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An index for diagnosing infant hip dysplasia using 3-D ultrasound: the acetabular contact angle
Myles G Mabee1, Abhilash Rakkunedeth Hareendranathan2, Richard B Thompson3
1Department of Radiology and Diagnostic Imaging, University of Alberta, 2A2.42 Walter Mackenzie Health Sciences Centre, Edmonton, Alberta, T6G 2B7, Canada. mmabee@ualberta.ca.
Insights
Three-dimensional (3-D) ultrasound reliably measures the acetabular contact angle (ACA) for diagnosing developmental dysplasia of the hip (DDH). This 3-D ultrasound method offers improved accuracy over traditional 2-D ultrasound for assessing infant hip dysplasia.
Area of Science:
- Medical Imaging
- Orthopedics
- Pediatric Diagnostics
Background:
- Developmental dysplasia of the hip (DDH) is a common infant condition requiring early treatment to prevent long-term complications like osteoarthritis.
- Current 2-D ultrasound diagnostic methods for DDH exhibit significant inter-scan variability, potentially impacting diagnostic reliability.
- Three-dimensional (3-D) ultrasound offers a potential improvement for assessing hip joint morphology and reliability in DDH diagnosis.
Purpose of the Study:
- To quantify developmental dysplasia of the hip (DDH) using the 3-D ultrasound-derived acetabular contact angle (ACA).
- To assess the reliability and diagnostic utility of the ACA measurement compared to traditional 2-D ultrasound methods.
- To evaluate the effectiveness of 3-D ultrasound in improving the diagnosis of infant hip dysplasia.
Main Methods:
- Prospective data collection from 114 hips in 85 children across normal, borderline, and dysplastic diagnostic groups.
- Custom software used for automated 3-D surface model generation and ACA calculation from 3-D ultrasound scans.
- Inter-observer and inter-scan variability assessed using repeatability coefficients; ROC curves generated for diagnostic accuracy.
Main Results:
- The 3-D ultrasound acetabular contact angle (ACA) demonstrated high reproducibility (95% within 6° for same scan, 9° for different scans).
- ACA showed significantly better reliability than the 2-D ultrasound alpha angle (9° vs. 14° inter-scan variability, P < 0.001).
- Receiver operating characteristic (ROC) analysis indicated superior diagnostic accuracy for ACA (0.954) versus the alpha angle (0.927).
Conclusions:
- Three-dimensional ultrasound measurement of the acetabular contact angle (ACA) is significantly more reliable than the 2-D ultrasound alpha angle.
- The ACA measurement demonstrates promising diagnostic utility for developmental dysplasia of the hip (DDH) with slightly higher accuracy.
- Further research into 3-D ultrasound for diagnosing and monitoring infant hip dysplasia is warranted.
Background:
Developmental dysplasia of the hip (DDH) is a common condition that is highly treatable in infancy but can lead to the lifelong morbidity of premature osteoarthritis if left untreated. Current diagnostic methods lack reliability, which may be improved by using 3-D ultrasound.
Objective:
Conventional 2-D US assessment of DDH has limitations, including high inter-scan variability. We quantified DDH on 3-D US using the acetabular contact angle (ACA), a property of the 3-D acetabular shape. We assessed ACA reliability and diagnostic utility.
Materials And Methods:
We prospectively collected data from January 2013 to December 2014, including 114 hips in 85 children divided into three clinical diagnostic groups: (1) normal, (2) initially borderline but ultimately normal without treatment and (3) dysplastic requiring treatment. Using custom software, two observers each traced acetabula twice on two 3-D US scans of each hip, enabling automated generation of 3-D surface models and ACA calculation. We computed inter-observer and inter-scan variability of repeatability coefficients and generated receiver operating characteristic (ROC) curves.
Results:
The 3-D US acetabular contact angle was reproduced 95% of the time within 6° in the same scan and within 9° in different scans of the same hip, vs. 9° and 14° for the 2-D US alpha angle (P < 0.001). Areas under ROC curves for diagnosis of developmental dysplasia of the hip were 0.954 for ACA and 0.927 for alpha angle.
Conclusion:
The 3-D US ACA was significantly more reliable than 2-D US alpha angle, and the 3-D US measurement predicted the presence of DDH with slightly higher accuracy. The ACA therefore shows promising initial diagnostic utility. Our findings call for further study of 3-D US in the diagnosis and longer-term follow-up of infant hip dysplasia.
