Biomedical subjects

M Frey

Publications and source records attributed to M Frey.

At least 37 records · Page 2Linked to original sources

PubMed2004

Optimised robot-based system for the exploration of elastic joint properties.

Numerous publications provide measured biomechanical data relating to synovial joints. However, in general, they do not reflect the non-linear elastic joint properties in detail or do not consider all degrees of freedom (DOF), or the quantity of data is sparse. To perform more comprehensive, extended measurements of elastic joint properties, an optimised robot-based approach was developed. The basis was an industrial, high-precision robot that was capable of applying loads to the joint and measuring the joint displacement in 6 DOF. The system was equipped with novel, custom-made control hardware. In contrast to the commonly used sampling rates that are below 100 Hz, a rate of 4 kHz was realised for each DOF. This made it possible to implement advanced, highly dynamic, quasi-continuous closed-loop controllers. Thus oscillations of the robot were avoided, and measurements were speeded up. The stiffness of the entire system was greater than 44 kNm(-1) and 22 Nm deg(-1), and the maximum difference between two successive measurements was less than 0.5 deg. A sophisticated CT-based referencing routine facilitated the matching of kinematic data with the individual anatomy of the tested joint. The detailed detection of the elastic varus-valgus properties of a human knee joint is described, and the need for high spatial resolution is demonstrated.

Biomechanical Phenomena↗

PubMed2004

The influence of dressings and ointments on the qualitative and quantitative evaluation of burn wounds by ICG video-angiography: an experimental setup.

Burn wound depth is difficult to determine. Even for experienced investigators the exact differentiation between superficial and deep dermal burns is not always possible. Therefore, methods for objective and reproducible measurements estimating the depth of burn wounds are of great clinical interest. One technique that appears to be able to differentiate between superficial and deep dermal burn wounds is ICG video-angiography. Since burn wounds are often covered with dressings and ointments or soiled with blood, it is necessary to evaluate the influence of these substances on ICG video-angiography and its performance as a measurement method. The most commonly used ointments and dressings were tested. All studied substances had a massive influence on ICG video-angiography and its measurements. They caused decreases by absorption of up to 63 +/- 36% and thereby falsely reported deeper burn wounds. The results of this study, suggest that in clinical practice, all dressings, ointments and blood should be completely removed at least 10 min prior to measurement by ICG video-angiography to gain exact and reproducible results.

Angiography↗

PubMed2004

Use of subatmospheric pressure therapy to prevent burn wound progression in human: first experiences.

Thermal trauma causes two different types of injuries within the burn wound. First, an immediate and irreversible injury, and, second, a delayed and partly reversible injury. It is a very common observation in burned patients that areas that initially seemed to be partial thickness burns have to be regarded as full thickness within the next day or days. The impairment of blood flow within the zone of stasis is due to the impairment of the vascular patency at the microvascular level. This progression is closely correlated to the degree of oedema formation. The aim of the study was to demonstrate that applied, controlled subatmospheric pressure is useful to prevent the progression of partial thickness burn injuries. Therefore, seven patients (mean age, 44.2 years; S.D., 22.4 years) with bilateral partial thickness hand burns were included into this treatment protocol. The more intense injured hand was treated with controlled applied subatmospheric pressure (V.A.C. (ATS)), the other and less injured hand conservatively by use of silver sulphadiazine creme. In the V.A.C.-treated hand a massive hyperperfusion was observed, being a possible reason for the prevention of burn progression. Moreover, a noteworthy amount of fluid was removed from the burn wound and a clinically obvious oedema reduction was observed in comparison to the contralateral side. In summary, we are of the opinion, that patients with partial thickness or mixed thickness burn may benefit from the application of subatmospheric pressure by reducing oedema formation and increasing perfusion.

Adult↗

PubMed2004

Carpal tunnel syndrome: a question of hand and wrist configurations?

This study investigated whether there is an association between hand and wrist configurations and the occurrence of carpal tunnel syndrome. The external hand and wrist dimensions of 50 subjects with carpal tunnel syndrome and 50 healthy volunteers were measured and compared. In addition carpal tunnel depth and width were determined with ultrasound. Our results showed that the hand length was significantly higher in the control group (hand length, 19.0; SD, 1.0 cm: patients' hand length, 18.2; SD, 1.1cm) and the palm width was significantly greater in the patients' group (palm width, 9.1; SD, 0.7 cm: controls palm width, 8.6; SD, 0.6 cm). Carpal tunnel syndrome patients had a squarer wrist (wrist ratio, 0.72; SD, 0.1) and carpal tunnel (carpal tunnel ratio, 0.48; SD, 0.1) than the controls (wrist ratio, 0.68; SD, 0.1; carpal tunnel ratio, 0.42; SD, 0.1). These findings indicate that the anatomy of the hand, wrist and carpal tunnel may predispose to carpal tunnel syndrome.

Anthropometry↗

PubMed2004

[The use of subatmospheric pressure to prevent burn wound progression: first experiences in burn wound treatment].

Thermal injury applied to living tissue results in zones of injury. Cell death is complete in the zone of coagulation. Beneath this area, there is the zone of lesser injury, where most of the cells are initially viable. If this zone of stasis is not reversed, the burn wound will progress. One of the major aspects to prevent progression is to reduce the edema formation and to preserve microcirculation. We present our first experiences to prevent the progression by use of topical negative pressure. Within the last months, all patients with bilateral partial thickness hand burns were included into this treatment protocol. Within one patient, one hand was treated with the V.A.C. (KCI, Austria), the contra lateral one by use of Flammazine (Smith and Nephew, Germany). Our first observations and data indicate, that both important factors (edema and microcirculation) could be influenced positively by use of the V.A.C.

Angiography↗

PubMed2004

Aerodynamic performance of a low-speed wind tunnel.

The determination of the odour mass flow emitted from a source is a very important step and forms the basis for all subsequent considerations and calculations. Wastewater treatment plants, as well as waste treatment facilities, consist of different kinds of odour sources. Unfortunately, most of the sources are passive sources, where no outward air flow-rate can be measured, but where odorants are obviously emitted. Thus, a type of sampling is required that allows to measure the emitted odour flow-rate (OFR). To achieve this, different methods are in use worldwide. Besides indirect methods, such as micrometeorological atmospheric dispersion models, which have not been used in Germany (in other countries due to different problems, direct methods are also used). Direct measurements include hood methods, commonly divided into static flux chambers, dynamic flux chambers and wind tunnels. The wind tunnel that we have been operating in principle since 1983 is different from all subsequent presented wind tunnels, in that we operate it at a considerably lower wind speed than the others. To describe the behaviour of this wind tunnel, measurement of the flow pattern in this low-speed tunnel are under way, and some initial results are presented here.

Air Pollutants↗

PubMed2003

Three-dimensional video-analysis of facial movements in healthy volunteers.

The aim of this study was to determine the mean distances of facial movements in 24 healthy individuals aged between 22 and 70 years, using the digitised three-dimensional video-analysis system developed by Frey et al. The subjects were divided into three groups of eight. The first group consisted of individuals aged between 20 and 30 years (mean+/-s.d.=25.0+/-2.33 years). Subjects in the second group were aged between 40 and 50 years (mean+/-s.d.=46.8+/-2.53 years), and the third group consisted of subjects aged between 60 and 70 years (mean+/-s.d.=63.6+/-3.07 years). In all groups the sexes were equally represented. No subject had had treatment to the face, nor did they have paralysis, scars or diseases of the skin. Males showed larger movements of the face than females, on average by 1.40+/-0.73 mm (15.08%). Subjects aged between 60 and 70 years demonstrated the largest movements of the face. The evaluation of facial movements in 24 healthy volunteers showed that sex and age affect facial dynamics. Thus study generated three-dimensional standard values for healthy facial movements.

Adult↗

PubMed2003

Treatment of patients with severe burn injuries: the impact of schizophrenia.

Four patients treated in one ward of a psychiatric clinic were admitted to our burn unit within 2 months due to severe burn injuries. The patients showed signs of a self-mutilation epidemic. All four patients were female and the mean age was 28 years. The psychiatric diagnosis was schizophrenia in all patients (ICD 10: F20.9). The ignition of flammable liquid was the most common method and the mean burned TBSA was 33%. The mean severity score (ABSI) was 8 and the median hospital stay was 50 days. All patients were characterised by a prolonged hospital stay in comparison to patients without additional psychiatric pathology (median 31 days). This prolonged stay was based on a delayed wound healing, more operations, extended time for mobilisation and difficulties in co-operation. It is possible that in patients with schizophrenia, changes in nutrition, activity, sleep and drug use could influence their immune system profoundly. Anxiety and depression is also associated with the impairment of cellular and humoural immunity. Poor sleep reduces the production of an anabolic endocrine environment and sleep disturbances can interfere with macrophage and lymphocyte functions. Poor appetite leads to malnutrition, which is also capable of producing delayed wound healing. On the other hand, apathy and a general lack of motivation interfere with therapeutic strategies, because poor appetite and weight loss often occurs after neuroleptic withdrawal, which is correlated with clinical decompensation. Moreover, this "self-destructive" behaviour, which is acting on the immune system, might make a patient more susceptible to infection. All these aspects and side effects of schizophrenia combine to make the treatment of burned patients with schizophrenia a very special and difficult task.

Adult↗

PubMed2003

Indocyanine green video angiographies help to identify burns requiring operation.

The key decision in the treatment of thermal injuries is the determination of the depth of the burn wound and the resultant decision on treatment options. The trend in the treatment of deep dermal and full thickness burns is toward very early excision and grafting to reduce the risk of infection, decrease scar formation, shorten hospital stay, and thereby reducing costs. Traditionally, this has involved serial clinical examinations, which involves primarily subjective judgment. Various objective examination techniques, supplementing the clinical diagnosis, have been suggested, but none has yet achieved widespread clinical acceptance. It has frequently been postulated that the blood flow in injured tissue indicates the extent of tissue damage. In this study, the clinical and scientific impact of indocyanine green (ICG) video angiography was tested in 20 patients. A wide range of depth of injury and etiology was included and analyzed. In all cases considered, video angiography was possible. The measurements and observations correlated well with the actual burn depth, which was assessed clinically (pre- and intraoperative assessment) and histologically (biopsies). In conclusion, ICG video angiography seems to be a practical method to describe vascular patency in a burn wound. The results indicate that ICG fluorescence angiography is a practical, accurate, and effective adjunct to clinical methods for estimating burn wound depth and thereby to assist in the rational assessment of treatment options. Furthermore, it allows an objective, qualitative and quantitative observation of the dynamic changes in burn wound depth, which are observed during the acute post-burn period, thereby indicating optimal timing of the first operation.

Adult↗

PubMed2003

[Pulmonary varicosity, a rare reason of solitary nodule].

Pulmonary varicosity is a very rare entity. Beside congenital varices, most combined with other malformations of the pulmonary vessels, varicosities are described above all in connection with mitral insufficiency. Most cases with pulmonary varicosity are diagnosed by chance, because of absence of any symptoms or only slight symptoms respectively. We demonstrate our own case with respect to the diagnostic requirements (computerized tomography, multi-slice CT) and the differential diagnostic aspects.

Aged↗

PubMed2002

The myth of Brucella L-forms and possible involvement of Brucella penicillin binding proteins (PBPs) in pathogenicity.

Brucella spp. L-forms have been proposed to be stationary phase organisms in the evolution of new variants and enduring entities in the host in complicated cases of brucellosis and during latent brucellosis. In vitro formation of Brucella L-forms has been achieved by treating the cells with sub-lethal doses of penicillin. Interestingly, Brucella spp. have classified during the evolution into two groups, penicillin susceptible or penicillin resistant, yet both types grow on 20 microg/ml of methicillin. Strains proven susceptible to penicillin grew in the presence of methicillin as L-forms as demonstrated by light and electron microscopy. In addition, the B. melitensis vaccine strain Rev.1, a penicillin susceptible organism, responded to sheep serum by development of L-form-like structures unlike wild type, strain 16M. The two strains grew normally in sheep macrophages. We propose, for the first time, a model that associates Brucella pathogenicity with the structure and activity of two of their penicillin binding proteins (PBPs). According to the model, PBP1 has evolved as the major cell wall synthesizing enzyme of the genus, capable of responding to host serum growth factor(s) necessary for Brucella survival in the host. This property is associated with high avidity to beta-lactam antibiotics. PBP2 complements the activity of PBP1. New beta-lactam antibiotics and improved vaccines might be developed based on this property.

Animals↗

PubMed2002

Serum cholinesterase activity reflects morbidity in burned patients.

Blood samples of 200 patients with thermal injuries were drawn apparently to determine the trend of the cholinesterase activity. In relation to the severity of the injury, a characteristic decrease was noted during the first days after admission. A recovery to normal values was achieved in all survivors (150 patients) after a proportionate period of time, but in the group of non-survivors (50 patients), no complete recovery to normal levels was found. Furthermore, a significant relationship between serum cholinesterase activity and the severity of morbidity was detected, the fall of the cholinesterase activity at the very beginning was significantly higher (P<0.004) in patients who died (1.3kU/l) than in patients who survived (0.7kU/l). Already 24h after admission, the mean activity was significantly lower (P<0.003) in non-survivors (2.5kU/l) than in survivors (3.2kU/l). It seems that the serum cholinesterase is a sensitive indicator for the morbidity of patients with severe burn injuries.

Analysis of Variance↗

PubMed2002

The influence of timing on the functional and morphological result after nerve grafting: an experimental study in rabbits.

Clinical experience and experimental work in sheep have shown that a two-stage approach to restoring muscle function with a long nerve graft and free muscle grafting seems to be more beneficial than a one-stage approach. Based on a standardised experimental protocol, one-stage and two-stage nerve grafting approaches in rabbits were compared, and the actual differences in muscle force, together with morphological data, were calculated. In 20 rabbits the saphenous nerve was used as a 7 cm nerve graft. Animals were separated into two groups. In group 1, 10 rabbits underwent a one-stage approach to reinnervate the rectus femoris muscle. In the left hindlimb, the proximal end of the graft was coapted to the cut motor nerve branch of the vastus medialis muscle, and the distal end was coapted to the nerve branch of the rectus femoris muscle. In group 2, 10 rabbits underwent a two-stage approach, leaving the distal end of the nerve graft unconnected to the rectus femoris muscle in the first stage. In the second stage, this end was coapted to the freshly cut motor nerve branch of the rectus femoris muscle. After 15 months, the maximum tetanic tensions in the reinnervated rectus femoris muscle and the contralateral unoperated muscle were determined. The graft and the motor branch distal to the graft were biopsied in order to count the number of regenerated myelinated nerve fibres. The mean+/-s.d. maximum tetanic tensions in the reinnervated rectus femoris muscles were 10.6+/-4.9 N in group 1 and 21.4+/-1.1 N in group 2. Compared with the unoperated side, the muscle force following denervation and reinnervation was 38.3% in group 1 and 58.9% in group 2 (P=0.01). The mean+/-s.d. numbers of regenerated myelinated nerve fibres distal to the graft in the rectus femoris muscle branch were 737+/-340 in group 1 and 1487+/-1004 in group 2 (P=0.05). These results show that the neurotrophic effect of an immediately connected target organ is far outweighed by the adverse effect of the longer period of muscle denervation. Therefore, nerve grafting and muscle transplantation should not be performed in the same operation.

Animals↗

PubMed2002

[Total ulnar nerve paralysis due to acute traumatic aneurysm at the forearm].

We are reporting a case of complete ulnar nerve paralysis due to compression from a false aneurysm located in the distal forearm. The aneurysm developed after the patient stabbed himself with a meat hook. The ulnar paralysis developed after a 14-day period of latency. The diagnosis was made using detailed patient history, clinical examination, and a sonogram. Early surgical decompression of the nerve led to complete restitution of all functions.

Adult↗

PubMed2002

Continuous free-flap monitoring with tissue-oxygen measurements: three-year experience.

Early recognition of flap failure is a prerequisite for flap salvage. Many methods are used to monitor free flaps. The time interval for re-establishing vascular patency is the limiting factor for a successful revision. Prompt re-operation and a rapid and sufficient correction of the microvascular anastomosis are necessary to maintain flap viability. The Licox Catheter pO 2 Micro-Probe instrument is used for continuous determination of oxygen partial pressure (pO 2 ) in body fluids and tissue (p ti O 2 ). Over a period of 3 years, 60 free tissue transfers to head and neck, trunk, and upper and lower extremities were monitored using the Licox Catheter Probe System. The flexible Licox Catheter pO 2 Micro-Probe detected circulatory changes and failure in all cases, with no false positives or negatives. In all cases in which the arterial pedicle failed, the p ti O 2 dropped rapidly; in cases of venous insufficiency, the p ti O 2 value decreased more or less slowly. In all failing flaps, a p ti O 2 decrease of 10 mmHg within a half-hour, or a p ti O 2 drop below 10 mmHg was observed. These are observations which are useful as precise indicators for vascular complications and flap failure. Based on the authors' observations and data, the Licox probe is a sensitive and accurate monitoring system for all types of free flaps.

Blood Gas Monitoring, Transcutaneous↗

PubMed2002

[Continuous free-flap monitoring with tissue-oxygen measurements: experiences of the last years].

Early recognition of flap failure is the prerequisite for flap salvage. Many methods are used to monitor free-flaps. The time interval for re-establishing vascular patency is the deciding factor for a successful revision. Prompt revision surgery and a quick and sufficient correction of the microvascular anastomosis are necessary to reestablish flap viability. The aim of this study was to evaluate the real impact of this probe as a continuous, precise and clinically relevant monitoring system in free-flap surgery. One of our main objectives was to create guidelines and "normal" ranges of p ti O 2 -values for the uncomplicated use of the Licox Probe in free-flap surgery for the first time. The Licox Catheter pO 2 Mikro-Probe instrument is used for continuous determination of oxygen partial pressure (pO 2 ) in body fluids and tissue (p ti O 2 ). Over a period of more than three years, 70 free tissue-transplantations to the head and neck, trunk, and upper and lower extremities were monitored by use of the implantable Licox Catheter Probe System. In all patients, a decrease of the p ti O 2 -levels was noted during the first minutes, until a more or less stable level was reached. At the time of weaning off, the p ti O 2 values decreased once again. After approximately 30 minutes, an almost stable but reduced p ti O 2 -level was reestablished (34,6 +/- 10,9 mm Hg). During the next days, we observed a more or less constant but reduced level. These values from the second day on were lower than the mean values of the first day. The mean value for all flaps was 23,1 +/- 6,5 mm Hg. Nevertheless, in all cases (10 of 70 flaps) where the p ti O 2 -level decreased more than 10 mm Hg within a half hour period, the flap showed vascular problems on re-exploration. Another clinically relevant value that was observed in all flaps with vascular problems was a drop of the p ti O 2 -value, below 10 mm Hg. In the cases of arterial thrombosis (2 of 10 flaps), a rapid decrease was noted. In the cases of venous complications (8 of 10 flaps), a more or less slow decrease of the p ti O 2 -value was observed. These observations may serve as precise indicators for vascular complications and flap failure. Based on our observations and data, it seems that the Licox-Probe is a sensitive and accurate monitoring system for a variety of free flaps.

Adult↗

PubMed2002

[Initial results with the Munich knee simulator].

In orthopaedics more than 50 different clinical knee joint evaluation tests exist that have to be trained in orthopaedic education. Often it is not possible to obtain sufficient practical training in a clinical environment. The training can be improved by Virtual Reality technology. In the frame of the Munich Knee Joint Simulation project an artificial leg with anatomical properties is attached by a force-torque sensor to an industrial robot. The recorded forces and torques are the input for a simple biomechanical model of the human knee joint. The robot is controlled in such way that the user gets the feeling he moves a real leg. The leg is embedded in a realistic environment with a couch and a patient on it.

Artificial Limbs↗

PubMed2001

The precision of ultrasound imaging and its relevance for carpal tunnel syndrome.

The carpal tunnel syndrome (CTS) is the most common peripheral entrapment neuropathy in human. The diagnosis is based on symptoms and on physical examination and is supported by nerve conduction tests. The aim of this study was to evaluate the precision and the valence of ultrasound (US) for CTS. An anatomic study was performed on 40 wrists of 20 unfixed human cadavers. The carpal tunnel and its important structures and contents were imaged and measured by ultrasound (7.5-MHz high resolution probe). The dorsopalmar diameter (DPD), the radioulnar diameter (RUD), the perimeter (P) and the cross-sectional area (A) were determined for the carpal canal and for the median nerve. These US images and measurements were directly compared with anatomic cross-sections gained from the same wrists at the same level. Our results showed that ultrasound is a very precise method to display the anatomy of the carpal tunnel and of the median nerve and thus the conditions of the median nerve. Significant differences could not be detected for each of these parameters either for the carpal tunnel or the median nerve. (Ultrasound: cross-sectional area of carpal tunnel: 162.4 +/- 29.3 mm2 and of the median nerve: 9.2 +/- 2.4 mm2; anatomy: cross-sectional area of carpal tunnel: 168.4 +/- 31.2 mm2 and of median nerve: 9.4 +/- 2.2 mm2).

Aged↗