There are several factors to consider when selecting which penile prosthesis would be best for you. Keep in mind that once the prosthesis is placed, however, there is no going back. The surgery destroys the body's natural ability to have erections. If you can achieve a partial erection, combination therapy should be attempted under a physician's close guidance. Some patients cannot afford the price of these medications making this option difficult. Others do not like the preparation necessary with more complicated treatments. These patients are often considered earlier for penile prosthesis.
A patient's dexterity must also be considered. Does the patient have adequate use of both hands? Is there a neurological or mental reason that the patient will not be able to operate a given device? A malleable (bendable) prosthesis requires less articulation. The patient will bend it up or straighten it when he is ready for sex. His partner may be able to do this as well. The two and three piece prostheses require the activation of a pump. This requires the use of both hands. The pump is positioned surgically in the scrotum. Patients may feel as though they have a third "testicle," but this is actually the prosthetic pump. The pump contains a way to fill the prosthesis (make the penis hard) and empty the prosthesis, or make it soft. The pump will usually require the use of both hands. One hand (usually the non-dominant hand) will stabilize the pump while the other squeezes the bulb-shaped pump to fill the penis. There is a second button on the pump that serves to release the fluid out of the penis making the penis soft again. Two hands are required for this maneuver as well.
The two and three piece prostheses differ by their reservoir. An inflatable penile prosthesis is filled with saline (salt water solution). When the water is not in the shaft portion of the penis causing an erection, it must be hidden. The two piece prosthesis has the reservoir in the scrotum with the pump (the pump is the reservoir where the water is stored). When the pump is squeezed to make an erection, the fluid leaves the scrotum and fills the penis. When the man hits the release button, the fluid goes back into the scrotum. The limitation here is that the scrotum cannot hold a very large reservoir and remain cosmetically concealed at the same time. Therefore, a criticism of the two piece prosthesis is that it never truly gets fully detumesced or soft. It will get as rigid as the others, however.
The third piece of the three-piece prosthesis is a distinct reservoir. This reservoir is large (almost 100cc) and is placed into the lower abdomen. When the pump is activated (squeezed to make an erection) the fluid leaves the reservoir and enters the penis. The advantage comes when the pump is released to make the penis soft. The fluid then goes back into the abdomen, hidden away for a nice cosmetic appearance.