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Updated: Jan 10, 2026
In Vivo Quantification of Hip Arthrokinematics during Dynamic Weight-bearing Activities using Dual Fluoroscopy
Published on: July 2, 2021
Sagittal Orientation of the Acetabulum and Its Relationship to Spinopelvic Alignment: Three-Dimensional Assessment of
Munif A Hatem1, Mohammadreza Movahhedi1, Jin-Young Kim1
1Department of Orthopaedic Surgery and Sports Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
Background:
The orientation of the acetabulum in the axial and coronal planes is well studied in the pathogenesis of impingement and instability of the hip. In contrast, the sagittal orientation of the acetabulum (SOA) is not well understood.
Purpose:
To determine (1) the SOA in a large cohort of mature hips and (2) to assess the relationship between the SOA and acetabular version, acetabular center-edge angles (CEAs), and spinopelvic alignment.
Study Design:
Descriptive laboratory study.
Methods:
A total of 3695 patients (7390 mature hips) who underwent computed tomography (CT) scans for assessment of nonorthopaedic abdominal and pelvic conditions were studied. An automated measurement software was utilized to reconstruct 3-dimensional models from CT scans and to measure the SOA, functional SOA (not neutralizing pelvic position on sagittal plane), acetabular version, as well as acetabular CEAs and spinopelvic alignment, including the pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI).
Results:
The SOA was on average (± SD) 19.6°± 7.5°. The functional SOA (not neutralizing pelvic position on sagittal plane) was on average (± SD) 20.5°± 5.7°. The functional SOA had a statistically significant but negligible correlation with PI (r = 0.13; P < .001) and SS (r = -0.06; P < .001), and a weak positive correlation with PT (r = 0.23; P < .001). The SOA had a positive moderate correlation with the cranial (r = 0.41; P < .001) and central acetabular version (r = 0.39; P < .001) and a strong correlation (r = 0.63; P < .001) with caudal acetabular version. A 10° increase in SOA was associated with a 6.6° increase on the caudal acetabular version. The SOA had a moderate negative correlation (r = -0.48; P < .001) with the CEA at 3 o'clock (anterior for left and right hips). A 10° increase in SOA was associated with a 4.9° decrease in CEA at 3 o'clock.
Conclusion:
The acetabulum is on average 19.5° cephalically oriented in the sagittal plane in asymptomatic individuals. The SOA correlates with acetabular version and cannot be presumed based on spinopelvic alignment.
Clinical Relevance:
The assessment of the SOA may aid in the diagnosis of hip impingement and instability, allowing a more precise correction of the acetabulum in hip arthroscopy and osteotomies.
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