The condition of penis captivus has been reported in the literature for many years, although descriptions vary somewhat as to predisposing factors, anatomy, and physiologic mechanisms involved. The famous obstetrician Scanzoni felt that the vagina contracted and locked the penis in. (Scanzoni is probably most famous for his vitriolic attacks on Semmelweis after Semmelweis suggested that obstetricians wash their hands prior to examining a patient.) It was in 1872 that Hildebrandt first suggested that the mechanism consisted of a spasm of the levator ani muscle and spasm of the constrictor cunni muscles (bulbospongiosi). Hildebrandt also gave a case history from his gynecologic practice that was similar, although not an exact duplicate, to the case described by E.Y. Davis. In Hildebrandt's case the female had been suffering from vaginismus (spasm of the bulbospongiosi, preventing entrance of the penis) since her wedding night and was said to be a very nervous and excitable person. However, Hildebrandt stated that the couple freed themselves after their unfortunate experience with penis captivus and he had only the history that the woman had given to him.

The anatomy involved is well described by Lachman, who in a recent letter to JAMA appeared to accept the documentation of cases of penis captivus. He states that the pubococcygeus part of the levator ani is the most important muscle in this condition, although the bulbospongiosus and the urogenital diaphragm also contribute. Lachman feels that the contraction of the muscle tissue in the vagina contributes little to the condition. The mechanism is described as being a dilation of the inner two thirds of the vagina (caused by the elevation of the uterus into the false pelvis) and a constriction of the lower third by the muscles mentioned above. This then causes venous engorgement of the penis and the formation of a "lock and turned key" situation with the engorged penis being inside a dilated cavity yet being pulled against a narrowed orifice in the attempt to remove the organ from the vagina. The fact there is generalized muscle spasm during sexual intercourse has been well documented by Masters and Johnson. The theory that the perineal muscle spasm was the result of spread from other muscle spasms was probably first postulated by Hildebrandt in his article.

Most authors agree that the condition of penis captivus is found only in cases where the female has a prolonged history of vaginismus. When penis captivus occurs it is necessary for the spasm of vaginismus to begin after the act of penetration has been successfully completed. Supposedly the vaginismus has a psychologic etiology. It is this point of time relationship and the male reaction to the spasm that causes the authors' doubts as to the validity of penis captivus as a true entity. Vaginismus is, indeed, a well-known clinical entity, but in the original article that gave the name "vaginismus" to this condition of perineal muscle spasm the type of vaginismus described by Davis and Hildebrandt was not mentioned. The original cases of vaginismus all happened in women who had muscle spasm of severe degree at the first attempt at sexual intercourse. It is the senior author's personal opinion that it is highly improbable for spasm of the pubococcygeus and bulbospongiosus to be severe enough after penetration to cause penis captivus. We also feel that the normal male response to a contraction of this type would be relaxation of the penis, allowing withdrawal.