The Effect of Functional Pelvic Tilt on the Three-Dimensional Acetabular Cup Orientation in Total Hip Arthroplasty Dislocations

BackgroundAnterior and posterior pelvic tilt appears to play a role in total hip arthroplasty (THA) stability. When changing from the standing sitting position, pelvis typically rotates posteriorly while hips flex this affects femoro-acetabular positions. This case-control study compares changes 3-D acetabular cup orientation during functional between THA dislocations vs stable THAs.MethodsStanding was compared fifteen 233 prospectively followed THAs. calculated using previously validated trigonometric algorithms on biplanar radiographs. Those combine angles three anatomical planes (coronal inclination, transverse version, sagittal ante-inclination) position with change calculate position.ResultsThe of dislocated THAs only characterized by lower coronal inclination (P = .039). Compared controls, sitting, they showed less < .001). led significant .001) ante-inclination but similar version .366).ConclusionsComparing THAs, there is increase all sitting. leads decreased which may lead an increased risk impingement ensued instability. By contrast, not significantly different both confirms importance data orientation.Level EvidenceDiagnostic, Level III.