Abstract
Intraoperative fluoroscopy can improve the precision of acetabular component positioning during direct anterior hip arthroplasty. However, changes in pelvic tilt with c-arm positioning may compromise accuracy. A geometric model of an acetabular component's projection onto fluoroscopy images was created and manipulated to simulate c-arm tilt. An apparently ideally-placed cup will have its effective anteversion changed by 7.5° with just 10° of caudal/cephalad tilt of the c-arm. This effect is greater in cups that are more horizontally placed or less anteverted. Accurate c-arm positioning is crucial, as small errors in tilt can have considerable effects on final cup position.