In total hip arthroplasty (THA), a high radiographic inclination angle (RI) of the acetabular component has been linked to an increased dislocation rate, liner fracture, and increased wear. In contrast to version, we have more proven boundaries when it comes to a safe zone for angles of RI. Although intuitively it seems easier to achieve a target RI, most studies demonstrate a lack of accuracy and the trend towards a high RI with all surgical approaches when using a freehand technique or a mechanical guide. This is due to pelvic motion during surgery, which can be highly variable. The current study had two primary aims, each with a different primary outcome. The first aim was to determine how accurate a surgeon could obtain the target operative inclination (OI) during THA when using a cementless cup using a digital protractor. The second aim was to determine how accurate a surgeon can estimate the target OI to obtain a RI of 40° based on the patient's hip circumference as demonstrated in a previous study. In this prospective study, we included 200 consecutive patients undergoing uncemented primary THA in the lateral decubitus position using a posterior approach. Preoperatively, the surgeon determined the target OI based on the patient's hip circumference (22.5°, 25°, 27.5° or 30°). Intraoperatively, the effective OI was measured with the aid of a digital inclinometer after seating of the acetabular component. Six weeks postoperatively anteroposterior pelvic radiographs were made and two evaluators, blinded to the effective OI, measured the RI of the acetabular component. The safe zone for inclination was defined as 30°-45° of inclination.Introduction
Methods
