To demonstrate the reliability of the EOS imaging system in measuring the internal diameters of the bony pelvis.

A prospective study comparing the results of the pelvimetry of 18 dry pelvises carried out on the EOS imaging system to measurements taken manually and using the two current gold standard CT methods. Pelvimetric measurements of each pelvic bone were obtained using four methods and compared: direct manual measurements, spiral and sequential CT pelvimetry, and 2D-3D low-dose biplanar X-rays. The various obstetric diameters were measured to the millimetre and compared.

There was no significant difference in the different diameters assessed, with the exception of the interspinous diameter. There was a highly significant correlation (P<0.001) between the values measured manually and by EOS for the Magnin index (Pearson=0.98), the obstetric conjugate diameter (Pearson=0.99), and the median transverse diameter (Pearson=0.87).

The EOS imaging system allows for an ex vivo determination of the obstetrical diameters that is reliable enough to estimate obstetric prognosis, producing comparable measurements to CT. In view of concerns about protection from radiation, this low-dose imaging technique could become, after in vivo prospective validation, the new gold standard for pelvimetry and therefore a good alternative to CT.