HISTOLOGICAL, IMMUNOHISTOCHEMICAL, ТЕМ AND SEM INVESTIGATIONS IN THE VALVE-CUSP FREE BORDER OF GREAT VARICOSE SAPHENOUS VEIN

The authors studied venous valve cusps from surgically removed great saphenous vein with essential lower limb varicosis from 20 patients without data about previous thrombophlebitis. Venous valves without varicose alterations were used as controls. The histological, immunohistochemical, ТЕМ and SEM techniques were applied. In morphologically complete valve cusps from non-varicose great saphenous vein, a small marginal thickening was observed by routine histology. The cells visualised in these thickenings showed positive reaction against anti-vimentin but negative reaction against anti—smooth muscle actin antibody. In varicose vein valve cusps a marginal thickening with considerably larger diameter was histologically observed. In the fibrin-like material which was disposed around these thickenings, proliferation of fibroblasts as well as collagen fibres' depositions were seen. The SEM study showed partial "rollings" of the free cusp border. In the marginal thickening, the cells showed negative reaction not only to anti—smooth muscle actin but they also lost the reaction to anti-vimentin monoclonal antibody. The process mentioned above advanced, it occupied a new part at the valve cusp and so the cusp shortened. According to our hypothesis, this was one of the ways of initiating and advancing incompetence in primary varicosis

Transrenal Deployment of a Modular Stent Graft to Repair AAAs with Short Necks: Experiments in Dogs

Severely angulated (> 60°) or short (< 15mm) proximal necks remain significant anatomical limitations for endovascular stent-graft repairs for abdominal aortic aneurysms. Ensuring proper proximal fixation of the stent-graft to the host artery without the short-or long-term risks of endoleak or migration represents a particular technical challenge for these anatomical circumstances. An innovative balloon expandable stent combined with a weft-knitted prosthesis was specifically designed for these situations by modelling the stent to the neck anatomy without overdistension or potential barotrauma allowing better incorporation of the device. The Latecba stent-graft consists of a 2 parts modular design. The first one, Module A, is deployed at the transrenal level and consists of a Palmaz type stent whose first half is bare and second half is sutured to a crimped weft-knitted polyester graft whose distal end holds a constriction. The second Module B is a non-crimped weft-knitted graft attached to 2 stainless steel stents. The first stent is entirely contained in the proximal textile tube, allowing fixation to module A. The second stent, which is left uncovered over the distal third, ensures proper fixation of the stent-graft distally. Following the creation of a prosthetic aneurysm in the infrarenal aorta in 32 dogs, 29 received the Latecba stent-graft for scheduled durations of 10 days, 1 month, 3 months and 6 months. Proper deployment of the stent-grafts was achieved without difficulty. All 29 animals survived and the devices were all patent at sacrifice. No device defects or migrations were observed and the stent-grafts proved to be efficient in this setting to exclude the aneurysm. Analyses of the explanted devices (gross observations, RX, CT scan, IVUS, angioscopy) confirmed the stability of this modular stent-graft. Further on-going clinical investigations are warranted to validate this concept before this stent-graft becomes commercially available without any restriction

Pivoting system fracture in a bileaflet mechanical valve: A case report

A leaflet escape occurred in a low profile bileaflet mechanical prosthesis manufactured by TRI-Technologies that had been implanted for 3 years in the mitral position of a 32 year old patient. The escaped leaflet had embolized and was subsequently located by an abdominal computerized axial tomography scan and ultrasound in the terminal portion of the aortic bifurcation. The embolized leaflet was removed 3 months after valve replacement surgery. In an attempt to determine the cause of the escape the retrieved embolized leaflet was investigated. Techniques employed included visual examination aided by stereo-microscopy, x-ray imaging and scanning electron microscopy. One of the ears had fractured and was missing from the leaflet. Chipping was observed at the leaflet ear position on both the inflow and outflow surfaces. Visual and SEM observations found fractographic river-lines that indicated an apparent origin at the inflow surface of the ear nearest to the straight ‘B-datum’ line or coaptation edge. The origin seemed to be in the radius between the leaflet ear and the leaflet body. SEM observation of the remaining intact ear showed wear marks on both the inflow and outflow sides of the leaflet ear that corresponded to the suspected origin of fracture. It is believed that the use of boron alloyed pyrolytic carbon material and the leaflet\u27s homogeneous monolithic structural design were factors that contributed to this adverse event

Surface pretreatments for medical application of adhesion

Medical implants and prostheses (artificial hips, tendono- and ligament plasties) usually are multi-component systems that may be machined from one of three material classes: metals, plastics and ceramics. Typically, the body-sided bonding element is bone. The purpose of this contribution is to describe developments carried out to optimize the techniques , connecting prosthesis to bone, to be joined by an adhesive bone cement at their interface. Although bonding of organic polymers to inorganic or organic surfaces and to bone has a long history, there remains a serious obstacle in realizing long-term high-bonding strengths in the in vivo body environment of ever present high humidity. Therefore, different pretreatments, individually adapted to the actual combination of materials, are needed to assure long term adhesive strength and stability against hydrolysis. This pretreatment for metal alloys may be silica layering; for PE-plastics, a specific plasma activation; and for bone, amphiphilic layering systems such that the hydrophilic properties of bone become better adapted to the hydrophobic properties of the bone cement. Amphiphilic layering systems are related to those developed in dentistry for dentine bonding. Specific pretreatment can significantly increase bond strengths, particularly after long term immersion in water under conditions similar to those in the human body. The bond strength between bone and plastic for example can be increased by a factor approaching 50 (pealing work increasing from 30 N/m to 1500 N/m). This review article summarizes the multi-disciplined subject of adhesion and adhesives, considering the technology involved in the formation and mechanical performance of adhesives joints inside the human body