Limb length disparity is a frequent complication after hip surgery inducing many surgeon-patients conflicts. To date no study has been able to precisely quantify such limb length disparity. EOS® system, currently validated to measure lower limb parameters, allows from two bi-dimensional numerical orthogonal radiographies in standing position to obtain a tri-dimensional reconstruction of lower limbs. A computerized system achieves the parameters calculation.

The aim of this study is to precisely measure the limb length disparities and the other hip parameters following total hip arthroplasty surgical procedure, by using a standard X-rays and using EOS® three-dimensional reconstructions.

Twenty-eight patients programmed for total hip arthroplasty have been included (i.e. thirty lower limbs). Two independent performers have carried out twice the measures either on standard X-rays and using three-dimensional reconstructions of the lower limb disparities prior and after the surgical procedure.

The inter and intra-observer reproducibility for the measure of the lower limb disparities have been of the EOS® measures have been respectively of 0.854 and 0.865 and for the standard X-rays of 0.717 and 0.726.

Mean length disparity observed was before Total Hip Arthroplasty of −0.328 cm (0.705; −1.266/0.530) and was of 0.088 mm (1.326; −1.635/0.632) after. We are able to decrease the lower limbs disparity in 69.1% and for the average of 0,416cm.

Using EOS® system has allowed assessing with greater precision the possibility to restore equal lower limb length.

This assessment has permitted introducing a new planning procedure including EOS® imaging associated to the fusion of the prosthetic tri-dimensional image in order to achieve adequate lower limb length.