Pelvic Tilt Cannot Be Accurately Predicted Using Anteroposterior Radiographs

Pelvic positioning during total hip arthroplasty (THA) can affect the functional position of the acetabular component. A comprehensive understanding of pelvic orientation prior to THA is necessary to allow for proper cup positioning and mitigate the risks of complications associated with component malpositioning. Measurements using anteroposterior (AP) radiographs have been described as an effective means of accurately predicting pelvic functional orientation. The purpose of our study was to describe the accuracy of assessing pelvic tilt using AP radiographs alone. METHODS: An online survey was created and sent to a cohort of fellowship-trained adult reconstruction surgeons. The survey consisted of 65 standing AP pelvis radiographs. Participants were asked to score each radiograph as 1) anterior pelvic tilt > 10 degrees, 2) posterior pelvic tilt > 10 degrees, or 3) neutral. Responses were then compared to measurements of pelvic tilt made on lateral standing pelvic radiographs. Categorical and continuous variables were compared using chi-squared, unpaired, two-tailed student’s T tests, and ANOVA. RESULTS: 135 surgeons completed the survey. The average correct predictive value of pelvic tilt between all surgeons was 53.2%. 51.2% of responding surgeons performed greater than 100 cases per year. 50% of surgeons reported that they were “not so familiar” or “somewhat familiar” with the principles of spinopelvic mobility. 43.5% of surgeons reported that they did not routinely use spinopelvic mobility principles in THA planning. DISCUSSION: The standing AP pelvis radiograph is poorly predictive of pelvic tilt. Pre-operative evaluation of spinopelvic parameters requires AP and lateral pelvic views for detailed assessment and accurate pre-operative planning.