The present invention is concerned with forms of incontinence caused wholly or partly by inadequate sphincter function. This may include forms of stress incontinence, urge incontinence and total incontinence. The invention has been developed initially for use in treating male incontinence and will be described principally with respect to that application. However, it will be appreciated by those skilled in the art that the invention is also applicable for use in treating female incontinence.
Incontinence is a major health problem, particularly with the ageing population, for which there is no well-accepted medical treatment. For females, surgically constructed slings are increasingly being used for stress incontinence and with increasing success. However, here is no low risk and reliably effective treatment for moderate to severe male stress incontinence particularly after treatment of prostate cancer. As the incidence of prostate cancer is increasing, this is a growing health issue.
The internal sphincter of the urethra consists of smooth muscle cells interposed with elastic tissue and is located in the proximal urethra. Its constant tone is crucial to maintaining mechanical resistance in the proximal urethra sufficient to hold back the passive pressure exerted by urine in the bladder. Weakness in this area is a common cause of urinary incontinence, for example after treatment for prostate cancer.
Prosthetic sphincter valves have been proposed in numerous forms, including mechanical, hydraulic and electrical devices which replace or supplement the defective damaged internal sphincter of the urethra (e.g. PT 101841, SE 931516, GB 2266844, FR 2638964, WO97/01309 and U.S. Pat. No. 4,619,245). Electrical stimulation of the muscles of the sphincter has also been proposed (DE 29614895). Other approaches have proposed the use of external or implanted electrodes to stimulate existing sphincter function.
A variety of approaches have been proposed in relation to the electrical stimulation of the muscles of the sphincter, most of which are directed towards stimulating an existing sphincter and/or muscles disposed about, for example, a bladder (DE 29614895).
Another group of prior art proposals for the treatment of incontinence are directed towards the stimulation of sacral nerves and the like. Such proposals again seek to use the existing muscle structures. (U.S. Pat. No. 4,771,779, U.S. Pat. No. 4,703,775, U.S. Pat. No. 4,607,639, U.S. Pat. No. 3,870,051, U.S. Pat. No. 4,688,575, U.S. Pat. No. 4,389,719 and U.S. Pat. No. 5,702,428).
Other stimulation means have been proposed, for example U.S. Pat. No. 5,562,717, wherein stimulating electrodes are disposed on the skin of a person to externally stimulate existing muscles to control incontinence. This method is disadvantageous in that it requires electrodes to be disposed in a predetermined location of the person and be electrically connected to a power source therefore not allowing complete freedom.
It has also been proposed to implant part of a small skeletal muscle from the thigh around the patient's urethra, and then to electrically stimulate the muscle to “retrain” it to function as a replacement sphincter (New Scientist, 29 Jun. 1996). However, this approach, even if successful, would require relatively high levels of electrical stimulation to allow sufficient contracture of the replacement sphincter.
It is an object of the present invention to provide an improved prosthetic device for use in treating incontinence.