1. Field of the invention
The present invention concerns a control device for an artificial sphincter for a natural bodily passage, in particular a urinary passage, and an implantable prosthesis comprising said control device.
2. Description of the Prior Art
One known means of remedying the inconveniences of urinary incontinence entails placing around the urethra (in men) or around the vesical cervix (in women) an artificial sphincter in the form of a collar or cuff which selectively compresses the urinary passage as a substitute for the defective natural sphincter.
Devices of this kind are well known and operate satisfactorily. Descriptions of them can be found in U.S. Pat. Nos. 3 863 622, 4 222 377 and U.S. Pat. No. 4 632 114, for example. They comprise, for example, a generally toroidal balloon with a flexible or rigid surround, the assembly being placed around the urinary passage. According to the pressure of the hydraulic fluid inside the balloon, the natural passage is compressed (continence state) or not (urination phase).
Other known artificial sphincter control devices inject a fluid into the cuff to compress the urinary passage or remove fluid from it to release the passage and allow urination. These devices can also be implanted, in the patient's abdomen, for example, and can be operated through the skin.
In the absence of any hardware device passing through the skin, the only simple manipulation that can be performed through the skin is to exert pressure on an implanted control device, by pressing with a finger, for example. Also, the continence state is the usual state, with the result that the artificial sphincter must remain pressurized for long periods, being released only during urination.
There is already known from U.S. Pat. No. 4 571 749 an implantable urinary sphincter system in which the control device comprises a bellows connected to a vessel filled with incompressible fluid comprising a flexible membrane. When the patient presses hard with the fingers on said membrane the length of the bellows is increased which in turn increases the volume of a chamber filled with incompressible fluid connected to the sphincter, so reducing the pressure in said sphincter. On the other hand, when no pressure is exerted on the membrane, the return force exerted by a diaphragm constituting one wall of said chamber tends to return the latter to its original volume, so as to compress the sphincter.
This device has a number of disadvantages, however. Firstly, the action of the patient on the membrane may not result in sufficient lengthening of the bellows because of the shape of the membrane or because the vessel may expand rather than the bellows. What is more, the end surface of the bellows, acting on the corresponding wall of the chamber connected to the sphincter, is small, which does not guarantee effective action of said bellows on said chamber. Also, the structure of the control device described in U.S. Pat. No. 4 571 749 is complex and therefore costly and unreliable.
An object of the present invention is to avoid these disadvantages and the invention consists in an artificial sphincter control device of simple, reliable and economical construction.