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Normal values and variation of radiographic and CT infant lateral iliac wall angles in normal and dysplastic hips
Vimarsha G Swami1, Lei Liu1, Myles Mabee2
1Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton - Canada.
Insights
The infant lateral iliac wall angle, measured via radiography, shows high reliability for assessing developmental dysplasia of the hip (DDH). This angle provides a stable reference for 3-D ultrasound imaging in pediatric hip assessment.
Area of Science:
- Orthopedics
- Radiology
- Medical Imaging
Background:
- 3-D ultrasound shows promise for developmental dysplasia of the hip (DDH) assessment.
- Accurate spatial orientation is crucial for 3-D ultrasound analysis.
- The lateral iliac wall angle is a potential reference axis for determining spatial orientation.
Purpose of the Study:
- To quantify normal values and variations of the infant lateral iliac wall angle using radiography.
- To compare radiographic measurements with computed tomography (CT) findings.
- To evaluate the reliability of the lateral iliac wall angle as a reference axis.
Main Methods:
- Pelvic radiographs and coronal CT scans of 200 and 20 infants (0-12 months), respectively, were analyzed.
- Acetabular and lateral iliac angles were measured.
- Statistical analyses included linear regression, t-tests, correlation coefficients, and intra-class correlation coefficients (ICC).
Main Results:
- The radiographic iliac angle averaged 53-56° in both DDH and normal hips, with high inter-reader (ICC=0.946) and intra-reader (ICC=0.965) reliability.
- Measurements showed weak correlation with age (r=0.25) and no significant difference between sexes.
- CT measurements showed a mean difference of 5.8° compared to radiographs (r=0.68).
Conclusions:
- The infant lateral iliac wall angle is a reliable radiographic measurement with a consistent range of variation (±15°).
- It serves as an unbiased reference axis, suitable for establishing spatial orientation in 3-D hip ultrasound.
- This finding supports its potential utility in DDH assessment using advanced imaging techniques.
Purpose:
Indices from 3-D ultrasound may have a role in developmental dysplasia of the hip (DDH) assessment, but require a way to determine spatial orientation relative to body axes. The lateral iliac wall angle is a potentially suitable reference axis in 3-D ultrasound. We sought to quantify normal values and variations of the infant iliac wall angle on radiography, and compare with computed tomography (CT).
Methods:
Acetabular and lateral iliac angles were measured on frontal pelvic radiographs of 200 patients (400 hips, 183 with DDH) and coronal CT of 20 patients (40 hips) aged 0-12 months. Relationships among morphologic indices and demographics were assessed using linear regression, Welch's t-test, Pearson's correlation coefficient (r) and coefficients of variance (CoV). Reliability was assessed using intra-class correlation coefficients (ICC).
Results:
The radiographic iliac angle averaged 53.0° ± 7.7° (mean ± standard deviation; 95% CI, 38°-68°) in DDH vs. 56.2° ± 6.7° (95% CI, 43°-69°) in normal hips (p<0.001), correlated weakly with age (r = 0.25), and showed no inter-sex differences (p = 0.79). Inter-reader and intra-reader reliability were ICC = 0.946 and 0.965. CT iliac angle had mean difference 5.8° ± 6.2° (p<0.01), CoV = 10% and r = 0.68 vs. corresponding radiographs.
Conclusions:
The radiographic infant lateral iliac wall angle has mean value 53-56° in dysplastic and normal hips with consistent range of variation approximately ±15°, was measured with high reliability, does not differ by sex, and is only slightly lower in the youngest infants. The iliac wall angle is an unbiased reference axis that may be suitable to establish general spatial orientation of 3-D hip ultrasound images.
