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Acetabular Morphotype Is Associated with Change in Acetabular Orientation Between Supine and Standing
Camille Vorimore1,2, Jeroen C F Verhaegen1,3,4, Chuan Kong1,5
1Department of Orthopaedic Surgery, The Ottawa Hospital, Ottawa, Ontario, Canada.
JB & JS Open Access
|July 10, 2026
Summary
Standing pelvic radiographs may offer a more accurate assessment of acetabular parameters due to compensatory mechanisms related to pelvic tilt (PT) changes. This study found that acetabular measurements vary between supine and standing positions, influenced by hip morphotype.
Area of Science:
- Orthopedic surgery
- Radiology
- Biomechanical analysis
Background:
- The optimal functional position (supine vs. standing) for radiographic assessment of the native acetabulum remains debated.
- Pelvic tilt (PT) significantly influences radiographic acetabular measurements.
- Understanding posture-related changes is crucial for accurate hip joint evaluation.
Purpose of the Study:
- To quantify changes in pelvic tilt (PT) from supine to standing in volunteers and patients.
- To assess alterations in acetabular parameters between supine and standing radiographic positions.
- To determine if changes in acetabular parameters vary based on acetabular morphotype.
Main Methods:
- Prospective cohort study involving 105 asymptomatic volunteers and 437 patients with no osteoarthritis.
- Standardized supine and standing anteroposterior pelvic radiographs were obtained.
- Pelvic tilt (PT) quantified by sacrofemoral-pubic (SFP) angle; acetabular morphotype classified using Ottawa criteria.
Main Results:
- Mean SFP angle decreased by -3.7° from supine to standing, indicating a change in pelvic tilt.
- Acetabular measurements showed no significant differences in change between volunteers and patients transitioning between positions.
- Anteroposterior coverage measurements changed significantly (p < 0.001), while lateral coverage changed minimally.
- Anterior dysplasia patients exhibited smaller PT changes (ΔSFP -1.5°) compared to others.
Conclusions:
- Comparable changes in PT and acetabular parameters were observed between supine and standing positions across groups.
- The magnitude and direction of positional changes are linked to acetabular morphology and compensatory mechanisms.
- Standing radiographs are suggested for acetabular assessment as they better reflect compensatory mechanisms.
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