Biomedical subjects

R Fuhrmann

Publications and source records attributed to R Fuhrmann.

At least 19 recordsLinked to original sources

PubMed2005

[Periprosthetic bone loss after total hip endoprosthesis. Dependence on the type of prosthesis and preoperative bone configuration].

The changes of the periprosthetic bone density were examined with DEXA in 81 patients over a period of 1 year after implantation of cementless total hip endoprosthesis. Four types of endoprostheses (Vision 2000/Duraloc, ALPHA-Fit/ALPHA-Lock Plus, CLS/Allofit, Mayo/Trilogy) were implanted. Information on the changes of the periprosthetic bone density depending on the type of the prosthesis and the bony situation at the femur before operation was expected from these measurements. In all types of stems the strongest reduction of the bone density was found in the region of the calcar femoris, and the smallest changes were found distally and medially of the tip of the prostheses. In the prosthesis with shorter stem the change of the bone density was altogether clearly lower than in prostheses with longer stem. With increasing size of the prosthesis with proximally porous coating made from cobalt-chrome alloy, proximal atrophy was observed more frequently, whilst in the prosthesis made from titanium alloy with completely rough-blasted surface the distal hypertrophy increased. A low preoperative corticalis-bone marrow index strengthened the proximal atrophy in proximally porously coated prosthesis made from cobalt-chrome alloy and led in the prosthesis with completely rough-blasted surface more often to distal hypertrophy of the bone.

Absorptiometry, Photon↗

PubMed2005

Plasma transglutaminase factor XIII induces microvessel ingrowth into biodegradable hydroxyapatite implants in rats.

Coagulation factor XIII is a member of the transglutaminase-family. Transgluaminases cross-link either fibrin monomers in blood coagulation or extracellular proteins in extracellular matrix formation. In early stages of bone healing migration and proliferation of endothelial cells lead to formation of new vessels. The aim of this study was to investigate the angiogenetic activity of plasma factor XIII in bone defects filled with nanoparticulate hydroxyapatite paste. A critical size defect was created in the tibial head of rats which was not filled in group I. In group II the defect was filled with hydroxyapatite paste, and in group III with hydroxyapatite paste enriched with factor XIII. Ten days after surgery angiogenesis in the defects was assessed using immunohistochemistry and confocal laser scanning microscopy. Ac16 antibody was used to detect activation of factor XIII into factor XIIIA. In defects without biomaterial (group I) vessel-rich connective tissue and diffuse distribution of capillaries was observed. In defects filled with pure hydroxyapatite (group II) formation of capillaries was limited to the host bone-hydroxyapatite interface. In contrast, addition of plasma factor XIII to hydroxyapatite (group III) stimulated formation of vessels within the biomaterial. The current study reveals that factor XIII can improve angiogenesis in hydroxyapatite.

Absorbable Implants↗

PubMed2005

Radiological changes around the stem after cementless hip implantation in case of the anatomic medullary locking hip system -- five years results.

INTRODUCTION: We present radiological results regarding the development of stress shielding around the stem of the AML hip endoprosthesis and discuss the clinical significance of it and preventive measures against stress shielding. MATERIAL AND METHODS: 391 patients (216 female and 122 male) with an AML-hip-endoprosthesis between 1991 and 1992 were followed clinically and radiologically during 5 years postoperatively. It was searched for a statistical correlation of stress shielding with a pre-existing osteoporosis of the proximal femur (Barnett-Nordin index), the diameter of the stem, a varus position of the stem and thigh pain. RESULTS: Stress shielding occurred in only 13.5 % of all patients. Atrophy of the proximal femur was detectable within 1 year, in 5 cases already after 3 weeks. Distal sclerosis reached its maximum after 1-2 years. Remarkably, women showed a tendency to more frequent stress shielding. In women more often than in men, a pre-existing osteoporosis of the proximal femur occurred. Cases with osteoporosis of the proximal femur experienced more often stress shielding. The same was seen in prostheses with diameters >13.5 mm. A slight varus position of the stem also favoured stress shielding, but it indicated an incomplete canal fit of the stems, too. Patients with stress shielding more often were suffered from thigh pain. CONCLUSION: Stress shielding is a result of the discrepancy between the elasticity of the bony femur and the stiffness of the stem. The AML-hip-prosthesis rarely shows this phenomenon. An osteoporosis of the proximal femur (coupled with an thinning of the cortex and generating higher elasticity of the bone), stems with higher diameters (what means higher stiffness) and incomplete canal fit more likely predisposed patients to stress shielding. To prevent stress shielding, the AML prosthesis should not be implanted in cases with known severe osteoporosis of the proximal femur. This prosthesis should be taken preferable in cases with diameters of the femoral canal smaller than 15 mm. Fully canal fit has to be achieved. The frequency of thigh pain, which occurs more often in patients with stress shielding, could be reduced by considering those factors.

Arthroplasty, Replacement, Hip↗

PubMed2004

Macrophage specificity of three anti-CD68 monoclonal antibodies (KP1, EBM11, and PGM1) widely used for immunohistochemistry and flow cytometry.

OBJECTIVES: To investigate the specificity of three anti-CD68 monoclonal antibodies (mAbs) for macrophages (Mphi) in immunohistochemistry (IHC) and flow cytometry (FACS). METHODS: IHC was performed on cryostat sections of rheumatoid arthritis (RA) and osteoarthritis (OA) synovial membranes using the anti-CD68 mAbs KP1, EBM11, and PGM1, and the fibroblast (FB) markers CD90 and prolyl 4-hydroxylase. Expression of CD68 was also analysed by FACS on the monocytic cell lines THP-1 and U937, as well as on synovial fibroblasts (SFB), skin FB, and gingival FB (both surface and intracellular staining). RESULTS: In IHC, there was an overlap between CD68 (mAbs KP1 and EBM11) and the FB markers CD90/prolyl 4-hydroxylase in the lining layer, diffuse infiltrates, and stroma of RA and OA synovial membranes. In FACS analysis of THP-1 and U937 cells, the percentage of cells positive for the anti-CD68 mAbs KP1 and EBM11 progressively increased from surface staining of unfixed cells, to surface staining of pre-fixed cells, to intracellular staining of the cells. Upon intracellular FACS of different FB, nearly all cells were positive for KP1 and EBM11, but only a small percentage for PGM1. In surface staining FACS, a small percentage of FB were positive for all three anti-CD68 mAbs. CONCLUSION: An overlap between CD68 (mAbs KP1 or EBM11) and the FB markers CD90 or prolyl 4-hydroxylase may prevent unequivocal identification of Mphi in synovial tissue by IHC or in monocytic cells and FB upon intracellular FACS. This may be due to sharing of common markers by completely different cell lineages.

Aged↗

PubMed2003

In vitro cytotoxicity testing of AB-polymer networks based on oligo(epsilon-caprolactone) segments after different sterilization techniques.

Recently developed versatile biodegradable polymeric biomaterial offer new therapeutic options in numerous medical fields. Biocompatibility is a crucial requirement for the biomedical application of biomaterials, including the sterilization of these materials with the use of accepted protocols. Ethylene-oxide (EO) and low-temperature plasma (LTP) sterilization are frequently used low-temperature sterilization technologies for heat-sensitive materials. The agarose diffusion assay is a recommended cell-screening test to assess the cytotoxicity of biomaterials in vitro. The sensitivity of the agarose assay can be increased by using a modified computer-based image-analysis system. The influence of EO and LTP sterilization on the cytotoxicity of a versatile polymer system of shape-memory polymer networks based on oligo (epsilon-caprolactone) dimethacrylate and n-butyl acrylate was investigated. Statistically significant differences in the rate of cell lysis after EO and LTP sterilization of the polymer samples were detected by using this modified quantification system. The influence of the different sterilization techniques on the cytotoxicity of the polymeric material, as well as the clinical relevance of the described differences, are discussed.

Animals↗

PubMed2003

Angiogenesis around new AB-polymer networks after one week of implantation in mice.

Biomaterials research is expected to forward new materials to be used as, e.g., implant materials or as scaffolds for tissue engineering. It is central for such a scaffold material to create the track on which those cells can inhabit the scaffold needed to rebuild functional tissue substitutes. The tissue engineering concept expects a gradual gain in functionality of the newly created tissues while the scaffold materials are degraded and subsequently eliminated. Not only for the elimination of the degradation products the angiogenesis of new blood vessels is thought to play an important role. In the present study, a new biomaterial, a non-porous polymeric AB-network based on oligo (epsilon-hydroxycaproate) and oligobutylacrylate, was implanted in animals. Male NMRI mice were implanted subcutaneously for one week. Immediately after the explantation, the probes were examined histologically. Already one week after implantation, there was a strong tissue-integration of the polymer. Importantly, blood vessels occurred at the polymer surface. There were also clusters of cells around the vessels, which were phenotypically similar to fat cells. The mechanism of the early integration of the polymer is not clear. The relationship between the new periimplant vessels and the integration of the polymer has to be studied.

Absorbable Implants↗

PubMed2002

[Detailed evaluation of the agarose diffusion test in biocompatibility study with a microscopic image analysis system. Effect of plasma sterilization on biocompatible of an improved photoset polymer].

In addition to sterilizability, biocompatibility is a further necessary property of biomaterials. The agarose diffusion test is an established standard in vitro procedure for investigating this property. The usual method of evaluating the agarose diffusion test, based on macroscopic determination of the size of the zone of decoloration, and microscopic assessment of cell lysis, limits the power of the test. To obtain more information on the impact of plasma sterilization on the biocompatibility of a new polymer, a high-resolution computer-aided morphometric image analysis system for the quantification of the agarose diffusion test at the cellular level has been developed. This was able to detect statistically significant differences in the cell lysis rate of plasma sterilized polymer specimens before and after 4 weeks of incubation in a physiological solution. The new method provides highly detailed information on the interaction of soluble material elements and cells. In addition to cell damage by potentially toxic elements, the sensitivity of the L929 fibroblasts used in the agarose diffusion test to mechanical stress also needs to be considered and verified by further investigations.

Animals↗

PubMed2001

Conditioning of enamel with Nd:YAG and CO2 dental laser systems and with phosphoric acid. An in-vitro comparison of the tensile bond strength and the morphology of the enamel surface.

UNLABELLED: MATERIAL AND METHOD 1: The first stage of a three-stage in-vitro investigation used 146 maxillary incisors to identify optimum setting parameters for two CO2 and Nd:YAG standard laser systems applied in enamel conditioning for bracket bonding. RESULTS: 31 of the 75 parameter combinations investigated for the Nd:YAG laser and nine of the 71 investigated for the CO2 laser proved appropriate for further investigation of tensile strength. MATERIAL AND METHOD 2: In a second stage, tensile bond strength for the selected laser settings was determined in comparison to the conventional acid-etch technique for a further 210 teeth as the control group. RESULTS: The highest average tensile strength for the Nd:YAG laser was 4.1 MPa, with comparable values of 3.3 MPa for the CO2 Laser and 4.9 MPa for the acid-etch technique. MATERIAL AND METHOD 3: The third stage of the investigation involved comparative scanning electron microscopy of enamel surface morphology following laser application and acid-etching. RESULTS: The CO2 laser was found to produce craters of various dimensions, while the Nd:YAG laser produced honeycomb structures regionally similar to enamel samples from the acid-etch technique. CONCLUSION: The CO2 and Nd:YAG dental lasers tested produce enamel conditioning and tensile bond strength sufficient to meet the requirements of bracket bonding.

Acid Etching, Dental↗

PubMed2001

[Overview of health care services in clinical and rehabilitation geriatrics and their development in Germany].

A survey of the 2000 statistics about the existing geriatric care structures in Germany showed that the number of inpatient geriatric care centers rose from 84 in 1993 to 318 in 2000. The number of day clinics rose in the same timeframe from 13 to 136. However, there are serious deficits in the area of ambulant geriatrics; in 2000 there were only 11 such institutions. The question is discussed as to why there are three different care structures for acute geriatrics, neurological early rehabilitation, and general early rehabilitation in hospitals. It is suggested how the existing care structures could be sensibly integrated.

Aged↗

PubMed2000

Perioperative progress check of interdental forces following extraction of the third molars. A prospective long-term study.

With the aim of checking the progress of mesially directed forces in a complete dental arch, we measured the interdental frictional forces in a population of 44 patients with erupting maxillary and mandibular third molars. The measurements were taken preoperatively and postoperatively 1, 2, 3, 7, and 12 weeks and also 1 year after extraction or surgical removal of the third molars in all 4 quadrants. In addition, the interdental frictional forces of a total of 40 test persons in 3 control groups were similarly measured in a state of inertia, after a period of 1 hour spent in supine position, and after a 5-minute period of chewing activity. Over the first 4 to 12 weeks the interdental forces showed a significant postoperative average decrease of 16.1% in the maxilla and 18.0% in the mandible. After 1 year the average reduction in the level of interdental forces in the patient population was 10.3% in the maxilla and 10.9% in the mandible. A significant postoperative reduction in force of 40.7% was registered for third molars with a mesial angle of 66 degrees to 90 degrees to the tooth axis of the second molar in the mandible. Following a 1-year control period, the level of interdental force in the patient population was found to be on average 27.4% below the preoperative baseline value. In control group I, the margin of fluctuation of interdental forces in a state of inertia was +/- 3.5% over a 3-month period. In control group II, a significant average decrease in interdental forces was measured in the maxilla (15.1%) and mandible (13.2%) following a 1-hour period in supine position. In control group III, a non-significant average reduction in interdental forces was established in the maxilla (7.8%) and mandible (8.6%) following a 5-minute period of chewing activity.

Adolescent↗

PubMed2000

Modified pendulum appliance including distal screw and uprighting activation for non-compliance therapy of Class-II malocclusion in children and adolescents.

In present-day orthodontics there is an increasing call for therapeutic procedures and appliances allowing those delivering the treatment maximum independence from patient cooperation. This requires both the development of new therapeutic appliances and the optimization of existing ones (via modification). The present study aims to analyze the therapeutic outcomes obtained by using a pendulum appliance (distal screw and integrated molar uprighting activation), modified and independent of patient cooperation. The dentoalveolar and skeletal outcomes and secondary outcomes were observed in 50 children and adolescents. The dentoalveolar outcomes were as follows: 72.5% of the clinically visible increase in space were gained by distal molar movement and 27.5% by mesialization of the anterior segment. The molars showed slight distal tipping and extrusion, while the incisors showed slight labial tipping. In terms of time, the molars were moved distally by an average of 0.67 mm per month. Skeletal changes taking place during treatment using the pendulum appliance are negligible. Further advantages of the pendulum appliance are independence from patient cooperation and good acceptance by patients.

Activator Appliances↗

PubMed1999

[Early rehabilitation in the hospital--time for structural changes].

Although it has long been undisputed that successful rehabilitation outcomes require early-onset, comprehensive rehabilitative intervention, research findings show that major shortcomings exist concerning the provision of rehabilitative care in hospitals. Contrary to the statutory premises at hand, a majority of hospitals continue to consider rehabilitation a treatment phase scheduled to set in only after completion of acute care. "Rehabilitation of the first day", a long-standing demand among the professional community, is hardly taking place at all. The rank of hospital-integrated early rehabilitation has now been confirmed in the framework of a model facility supported by the Federal ministry of labour and social order, with the recently completed scientific follow-along of the Ingolstadt Klinikum department for transdisciplinary early rehabilitation having made available research evidence of the effectiveness and efficiency of early-onset, comprehensive rehabilitation interventions in the hospital, and presented in this article for the first time.

Early Ambulation↗

PubMed1998

Biocompatibility analysis of different biomaterials in human bone marrow cell cultures.

A cell culture system for biocompatibility testing of hip implant materials is described. Human bone marrow cells have been chosen because these cells are in direct contact with the biomaterial after implantation in situ. The sensitivity of this method is evaluated for materials which are already being used as implants in humans and animal, e.g., hydroxyapatite (HA) ceramic, pure titanium, and ultra-high-molecular-weight polyethylene (UHMWPE). As indicative parameters of biocompatibility primary cell adherence, cell number, cell proliferation, production of extracellular matrix, cell vitality, and cell differentiation are described. After 2 weeks in culture, obvious differences between the biomaterials with respect to the indicative parameters could be observed. Cell numbers were greatest on the HA specimens. In the case of titanium alloys, we observed a decreased number of cells. The production of extracellular matrix was high for the HA ceramics but reduced for titanium specimens. The polymers allowed only a few adherent cells and showed no signs of extracellular matrix production. The results can be correlated astonishingly well to animal experiments and clinical experiences. Therefore, we suggest that this cell culture system seems to be a useful tool for biocompatibility testing of bone implantation materials. It also helps reduce animal experiments. With the help of flow cytophotometry, we analyzed the influence of biomaterials on large numbers of cells with respect to differentiation. There were similar populations of T cells and monocytes on all specimens tested. Extended B-cell and granulocyte populations, however, were observed with titanium and UHMWPE. Most osteocalcin-containing cells adhered to the HA ceramics.

Aged↗

PubMed1998

In vitro evaluation of a measurement method to analyze the interdental, mesially directed force.

In order to evaluate interdental forces as a benchmark for mesial drift, a measurement technique was tested and evaluated on a human specimen. The measurement technique is based on the principle that a mesially directed horizontal force (FH) within a complete dental arch has an effect on interdental friction at the points of contact. The dynamic force (FZ), needed to pull out a defined metal strip from the interdental space is equal to the interdental frictional force (FR). Assuming unmodified approximal surfaces and unchanged tooth mobility in a complete dental arch, relative modifications of the interdental frictional force level provide a way of measuring horizontal force fluctuations. The validity of this measurement technique was measured by applying mesially directed forces of 1 to 5 N to the distal surface of the 2nd molar in a human specimen. The frictional forces measured increased in proportion to the distally applied force. The mesially directed force on the 2nd molar was transmitted in the dental arch anteriorly up to the incisor region and resulted in an increase of frictional forces. The reproducibility of this measurement technique was tested by quantitative analysis of potential measurement errors in the human specimen. The effect on interdental force measurement of the speed at which the metal strip is pulled was evaluated in a range of 50 to 500 mm/min. At the maximum pulling speed of 500 mm/min, a maximum scatter of 8% was recorded. Dependency of the dynamic force on direction of pull was measurable only when the metal strip was angled at more than 15 degrees. Experimental tests on the human specimen confirmed that the measurement technique presented here is sufficiently valid and reproducible for clinical long-term studies of interdental forces.

Bite Force↗

PubMed1998

The operative management of a malignant proximal humerus tumor represented by secondary Paget's osteosarcoma.

PURPOSE: Malignant tumors at the proximal humerus are an operative challenge. Radical removal is a principal of tumor surgery but as much functionality as possible should be retained. These conditions often conflict so a compromise has to be reached. This paper proposes a solution to this dilemma, introducing an operative approach, with a new modular prosthesis, to a secondary Paget's osteosarcoma in the proximal humerus. METHODS AND RESULTS: A recently developed humerus modular prosthesis is described, which has been implanted into a patient with Paget's osteosarcoma. In these, mostly elderly, patients, successful operative therapy should combine radical removal with early mobilization. Paget's osteosarcoma is a recognized complication of the disease, and its prognosis is poor. In our patient, the implanted humerus prosthesis allowed a limb-saving procedure to be combined with radical removal of the tumor and postoperative early mobilization. A 3-month follow-up yielded good results with no recurrence of the disease and the patient had satisfactory movement. She was able to resume normal daily life shortly after the operation. CONCLUSION: Implantation of a modular prosthesis of the humerus may allow radical removal of a malignant tumor in that area while achieving early motion. In the literature, amputation is often advocated, as radical treatment with chemotherapy is not a successful option in this elderly patient group. We think the alternative use of a modular prosthesis of the humerus is possible in selected cases. We have encountered no other case in the literature where a limb-saving procedure attempts to preserve as much functionality as possible in Paget's osteosarcoma.

Aged↗

PubMed1997

Radiological assessment of artificial bone defects in the floor of the maxillary sinus.

OBJECTIVE: To compare dental radiographs and axial high resolution (HR) CT scans for the identification of artificial bone defects between the maxillary sinus and the roots of the adjacent teeth and to evaluate the accuracy of HR-CT. METHODS: Artificial bone defects of different dimensions were produced in the antral floor adjacent to 40 roots of 23 premolars and molars in 21 human autopsy specimens of the posterior maxilla. Periapical radiographs were obtained together with 1 mm axial HR-CT scans. The macroscopic and radiological findings of both sets of images were compared. Histological sections were prepared corresponding to the CT scans and the accuracy of the scans evaluated by measurement of five parameters. RESULTS: None of the artificial bone defects could be identified on the dental radiographs. In contrast 62.5% of the antral bone defects could be identified in the axial HR-CT scans. Identification of their margins depended on the location on the tooth root, adjacent bone morphology and visualization of the periodontal ligament space. When the periodontal ligament space was visualised identification of an antral floor between 0.2 and 0.5 mm thick was feasible. CONCLUSION: In certain clinical situations HR-CT is appropriate for identifying antral bone detects between the maxillary sinus and the roots of the adjacent teeth.

Alveolar Process↗

PubMed1997

Primary surgery of skeletal dysgnathias.

Three case studies from the patient population of the University Hospital of Aachen (RWTH) are used to describe indications for primary surgical intervention in skeletal dysgnathia. Such preconditions may apply in the case of mandibulo-alveolar protrusion, anomalies where there is little or no option to fixing orthodontic appliances (enamel hypoplasia or shortened crowns), severe transversal discrepancies and skeletal dysgnathia with pronounced malpositioning in the alveolar process and the teeth. The advantages are improved compliance (through the patient experiencing success at the outset of treatment) and limitation of postoperative orthodontic treatment to occlusive fine adjustments of the occlusion, resulting in an appreciable reduction in both the degree and duration of tooth movement and tissue damage.

Adult↗

PubMed1997

[Basic considerations for increasing flexibility of services in medical rehabilitation].

Medical rehabilitation measures continue to be delivered nearly exclusively on an inpatient basis. A graded treatment concept comparable to those in place for instance in the acute or long-term care fields, is non-existent, while the medical need for a community-based ambulatory rehabilitation system is uncontested. Not least before a background of ever scacer financial resources among the rehabilitation agencies involved, non-inpatient rehabilitation has been gaining significance as it is generally hoped to achieve greater economy of service delivery. As a logical consequence, the demand for greater flexibility in delivering medical rehabilitation services and benefits is a focus of attention in the current rehabilitation policy debate. Greater flexibility in medical rehabilitation delivery means replacing portions of rehabilitation measures currently provided on an inpatient basis by partial-hospitalization or ambulatory service delivery; or continuing and complementing inpatient rehabilitation measures by non-inpatient ones; or using non-inpatient measures to provide aftercare post-discharge from inpatient rehabilitation. Moreover, ambulatory rehabilitation is intended to reach the population unamenable to attending far-away inpatient programmes. It is of utmost significance for the future evolution of ambulatory rehabilitation that the various financially responsible agencies involved in rehabilitation take a joint position on the subject of non-inpatient rehabilitation. Several proposals are submitted in this respect; for indications in the fields of neurology, orthopedics, cardiology, and geriatrics, catalogues of degrees of severity considered suitable for ambulatory rehabilitation are first presented.

Adult↗