Evaluation of the efficacy and performance of medical implants: a review.

An implant can be defined, in a medical context, as biological or artificial materials inserted or grafted into the body. Implants may be sensory devices (cochlear, ocular), mechanical devices that are 'passive' (orthopedic joint replacements and fixation plates, dental implants, coronary artery stents and vascular grafts) or 'active' (left ventricular assist devices, heart valves) electrophysiological stimulation devices (cardiac or gastric pacemakers, implantable cardiac defibrillators, functional electrical stimulators for epilepsy or Parkinson's disease) or medication administration devices (insulin or analgesic delivery pumps) or intra-ocular sustained drug release implants. Implantation has had a long history in several subspecialties of medicine. Evaluation of the efficacy of implants is a multifactorial issue. Several variables need to be considered while studying the rejection of the implants such as pathophysiological mechanisms, malfunction, design shortcomings and improper implementation/implantation by a medical team. This paper identifies a variety of modes of failure and how they affect the overall efficacy of the device technologies. Suggestions for improvement, as outlined in the literature, will be examined.