Word of the Month: Bossi Dilator

Our Word of the Month for April is Bossi’s Dilator.

One glance is all you need to tell that a Bossi Dilator is a pretty grim looking instrument. Dating back to late 19th century, the Bossi dilator was used to open the cervix during examinations and childbirth.  This model was designed by L.M. Bossi, professor of obstetrics and gynaecology at the University of Genoa in 1892. Bossi endorsed his four-bladed design, pointing to its removable lipped caps that helped maintain its position within the cervix and provide greater degrees of dilatation.


The dilator features a complex pivot and thumbscrew arrangement which controls the blades when in use on a patient. These tools were used where a speedy delivery was the priority rather than patient comfort.

These instruments were used toward the end of the 18th century to achieve rapid delivery in cases of eclampsia and antepartum haemorrhage. Bossi produced three, four and eight blade versions of his instrument. The extra blades were designed to distribute the stretching force of the instrument more evenly, which would in theory reduce trauma to the cervix. However, there is no evidence that this goal was ever reached and the resultant trauma to the patient was often more harmful than the condition the instruments were made to treat.

A four-bladed Bossi Dilator from the RCOG Museum collection. The caps at the end were designed to go over the ends of each blade to help hold the dilator in the cervical canal. This model was meant to be easier to control and assemble as well as easier to clean.

Scottish Obstetrician John William Ballantyne (1861–1923) wrote up eight cases he had witnessed where the Bossi Dilator was used, for the Edinburgh Obstetrical Society in 1904. He called the Bossi Dilator ‘an exceptional remedy for exceptional conditions’. Ballantyne identified two major problems with the tool: one was the risk of severe laceration of the cervix and the second the risk of sepsis as the instrument was notoriously hard to keep clean.

Instruments like these were phased out by the development of safer methods for handling difficult births, such as by Caesarean section.

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