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Biomedical subjects

D F Gibbons

Publications and source records attributed to D F Gibbons.

15 recordsLinked to original sources
PubMed1985

Experimental mechanical and histologic evaluation of the Kennedy ligament augmentation device.

Reconstruction of the knee with a chronic injury to the anterior cruciate ligament is an unsolved problem. Biologic graft substitutes have failed to maintain knee stability in the longer postreconstruction intervals. In an attempt to overcome the limitations in graft performance, synthetic materials have been proposed to augment the biologic tissue. In this study, a 6-mm polypropylene braid Ligament Augmentation Device (LAD) possessing a tensile strength of 1500 N and excellent fatigue and creep properties was investigated as an adjunct to the MacIntosh/Marshall Over-the-Top repair. A two-year animal study of 54 adult goats was conducted in which experimental ACL defects were created and reconstructed with a transplant consisting of a portion of the rectus femoris tendon, prepatellar tissue, and the central one-third of the patellar tendon. The goats were equally divided between nonaugmented and LAD-augmented groups and sacrificed at three, six, 12, and 24 months after surgery. Mechanically, the augmented transplants were substantially stronger at the time of initial implantation (364N versus 26N) and again at two years (841N versus 528N). Intermediate times did not demonstrate a difference in strength. Histologically, the augmented transplants consisted of a loosely organized fibrous capsule surrounding the LAD. At 24 months, "insertion fibers" were noted to provide continuity between the fibrous tissue and bone on both the tibia and femur.

Animals↗
PubMed1979

Effect of implant surface chemistry upon arterial thrombosis.

A series of poly(alpha-amino acid)s with controlled chemical variations were investigated in order to assess the effect of different chemical moieties upon arterial thrombosis. The gross implant surface properties ranged from hydrophobic to hydrophilic ionic and nonionic. The materials were tested by implantation within canine femoral and carotid arteries. Results were compared with the response to the polyurethane Biomer. The changes in implant surface chemistry elicited a range of response that varied from intense thrombosis and rapid vessel occlusion to minimal thrombosis and endothelialization. The results showed that no simple relationship exists between a gross surface property, such as hydrophobicity, and the degree of thrombosis resistance. Some hydrophobic and hydrophilic materials were found to have good thrombosis resistance, while others were found to have poor thrombosis resistance. Leukocytes were shown to play an important role in both initial thrombosis and endothelialization. The major difference between materials that progressed to rapid vessel occlusion and materials that remained patent was the degree of direct leukocyte adherence and spreading on the implant surface prior to extensive platelet aggregation (less than 30 min). It was consistent for both hydrophobic and hydrophilic materials that the lack of direct leukocyte adherence to the implant surface was associated with intense thrombosis and rapid vessel occlusion. Conversely, the presence of numerous leukocytes directly adherent to either hydrophobic or hydrophilic surfaces appeared to have a moderating effect upon thrombosis and vessels with these implants remained patent. In instances when thrombosis was nonocclusive, the surfaces of the thrombi became endothelialized, primarily through the transformation of mononuclear leukocytes into endothelial cells. This article includes a hypothetical model representing the sequence of events and alternative pathways occurring at the blood-material interface, with special attention given to the involvement of leukocytes in arterial thrombosis.

Animals↗
PubMed1978

An in vivo method to evaluate the effect of materials upon arterial thrombosis.

An in vivo method to evaluate the effect of materials upon arterial thrombosis was developed that minimized the effect of surgical artifacts and provided a test which was critically sensitive to the surface properties of the materials. The procedure has general applicability to elastomers, either solvent cast or mold polymerized, and involves the implantation of segments of the test materials within canine femoral and carotid arteries. The sensitivity of this technique was demonstrated by comparing two surface preparations of a segmented polyurethane: as-cast and ion sputtered. There was a striking difference in the rate of thrombus development on as-cast polyurethane implants compared with sputtered polyurethane implants. After 1 hr. of implantation the surface of the as-cast polyurethane was covered with a monolayer of platelets and leukocytes, whereas thrombus development progressed more rapidly on the sputtered polyurethane surface and at 1 hr. it was covered with pillars of platelets and leukocytes with fibrin accumulation between pillars. The method was also useful for long-term studies, which showed that a thin layer of thrombus developed on both polyurethane surfaces and by 1 wk. after implantation the surfaces of the thrombi became endothelialized.

Animals↗
PubMed1978

Effect of polyurethane morphology on blood coagulation.

A series of polyurethanes based on the hard segment MDI and soft segment PTMG were synthesized. The molecular weight of the PTMG was 730, 1000, and 2000, and ethylene diamine was used as chain extender. The fabrication process was varied so as to achieve the maximum disorder (nonequilibrium state) and maximum order, fully annealed. It was demostrated that the "quenched" non-equilibrium state reduces the rate of activation of the intrinsic systems, factor XII pathway, when compared to the fully annealed state. Platelet attachment is primarily affected by phase separation.

Blood Coagulation↗
PubMed1978

In vitro cytotoxicity and in vivo acute responses to some amino acid copolymers and their esters.

The present study was performed in order to establish if there is any correspondence between specific parameters of tissue reaction to implanted biomedical materials and in vitro cytotoxicity. The presence of various types of inflammatory cells and/or necrosis in rats implanted subcutaneously with a series of 42 alpha-amino acid copolymers and their esters was compared with their in vitro toxic effects, as determined by an agar overlay technique. Only necrosis appeared to correlate with reactions scored as strongly positive by tissue culture procedures. Future studies with slightly toxic materials should assess if tissue culture methods could be helpful in predicting other levels of reaction at the polymer-tissue interface.

Amino Acids↗