The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex m... more The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex mesh reinforced with a continuous Teflon spiral, and it is grafted and coated with pig collagen, with the aim of promoting connective tissue infiltration and providing air-tightness during the initial stage of implantation. Complete surgical resection and replacement of a 4-6 tracheal ring segment of the cervical trachea was performed in 13 adult mongrel dogs. Except for two dogs that developed anastomotic insufficiency, the prostheses in all dogs were infiltrated by the surrounding connective tissue, and were completely incorporated by the host trachea at the anastomotic sites. Formation of respiratory epithelium that lined the prosthesis lumen, was seen to varying degrees, and in one dog killed at 4 months after reconstruction, this was confirmed histologically from the upper to the lower anastomosis of the prosthesis. Stenosis of the lumen often occurred, however, due to deformation of the prosthesis and overgrowth of granulation tissue. The authors conclude that this tracheal prosthesis is highly biocompatible, and might be useful for repairing tracheal defects by improving prosthesis processing, especially that used for insertion of stents.
We have attempted to develop an artificial articular cartilage on the basis of a new viewpoint of... more We have attempted to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which lubrication and load-bearing mechanisms of natural and artificial joints are compared. We investigated poly(vinyl alcohol)-hydrogel (PVA-H) which has been recognized as a rubber-like gel and have improved the mechanical properties of this gel through a new synthetic process. In this article we report the biocompatibility and various mechanical properties of the new, improved PVA-H from the aspect of its usefulness as artificial articular cartilage. As regards the lubrication, we measured the change of thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading and found that the PVA-H had a thicker fluid film under higher pressure than polyethylene (PE). The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times as large as that of PE. Histological findings of the articular cartilage and synovial membranes around the PVA-H implanted for 8-52 weeks showed neither inflammatory nor degenerative changes. The PVA-H artificial articular cartilage could be attached to the underlying bone using an osteochondral composite material. Although there remain still some problems to solve, PVA-H seems to be a very interesting and promising material which meets the requirements of artificial articular cartilage.
Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive l... more Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive lesions in the extracranial cerebral vessels, such as carotid or vertebral arteries. In contrast, cerebral revascularization using an artificial blood vessel has not been so common. This is due to the fact that conventional artificial blood vessels have been too firm or too rigid for use in the neurosurgery. Another reason is that the long term patency rate of small caliber artificial blood vessels has usually been inferior to that found in autologous vein grafts. The purpose of this study was to develop a soft and compliant artificial blood vessel suitable for cerebrovascular surgery. This new artificial blood vessel is made of polyurethane, porous in structure (porous polyurethane). Thus, multiple small-sized pores exist both in the inner and outer surfaces, and in the wall of the porous polyurethane graft. To test its mechanical properties, we evaluated stress-strain curves and compliance. In comparison to expanded polytetrafluoroethylene graft (Goretex), which has been one of the most commonly used artificial blood vessels in the cardiovascular surgery, the mechanical properties of the porous polyurethane graft more closely resembled those of the common carotid artery in dogs. Thus, porous polyurethane graft was shown to be a soft and compliant new artificial blood vessel. This means not only that it can be maneuvered with technical ease for anastomosis but also that there is a reduction of compliance-mismatch between the host vessel and the artificial vessel. Compliance mismatch has been documented as a major factor in the inducement of intimal hyperplasia, which causes a delayed occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)
The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex m... more The efficiency of a new tracheal prosthesis was studied. The prosthesis consists of fine Marlex mesh reinforced with a continuous Teflon spiral, and it is grafted and coated with pig collagen, with the aim of promoting connective tissue infiltration and providing air-tightness during the initial stage of implantation. Complete surgical resection and replacement of a 4-6 tracheal ring segment of the cervical trachea was performed in 13 adult mongrel dogs. Except for two dogs that developed anastomotic insufficiency, the prostheses in all dogs were infiltrated by the surrounding connective tissue, and were completely incorporated by the host trachea at the anastomotic sites. Formation of respiratory epithelium that lined the prosthesis lumen, was seen to varying degrees, and in one dog killed at 4 months after reconstruction, this was confirmed histologically from the upper to the lower anastomosis of the prosthesis. Stenosis of the lumen often occurred, however, due to deformation of the prosthesis and overgrowth of granulation tissue. The authors conclude that this tracheal prosthesis is highly biocompatible, and might be useful for repairing tracheal defects by improving prosthesis processing, especially that used for insertion of stents.
We have attempted to develop an artificial articular cartilage on the basis of a new viewpoint of... more We have attempted to develop an artificial articular cartilage on the basis of a new viewpoint of joint biomechanics in which lubrication and load-bearing mechanisms of natural and artificial joints are compared. We investigated poly(vinyl alcohol)-hydrogel (PVA-H) which has been recognized as a rubber-like gel and have improved the mechanical properties of this gel through a new synthetic process. In this article we report the biocompatibility and various mechanical properties of the new, improved PVA-H from the aspect of its usefulness as artificial articular cartilage. As regards the lubrication, we measured the change of thickness and fluid pressure of the gap formed between a glass plate and the specimen under loading and found that the PVA-H had a thicker fluid film under higher pressure than polyethylene (PE). The momentary stress transmitted through the specimen revealed that PVA-H had a lower peak stress and a longer duration of sustained stress than PE, suggesting a better damping effect. The wear factor of PVA-H was approximately five times as large as that of PE. Histological findings of the articular cartilage and synovial membranes around the PVA-H implanted for 8-52 weeks showed neither inflammatory nor degenerative changes. The PVA-H artificial articular cartilage could be attached to the underlying bone using an osteochondral composite material. Although there remain still some problems to solve, PVA-H seems to be a very interesting and promising material which meets the requirements of artificial articular cartilage.
Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive l... more Saphenous vein interposition grafts have been commonly used for the reconstruction of occlusive lesions in the extracranial cerebral vessels, such as carotid or vertebral arteries. In contrast, cerebral revascularization using an artificial blood vessel has not been so common. This is due to the fact that conventional artificial blood vessels have been too firm or too rigid for use in the neurosurgery. Another reason is that the long term patency rate of small caliber artificial blood vessels has usually been inferior to that found in autologous vein grafts. The purpose of this study was to develop a soft and compliant artificial blood vessel suitable for cerebrovascular surgery. This new artificial blood vessel is made of polyurethane, porous in structure (porous polyurethane). Thus, multiple small-sized pores exist both in the inner and outer surfaces, and in the wall of the porous polyurethane graft. To test its mechanical properties, we evaluated stress-strain curves and compliance. In comparison to expanded polytetrafluoroethylene graft (Goretex), which has been one of the most commonly used artificial blood vessels in the cardiovascular surgery, the mechanical properties of the porous polyurethane graft more closely resembled those of the common carotid artery in dogs. Thus, porous polyurethane graft was shown to be a soft and compliant new artificial blood vessel. This means not only that it can be maneuvered with technical ease for anastomosis but also that there is a reduction of compliance-mismatch between the host vessel and the artificial vessel. Compliance mismatch has been documented as a major factor in the inducement of intimal hyperplasia, which causes a delayed occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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Papers by Yoshito Ikada