© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.2.1 Biocompatibility of Traditional Medical Implants

During the 20th century, artificial materials and devices were developed to the point at which they could be used successfully to replace parts of living systems in the human body [238]. These special materials – able to function in intimate contact with biological fluids or living tissue, with minimal adverse reaction or rejection by the body – are called biomaterials [239-243]. Devices engineered from biomaterials and designed to perform specific functions in the body are generally known as biomedical devices or implants. By the mid-1990s, biomaterials were found in ~2700 different kinds of medical devices, ~2500 separate diagnostic products, and ~39,000 different pharmaceutical preparations [233].

The earliest successful medical implants were bone plates [244], first introduced in the early 1900s to stabilize bone fractures and assist in the healing of skeletal fractures. (The plate was often removed once the bone had healed and the bone could support loads without refracturing [245], or else the plate was designed to be bioabsorbable [246-248].) Advances in materials engineering and surgical techniques led to blood vessel replacement experiments in the 1950s. Artificial heart valves and hip joints were under development in the 1960s [239]. By the end of the 20th century, biomaterials came to play a major role in replacing or improving the function of every major human body system, and became important in extracorporeal systems such as oxygenators, dialyzers, and apheresis systems. Some common implants [233, 238] include: (1) orthopedic prostheses such as total knee and hip joint replacements, spinal implants, bone fixators, and tendon and ligament prostheses [305]; (2) cardiovascular implants [241] such as artificial heart valves, vascular grafts and stents, pacemakers, and implantable defibrillators; (3) neural implants (e.g., cochlear implants) and cerebrospinal fluid drainage systems (e.g., hydrocephalus shunts); (4) plastic and reconstructive implants such as breast augmentation or reconstruction, maxillofacial reconstruction, artificial larynx, penile implants, and injectable collagen for soft tissue augmentation; (5) dental implants to replace teeth/root systems and bony tissue in the oral cavity; (6) ophthalmic systems including contact and intraocular lenses; (7) catheters and bladder stimulators; (8) drug-dispensing implants such as insulin pumps; and (9) general surgical systems such as sutures, staples, adhesives, and blood substitutes. It has been estimated that 674,000 adults in the U.S. were using 811,000 artificial hips (Section 15.2.1.1) by 1988 [249]. About 170,000 people worldwide (60,000/year in the U.S.) received artificial heart valves (Section 15.2.1.2) in 1994 [238, 1147], and ~1 million joint replacement prostheses were installed worldwide in 1996 [594]. About 100,000 external insulin pumps (in U.S.) and ~1100 internal (implanted) insulin pumps (worldwide) had been placed in patients by 2001 [5925].

Last updated on 30 April 2004