The craft of surgery has revolved around correcting the structural and anatomic consequences of diseases. Malignant growths require the removal of entire organs or tissues and even radical resection of adjacent areas. However, there is always the conflict of goals, between removing enough tissue and conserving enough organ function. Transplantation has been a growing discipline because of the opportunity to remove entire organs and then replace their function with a donated organ. However, the supply is limited, and rejection is a constant problem. Tissue engineering artificial organs has progressed to a level where small amounts of organs are being synthetically grown. Vacanti and coworkers at Massachusetts General Hospital have been able to grow an artificial blood vessel system from endothelial stem cells, and are now using that vascular tree with hepatic stem cells to grow artificial livers (5). These, and other approaches by different researchers, point to a time in the near future when it will be possible to grow a new organ from a patient's own stem cells. If this becomes the case, then it is theoretically possible that for nearly every disease, the surgeon will simply remove the patient's diseased organ and replace it with a new one (grown from the patient's own stem cells), without the fear of rejection. Therefore it may be that the future surgeon will perform only one operation for each organ system, no matter what the disease—remove the old one and replace it with a new one. This will dramatically impact the way the surgeon will practice, either by having a single operation for all patients in a practice (in the case of specialists) or a return of preeminence of general surgery, where every practice will consist a few operations to take care of all the major organ systems.
The replacement of human organs or functions has also been addressed by the use of prostheses; however, with the exception of the cardiac pacemaker, all prostheses have been inert and "dumb," that is, they do not respond the changing conditions in the body. Once implanted, artificial hips keep their position, and over time either wear out or cause problems such as loosening or damage to surrounding structures. Now prostheses are becoming "smart," with micro-electro-mechanical system sensors to detect changes and actuators to adjust the prostheses. This same feedback is being programmed into implantable devices, such as an insulin pump for diabetes (6). Ophthalmologists are implanting the first generation of artificial retinas into patients (7). This implies a future where surgeons will be asked to implant more and more artificial "parts," to either replace or enhance human function.
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