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In order to further evaluate the role of lasers in microvascular tissue closure, we modified an existing CO2 surgical laser (Xanar XA-20) by adding a partially reflecting mirror to attenuate the beam. This allowed the laser to operate at an output of approximately 100 mW, which was appropriate to achieve microvascular closures. In each of 43 rats, one carotid artery was transected and then anastomosed with standard suture technique with 10 to 12 simple interrupted sutures of size 10-0 Ethilon nylon suture (Ethicon, Inc.). The opposite carotid in each rat was anastomosed by the placement of three stay sutures followed by the application of laser irradiation to the tissue between the stay sutures at 90 to 100 mW, spot size of 0.2 mm, pulse duration 0.2 seconds, approximately 20 to 30 pulses per anastomosis. In vivo test periods were 1 hour, 1 day, 3 days, 7 days, 10 days, 14 days, 28 days, 91 days, and 180 days. All anastomoses were evaluated for patency, and selected samples were utilized for light microscopy, and mechanical testing (intraluminal pressure raised to 300 mmHg). It was determined that similar patency rates and slightly faster time to perform the same procedure could be achieved with the use of the low-powered CO2 laser. However, histologic evidence of significant medial damage raises concern about the long-term risk of a higher aneurysm rate. Vessel damage and the lack of simple intraoperative methods to verify the quality of the laser technique restrict these authors from advocating the clinical introduction of the procedure until further advances are made.(ABSTRACT TRUNCATED AT 250 WORDS)

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A new anastomotic device is demonstrated that is suitable in microvascular surgery for repairing severed blood vessels and inserting vein grafts. Initial pilot studies indicate a 100% patency rate for vessel anastomosis, and a one-year study produced a 96% success rate. However, histological examination revealed notable vessel deterioration with a rigid device. Therefore, an absorbable anastomotic coupler was developed that demonstrates a high patency rate (92%) in both arteries and veins, with substantial absorption of the device by 70 days. Healing at the anastomotic site was qualitatively similar to that obtained with a sutured anastomosis; there was endothelialization by 14 days and absorption of the device by 70 days.

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Transmission electron microscopy was used to study the ultrastructure of cells at the interface with an implanted biodegradable polymer, Polyglactin 910. Various stages of implantation were observed from 1 day to 63 days, when absorption of the polymer was essentially complete. Events occurring at the interface include initial adhesion of macrophages on the implant surface; phagocytosis of wound debris; and subsequent erosion, invasion, and phagocytosis of the polymer by macrophages and giant cells. A vascular perfusion technique for fixation of the polymer sites implanted in soft tissue is also described.

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Studies were designed to demonstrate the need for standardization of shape of samples used as implants to evaluate histotoxicity of polymer materials. Six medical-grade polymers (polypropylene, polyethylene, polyurethane, silicone rubber, poly(vinyl chloride), and Teflon) were extruded as rods with circular-, triangular-, and pentagonal-shaped cross sections, and were implanted in rat gluteal muscles for 14 days. Evaluation of the tissue response was assessed by quantitating cellular lysosomal acid phosphatase enzyme activity by using microspectrophotometry. All triangular-shaped implants showed the highest enzyme activity and cellular response; pentagon shapes showed less, and circular rods showed the lowest activity. The results demonstrate the need for standard sample shape for valid comparative studies of tissue response to implanted polymers.

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Enzyme histochemical procedures for both hydrolase and oxidoreductase enzyme activity were applied to cryostat sections of polyglactin 910 suture implant sites. Sutures were implanted either solely in tissue or in a combination of in vitro incubation followed by implantation in vivo for total time periods of seven to 56 days. Suture absorption rates were also measured. It is concluded from the results that neither cellular nor enzyme activity is necessary for the degradation and absorption of polyglactin 910 sutures. This conclusion is based on similar absorption rates for sutures implanted solely in vivo and sutures treated in vitro and then implanted in tissue to give equivalent time spans. There were strong indications, however, that the products of suture hydrolysis are probably metabolized through the oxidative enzyme systems of cells adjacent to the suture. This mechanism of polyglactin 910 suture absorption is quite different from that observed and reported for catgut absorbable sutures.

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The rabbit ear chamber provides a unique system for viewing an in vivo environment from outside the body. The plastic chamber, modified for our use, is described. Once surgically implanted into the ear of a Laboratory Lop rabbit, a thin tissue bed which grows between the layers of the chamber can be viewed through the microscope. The absorption of biomaterials placed into the chamber can then be observed as a dynamic process.

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The hydrolytic enzyme activity associated with the tissue reaction to implanted polyvinyl chloride rods containing graded concentrations of an organotin stabilizer was quantitated by microphotometry of tissue sections. The procedure was more sensitive to the effects of the additive than the usual histologic evaluation. It is considered that this type of approach offers a sensitive and objective index to supplement the more subjective morphologic observations in judging the acute histotoxicity of implants.

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