Brief History of Biomedical Materials

There have been enormous strides in the development of novel biomedical materials over the past three decades. A biomedical material (also known as a biomaterial) is a polymer, metal, ceramic, or natural material that provides structure and/or function to an implantable medical device. In one generation, a large number of biodegradable polymers, bioactive ceramics, and wear-resistant metal alloys have made their way from research laboratories into widely-used medical devices. This heavy flurry of recent progress by materials scientists has partially overshadowed the efforts of surgeons, who previously led research efforts to develop biomedical materials. Until the 1960's, surgeons were at the forefront of efforts to find new materials for use in medical prostheses. Surgeons were driven by their clinical duties to improve the treatment of those suffering from congenital malformations, trauma, or disease. These surgeon-scientists attempted to alleviate patient suffering using "off-the-shelf" materials, which were developed for non-medical applications. This brief historical perspective describes some initial efforts to develop novel biomedical materials.

Bronze or copper have been used for thousands of years to repair fractured bones. However, use of bronze or copper was limited due to copper accumulation in the eyes, liver, brain, and other body tissues. Two developments in the late nineteenth century accelerated the use of synthetic materials in the human body. The development of the X-ray revealed that conventional external treatments were insufficient and stimulated the development of internal fixation procedures. In addition, broad acceptance of Lister's antiseptic procedures allowed for internal treatment of medical conditions with minimal risk of infection. Lister himself used antiseptic procedure to successfully suture fractured patellae with silver wire in 1885. Themistocles Gluck described replacement of both the acetabulum (pelvis) and femur (hip bone) using carved ivory at the 10th International Medical Congress in 1890; however, bone resorption and concomitant infection eventually caused these prostheses to fail. Neither acceptable materials nor designs were available at the time to fabricate medical devices.

Surgeons made several advances in biomedical materials development in the early-to mid-twentieth century. At the turn of the century, many European surgeons were experimenting with celluloid, rubber, magnesium, zinc, and other materials. In 1924, A. A. Zierold described an animal study on the interaction between bone and several metals, including aluminum, aluminum alloy, copper, low carbon steel, cobalt-chromium alloy, gold, iron, lead, magnesium, nickel, silver, and zinc. X-ray and histological sections of canine bone-material interface revealed that gold, silver, stellite, lead, and aluminum were encapsulated by tissue and were well-tolerated by the animals. Venable, Stuck, and Beach demonstrated the electrolysis of implanted biomedical materials in a 1937 study. They placed aluminum, brass, carbon, cobalt-chromium alloy, copper, galvanized iron, gold, lead, magnesium, nickel, silver, stainless steel, vanadium steel, and zinc in bones of experimental animals. Their biochemical, radiographic and clinical findings demonstrated that ion transfer between different metals in the body occurred in accordance with electromotive force. Their work also demonstrated that cobalt-chromium alloy was essentially nonelectrolytic; this material has remained a mainstay medical alloy to the present day.

The orthopedic surgeon Sir John Charnley made several significant advances in the field of biomedical materials, including (a) the introduction of the metal-ultra high molecular weight polyethylene bearing couple; (b) the use of poly (methyl methacrylate) for fixation; (c) the reduction of postoperative sepsis due to the use of laminar flow air-handling systems and prophylactic antibiotics; and (d) the placement of antibiotics in bone cement. In the 1950's, Charnley discovered that natural joints exhibit boundary lubrication. He then attempted to find a synthetic material with similarly low frictional properties. His first choice for an acetabular cup material, polytetrafluoroethylene, demonstrated poor wear properties. Unfortunately, this issue only became evident after a large clinical trial involving polytetrafluoroethylene implants had begun. More than three hundred polytetrafluoroethylene implant surgeries had to be revised due to poor wear properties, necrosis, and implant loosening. Charnley's laboratory assistant subsequently examined ultra high molecular weight polyethylene, which had found use in mechanical looms. Charnley noted that: (a) polyethylene had better wear characteristics than polytetrafluoroethylene; and (b) polyethylene was capable of being lubricated by synovial fluid. The use of novel materials and surgical procedures revolutionized the practice of joint replacement surgery and raised the success rate of this procedure to an exceptionally high level (>90%). Charnley's total hip replacement is considered the gold standard for joint replacement; few changes have been made to this prosthesis design in the past forty years. However, the Charnley prosthesis does have several disadvantages. One is an unacceptable rate of wear (about 200 μm/year). Metallic and, more commonly, polymeric wear particles cause a severe foreign-body reaction in the tissues that surround the prosthesis, which can lead to implant loosening.

The modern field of biomedical materials science owes a great deal to these pioneering individuals, who utilized existing knowledge at the interface of materials science and biology in order to improve the quality of life for others. In a similar manner, current-day biomedical materials researchers who work on porous coatings, bulk metallic glasses, artificial tissues, and nanostructured biomedical materials are utilizing modern concepts at the interface of materials science and biology in order to further knowledge in this rapidly developing area.

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