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Biomedical subjects

M Kon

Publications and source records attributed to M Kon.

At least 73 records · Page 4Linked to original sources
PubMed1997

Adventitial stripping does not strip the adventitia.

This study investigates the process of stripping the adventitia off a blood vessel, which is a normal procedure prior to performing a microvascular anastomosis. In five rats, the common carotid and the superficial femoral arteries of one side were stripped sharply, whereas the arteries of the other side were left unstripped to serve as controls. In a further set of five rats, the arteries were stripped bluntly. Immediately following stripping, experimental and control arterial segments were removed. Histology of cross sections of the segments was studied. In no case was there complete removal of the adventitia. When stripped and control arterial sections were compared, no significant difference between cross-sectional adventitial areas could be demonstrated. Morphologic study revealed that stripping mainly removes large collagen fibers from the adventitia. The small collagen fibrils that are still in place fan out in such a way that although considerable tissue is removed, the volume that the adventitia occupies remains the same. Stripping the adventitia does not cause complete removal of the adventitia, and in this study no significant reduction in the adventitial volume could be found. Stripping does, however, allow a better view of the cut edge of the vessel wall under an operating microscope. Since blunt stripping could cause damage to other vessel wall layers, sharp stripping is to be preferred.

Anastomosis, Surgical↗
PubMed1996

Anatomy of the feeding blood vessels of the cremaster muscle in the rat.

Since the early seventies over 300 studies have used the cremaster muscle as a flap model, yet little has been reported on the upstream feeding vessels of this muscle. The purpose of this study was to investigate the anatomy of the cranial feeding vessels of the left and right cremaster muscle in Sprague-Dawley rats. An additional aim was to compare these results with the anatomy of the feeding vessels of the cremaster muscle in another strain (Wistar). To permit identification of the cranial feeding vessels, the pedicle was dissected very carefully and thereafter perfused with green dye, which was administered through a cannula placed in the distal femoral artery. In Sprague-Dawley rats it was found that the cremaster muscle in only 30% of the animals received its total blood supply through the superior external pudendal artery. In Wistar rats the same was true in less than 45%. The cremaster muscle of the rest of the animals appeared to receive its blood either in part or in total from the hypogastric trunk. We suggest that the name pudic-epigastric trunk be abandoned.

Animals↗
PubMed1996

Experimental orthotopic small bowel transplantation: a revised model.

Small bowel transplantation is emerging as an alternative treatment for end-stage intestinal failure. To date, immunological and technical problems are still hampering clinical success. Functional experimental small bowel transplantation models have traditionally been plagued with a high technical complication rate. The purpose of this study was to describe in detail the harvesting and transplantation procedure in rats. In this paper the technical aspects of the one-stage, isogenic orthotopic partial small bowel transplantation model with systemic drainage are illustrated. Because of the achieved acceptable survival rate and the favourable functional outcome, the model is considered reliable and reproducible.

Animals↗
PubMed1996

Non-decay type fast-setting calcium phosphate cement: setting behaviour in calf serum and its tissue response.

Non-decay type fast-setting calcium phosphate cement (nd-FSCPC) was evaluated in terms of its setting behaviour in calf serum and its tissue response to investigate the feasibility of its clinical use in surgical applications. Non-decay type cements were prepared by adding various amounts of sodium alginate to the liquid phase of base cements, fast-setting calcium phosphate cement (FSCPC) and conventional calcium phosphate cement (c-CPC). Cement pastes were immersed in serum at 37 degrees C immediately after mixing, and decay behaviour, setting time and mechanical strength were measured to evaluate the possibility of their use in surgical applications. Also, nd-FSCPC was implanted into rat subcutaneous tissue for the initial evaluation of biocompatibility of this potential bioactive cement. nd-FSCPC set in approximately 6-7 min in serum, even when the cement paste was immersed in the serum immediately after mixing, whereas c-CPC and FSCPC decayed completely upon immersion. nd-FSCPC transforms to hydroxyapatite (HA) within 24 h and shows a diametral tensile strength of approximately 4-5 MPa. As a result of transformation to HA, nd-FSCPC showed excellent tissue response when implanted subcutaneously in rats. We conclude that nd-FSCPC has good potential value for use in orthopaedics, plastic and reconstructive surgery, and oral and maxillofacial surgery, where the cement is exposed to blood.

Animals↗
PubMed1996

Dysfunctional postures of the hand as part of a conversion reaction.

A dysfunctional posture of the hand could be due to an anatomical disorder or a conversion reaction. A conversion reaction implies that an unconscious intrapsychic conflict is expressed in a physical dysfunction. Treatment of dysfunctional postures due to conversion reactions is often difficult, and case reports are used to outline management. The need for a multidisciplinary approach is stressed.

Adult↗
PubMed1996

Correction of severe blepharoptosis.

An analysis is made of 81 patients with severe blepharoptosis who underwent correction with autogenous fascia. In case of severe blepharoptosis, which means a levator function of less than 5 mm, correction by levator resection gives insufficient results. Better results are obtained by frontalis suspension, whereby the upper eyelid is connected to the frontalis muscle using fascia lata strips according to Crawford. The operative technique is described in detail. Particular interest has been paid to the width of the vertical lid fissure and symmetry between both upper eyelids after operation. The overall results were rated satisfactory to excellent with an average of 9 mm of postoperative vertical lid fissure. Comparison of the results of unilateral versus bilateral blepharoptosis correction revealed better results in the group of bilateral ptosis correction. In 76% of the bilateral patients, there was an asymmetry of less than 0.5 mm between both palpebral fissures, while in the unilateral group this result was achieved in only 35% of the cases. Symmetry is difficult to achieve in the unilateral group, especially when the vertical lid fissure of the nonptotic eye is 10 mm or more. In these cases, correction of both upper eyelids should be considered. The best time to operate on patients with severe congenital blepharoptosis is around the age of 4 to 5 years, because lagophthalmus after operation is better tolerated and the leg has developed sufficiently to provide an adequate amount of fascia. The correction of severe blepharoptosis by frontalis suspension with autogenous fascia shows a high rate of success and few complications.

Blepharoptosis↗
PubMed1996

Fascia lata suspension of malpositioned ears.

A new technique for the correction of malpositioned ears in congenital or acquired disorders is described. The use of a fascia lata strip makes a rigid fixation of the ear to the pericranium possible without total fixation of the ear in all directions. The configuration of the auricle is not altered, and the scars are inconspicuous.

Adolescent↗
PubMed1996

Auricular hypermobility due to agenesis of the extrinsic muscles.

A patient is presented with complaints of a hypermobile right ear due to agenesis of the superior and posterior auricularis muscles and a thin concha cartilage. Suturing the concha cartilage to the mastoid bone and temporal fascia gave sufficient support of the external ear without creating a gross difference in appearance of both ears.

Adult↗
PubMed1996

Effect of barium in porcelain on bonding strength of titanium-porcelain system.

The bonding strength to titanium, thermal expansion, and bending strength of glassy porcelain containing barium of 5, 10, and 15 mass% were estimated and compared with those of barium-free porcelain, to estimate the effect of barium content on bonding strength to titanium. The three different glassy porcelains containing barium were made by melting at 950 degrees C. The bonding strength of a commercial porcelain to titanium increased with the addition of barium. Bending strength and thermal expansion were not affected by the barium content. Therefore, the addition of barium to porcelain is effective for strengthening the bonding of porcelain to titanium.

Analysis of Variance↗
PubMed1995

Microsurgery without a microscope: laboratory evaluation of a three-dimensional on-screen microsurgery system.

In microvascular surgery, procedures may be both technically and physically demanding. Precise movements sustained over long hours in addition to typically compromised surgeon and assistant positioning lead quickly to physical and mental fatigue. Many of the positioning problems encountered are related to the fact that the eyes of the surgeon must be continually fixed to the microscope eyepieces. This study explores a possible solution: a microscope system that eliminates the need to view the operative field through the microscope eyepieces. A Three-dimensional On-screen Microsurgical System (TOMS) was used and contrasted with conventional operative microvascular surgery in the laboratory setting. The surgeon's comfort, his ability to instruct microsurgical technique, pertinent technological performance, and the procedure itself were evaluated using a standardized questionnaire. Based on data collected in this study, we conclude that divorcing the surgeon's eyes from the microscope eyepieces using the TOMS may make prolonged microvascular procedures less physically demanding and may increase the comfort level of both the surgeon and his assistant, although refinements to the technology are required.

Anastomosis, Surgical↗
PubMed1995

Oxidative processes and free radical scavengers in ischaemia-reperfusion injury in adipocutaneous flaps: in vitro lipid peroxidation assessment.

An in vitro lipid peroxidation study measuring Schiff base and TBAR formation in homogenates of the fat and skin fractions of epigastric free flaps of DA-rats was performed to determine the role of oxygen-derived free radicals (ODFRs) in the aetiology of ischaemic injury and of ischaemia and reperfusion injury following cold (0-1 degree C) storage. The storage intervals were 0, 48, 72, 96 and 120 h in the study on ischaemic injury and 72 and 96 h in the study on combined ischaemia and reperfusion injury. Reperfusion was accomplished by anastomosing the pedicle vessels of the flap to the femoral vessels of a recipient; the reperfusion period was 15 min. In addition to a control group (C), three experimental groups were created to test the benefit of a preischaemic single passage perfusion with a hypertonic citrate solution (HCA), a pre- and postischaemic treatment with desferrioxamine (DFX) and a pre- and postischaemic treatment with lipoic acid (LA). The susceptibility of homogenates of skin and fat fractions of epigastric free flaps in DA-rats for lipid peroxidation increased significantly whenever the cold (0-1 degree C) ischaemic interval was prolonged from 0 to 72 h. These findings offer circumstantial evidence for the role of ODFRs in the aetiology of ischaemic injury. Following a short reperfusion period after extended periods of cold (0-1 degree C) ischaemia, no significant increase in susceptibility for lipid peroxidation could be found. Furthermore, no unequivocal role in the prevention of ischaemia and/or reperfusion injury by the use of either HCA, or DFX or LA could be found. The exact role of ODFRs in the aetiology of ischaemia-reperfusion injury in this setting remains unclear.

Adipose Tissue↗
PubMed1995

Non-decay type fast-setting calcium phosphate cement: composite with sodium alginate.

Non-decay type fast-setting calcium phosphate cement (nd-FSCPC) was prepared by introducing sodium alginate (0-2.0 wt%) into the liquid phase of FSCPC. nd-FSCPC was stable even when the cement paste was immersed in distilled water immediately after mixing, whereas conventional FSCPC (c-FSCPC) decayed completely within 1 min upon immersion. The setting time of the cement, approximately 5 min, was not dependent on the presence of sodium alginate. In contrast, the introduction of sodium alginate into conventional CPC, i.e. CPC without neutral phosphate in the liquid phase, resulted in no setting when the amount of sodium alginate introduced was more than 1 wt%. Powder X-ray diffraction analysis revealed no significant difference for the conversion of cement to apatite for any concentrations of sodium alginate studied (0-2.0 wt%). The mechanical strength of the cement increased rapidly with the addition of sodium alginate up to 0.8 wt% when the cement paste was immersed and kept in distilled water at 37 degrees C, whereas further addition of sodium alginate decreased the mechanical strength. The results obtained in this investigation, taken together with sodium alginate's known excellent biocompatibility and absorption behaviour, indicate that the use of sodium alginate composite FSCPC as nd-FSCPC should be of value in orthodontics and oral and maxillofacial surgery where the cement is exposed to blood.

Alginates↗
PubMed1995

In vivo setting behaviour of fast-setting calcium phosphate cement.

The in vivo setting behaviour of fast-setting calcium phosphate cement (FSCPC) between femoral muscles of the rat was investigated to evaluate the possible value of FSCPC for medical and dental application. Conventional CPC (c-CPC) and FSCPC were implanted between femoral muscles, and various aspects of the setting behaviour such as setting time, mechanical strength and conversion ratio of cement into hydroxyapatite (HAP: Ca10(PO4)6(OH)2) were measured by the Vicat needle method, diametral tensile strength (DTS) measurement, and quantitative powder X-ray diffraction (XRD) analysis, respectively. The setting time of FSCPC in vivo was 5-7 min, in contrast to 48 min for c-CPC. As a result of its fast setting, set specimens of FSCPC showed higher mechanical strength from the initial stage than c-CPC. Higher DTS values were observed in FSCPC than c-CPC implanted after 24 h. Powder XRD analysis revealed faster conversion of FSCPC than c-CPC into HAP, which was responsible both for the faster setting and higher mechanical strength from the initial stage. We concluded, therefore, that FSCPC may be used for a wide range of clinical applications, i.e. fields where fast setting is required such as orthopaedic, plastic and reconstructive, and oral and maxillofacial surgery.

Animals↗
PubMed1995

Development of calcium phosphate based functional gradient bioceramics.

A functional gradient bioceramic that can function gradually with respect to body tissue was studied by changing the composition of calcium phosphate gradually from the surface to the inside. Diamond powder was spread on the surface of compact hydroxyapatite (HA) powder and fired at 1280 degrees C under reduced pressure, followed by firing under atmospheric conditions. The sintered body thus prepared was dense and alpha-tricalcium phosphate (alpha-TCP: alpha-Ca3(PO4)2) was found on its surface. The content of alpha-TCP gradually decreased with increasing depth from the surface. In contrast, the content of HA increased with increasing depth from the surface. The gradient ratio of alpha-TCP and HA depends on the firing time for each condition, i.e. reduced or atmospheric pressure. The alpha-TCP formation was ascribed to the decomposition of HA due to the spontaneous combustion of diamond powder.

Biocompatible Materials↗