Does hemipelvis structure and position influence acetabulum orientation?

Area of Science:

• Anatomy
• Biomechanics
• Radiology

Background:

• Acetabulum orientation is anatomically and radiographically established, yet its relationship with the innominate bone is under-explored.
• Investigating this relationship may elucidate the pathomechanisms of complex hip disorders such as femoroacetabular impingement (FAI).
• This study aimed to evaluate the influence of pelvic bone position and structure on acetabular spatial orientation.

Purpose of the Study:

• To describe the relationship between innominate bone structure and acetabular orientation.
• To explore the clinical implications of this relationship for hip disorders.

Main Methods:

• Retrospective analysis of computed tomography (CT) scans from 31 male pelvises, creating 3D models.
• Measurement of acetabular orientation (inclination, tilt, anteversion) and pelvic parameters (iliac opening/tilt angles, ISD, ITD, HP, and ratios).
• Statistical analysis using Pearson's and Spearman's correlation to assess relationships between acetabular angles and pelvic measurements.

Main Results:

• Significant positive correlation found between acetabular anteversion and iliac opening angle in the horizontal plane.
• Significant positive correlation observed between acetabular inclination and iliac tilt angle in the frontal plane.
• Acetabular inclination also positively correlated with the interspinous distance/intertuberous distance/height of the pelvis (ISD/ITD/HP) ratio.

Conclusions:

• Hemipelvic structure and acetabular orientation are significantly correlated under anatomical conditions, particularly in frontal and horizontal planes.
• Innominate bone tilt influences acetabular axis orientation: downward tilt leads to a more caudal axis (AP view), while the horizontal relationship is reversed.
• Findings provide a basis for understanding the pelvis's role in common hip disorders.