in only five subjects, while there was no correlation between these parameters in the other 11 subjects. To summarize, an increase in IMP correlated with a decrease in pO(2) and a drop in MF in only five out of 16 subjects. High intramuscular pressure values are not always associated with a hypoxia in muscle tissue. Tissue hypoxia is not automatically associated with a median frequency shift in the EMG signal's power spectrum.

Adult↗
PubMed2004

In vitro low-speed side collisions cause injury to the lower cervical spine but do not damage alar ligaments.

Whether injuries to the alar ligaments could be responsible for complaints of patients having whiplash injury in the upper cervical spine is still controversially discussed. It is known that these ligaments protect the upper cervical spine against excessive lateral bending and axial rotation movements. The objective of the present in vitro study was therefore to examine whether the alar ligaments or any other structures of the cervical spine are damaged in side collisions. In a specially designed acceleration apparatus, six human osteoligamentous cervical spine specimens were subjected to incremental 90 degrees side collisions from the right (1 g, 2 g, 3 g, etc.) until structural failure occurred. A damped pivot table accounted for the passive movements of the trunk during collision, and a dummy head (4.5 kg) ensured almost physiological loading of the specimens. For quantification of functional injuries, the three-dimensional flexibility of the specimens was tested in a spine tester before and after each acceleration. In all six specimens, structural failure always occurred in the lower cervical spine and always affected the facet joint capsules and the intervertebral discs. In four specimens, this damage occurred during the 2 g collision, while in the other two it occurred during the 3 g and 4 g collision, respectively. The flexibility mainly increased in the lower cervical spine (especially in lateral bending to both sides) and, to a minor extent, in axial rotation. In vitro low-speed side collisions caused functional and structural injury to discoligamentous structures of the lower cervical spine, but did not damage the alar ligaments. Since the effects of muscle forces were not taken into account, the present in vitro study reflects a worst-case scenario. Injury thresholds should therefore not be transferred to reality.

Acceleration↗
PubMed2004

[Complications of malignant tumors--pathological fractures].

Advances in the treatment of tumors have improved the life expectancy of cancer patients appreciably. As a consequence the incidence of bone metastases has also increased. Surgical interventions must achieve a maximal palliative effect with minimal morbidity and mortality. Major objectives are reduction of pain while preserving stability and function. Surgical treatment of primary and secondary bone tumors is complicated and thus also burdened with complications. However, interdisciplinary therapy comprising surgical resection and stabilization, radiotherapy and/or chemotherapy improves life expectancy and the quality of life of the cancer patient.

Bone Neoplasms↗
PubMed2004

[Cost effectiveness of intraoperative three-dimensional imaging with a mobile surgical C-arm].

DRGs lead to a new definition of refunding medical treatment. The calculated DRG covers all costs of the individual hospital stay of each patient. Any revision surgery is not refunded separately. Especially in spine surgery and in articular fractures, postoperative X-ray control sometime reveals malposition of implants that later require operative revision. The latter causes additional costs that can be in the range of 50% of the whole refund as shown here for tibia plateau and calcaneus fractures. New intraoperative 3D fluoro techniques provide CT-like images of bones and joints that enable the surgeon to optimize implant positions immediately. Despite higher initial costs as compared to conventional imaging devices, these technologies help to increase process quality in the OR and clearly save costs.

Cost-Benefit Analysis↗
PubMed2004

[Accident analytics for structural traumas of the cervical spine].

The differentiation between degenerative syndromes of the cervical spine and post-traumatic symptoms requires accident analysis. Experiments with human subjects yield data only in the low-energy range, and there are still no accident analyses of structural traumas of the cervical spine. From 1 January 2000 to 30 April 2002, 15 patients with structural injuries to the cervical spine due to car accidents were treated in the Department of Trauma Surgery of the University of Ulm. In 11 of these cases, the DEKRA Ulm completed an appraisal of the accident process.With lateral impacts, structural injuries to the cervical spine can occur even at speeds of only ca 10 km/h. Injuries to the alar ligaments are produced by frontal collisions with substantial differences in speed. Data from accident analysis of structural injuries to the cervical spine must be taken into consideration in causality examinations of distortions of the cervical spine.

Accidents, Traffic↗
PubMed2004

A new acceleration apparatus for the study of whiplash with human cadaveric cervical spine specimens.

The biomechanics of whiplash is often studied using cadaveric cervical spine specimens. One of the most important points in this kind of study is to create realistic loading conditions. The aim of the present project therefore was to develop an acceleration apparatus, which allows the study of whiplash with human cadaveric cervical spine specimens under as realistic loading conditions as possible. The new acceleration apparatus mainly consisted of a sled, a pneumatic acceleration unit and a railtrack and offered several unique features to create more realistic loading conditions. Among these features, the possibility to simulate the passive movements of the trunk is of capital importance. In this new apparatus, first, the general feasibility of whiplash experiments was studied, second, the reproducibility of the impacts was quantified and third, the effect of simulated movements of the trunk on accelerations and loads was examined. In the new acceleration apparatus various types of collisions could reproducibly be simulated. Simulated passive movements of the trunk strongly influenced the loading pattern of the neck. Without pivoting a steep increase of all loading parameters could be observed. This increase was less pronounced if pivoting was allowed. In conclusion, biomechanical aspects of whiplash could reproducibly be examined in the new acceleration apparatus. Due to its significant effects on the loading of the neck, pivoting of the trunk should always be taken into account in future experiments on the biomechanics of whiplash in which isolated cervical spine specimens are used.

Acceleration↗
PubMed2003

Thoracolumbar fracture stabilization: comparative biomechanical evaluation of a new video-assisted implantable system.

Minimally invasive techniques for spinal surgery are becoming more widespread as improved technologies are developed. Stabilization plays an important role in fracture treatment, but appropriate instrumentation systems for endoscopic circumstances are lacking. Therefore a new thoracoscopically implantable stabilization system for thoracolumbar fracture treatment was developed and its biomechanical in vitro properties were compared. In a biomechanical in vitro study, burst fracture stabilization was simulated and anterior short fixation devices were tested under load with pure moments to evaluate the biomechanical stabilizing characteristics of the new system in comparison with a currently available system. With interbody graft and fixation the new system demonstrated higher stabilizing effects in flexion/extension and lateral bending and restored axial stability beyond the intact spine, as well as having comparable or improved effects compared with the current system. Because of this biomechanical characterization a clinical trial is warranted; the usefulness of the new system has already been demonstrated in 45 patients in our department and more than 300 cases in a multicenter study which is currently under way.

Biomechanical Phenomena↗
PubMed2003

[Occupational disease 2108. Degenerative changes of the cervical spine as a causality criterion in the assessment of discogenic diseases according to BeKV 2108].

With the second amendment to the Ordinance on Occupational Diseases (BeKV) of 18 December 1992, discogenic diseases of the spine are included in the disease register of occupational diseases for the first time. If occupations that impose stress on the spine have been practised for many years, the possibility exists of recognizing degenerative diseases as an occupational disease. In assessment practice, the radiological data on the spine exposed to stress is compared with that of regions which are remote from the stress (cervical/thoracic spine). This pattern of the distribution of degenerative disease is then used as the basis for determining a causal relationship between the occupation causing the stress and disease of the axial skeleton. The pattern of degeneration of the cervical spine was investigated in two groups, one with ( n =153) and one without ( n =333) occupations that impose stress on the lumbar spine. A cumulative score of degenerative changes was elaborated and presented as a new classification. No differences were found between the groups with regard to either the frequency of occurrence, segmental distribution or severity of disease. In both groups, degenerative changes correlated with age. The prevailing assessment practice is discussed on the basis of these data.

Adult↗
PubMed2003

[OR-manager: surgeon or anaesthetist?].

The heart of any surgical department is the operating room (OR) area. Any disturbances in the daily routine will affect the work flow of the whole hospital. On account of its central function, with numerous connections to other departments, the OR is the crystallisation point for deficiencies in various events and processes. As an example, the major complaints made by a surgical department regarding workflow and communication are outlined. To solve these problems, an "OR organization" team was established, which worked on the basis of a newly developed OR statute. Within 1 year the employees were more contentment and the workflow had improved. However, even in the second year of central OR management there is still the need to further stabilize the system as mismanagement still occurs.

Anesthesiology↗
PubMed2003

[Navigation of tumors and metastases in the area of the thoraco-lumbar spine].

In this clinical feasibility study, CT-based verification of the efficacy of navigated decompression and pedicle screw placement in patients who had tumor-related posterior surgery was demonstrated. Eighty-six percent of the pedicle screws were positioned centrally in the bone without perforation; in all patients accurate decompression was seen. The accuracy of transpedicle screw implantation postoperatively was investigated with CT. In contrast to other published studies, no postoperative neurologic deterioration was seen in the patients as a result of using computer-aided surgical procedures. At the same time we were able to achieve complete decompression of the neural structures for radiologic and neurologic findings. Because of inaccurate registration, it was not possible to use computer-aided implantation surgery for 15% of the pedicles and, therefore, a conventional fluoroscopic approach was used. Our initial results indicate that computer-aided frameless navigation of tumor surgery of the spine is a safe technique which improves surgical performance during posterior decompression and transpedicle stabilization. In addition, CAS surgery improved the intraoperative information about the tumor and the current surgical intervention during decompression. Nevertheless the technique should be used only by experienced surgeons who can, if required, continue the operation using conventional techniques. Furthermore, the surgeon should have a complete theoretical understanding of the navigation system to minimize possible misinterpretation of computer guidance information.

Bone Screws↗
PubMed2003

Guidelines for the intramuscular positioning of EMG electrodes in the semispinalis capitis and cervicis muscles.

The objective of the study was to establish guidelines for the application of fine-wire or needle electrodes in the semispinalis cervicis and semispinalis capitis muscles. First of all, measured data for the puncture angle and puncture depth of each muscle were determined in CT scans. Using a regression approach, a model relation of these data with the neck circumference was established. This made it possible to accurately determine the puncture angle and puncture depth on the basis of the known neck circumference. In a further step, the neck muscles of seven human cadavers were punctured with wires in order to check the workability of these guidelines. At the same time, the wires' positions in relation to important structures (nerves, vessels) were studied. Both muscles can be punctured with a high degree of reliability. However, when puncturing the semispinalis cervicis muscle, one has to pass through a layer that contains vessels, nevertheless the risk of injury is regarded as very small. The technique enables intramuscular EMG measurements of the two muscles in manifold clinical problems.

Electrodes↗
PubMed2002

[Flat rate reimbursement system for minimally invasive management of unstable vertebral fractures. An analysis of costs and benefits].

Some 30% of unstable vertebral fractures of the thoracic and lumbar spine involve a destruction of the ventral column and thus of the supporting structures of the spine. This requires extensive surgical reconstruction procedures, which are carried out using minimally invasive techniques. The disadvantages of the minimally invasive methods are the high cost, the technical equipment and the expenditure of time required in the initial phase for the performance of the surgical procedure. With the structural reform of the health care system in the year 2000, the private-sector regulatory bodies were called upon to introduce a flat-rate compensation system for hospital services according to section 17b of the Hospital Law (KHG). The previous financing system which involved per-diem operating cost rates has thus been abolished. Calculations of individual entities are now required. Considering the case values to date, a contribution margin deficit of EUR 4628.45 has been calculated for our patients with fractures of the thoracic and lumbar spine without neurological defunctionalization symptoms. An economically efficient medical care is thus no longer possible. Consequently, an adjustment of the German relative weights must urgently be demanded in order to guarantee a high-quality medical care of patients.

Cost Control↗
PubMed2002

[MAC-TL twin screw. A new thoracoscopic implantable stabilization system for treatment of vertebral fractures--implant design, implantation technique and in vitro testing].

Due to the lack of an appropriate instrumentation system for minimally invasive procedures to treat spinal fracture, a new thoracoscopically implantable stabilization system was developed. This report describes the new implant design and implantation technique. In a biomechanical in vitro study, an anterior corpectomy model representing the worst case of burst fracture instability was simulated, and the primary stability parameters of the new system were evaluated in comparison to a dorsal stabilization system. With the interbody graft and fixation, the new system demonstrated higher stabilizing effects in flexion/extension and lateral bending and restored axial stability beyond the intact spine and the dorsal stabilization system. Considering all the advantages of the endoscopic procedure and this biomechanical characterization, the clinical trial is warranted; its usefulness has been demonstrated in more than 150 cases in a multicenter study to date.

Aged↗
PubMed2002

[MACS-TL polyaxial screw XL. A new concept for increasing stability of ventral spondylodesis in the presence of dorsal injuries].

The influence of additional dorsal structure damage on anterior stabilization of thoracolumbar fracture is still unknown. Screw cement enhancement is a possibility to reinforce the stability of anterior instrumentation. A new anchorage system has been developed for fixation of anterior stabilization devices, adapted through geometric optimization and the possibility of optional additional cementation after screw insertion in cases of poor bone quality. Is this enhancement strong enough to support a single anterior procedure such as the thoracoscopic technique and still compensate for dorsal instability? A biomechanical in vitro study simulating an anterior corpectomy, strut grafting, and overbridging stabilization with a dorsal laminectomy as dorsal structure damage was performed, and the primary stability parameters were evaluated with and without screw cement enhancement. The additional cementation enhanced the primary stability of the anterior instrumentation and compensated for dorsal instability.

Aged↗
PubMed2002

Mechanically simulated muscle forces strongly stabilize intact and injured upper cervical spine specimens.

Although muscles are assumed to be capable of stabilizing the spinal column in vivo, they have only rarely been simulated in vitro. Their effect might be of particular importance in unstable segments. The present study therefore tests the hypothesis that mechanically simulated muscle forces stabilize intact and injured cervical spine specimens. In the first step, six human occipito-cervical spine specimens were loaded intact in a spine tester with pure moments in lateral bending (+/- 1.5 N m), flexion-extension (+/- 1.5 N m) and axial rotation (+/- 0.5 N m). In the second step, identical flexibility tests were carried out during constant traction of three mechanically simulated muscle pairs: splenius capitits (5 N), semispinalis capitis (5 N) and longus colli (15 N). Both steps were repeated after unilateral and bilateral transection of the alar ligaments. The muscle forces strongly stabilized C0-C2 in all loading and injury states. This was most obvious in axial rotation, where a reduction of range of motion (ROM) and neutral zone to <50% (without muscles=100%) was observed. With increasing injury the normalized ROM (intact condition=100%) increased with and without muscles approximately to the same extend. With bilateral injury this increase was 125-132% in lateral bending, 112%-119% in flexion-extension and 103-116% in axial rotation. Mechanically simulated cervical spine muscles strongly stabilized intact and injured cervical spine specimens. Nevertheless, it could be shown that in vitro flexibility tests without muscle force simulation do not necessarily lead to an overestimation of spinal instability if the results are normalized to the intact state.

Aged↗