Why is the Catholic teaching that Mary's hymen remained intact during childbirth important?

I am asking this question because the entire comment thread in which I asked the question appears to have gone missing, including references to Aquinas (*Summa Theologica* q. 35 a. 6 ), Ludwig Ott (*Fundamentals of Catholic Dogma* bk. 3, pt. 3, ch. 2, §5, 2.), Pohle (*Mariology* pt. 2, ch. 1, §3, Theses II), and others. Wikipedia lists St. Lucia of Syracuse (283-304) as the patron saint of of the blind within Roman Catholicism. She is venerated, along with St. Agnes (patron saint of virgins) among Roman Catholics, Anglican, Lutheran, and Eastern Orthodox churches. She is one of only 8 women explicitly commemorated by Roman Catholics in the Canon of the Mass. There is, within the tradition regarding St. Lucia, the possibility that she was assigned to defilement within a brothel by the Governor of Syracuse. Paschasius ordered her to burn a sacrifice to the emperor's image. When she refused, Paschasius sentenced her to be defiled in a brothel; a particularly heinous crime against someone who had dedicated her chastity to God. In a question regarding the Catholic tradition that Mary (Jesus' mother) did not suffer pain in childbirth (https://christianity.stackexchange.com/questions/7451/where-does-the-catholic-tradition-that-mary-did-not-have-pain-giving-birth-to-je?noredirect=1#comment225832_7451) , included in the comments of a particular answer, came the assertion that, even if Lucia was raped and even if she had survived and produced a child from this violation, she would still be honored by name in the Catholic Mass as a martyred virgin even though her bodily integrity was ruined . This was explained as because an intact hymen is accidental to virginity while the commitment of the will is essential to virginity. In other words the taking of sexual liberty by force and against one's will does nothing to impinge upon one's state of virginity even though it may change the state of one's bodily integrity. Therefore the state of one's bodily integrity has nothing to say, directly, to one's virginal condition. The reference to St. Lucia came about as the bodily integrity of Mary (i.e. no ruptured hymen in childbirth) was indicated as integral to her "perpetual virginity" which is in turn linked to her sinlessness which is in turn linked to her painless childbirth. It seems to me, however, that if an intact hymen is accidental to virginity then a ruptured hymen must surely be accidental to the birth of a virginally conceived child. If St. Lucia would still retain her virginal status in the eyes of the Catholic Church regardless of the state of her bodily integrity following rape, why is it so important for Mary's bodily integrity to remain intact as regards her "perpetual" virginity during childbirth?