Acetabular Morphology and Spinopelvic Characteristics: What Predominantly Determines Functional Acetabular Version?

Area of Science:

• Orthopedics
• Biomechanical analysis
• Hip morphology

Background:

• Acetabular version measurement is influenced by acetabular rim size, pelvic positioning, and the calculation plane.
• Understanding these factors is key for accurate assessment of hip joint morphology.

Purpose of the Study:

• To quantify the impact of pelvic and acetabular characteristics on morphological and functional acetabular version.
• To differentiate between version measured relative to the anterior pelvic plane angle (APPA) and the horizontal table.

Main Methods:

• Cross-sectional study involving 50 acetabular dysplasia patients and 109 controls.
• 2D CT scans analyzed for pelvic incidence, tilt, sacral slope, APPA, morphological/functional acetabular versions, and subtended angles.
• Correlation and multivariable regression analyses used to identify predictors of acetabular version.

Main Results:

• Morphological version correlated with subtended angle differences (R=0.68, R=0.57).
• Functional version correlated with pelvic tilt angle (R=0.56) and subtended angle differences (R=0.61, R=0.50).
• Multivariate models predicted morphological (R²=0.44) and functional version (R²=0.58), with pelvic tilt angle being the strongest predictor for functional version.

Conclusions:

• Functional acetabular version is primarily determined by pelvic tilt angle, not acetabular rim prominence.
• Pre-operative assessment of pelvic mobility in functional positions is recommended for version abnormalities.
• Corrective osteotomy is suggested for patients with minimal dynamic pelvic tilt changes to improve functional version.