The EOS imaging system for understanding a patellofemoral disorder following THR.

An aspect of patellofemoral syndrome secondary to total hip replacement (THR) is mainly suggestive of a problem of femoral implant torsion. We here present the first reported case of patellofemoral syndrome secondary to THR relating to limb-length discrepancy, with no abnormality of femoral torsion. The pelvis adapted to the length inequality by axial rotation rather than frontal tilt, and this went undetected on standard X-ray and CT-scan. 3D imaging in upright posture on the EOS system enabled the situation to be clearly described and analyzed, and adapted surgical correction to be indicated.