title: Placement of the acetabular component.
abstract: Ideal placement of the acetabular component remains elusive both in terms of defining and achieving a target. Our aim is to help restore original anatomy by using the transverse acetabular ligament (TAL) to control the height, depth and version of the component. In the normal hip the TAL and labrum extend beyond the equator of the femoral head and therefore, if the definitive acetabular component is positioned such that it is cradled by and just deep to the plane of the TAL and labrum and is no more than 4mm larger than the original femoral head, the centre of the hip should be restored. If the face of the component is positioned parallel to the TAL and psoas groove the patient specific version should be restored. We still use the TAL for controlling version in the dysplastic hip because we believe that the TAL and labrum compensate for any underlying bony abnormality. The TAL should not be used as an aid to inclination. Worldwide, > 75% of surgeons operate with the patient in the lateral decubitus position and we have shown that errors in post-operative radiographic inclination (RI) of > 50° are generally caused by errors in patient positioning. Consequently, great care needs to be taken when positioning the patient. We also recommend 35° of apparent operative inclination (AOI) during surgery, as opposed to the traditional 45°.
authors.affiliation: Musgrave Park Hospital, Belfast Health and Social Care Trust, Stockman's Lane, Belfast BT9 7JB, UK.
authors.forename: D E
authors.initials: DE
authors.lastname: Beverland
authors.affiliation: Musgrave Park Hospital, Belfast Health and Social Care Trust, Stockman's Lane, Belfast BT9 7JB, UK.
authors.forename: C K J
authors.initials: CK
authors.lastname: O'Neill
authors.affiliation: Queen's University Belfast, Ashby Building, Stranmillis Road, Belfast BT9 5AH, UK.
authors.forename: M
authors.initials: M
authors.lastname: Rutherford
authors.affiliation: Musgrave Park Hospital, Belfast Health and Social Care Trust, Stockman's Lane, Belfast BT9 7JB, UK.
authors.forename: D
authors.initials: D
authors.lastname: Molloy
authors.affiliation: Musgrave Park Hospital, Belfast Health and Social Care Trust, Stockman's Lane, Belfast BT9 7JB, UK.
authors.forename: J C
authors.initials: JC
authors.lastname: Hill
mesh_terms: D000077:Acetabulum; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D006622:Hip Prosthesis; D006801:Humans; D056888:Patient Positioning
keywords: Acetabular cup orientation; patient positioning; pelvic orientation; total hip arthroplasty