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.