For centuries man has been concerned whether human population will exceed the food supply. This concern is particularly acute in certain countries where the percentage of the world population in that country is as high as three times the percentage of arable land in that country.
In recent years, man has become aware that he is rapidly depleting nonrenewable natural resources and is consuming renewable resources at a far greater rate than he is replacing them. This depletion is due in large part to the current unparallelled increase in the world's population, and will affect the future of the developed countries as well as the lesser developed countries.
For these and other reasons, many countries promote and encourage birth control. Indeed, some countries proscribe and sanction the multiple dependent family. In most of the world, various forms of birth control are available to men or women desiring to utilize them.
Historically, people have controlled contraception by relying on male methods of contraception. The condom was developed in the fourteenth century as a prophylactic against veneral disease. Recent studies have shown it to be a remarkably effective contraceptive. It is today the world's most widely used contraceptive, although the second most widely used method in the United States.
The single most widely used contraceptive in the United States is the female oral contraceptive. It is highly effective, but relatively expensive and causes unacceptable side effects in certain women. Other female contraceptives have well known advantages and disadvantages. Because of these limitations, male contraceptive is an alternative which is attractive to many people.
The mode and proven methods of male contraceptives all involve stopping the production, the passage, or the transport of the sperm. Each of these in turn separate into the permanent and reversible methods.
The vas deferens is a tube running from the epididymis up the scrotum and the inguinal canal behind the bladder where it joins the seminal vesicles, which are both connected to the ejaculatory duct, which in turn joins the urethra. The function of the vas deferens is to carry sperm from the testicle.
The vas deferens is about 2.5 to 3 mm in diameter and contains a central lumen about one tenth of the total diameter. Surrounding the lumen are circular muscle fibers surrounded by longitudinal muscles and nerves. The function of the muscles and nerves is to squeeze the sperm progressively up along the lumen to the outside of the body.
A vasectomy involves surgically severing the vas deferens. Additionally, steps are taken to prevent accidental recanalization. These include fulguration to destroy the mucosal surface and interposing a connective tissue. For these reasons, the propulsive properties of the vas deferens may be permanently damaged by a vasectomy. While recent results of vasovasectomy indicate higher success rates in the return of sperm, the operation must be considered a permanent and irreversible operation since fertility cannot be ensured following reanastomosis of the vas deferens.
Several surgical procedures have been developed for reversible vas deferens occlusion. The first was the insertion of a surgical thread into the lumen of the vas deferens. A surgically implanted intravascular plug is disclosed in U.S. Pat. No. 3,589,355.
The vas deferens may be surgically severed and hollow plastic tubes attached to the two ends. These tubes may then be connected by a solid plug to prevent sperm transport. A hollow plug may be inserted to surgically reverse the procedure. This is disclosed in U.S. Pat. No. 3,990,434.
The vas deferens need not be completely severed, but only surgically slit to insert a cylindrical plug, which is attached through the slit to a hollow cylinder surrounding the vas deferens. The use of this device, discussed in U.S. Pat. No. 4,200,088, is said to cause less damage to the muscles of the vas deferens, increasing the chances the operation may be successfully reversed and fertility restored.