Ilio-femoral impingement angle: a new radiographic measurement.

Background: Hip dislocations after total hip arthroplasty (THA) are a debilitating complication, often occurring in deep flexion. Current 3D modelling allows for simulating the flexion angle at which bone-on-bone impingement occurs, but it is resource-intensive and not widely available for routine clinical use. Therefore, we propose the ilio-femoral impingement angle (IFIa) as a novel, simple radiographic measure to help identify patients at higher risk for dislocation using standard radiographs.