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Biomedical subjects

R Ascherl

Publications and source records attributed to R Ascherl.

At least 19 recordsLinked to original sources

[Interspecies comparison of healing standardazed bone defects with and without autogenous bone transplantation].

This study tries to establish a basis for comparison of animal studies regarding bone defect healing. Pigs, sheep and rabbits were operated on according to a standardized scheme where each received bilateral defects of the femoral condylus. One of the defects was filled with cancellous autograft, the other remained empty. Bone defect healing was followed with several different methods of investigation, the results were put into perspective with the help of a standardized score-scheme.

Animals↗

Erythrocytes and proinflammatory mediators in wound drainage.

BACKGROUND AND OBJECTIVES: Retransfusion of shed blood collected after operation has become popular, but recent reports of side effects led to a search for possible causes. MATERIALS AND METHODS: In a randomized study of 28 patients undergoing total hip arthroplasty, shed blood was collected in Solcotrans, Orth-Evac, and ordinary Redon drainage. Osmotic fragility was measured and electron-microscopic pictures of erythrocytes from selective samples were taken. Serotonin, prostaglandin E2 (PGE2), and histamine were measured with enzyme-linked immunosorbent assays. RESULTS: Higher osmotic fragility of erythrocytes collected with Solcotrans appeared to be due to ACD which was used only with that system. Serotonin concentrations did not differ significantly. However, there was a great increase in histamine (Solcotrans 477.7, Orth-Evac 344.0, Redon drainage 453.1 nmol/ml) and PGE2 (Solcotrans 1,908.3, Orth-Evac 1,225.0, Redon drainage 2,666.7 microgram/ml) in shed blood compared with venous blood (histamine 9.5 nmol/l, PGE2 4.2 microgram/ml). CONCLUSION: Unwashed wound drainage blood collected after operation contains levels of proinflammatory mediators that can account for the reported side effects.

Aged↗

[Tribological properties of carbon fiber-reinforced plastic. Experimental and clinical results].

Wear of the articulating components (especially PE-UHMW) of total hip endoprostheses is the most important technical factor limiting the functional lifetime. To minimize wear debris, ceramic heads, according to ISO 6474 (Al2O3), have been used, from 1969 paired with Al2O3 and since 1975 paired with PE-UHMW. Al2O3 balls articulating with cups made from CFRP have been in clinical use since 1988. Laboratory experiments and in-vivo testing showed minimized wear debris and mild biological response to wear products using CFRP (carbon fiber reinforced plastic) instead of PE-UHMW as the cup material. The articulating surfaces of retrieved ceramic heads (Al2O3-Biolox) and cementless CFRP cups (carbon fiber reinforced plastic, Caproman) were compared using sphericity measurement techniques, scanning electron microscopy (SEM) and roughness measurements (including advanced roughness parameters Rvk or Rpk according to ISO 4287). Altogether, the first results of the clinical study showed that the combination Al2O3-ball/CFRP-cup came up to the expected lower wear rates compared with the conventional combinations. The wear rates are comparable with the combination Al2O3/Al2O3 without the material-related problems of ceramic components in all ceramic combinations.

Aluminum Oxide↗

[Rapid prototyping. Construction of a model in the preoperative planning of reconstructive pelvic interventions].

X-ray or CT images allows only a limited three-dimensional orientation in presurgical planning. Especially for the planning of internal hemipelvectomies with custom-made endoprosthesis and for peri-acetabular osteotomies a high-grade orientation is necessary. This orientation is improved by a 3D CT-controlled manufactured 1:1 model of the pelvis. This enables and exact classification of defect and deformity, planning of resection planes, design of the suitable custom-made implant and simulation of the operation technique as preoperative quality control.

Adult↗

Extracorporeal irradiation and incorporation of bone grafts. Autogeneic cortical grafts studied in rats.

The incorporation of resected, extracorporeally irradiated (1, 5, 25 and 50 kGy) and orthotopically reimplanted autogeneic cortical bone was investigated in 116 adult Wistar rats. 7 mm-long diaphyseal segments of the tibia were resected, irradiated and reimplanted using K-wire osteosynthesis. Autogeneic fresh grafts served as controls. Graft healing was evaluated by radiography and histomorphometric study at 3, 6, 9, and 12 weeks. At 3 weeks, two thirds of the 50 kGy irradiated grafts were fractured and therefore the series with this dose was interrupted because of mechanical graft insufficiency. After 3 and 6 weeks there were no statistically significant differences among the control group and 1 or 5 kGy irradiated grafts. The healing of 25 kGy irradiated grafts was delayed from the sixth week onwards and continued until the end of the experiment at 12 weeks (50% reduction of incorporation). The incorporation of 1 and 5 kGy irradiated grafts showed a 16% (1 kGy) to 24% (5 kGy) delay at 12 weeks, compared to autogeneic fresh grafts. 1 and 5 kGy irradiated autogeneic bone grafts retain most of their biological potential. Resection, extracorporeal irradiation and reimplantation of bone tumors may therefore be a possible alternative to allografting.

Animals↗

[Biomechanics of healing of cortical autotransplants after intramedullary nailing and device removal].

The aim of the study was to investigate the biomechanical properties of segmental cortical autografts subjected to extracorporeal treatment. For this purpose, 12 beagle dogs were submitted to tibial osteotomy, when 25 mm-long diaphyseal segments of bone were removed and treated outside the body by autoclaving or gamma radiation (Co, 5 kGy). Subsequently, osteosynthesis involving the use of medullary nailing was performed. After 36 weeks, the dogs were killed painlessly and, after removing the nails, the tibias were tested for the biomechanical properties. In comparison with the contralateral tibia, a mean stiffness of 47% and 32% was measured for tibia treated by irradiation and autoclaving, respectively, while bending showed an increase of up to 590%. These results show the need to allow plenty of time for healing in the case of weightbearing transplants. When bealing is undisturbed, no biomechanical differences are found between proximal and distal osteotomies, although in the X-ray image the osteotomy gap (fracture line) remains visible, and scintigraphic activity persists for a longer period. This means that the radiological aspect of the former does not necessarily reflect actual biomechanical strength.

Animals↗

[Preservation and sterilization of cortical bone--biomechanical studies of the rat].

The biomechanical properties of cryopreserved, autoclaved, irradiated and chemically treated cortical bone harvested from rat tibiae were evaluated in three-point bending. Biomechanical parameters (maximum bending load, deflection, failure energy and stiffness) are not altered by cryopreservation (-70 degrees C, 28 days) or irradiation with doses of 1 kGy or 5 kGy. The maximum bending load of autoclaved (134 degrees C, 3 min) or irradiated (25 kGy) cortical bone is reduced to 82% and 74% compared that of controls tested immediately after death (100% = 74.4 +/- 6.6 N). Extension of the autoclaving time from 3 to 5 min or irradiation with 50 kGy diminishes the bending load (28% after autoclaving, 48% after irradiation), deflection and failure energy. Stiffness is altered by autoclaving only. If a sterilization process is combined with deep freezing, better biomechanical values are obtained by sterilizing the bone before deep freezing than vice versa. The bending loads for autoclaving and irradiation before deep freezing are 68.8 +/- 9.4 N and 50.8 +/- 7.9 N, as against 51.7 +/- 2.7 N and 43.1 +/- 3.9 N for autoclaving and irradiation of previously cryopreserved bone. Whereas treating bone with tetrahydrofurane does not alter its biomechanical behavior, 80% ethanol leads to a reduction of structural properties.

Animals↗

Effects of preservation and sterilization on cortical bone grafts. A scanning electron microscopic study.

The effects of preservation and sterilization on the structural properties of cortical bone were investigated. Specimens of cortical bone from rat tibiae were frozen (-70 degrees C for 28 days), freeze-dried, irradiated (1, 5, 25 and 50 kGy) or autoclaved (at 134 degrees C for 3 or 5 min), and examined by scanning electron microscopy. Cryopreservation and irradiation had no deleterious effects on the surface structure of the cortical bone. Freeze-drying caused microcracks running parallel to the mineralized fiber bundles. After autoclaving, a time-dependent distension, swelling and amalgamation of the fibrillary matrix was observed. This denaturation of the organic matrix was more pronounced after 5 min than 3 min autoclaving. The alterations of the fibrillary structure described above might be due to a preservation- and sterilization-induced decrease of the biological and biomechanical potential of bone grafts.

Animals↗

[Biomechanical studies of change in the patellar tendon after transplant removal].

The reconstruction of the anterior cruciate ligament deficient knee with the patellar tendon is the "gold standard". Dislocation of the patella, rupture of the patellar tendon and fracture of the patella were reported to occur. In this biomechanical investigation on the changes of the patellar tendon following harvesting of a graft, 51 sheep knee underwent destructive testing at t0 (n = 11), 4 weeks p.op. (n = 5), 3 months p.op. (n = 14), 6 months p.op. (n = 15), and 12 months p.op. (n = 6). Harvesting of a graft produces a stiffness and strength of the patellar tendon of 50-70% of normal. There was no significant change of free patellar tendon length up to 12 months p.op. The cross-sectional area is definitely increased (p < 0.05). The tensile stress is always above normal, nevertheless the strength shows a massive decline until 6 months p.op. and does not regain normal strength by one year p.op. Stiffness shows comparable biomechanical pattern like tensile stress. There are time-dependent changes, the structural weakness is compensated by an increase of cross-sectional area. There is no restitution of the patellar tendon ad integrum, the remainder is a defect with scar tissue and alterated biomechanical properties. Revision surgery using the same host patellar tendon cannot be recommended.

Animals↗

[Partial endoprosthetic reconstruction of the pelvis in malignant tumors].

Twenty-five patients underwent an internal hemipelvectomy with endoprosthetic reconstruction of the pelvis for primary bone tumor (n = 17) or bone metastasis in the pelvis (n = 8). According to the Enneking tumor classification system, there were 9 stage II B tumors and 16 stage III. Conventional metal or polyacetal prostheses were used in 5 cases, and in 20 anatomically adaptable modular prostheses with intramedullary anchorage were implanted. In the last 11 cases a 3D CT-controlled manufactured model of the pelvis was used. The functional results according to Enneking were good in 5 cases, fair in 11, and poor in 7. The last endoprosthetic system showed better results, because it is easier to implant and the possibility failure is reduced. The learning curve of the surgeon is important, too.

Adolescent↗

[Radioactivity of bone cement].

A total of 14 samples of different types of bone cement from five different manufacturers were examined for their radioactivity. Each of the investigated bone cements showed a low radioactivity level, i.e. between < 1 and 100 Bq/kg. The content of U-238 and K-40 always was below the limit of detection (< 1-< 10 Bq/kg). Significant differences were detected in the amount of Ra-226, Pb-210, and Ra-228 detected between different samples of the same product from the same manufacturer, as well as between various types of cements. The highest radioactivity level was measured for Ra-226. Although stochastic radiation effects can not totally be excluded, it is extremely unlikely that the small amount of radioactive substances additionally transferred into the body by the bone cement has negative effects on the recipient's organism or on the fate of the alloplastic implant: "The risk factor and extrapolation in a low dosage range ... do not lead to an underestimation but more likely to an overestimation of the radiation hazard" [18].

Bone Cements↗

Cementless prosthesis of the hip joint with "spongy metal" surface. A prospective study.

Our investigations in human specimens and animal experiments show that prostheses with a spongy metal surface can become fixed by bony ingrowth to varying degrees. After consistent clinical and radiological follow-up over 12-65 months (mean 34 months) in a prospective study of 100 consecutive patients in whom 106 cementless total hip replacements had been carried out, we were able to show that after 1 year 82% of patients were pain-free with the prosthesis fixed by bony ingrowth, 8% were pain-free with the prosthesis fixed by dense fibrous tissue and 10% were not pain-free, but did not want revision surgery. Thigh pain decreased steadily from 53% 3 months postoperatively to 6.6% 15 months after operation. We believe that, when the implantation technique is exact, a high percentage of cementless spongy metal prostheses are fixed by bony ingrowth, and that a cementless prosthesis should be implanted only in patients under 60 years of age without osteoporosis.

Female↗

[The value of epidemiologic studies of ski injuries].

The Garmisch-Partenkirchen experience--15,513 skiing injuries between 1972 and 1990--was compared to the results of an inquiry into the skiing injuries among 565 persons of the medical profession, that were active skiers over an average of 18 years. The parameter injuries per 1000 skiing days was calculated from the outpatient clinic data as well as from all skiing injuries that had happened in the interview group and those that required surgical treatment. The mean value of 2.7 injuries/1000 skiing days--corrected for the number of patients--from the literature and the clinical data with 2.1 is comparable to the 1.8 injuries/1000 skiing days (injuries that required surgical treatment) but stands sharply against the 4.2 arising from the total number of injuries in the inquiry group.--Thus, every epidemiological study clearly underestimates the actual rate of skiing injuries. This fact may be defined as the "bypass-effect". The comparison between clinical setting and inquiry allowed for a quantification: Depending on the type of injury and the study design, a true prevalence of skiing injuries that is between 10% and 200% higher than the published data has to be expected.--Descriptive, not controlled epidemiologic studies on skiing injuries are justified and give valid trends on which therapeutic and prophylactic measures can be based--but exclusively under the following prerequisite conditions: 1. a standardized study protocol; 2. an observation.

Adult↗

[Experimental studies of thermal disinfection and sterilization of allogeneic bone transplants and their effects on biological viability].

Thermal energy (80 degrees) for the disinfection of cancellous allogenic bone grafts was employed, and it proved to be an advantageous, safe and easily accessible method. The effects of this treatment on biological values were examined in terms of biomechanical and biodynamic (graft incorporation) loss of the treated grafts versus the autoclaved and untreated samples. Given the thermolability of the pathogens in question, the thermal approach presented here has the advantage of being readily controllable. The lack of toxic or mutagenic risks through this method and its accessibility represent further advantages. In thermal treatment of bone allografts, it is essential that one knows the thermoconductivity of the bone sample and that one can demonstrate pathogen inactivation through the entire graft volume. All of the parameters in the 80 degrees C group that were measured in this study indicate clear biological superiority over the autoclaved group. A newly developed thermoincubator is introduced for gentler disinfection of allogenic bone grafts and it inactivates common vegetative pathogens as well as HIV. It is still necessary to conduct serological screening for hepatitis antigens in the donor pool, however. Based on these results, we conclude that the clinical use of autoclaved allogenic bone grafts needs to be reviewed and possibly limited.

Animals↗

Quantitative effects of allogeneic small-bowel transplantation on nutrient digestion and on body protein balance as determined in vivo in rats.

Heterotopic and orthotopic small-bowel allotransplantation was carried out in Wistar rats using grafts reduced to one-half of the original length. Portocaval venous anastomoses and intestinal end-to-end anastomoses were performed. Animals either with complete or with partially reduced native small-bowel served as control. In a total of 51 rats, 88 quantitative in vivo measurements of apparent digestion and absorption of dietary dry matter, organic matter, energy, protein, fat, total ash, and glucose were carried out. Body protein retention was calculated from intake and losses with feces and urine. The digestion trials comprised 8 days of adaptation and 10 days of continual recording of nutrient balance data. In experiments 1 and 2, digestibility coefficients were obtained before and after transplantation within the same animals, untreated or initially treated with cyclosporine A after surgery. Similar groups of rats untreated, with partial resection and with transplantation of the small-bowel, followed by temporary cyclosporine treatment, were used in experiment 3. In experiment 4, rats with transplanted intestines from experiments 1 and 2 were subjected to a further digestion trial 4 to 6 months after the respective first trial. With transplantation of the small intestine, apparent digestion and absorption of nutrients, as well as protein retention, tended to be lower. Significant depression occurred in the digestion of fat and ash. In long-term survivors all parameters decreased further. The adverse effects on fat and ash digestion seemed to be pronounced when rejection occurred. Fecal fat excretion might therefore be an indication of dysfunction of small-bowel grafts. Digestion was less imparied if cyclosporine was applied, and part of the effects on digestion and protein balance could be attributed to the shortened bowel.

Animals↗