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Biomedical subjects

K Messner

Publications and source records attributed to K Messner.

At least 73 records · Page 4Linked to original sources
PubMed1994

The concept of a permanent synthetic meniscus prosthesis: a critical discussion after 5 years of experimental investigations using Dacron and Teflon implants.

The requirement of biocompatibility severely limits the access to synthetic materials for meniscal substitution with adequate material properties. Therefore, the possible advantages of a synthetic meniscal substitute over allografts, such as availability and freedom from disease transmission, are overshadowed by factors such as sizing problems, inferior material properties and wear. Using some of the available materials, such as Dacron and Teflon, knee joint stability with intact cruciate ligaments seems to be a basic requirement for the incorporation and fixation of the synthetic material into the biological environment. Similar to using allografts or biological implants, normal posterior and anterior attachment sites could not be reconstructed with the synthetic materials, which may be one of the main causes of insufficient cartilage preservation after meniscal substitution. Further, it was shown that synthetic implants without a polyurethane coating failed because of wear and changes in shape; meanwhile the coated, more inflexible implants often caused osteophyte formation and synovitis. In conclusion, with the materials and designs tested the concept of a permanent meniscal prosthesis does not seem clinically applicable at the moment. Nevertheless, the beneficial effects on cartilage preservation which were seen with slight improvements in prosthesis size, design and material properties may point to a future potential for this concept.

Animals↗
PubMed1994

Meniscal substitution with a Teflon-periosteal composite graft: a rabbit experiment.

A Teflon-periosteal composite graft was used as a substitute for the medical rabbit meniscus and was followed for a 3 month period. The results were compared to joints with autotransplantation of the medial meniscus and to non-operated control knees. Joint in vitro mechanics were similar to the non-operated controls for both treatments. Macroscopically, all composite menisci had changed in shape and the graft was found as a small remnant at the capsular periphery with prolonged or detached attachments resulting in an insufficient coverage of the tibial plateau. Except for one case, the autografts had healed in, but showed, similar to the composite menisci, prolongation of the attachments and insufficient coverage of the tibial plateau. The femoral and tibial cartilage showed osteoarthritic changes after both treatments. Except for one specimen, the artificial material was covered and penetrated by fibrocytes, and was fixed to the capsule without gap formation; however, fibrochondrocytes were not seen. The biological coat was thin and Teflon particles extruded from the matrix in some specimens, which was reflected by synovitis with foreign body reaction. Knees with autografts had a similar low-grade synovitis without any foreign body reaction. The importance of the attachment sites as well as the normal material properties of the substitute is pointed out.

Analysis of Variance↗
PubMed1994

Durability of artificial implants for repair of osteochondral defects of the medial femoral condyle in rabbits.

Full-thickness osteochondral defects in the femoral condyles of 25 rabbits were repaired using artificial implants made of Teflon or Dacron. The 6 and 12 month results were compared with ungrafted defects (natural repair) and periosteal grafting. Throughout the observation period, all repair sites were three-fold more compliant than normal cartilage (P < 0.01). The adjacent cartilage was unaffected. Splits between the repair sites and the adjacent cartilage were common. At 6 months, the Dacron repairs had higher scores than natural repair (P < 0.05). Between 6 and 12 months, no significant change in appearance was noted for the artificial repairs. At 1 yr, the scores for natural and Dacron repairs were similarly high, but natural repair had more surface fibrillation (P < 0.05). Periosteal grafting had a lower score than Dacron repair (P < 0.01). Synovitis and artificial debris tended to decrease with time (n.s., P < 0.06). In the present model, Dacron repair of small cartilage defects at 1 yr showed better neocartilage quality than periosteal grafting. Dacron had earlier neocartilage formation than unrepaired defects, and showed no late deterioration, but normal cartilage mechanics and morphology were not attained.

Animals↗
PubMed1994

Acute patellar dislocation during eccentric muscle testing on the Biodex dynamometer.

Isokinetic training and muscle torque measurements are commonly used during rehabilitation after knee ligament injuries. Isokinetic maximal muscle strength tests are performed to monitor the progress in muscle rehabilitation. The muscle power is evaluated by measuring the applied force in the direction of motion (concentric muscle power) or the force against the direction of motion (eccentric muscle power). Both legs are examined to compare the total muscle work and peak torques of the involved leg with those of the uninvolved leg. We report the case of an acute patellar dislocation during eccentric testing of the uninvolved leg on the Biodex isokinetic dynamometer testing device (Biodex Corporation, Shirley, NY).

Acute Disease↗
PubMed1994

Decrease in valgus stiffness after medial knee ligament injury. A 4-year clinical and mechanical follow-up study in 38 patients.

The clinical outcome after partial rupture of the medial collateral knee ligament is reported to be good, but there is a lack of objective assessment of persistent valgus laxity. We prospectively followed 38 consecutive patients with an isolated partial medial ligament rupture. After diagnostic arthroscopy, all patients were treated by early functional rehabilitation. At 4 years, besides clinical routine laxity tests, varus/valgus rotation, internal/external tibial rotation, initial and endpoint valgus stiffnesses, initial and endpoint internal/external rotational stiffnesses were measured by instrumented computerized passive motion analysis (Genucom). Most patients had normal knee function and muscle strength as early as 3 months after injury and returned to their pre-injury activity level without problems. At 4 years, 2 knees had minor residual valgus laxity at the manual examination, all other knees appeared stable. The instrumented tests also showed equal varus/valgus rotations and internal/external rotational stiffnesses in injured and healthy knees, but a decrease in the initial valgus stiffness and a decrease in the internal/external tibial rotation of the injured knee.

Adolescent↗
PubMed1994

The attachments of the rabbit medial meniscus. A morphological investigation using image analysis and immunohistochemistry.

In the search for a suitable experimental model the rabbit has increasingly been used for investigations on the meniscus. The present study focused on the morphology and innervation of the anterior and posterior medial meniscal attachments in adolescent and adult rabbits in comparison with man. Grossly, the posterior attachment has a similar anatomical position as in man, but the anterior is inserted more anteriorly and more laterally, with a long ligament-like structure between the osseous insertion and the meniscal horn. As in man, the attachment resembles a ligamentous insertion and contains zones of uncalcified and calcified fibrocartilage and subchondral bone. The proportion of the calcified cartilaginous zone in the attachment increases during maturation as in articular cartilage. Nerve fibres were found not only at the horns but also in the uncalcified and calcified fibrocartilaginous zones and the underlying bone. The differences between rabbit and human menisci should be borne in mind when interpreting data from animal experiments.

Animals↗
PubMed1993

Neocartilage after artificial cartilage repair in the rabbit: histology and proteoglycan fragments in joint fluid.

Repair of full-thickness cartilage defects of the rabbit medial femoral condyle with artificial plugs and periosteal grafts was followed for 1 year. The morphological characteristics of the neocartilage after repair and the concentration of proteoglycan fragments in the joint fluid (CPFF) were evaluated. The CPFF showed only a weak correlation to the histological score of the neocartilage. Normal cartilage and subchondral bone did not develop with any of the repair alternatives. With a Dacron plug, neocartilage formation appeared earlier than with natural repair and was better than with periosteal grafting. Increased CPFFs were found in all specimens with repair at 3 months, probably reflecting the remaining effect of surgery. At 6 months, the CPFFs had normalized to control values. At 1 year, the CPFFs were again similar to those at the 3-month evaluation. This was paralleled by a degeneration of the neocartilage. We conclude that Dacron plugs could serve as a scaffold for neocartilage formation. The CPFF reflected surgical trauma and late degeneration of neocartilage but did not indicate minor differences in quality between cartilage repair techniques, probably because of the limited size of the grafted defect.

Animals↗
PubMed1993

Prosthetic replacement of the rabbit medial meniscus.

Implants of polyurethane-coated polyester (Dacron), polyurethane-coated PTFE (Teflon), or uncoated PTFE were used to substitute the medial rabbit meniscus, and were observed over a 3-month period. Joint mechanics were similar for sham-operation, meniscectomy, or substitution with a coated implant. Joints with an uncoated PTFE prosthesis tended to be less compliant and to show greater load dissipation during relaxation. Cartilage indentation showed softening with all alternatives compared to sham-operation. Ingrowth into the prosthesis periphery was best with the PTFE implants. Both types of coated prosthesis retained their original shape, in contrast to the uncoated prostheses. To the naked eye the cartilage appeared unaffected only after sham-operation or implantation of a coated PTFE prosthesis. Osteophyte formation was common with all alternatives except sham-operation. We conclude that replacement of the medial meniscus with coated prostheses, especially the PTFE, was better than meniscectomy or using the uncoated prosthesis. However, cartilage softening and osteophyte formation indicate that joint mechanics were not restored to normal.

Animals↗
PubMed1993

Hydroxylapatite supported Dacron plugs for repair of isolated full-thickness osteochondral defects of the rabbit femoral condyle: mechanical and histological evaluations from 6-48 weeks.

The early degeneration of neocartilage commonly observed after experimental cartilage repair is attributed in part to the impaired cartilage-bone mechanics caused by an insufficient regrowth of the subchondral bone plate. In order to enhance bone regrowth after cartilage repair Dacron plugs supported by hydroxylapatite were implanted into 3 mm diameter full-thickness defects of both medial femoral condyles in 21 rabbits. In addition, the plug in one knee of each animal was wrapped with autologeous periosteum from the proximal tibia. The repair sites were evaluated at 6, 12, 24, and 48 weeks. Except for the mechanics of the repair site at 24 weeks additional periosteum did not improve the overall results. In specimens with additional periosteum the compression compliance of the repair sites improved gradually from abnormal high to almost normal values at 24 weeks, but were found softened again at 48 weeks. All other repairs were softer than normal cartilage at all time intervals. In all specimens a well-defined but irregularly shaped, subchondral bone plate had developed by 12 weeks. The neocartilage was initially thicker than normal cartilage, but the thickness decreased gradually and reached normal values by 48 months. Neocartilage formation with moderate morphological scores appeared already at 6 weeks, but the scores did not improve with time. High variations in quality of the regenerated tissue, from insufficient regeneration to hyaline-like cartilage, were found at all time intervals, but none of the specimens had developed normal cartilage. Most knees had a low-grade synovitis and some had particle debris.

Animals↗
PubMed1993

Cartilage mechanics and morphology, synovitis and proteoglycan fragments in rabbit joint fluid after prosthetic meniscal substitution.

The effects of meniscal substitution with a Dacron or Teflon prosthesis on rabbit knee-joint cartilage were studied by indentation tests, gross and histological inspection, analysis of proteoglycan fragments in joint fluid and an evaluation of synovial changes. Cartilage mechanics and cartilage morphology were similarly abnormal after meniscectomy and meniscal substitution. The elevated concentrations of proteoglycan fragments in joint fluid and the more severe synovial changes in joints with a meniscal substitute, as compared to meniscectomy, probably resulted from irritation of the artificial implant, but also reflected the remaining effects from the necessary bone drilling. In this short-term experiment, the use of an artificial meniscal substitute could not prevent cartilage degeneration after meniscectomy.

Analysis of Variance↗
PubMed1993

Synthetic implants for the repair of osteochondral defects of the medial femoral condyle: a biomechanical and histological evaluation in the rabbit knee.

Polyurethane-coated and uncoated polytetrafluoroethylene (PTFE) (Teflon) and polyester (Dacron) felts were used for repair of full-thickness cartilage defects in the rabbit knee. At 3 months the indentation characteristics and the histological appearance of the repairs were compared with those of a sham-operation, natural repair, and periosteal grafting. Joint compressive load-displacement and indentation characteristics of the cartilage adjacent to the defect were normal for all alternatives. All the repair sites had a higher compliance than had normal cartilage-bone, but synthetic grafting had values closer to normal than periosteal grafting. The adjacent cartilage appeared macroscopically normal, except with periosteal grafting and coated PTFE implants where it showed surface irregularities in some cases. With periosteal and uncoated synthetic implants the defects were completely filled, but not in the natural repair sites. Most of the coated implants failed by separation within the implant. On histological examination, ingrowth of trabecular bone from the base of the defect into the synthetic material was seen in all the specimens. The neocartilage 'score' was equally low with all the repairs reaching only one-third of the maximum points. All the repairs were associated with synovitis. Further, some of the knees with the synthetic materials repair had debris particles in the synovium. We conclude that none of the biological resurfacing techniques described achieved normal articular cartilage characteristics at 3 months, although the compliance of the repair site was closer to normal with synthetic than with periosteal grafting.

Animals↗
PubMed1993

Detection of eating disorders in a small rural town: an epidemiological study.

The occurrence of eating disorders among 517 school girls (11 to 20 years of age) in a small rural Italian town was studied using a three-stage prospective procedure. The screening stage was aimed at defining risk and sub-risk groups. One year later, the risk group (N = 44) and a random sample of the sub-risk (N = 25) and of the screen-negative group (N = 32) were interviewed to detect cases of anorexia/bulimia nervosa. The case registers of four hospitals over a period of 3 years were investigated to detect any additional cases that may have been overlooked in the survey. A minimum point prevalence rate of 1.30% clinical anorexia nervosa, 1.30% sub-clinical anorexia nervosa and 0.87% sub-clinical bulimia nervosa was found for age 15 and above. No case of clinical bulimia nervosa was detected. For age 15 and below no clinical or sub-clinical cases were found. All cases of (sub-)clinical eating disorder initially belonged to the predefined sub-risk and risk groups. Because of the low positive predictive value of any single risk factor, this study shows that early case detection can be improved by using multiple risk indices. In this rural area the prevalence was as high as in metropolitan or urban areas. Urban-rural differences should be assessed in further studies.

Adolescent↗
PubMed1993

Proteoglycan fragments in rabbit joint fluid correlated to arthrosis stage.

Proteoglycan fragment concentrations in joint fluid of rabbit knees with various degrees of secondary arthrosis after meniscal resection, meniscal substitution, and anterior cruciate ligament transection, were related to the gross appearance of the articular cartilage. Knees with normal cartilage were distinguishable by the concentration of proteoglycan fragments in joint fluid from knees with arthrosis. We found a correlation (r 0.61) between increasing arthrosis and increasing concentrations of proteoglycan fragments.

Animals↗
PubMed1993

Collagen repair not improved by fibrin adhesive. Cruciate ligament ruptures studied in dogs.

The anterior cruciate ligament in 30 dogs was transected and repaired by simple suture. In every other dog, fibrin adhesive (Tisseel Kit, Immuno AG, Vienna, Austria) was applied to the transection area before suturing. The proportion of organized versus unorganized and inflammatory tissue formation was assessed histologically. At 3 weeks, the amount of normal organized collagenous tissue was reduced to 20 percent both without and with fibrin adhesive. After 6 weeks, a substantial increase of organized collagenous tissue was observed after suture only, which at 12 weeks reached about 70 percent of the total area. In contrast, repair with fibrin adhesive had at 12 weeks only 30 percent of normal collagenous tissue.

Animals↗
PubMed1992

[Bronchial asthma and systematic family therapy: treatment concept, initial contact and therapy follow-up].

Psychosocial factors play an important role in pathogenesis and maintenance of bronchial asthma. However, besides conventional treatment family therapy seems to be less applied. A treatment plan for the integration of systemic family therapy into pediatric management of asthma has been developed and validated. Its special feature is an invariant family treatment offer after the initial session, with the decision of acceptance or rejection upon the family. The main focuses of family therapy are coping and family interaction, thus indirectly influencing the course of illness. Up to now 66 family sessions have been conducted with 11 families; five families agreed to the first session only. In a mean observation time of two years after the end of family therapy we found a drastic reduction in hospital readmissions of the asthmatic patients, even in the patients of families who took part in the initial session only. This may indicate a better control of asthma symptoms in patients and families. Family therapy is suggested as a valuable and additional tool in treatment of asthmatic children, irrespectively of their allergic status.

Adaptation, Psychological↗
PubMed1992

Immunoluminometric assay of chromogranin A in serum with commercially available reagents.

Chromogranin A (Cg A) is a useful marker of neuroendocrine neoplasia in humans. Here we describe an immunoluminometric assay (ILMA) for measuring Cg A in serum, with use of a new tube as a solid phase. The new tube has a large surface area and is coated with a polyclonal antibody. Optimized coating conditions provide a high IgG adsorption to the polystyrene wall. Serum is added to the coated tube and incubated for 2 h or overnight. After washing the tubes, acridinium ester-labeled monoclonal antibody against Cg A is added and incubation is continued for 2 h. The tubes are washed again and the bound luminescence is measured. The assay is very sensitive (detection limit 1 microgram/L, if 25 microL of serum is used), is specific for human Cg A, and offers a wide dynamic range (1-1000 micrograms/L). The range in healthy humans is 10-53 micrograms/L (median 30 micrograms/L). The correlation of serum Cg A to creatinine and parathyroid hormone is described. We also report the influence of intravenous calcium injection on Cg A concentrations in serum.

Antibodies, Monoclonal↗
PubMed1991

Oxidative degradation of high molecular weight chlorolignin by manganese peroxidase of Phanerochaete chrysosporium.

Phanerochaete chrysosporium was able to degrade high molecular weight chlorolignins (Mr greater than 30,000) from bleach plant effluents, although a direct contact between ligninolytic enzymes and chlorolignin was prevented by a dialysis tubing. In the absence of the enzymes, Mn3+ depolymerized chlorolignin when complexed with lactate causing the color, chemical oxygen demand (COD) and dry weight to decrease by 80%, 60% and 40%, respectively. Manganese peroxidase effectively catalyzed the depolymerization of chlorolignin in the presence of Mn2+ and H2O2. It can be concluded from these results that manganese peroxidase plays the major role in the initial breakdown and decolorization of high molecular weight chlorolignin in bleach plant effluents by P. chrysosporium in vivo.

Agaricales↗