Chapter 8
Fibers in Medicine From Antiquity to the Future D. J. Lyman
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Department of Materials Science and Engineering, University of Utah, Salt Lake City, UT 84112
Fibrous materials will always play an important role in the advancement of medicine and surgery. Their uses range from non-implantables to extracorporeal devices and implants. Some examples of implants and the extracorporeal devices are discussed to show how the past is guiding us to the future.
Fibrous materials and fibers have always intrigued mankind with their potential uses. This is understandable when one considers that these materials can be tied, woven, knitted or made into paper. Indeed, if we look at the first uses of foreign materials in medicine, they are of fibrous materials and date back to well over 4000 years ago. Thefirstrecorded use is mentioned in the Edwin Smith Surgical Papyrus (1), nearly 4000 years old, describing the use of stitches (sutures) in wound repair. Extensive use of a variety of suture materials was also recorded in the Indian literature (1). The Susruta Samhita, written 2500 years ago, describes suturing materials of braided horsehair, leather strips, cotton fibers, animal sinews, and the fibrous bark from the Ashmantaka tree. Today, fibers are utilized in almost every facet of medicine and surgery (see Table I). While the major volume of uses are for the nonimplantables, we will be discussing some of the extracorporeal and implantable applications of fibers and fibrous materials that are used in affecting repair of the body. Fibers in Implants and in Extracorporeal Devices. Sutures. A suture is a strand of material, either monofilament or multifilament, used to tie (ligate) or to sew (suture) tissue. Many materials have been used throughout the centuries of medicine: bark, animal tendons and leather strips, intestinal tissue, gold, silver, iron wire, silk, linen, cotton, and now stainless steel wire and synthetic polymers. While ideally one should only be concerned with the tensile strength of the suture (i.e. its strength must be in excess of that required to hold tissue in opposition to whatever strains are imposed by 0097-6156/91/0457-0116$06.00/0 © 1991 American Chemical Society
In High-Tech Fibrous Materials; Vigo, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1991.
8.
LYMAN
Fibers in Medicine: From Antiquity to the Future
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Table I. Fibers in Medicine Nonimplantables Drapes, pillows, wash cloths, surgical dressings, gauze, elastic stockings. Gowns, caps, surgical masks.
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Extracorporeal Fabric reinforcements for dialysis and oxygenator membranes, silicone rubber, U V curable cast materials and catheters. Hollow fibers for dialyzers and oxygenators. Implantables Sutures Fabrics for sewing rings (heart valves, percutaneous leads), patches for heart repair, surgical reinforcement meshes. Vascular grafts, reinforcement tubular meshes for veins and polymer grafts. Velours for blood contacting surfaces (artificial heart and assist devices). Fiber reinforcement for hard polymers (bone plates, etc) and soft polymers (ligaments, etc). Restraining loops for intraocular lenses. postoperative conditions), in actual use one must be concerned about a number of characteristics. These are: a) absorption. A suture must not be absorbed nor lose its tensile strength for a period of 10 to 12 days after implantation so that sufficient healing can occur to restore strength to the wound; b) pliability. This refers to the resistance of a strand to bending forces. The suture should handle comfortably and naturally to the surgeon without too much stiffness or kinking; c) knot tying and holding. Strands should not be too wiry and resist the firm setting of the knot (for example, the springy polyproplene would actually untie itself) nor have too hard or smooth a surface which would allow the knot to slip or loosen; d) tissue reaction. The suture must cause only a minimal tissue reaction. Degradation (absorption) of the suture must not cause any excess chemical irritation. Infection has also become a concern in terms of suture selection (2,3). For example, monofilament polymeric sutures elicited less infection than multifilament polymeric sutures or metallic sutures. Also, the chrome crosslinked collagen sutures elicited less infection than untreated collagen sutures. A general ranking of the potential of a variety of sutures to develop wound infection is as follows: polypropylene, polyglycolic and lactic acid esters, nylon < collagen, polyethylene terephthalate
