摘要:

The ultimate goal of clinical research is to improve the quality and longevity of individuals. Prior to 1976, clinical research on medical devices was conceived and conducted with very little federal government intervention. Medical device amendments to the Federal Food&Drug Law were enacted in 1976 and resulted in new influences on the manner in which clinical research is conducted.

ISSN:0894-1939    

DOI:10.3109/08941938909016498

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

In the protracted search for segmental arterial replacements, the ideal substitute still remains autogenous artery. However, since obvious, severe limitations on their harvesting and use exist, the autogenous vein has become the practical bypass material of choice.’Because even vein is occasionally not available in suitable diameter or length, or for other reasons cannot be used, surgeons have either employed substitutes derived from polymer chemistry2-4or used homologous5or modified heterologous6blood vessels. While plastic prostheses can satisfy some needs as large vessel substitutes, they usually fail when employed as bypasses around obstructed smaller arteries. This paper will attempt a historical review of experiences to date in the development of prostheses of biologic origin, with a review of past rationales and of production techniques based on those rationales, nales.

ISSN:0894-1939    

DOI:10.3109/08941938909016499

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Percutaneous implants have been associated with numerous problems. However, by using skin-penetrating, bone-anchored titanium implants, developed by Professor Brånemark at the Department of Anatomy, University of Göteborg, good long-term results have been observed. These implants have been in clinical use for anchorage of bone-conducting hearing aids and facial prostheses since 1977 and 1979, respectively. The total number of implants is approximately 700. Less than 4% of the observations have shown significant irritation. Biopsies from 33 patients were collected for histological studies. In the irritated skin there was an increased number of inflammatory cells, mainly polymorfonuclear cells, B-cells, and plasma cells but not T-cells. This suggests a response directed against exogenous agents rather than an allergic reaction against the implant per se.

ISSN:0894-1939    

DOI:10.3109/08941938909016500

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

A percutaneous device system for long-term intracorporeal access is presented. A technical description of the device is given as well as results from healing in of device dummies and everyday functioning devices both in the short-and long-term perspectives in experimental animals and in human volunteers and patients. Major complications have not been observed by clinical inspection. Histological analyses of the animal experiments indicated that the downgrowth of the epidermal cells was arrested at the most superficial borderline of a preformed cavity region. An increased subepithelial cell density was observed lateral to a moderate sinus tract, but there were no heavy inflammatory cell infiltrations. The clinical success of the implants evaluated appears to be based on the following design factors: (1) selection of titanium as the tissue interfacing surface, (2) surface geometry factors applied, (3) a system of preformed cavities promoting connective-tissue interdigitation, (4) stress relief design of the subcutaneous flange, (5) high-precision surgical instrumentation and method. It is concluded that the results obtained so far are sufficiently promising to justify further controlled clinical trials and extended observation periods.

ISSN:0894-1939    

DOI:10.3109/08941938909016501

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

The major fact in determining percutaneous implant success is the formation of a stable skin-implant junction. However, the characteristics an implant material must meet to secure a durable percutaneous seal are still unknown. The objective of this study, therefore, is to gain more insight into the mechanisms underlying implant-skin reactions by means of in vitro cell culture and in vivo animal experiments. For the in vitro experiments rat palatal epithelial cells were cultured on various implant materials and the possible influence of the initial surface free energy and state of cleanliness of these materials on the growth rate of cells was studied. The results of these experiments demonstrate no significant relation between these parameters and cellular growth. In the in vivo experiments, plasma-sprayed and dense hydroxyl-apatite percutaneous implants were inserted into the tibia and dorsum of guinea pigs and into the tibia and onto the cranium of rabbits. The implants were left in situ for 3 weeks to 8 months. Clinical and histological investigations were performed. The results show, that stabilization of a percutaneous implant by bony skeletal tissue is effective in the maintenance of a permanent percutaneous passage.

ISSN:0894-1939    

DOI:10.3109/08941938909016502

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Implants placed in soft tissue evoke a foreign body reaction. Polymeric implants having smooth surfaces, such as silicone rubber implants, develop a nonadherent fibrogranulous tissue capsule which contracts over time and stiffens. Conventional porous implants, such as those made from textiles, usually have pores larger than 20μm and they become infiltrated with inflammatory tissue. The in vivo cell reaction to polymeric surfaces having pores smaller than 10μm has not been investigated systematically. In this study the histocompatibility of materials having mean pore diameters from 0.4 to 10μm was assessed. A material available with several different defined pore sizes Versapor filter material) was tested in vivo to determine relation between pore size and qualitative tissue response. Silicone-coated samples were also tested to determine the dependence of the observed tissue response on the implant surface chemistry. Results showed nonadherent, contracting capsules around implants having pore diameters smaller than 0.5μm. Implants with pores ranging from 1.4 to 1.9μm evoked thin, tightly adherent fibrous capsules without inflammatory cells. Porosities of 3.3μm and larger became infiltrated with inflammatory tissue. Results indicate that the obsexrved tissue response is predominantly dependent on implant surface topography and that variation in implant material may have little effect. It is concluded that a defined surface topography of 1 to 2 pm appears to allow direct fibroblast attachment to the surface independent of its chemical or electrochemical nature. Attached fibro-blasts then produce a minimal connective tissue response to the implant and prevent or diminish the presence of inflammatory cells at the implant/tissue interface.

ISSN:0894-1939    

DOI:10.3109/08941938909016503

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

This study evaluated the pony as a potentially suitable model for vascular implant research. Healthy, conditioned ponies were randomly assigned to one of three groups: group I, carotid artery autografts (n = 6); group II, e-PTFE carotid interpositional grafts (n = 5); and group III, e-PTFE carotid interpositional grafts plus aspirin (10 mg/kg) and dipyridamole (3.5 mg/kg) drug administration. It was found that autografts remained patent longest (mean = 396.2 days; grafts were still patent at time of writing) followed by group III grafts (157.5 days), with group II grafts remaining patent for the shortest duration (61.1 days), (p<0.01). Patency was determined using two-dimensional real-time ultrasonography with Doppler velocimetry and/or arteriography. It was demonstrated that the pony's response to antithrombotic drugs was consistent and comparable to that in other animal models, both with respect to platelet function and affect on patency rate. The combination of the ease of surgical manipulation, drug administration, and platelet function testing, the comparable size of the pony and its heart and blood vessels to that of an adult human, the long life span of ponies, and the patency results of this study have demonstrated that the pony is a valuable animal model for vascular research.

ISSN:0894-1939    

DOI:10.3109/08941938909016504

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor