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Evaluation of Operator Variability and Validation of an AI-Assisted α-Angle Measurement System for DDH Using a
Yusuke Ohashi1, Tomohiro Shimizu1, Hidenori Koyano2
1Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan.
Bioengineering (Basel, Switzerland)
|September 27, 2025
Summary
Operator variability in hip ultrasound for developmental dysplasia of the hip (DDH) is a challenge. An AI-assisted system using dynamic ultrasound analysis significantly improved measurement accuracy and consistency, enhancing reliability in DDH screening.
Area of Science:
- Medical Imaging
- Artificial Intelligence
- Pediatric Orthopedics
Background:
- Ultrasound using the Graf method is standard for developmental dysplasia of the hip (DDH) detection.
- Significant intra- and inter-operator variability limits the reliability of manual hip ultrasound assessments.
- Automated measurement systems are needed to enhance reproducibility in DDH screening.
Purpose of the Study:
- To quantify operator variability in hip ultrasound assessments for DDH.
- To validate an AI-assisted system for automated alpha-angle measurement.
- To improve the reproducibility and reliability of hip ultrasound in DDH screening.
Main Methods:
- Thirty participants (clinicians, residents, students) performed hip ultrasound scans on a standardized infant hip phantom.
- Analysis included examination time, iliac margin inclination, and alpha-angle measurements to assess variability.
- An AI system was developed for automated landmark detection and alpha-angle calculation from static images and dynamic videos.
Main Results:
- Clinicians showed shorter examination times and better reproducibility than less experienced operators.
- Manual alpha-angle measurements consistently underestimated the reference value.
- AI-assisted dynamic ultrasound analysis achieved the highest accuracy (mean 69.2°) and consistency, outperforming manual measurements.
Conclusions:
- Substantial operator variability exists in manual hip ultrasound assessments for DDH.
- AI-assisted dynamic ultrasound analysis offers improved accuracy and consistency over manual methods.
- This technology holds promise for enhancing the reliability of routine DDH screening.

