Rapid dilatation of the cervix is usually not difficult when one uses half graduated cervical dilators. It becomes even easier when the woman has been treated with 200 micrograms of misoprostol a few hours prior to the procedure. However once in a while one comes across a case in which the cervix refuses to get dilated beyond a certain size. If the intrauterine procedure planned cannot be achieved through the dilatation achieved, one is forced to try and achieve more dilatation of the cervix. What happen in such cases is as shown in 'A' of the following diagram.
With traction on the vulsellum applied to the anterior lip of the cervix (black arrow) and inward push on the cervical dilator (red arrow), the cervix tends to tear along the direction of the interrupted blue arrow, or the vulsellum cuts through the cervix and tears it at the site of its bite.
Considering the vectors at work, the only way to avoid both of these complications and achieve cervical dilatation is to apply one Allis' forceps on the anterior lip of the cervix, another on the posterior lip of the cervix, and then dilate the cervix, making traction on both of the Allis' forceps simultaneously. As shown in 'B' of the diagram above, the vectors of traction on cervix with Allis' forceps nullify each other, so that the push of the dilator acts along the cervical canal and cervix dilates without tear or cutting out of the instrument on the cervix.
With traction on the vulsellum applied to the anterior lip of the cervix (black arrow) and inward push on the cervical dilator (red arrow), the cervix tends to tear along the direction of the interrupted blue arrow, or the vulsellum cuts through the cervix and tears it at the site of its bite.
Considering the vectors at work, the only way to avoid both of these complications and achieve cervical dilatation is to apply one Allis' forceps on the anterior lip of the cervix, another on the posterior lip of the cervix, and then dilate the cervix, making traction on both of the Allis' forceps simultaneously. As shown in 'B' of the diagram above, the vectors of traction on cervix with Allis' forceps nullify each other, so that the push of the dilator acts along the cervical canal and cervix dilates without tear or cutting out of the instrument on the cervix.
