Increased anterior pelvic tilt in patients with acetabular retroversion compared to the general population: A radiographic and prevalence study

Abstract

Introduction: The prevalence of acetabular retroversion is sparsely investigated. It may be associated with increased anterior pelvic tilt. The purpose of this study was to investigate whether patients with symptomatic and radiographically verified acetabular retroversion demonstrated increased anterior pelvic tilt compared to a control group, and furthermore to evaluate the prevalence of acetabular retroversion in the general population.

Methods: Anteroposterior pelvic radiographs in standing position of 111 patients with acetabular retroversion prior to anteverting periacetabular osteotomy (PAO) and 132 matched controls from the general Danish population were assessed. Pelvic tilt was assessed by the sacrococcygeal joint-symphysis distance and pelvic-tilt-ratio. Acetabular retroversion was defined as positive cross-over sign and posterior wall sign. Prior to assessments, interrater reliability analysis was performed. Measurements were agreed by two independent assessors. A nonparametric regression model was used to test between-group differences in median pelvic tilt. The prevalence was calculated as the ratio of subjects and hips with acetabular retroversion, respectively.

Results: The patient group had significantly larger median anterior pelvic tilt of 14.3 mm in sacrococcygeal joint-symphysis distance and -0.08 in pelvic-tilt-ratio, compared to controls. The prevalence of subjects in the general population with either unilateral or bilateral acetabular retroversion was 24% and 18% for all hips.

Conclusion: Our data demonstrated that patients with symptomatic acetabular retroversion have increased anterior pelvic tilt compared to the general population. Radiographic sign of acetabular retroversion was highly prevalent in the general population.

Implication for practice: Increased anterior pelvic tilt should be considered when diagnosing and treating patients with hip pain, as symptoms may be related to the functional position of the pelvis and not necessarily solely come from the radiographic verified acetabular retroversion.

Keywords: Femoroacetabular impingement; Hip; Pelvis; Retroversion; Tilt; X-ray.