Acetabular version and long posterior wall cup in total hip replacement.

This study discusses the definition of operative, anatomic and radiographic acetabular anteversion and their effect on a long posterior wall cup. In this cadaveric study, anteversion was modelled radiographically with a Charnley double wire marker Long Posterior Wall (LPW) cup and the position of the long posterior wall was studied with relation to different anteversion angles, and also correlated with computer generated line diagrams of the acetabular cup. The position of a long posterior wall varies when different types of anteversion are applied. By increasing the operative anteversion the long posterior wall comes to lie inferiorly and the advantage of the long posterior wall is lost. In light of prior confusion with definitions and in an attempt to make the terms more relevant to the surgical technique we propose the simplified alternate terms of 'flexion-anteversion' previously called 'operative anteversion', 'internal rotation-anteversion' previously called 'anatomic anteversion' and 'combined anteversion' previously called 'radiographic anteversion'. If the surgeon elects to use LPW it is important to understand the effect of each type of anteversion on eventual position of the raised wall.