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Biomedical subjects

R Hammer

Publications and source records attributed to R Hammer.

At least 55 records · Page 3Linked to original sources
PubMed1987

Improved external skeletal fixation for unstable fractures.

A novel external fixation device (EX-FI-RE) is described with which it is possible to manipulate fracture fragments under complete control of stability. EX-FI-RE is a unilateral, telescopic, single-frame device, consisting of two functionally separate components, the correction unit and the fixation unit. The correction unit allows reduction of angular, parallel, and longitudinal dislocations. Sustained transverse compression of an oblique fracture is a special feature. After reduction has been achieved, pin retainers and transcutaneous pins can be transferred to the fixation unit without change of position of the fracture fragments. Its mechanical behavior under load is analyzed and compared with that of a Hoffman-Vidal Adrey quadrilateral system. In axial loading, the two systems were similar within the loading range of 0-1000 N. In the anteroposterior plane, the stiffness ratio of the EX-FI-RE was significantly higher. In lateral bending and axial loading, the two systems were comparable. The turning moment required to induce a 5 degree angular deformation of the quadrilateral system was 4.8 +/- 0.6 Nm; the corresponding figure for the unilateral system was 8.8 +/- 0.4 Nm. After more than two years of clinical experience with this new device, closed atraumatic reduction, sustained transverse compression, and early weight-bearing were found to promote union. There were no pin tract infections or mechanical failures in more than 70 cases treated.

Biomechanical Phenomena↗
PubMed1986

Binding profile of a novel cardioselective muscarine receptor antagonist, AF-DX 116, to membranes of peripheral tissues and brain in the rat.

The heterogeneity of muscarine receptors was examined in two brain regions (cerebral cortex and cerebellum) and in some parasympathetically innervated peripheral tissues (heart, salivary gland and intraorbital lacrimal gland), by in vitro binding techniques. As a tool, we used a new antimuscarinic compound, AF-DX 116 (see text for structural formula and chemical name). In competition experiments against 3H-N-methylscopolamine (3H-NMS) or 3H-pirenzepine (3H-PZ), AF-DX 116 was found to bind with high affinity to muscarine receptors in the heart and cerebellum (KD's approximately equal to 115 nM), with intermediate affinity to M1 receptors in neuronal tissue (KD = 760 nM) and with low affinity to receptors in exocrine glands (KD's approximately equal to 3200 nM). Its receptor interaction was found to be of the simple, competitive type. Thus, AF-DX 116 shows a novel cardioselective profile. On the basis of the results which demonstrate that the muscarine receptors in the heart and exocrine glands are clearly distinct, it is proposed that these receptors may be subclassified as M2 cardiac type and M2 glandular type muscarine receptors.

Animals↗
PubMed1985

External fixation of tibial shaft fractures. A review of 42 fractures by the Hoffman-Vidal-Adrey external fixation system.

Over a 6-year period (1977-1983), 59 patients with 61 tibial shaft fractures were treated by external fixation. Of these patients, 42 with 42 fractures were followed up until solid union. Thirty-seven fractures were caused by high-energy impact, mainly road accidents. Seventeen fractures were closed and 25 were open. In 33 patients an external quadrilateral frame system was applied primarily, and in the remaining nine within 1-2 weeks. No predrilling was done, and in 16 patients nonthreaded connection rods were used throughout the period in the fixator. The process of union was monitored by repeated noninvasive measurements of stability. Average time form injury to dismantling of the external fixation was 5.2 months (range 2-12.5 months) and time-to-union for the whole series was 10.0 +/- 5.5 months (range 4-31 months). Sixteen fractures failed to unite. Compared with other published series treated by external fixation, the incidence of non-union in the present series is high. On the basis of the present findings it is concluded that a compression device should be mounted either primarily or as soon as possible during the process of union, and that compression should be applied at regular intervals. If an external fixator is used, the surgeon must bear in mind the possible complications. It is probably safer to reduce rather than to prolong time-to-removal of the external system.

Adolescent↗
PubMed1985

Do community mental health centers serve the chronically ill? The New York experience.

Some critics of the community mental health movement have contended that fewer clients with serious mental disorders are seen by local mental health centers. This statewide study compared patients being treated at community health centers (CMHC) with those seen at state psychiatric hospitals in New York State. Minor differences in psychiatric diagnoses and requisite levels of care needed emerged between short-term state psychiatric patients and CMHC inpatients. Suggestions for future research are offered.

Adult↗
PubMed1985

Inhibition of human leukocyte metabolism and random mobility by local anaesthesia.

Hexose-monophosphate shunt (HMS) activity, myelo-peroxidase-(MPO)-mediated iodination and random mobility in human polymorphonuclear leukocytes (PMNs) were studied in the presence of lignocaine. Incubating the PMNs with 0.1% lignocaine during phagocytosis inhibited the 14CO2 produced from glucose-1-14-C via the HMS shunt by 33%. On increasing the concentration of lignocaine, a dose-dependent inhibition was noted. The MPO-mediated iodination was inhibited by 73% in the presence of 0.1% lignocaine, and complete inhibition took place when the concentration was increased to 0.5%. The random mobility of leukocytes was studied by an opto-electronic technique. In the presence of 0.5% lignocaine, all leukocytes examined were completely immobilized; in the presence of 0.1% lignocaine immobilization took place within 45-65 min.

Anesthetics, Local↗
PubMed1985

Selective labelling of M1-receptors in autonomic ganglia with 3H-pirenzepine.

Using the classical muscarinic antagonist 3H-N-methyl-scopolamine as radioligand and unlabelled pirenzepine (PZ) as displacing agent, a heterogeneous muscarinic receptor population consisting of about 70% M1-receptors and 30% M2-receptor, can be demonstrated in crude membranes of calf sympathetic ganglia. In the same preparation only low and variable specific binding is detectable when 3H-PZ is used as marker ligand. The situation clearly improves when synaptosomes are prepared from the ganglia. Then binding of 3H-PZ can be measured with a favourable specific to non specific binding ratio and with features compatible with the selective labelling of ganglionic M1-receptor sites. It is concluded that the 3H-PZ binding assay in synaptosomes of autonomic ganglia is a novel method for the characterization of the peripheral M1-receptor.

Animals↗
PubMed1985

Cimetropium: characterization of antimuscarinic and spasmolytic properties.

Cimetropium displaced 3H-NMS binding from membranes derived from gastrointestinal smooth muscle. The affinity of cimetropium for intestinal muscarinic receptors was in the range 70-100 nM. The competitive antagonism of cimetropium was demonstrated in guinea-pig ileum and taenia coli stimulated by bethanechol. Comparing pA2 values, cimetropium (8.19 and 7.91, resp.) was 0.3 times as potent as atropine (8.52 and 8.41, resp.). Cimetropium displayed strong inhibitory effects towards BaCl2 and 5-hydroxytryptamine induced contractions of the guinea-pig ileum. The compound was devoid of antihistaminic or Ca++ channel blocking activity. A binding study performed in vivo confirmed the ability of i.v. cimetropium to displace 3H-N-methylscopolamine binding from muscarinic receptors in peripheral organs. In addition, when injected into ileal loops, cimetropium displaced 3H-NMS binding solely from the surrounding tissue of the loop, indicating a topical effect of the compound.

Animals↗
PubMed1984

The stability of union in tibial shaft fractures: its measurement by a non-invasive method.

The stability of the union in tibial shaft fractures was followed by repeated non-invasive radiographic measurement of a deflection induced in the area of the fracture. By means of a Shift Comparator the difference in the angle between the two fragments before and during application of the deflecting force can be measured. The relative measure of the strength of the union is furnished by a quantity, the deflection ratio, which is based on the quotient of the induced deflection by the magnitude of the applied bending moment. When this ratio falls below a certain value the union is considered to be stable enough for full weight bearing during walking. A plot of the deflection ratio against time, with logarithmic scales on both axes had a negative slope and was more or less linear. This graph can serve as an aid in detecting the course of union, in deciding when the cast should be removed, and in detecting any irregularity in the process of union. In the management of 207 fractures of the tibial shaft 508 such deflection measurements were performed.

Biomechanical Phenomena↗
PubMed1984

Stability of union after tibial shaft fracture. Analysis by a non-invasive technique.

The stability of union following the conservative treatment of tibial shaft fractures has been examined in 157 patients by a non-invasive method. With this technique it is possible to ascertain when the fragments are united and whether the strength of union is sufficient for full weight-bearing without protection. The mean time required for union was 14.0 +/- 9.2 weeks, with a range of 4 to 48 weeks. In 31 cases union was judged to be delayed; in 22 of these, intended operations were avoided because repeated stability determinations indicated progressive union. Of nine fracture variables examined, the only ones which significantly affected the time required to achieve union were the age and the weight of the patient. Irrelevant factors were the type and level of the fracture, the energy of trauma, soft-tissue injury and the presence of multiple injuries.

Adolescent↗
PubMed1984

Evaluation of fracture stability. A mechanical simulator for assessment of clinical judgement.

To test the surgeon's clinical ability to detect small movements in fractures, a simulator with elastic behaviour was constructed. The bending moment required to produce a certain deflection was adjusted at four different levels. With the lowest stiffness, all surgeons in the test series reported that the fracture was unstable at a deflection of 3-4 degrees. With increasing stiffness, an increase in stability was reported--the registered deflection, however, was always 3-4 degrees. These observations confirm that manual tests of fracture stability are uncertain.

Body Weight↗
PubMed1984

Instruments for routine arthroscopic surgery of the knee.

The use of operating instruments for routine arthroscopic operations was analysed on 2397 arthroscopies with 986 operations. The biggest group was meniscectomy (n = 358). The most common instrument combination was knife, a straight 4 mm grasper, a 3-4 mm basket forceps and a suction device, which was used in 53% of the cases. Instrument breakage rates were analysed and found to be rather high especially for straight basket forceps (2/100 operations) and grasping forceps (3.6/100 operations). In two cases arthrotomy had to be done to retrieve a broken piece of grasping forceps. 30 degree telescopes used together with a TV-system had to be replaced at a rate of 0.8/100 operations and 70 degree telescopes at 0.2/100 operations.

Arthroscopes↗
PubMed1983

Ultrastructure of macrophages of the murine Peyer's patch dome.

The ultrastructure of macrophages located in the dome of murine Peyer's patches was examined by transmission electron microscopy. Aggregates of carbon particles as well as numerous other phagocytic and lysosomal inclusions were consistently observed in dome macrophages of carbon-fed mice. Macrophages of both particle-fed and control mice exhibited morphological features of activation. Degenerating macrophages were observed, and evidence is presented that their disintegration involves invasion by other cells. The morphological findings are in accordance with other evidence that the Peyer's patches receive an influx of material from the intestinal lumen. The potential importance of macrophages in the initiation of intestinal inflammations is emphasized.

Animals↗
PubMed1983

Comparison of radiographic images. A new method for analysis of very small movements.

A new method, shift comparisoN, for comparing 2 radiographic images is described. The method may be used for many purposes, but is particularly suitable for detecting small provoked motions between skeletal parts. Defective union in fractures or osteotomies is easily diagnosed by such a comparison. Films are exposed before and during the application of force to one of the fragments. By examining the films in the Shift Comparator small movements caused by the force may be detected. The technique has also been used for measuring the development of stability of union of tibial fractures by determining th deflection of the fracture caused by a bending moment.

Biomechanical Phenomena↗