Mohammad Reza Yousefi - Department of radiology, faculty medicine, Mashhad University of medical science, Iran
Mojgan Yazdanparast - Department of radiology, faculty medicine, Mashhad University of medical science, Iran
Hashem Neshati - Department of radiology, faculty medicine, Mashhad University of medical science, Iran
Reza Abdi - Department of Pediatric Orthopedic Surgery, Mashhad University of Medical Science, Iran
Mohammad Hasanian - Department of Radiology, faculty medicine, Arak University of Medical Sciences, Arak, Iran
Seyed Ali Alamdaran - Department of radiology, faculty medicine, Mashhad University of medical science, Iran

Objectives: The ultrasound examination of the hip joint is performed in the static (Graf) technique in the lateral recumbent position and in the dynamic technique in the supine position. This study compares the two static and dynamic techniques and assesses the role of the patient's position in the examination of DDH.Methods: This cross-sectional study was conducted in ۲۰۲۰-۲۰۲۱ at Akbar Hospital, Mashhad University of Medical Sciences, Iran. ۱۲۶ patients suspected of having DDH (۱۹۹ hip) infants were enrolled in the study. All ultrasound examinations were performed with two static and dynamic techniques by a pediatric radiologist.Results: In the static and dynamic ultrasound examinations, the average alpha angle was ۵۱.۵۷ ± ۶.۴۱ degrees, and ۵۳.۴۱ ± ۶.۹۴ degrees, respectively. These changes were not statistically significant (P = ۰.۳۱۲). The relationship and agreement between instability with dynamic technique and instability with static technique (IIC unstable, D, III, and IV) were investigated. Significant agreement (Kappa=۰.۷۷ (۹۵% CI: ۰.۶۶-۰.۸۷) with excellent clinical significance was obtained between the two ultrasound examination method. Also, in terms of DDH types in the static method with instability types in the dynamic method, a substantial agreement was found between the two examination methods (Kappa =۰.۶۷; (۹۵% CI: ۰.۵۹-۰.۷۵) with good clinical significance.Conclusion: In the ultrasound examination of DDH with static and dynamic techniques, the change in the alpha angle was not statistically significant. Therefore, the hand of the radiologist is open in measuring alpha angles and there is no need to emphasize a specific position. The type of DDH in the static technique completely corresponded to the type of stability or instability in the dynamic technique. Level of evidence: IV

Developmental Dysplasia of the Hip (DDH), Dynamic Technique, Hip Ultrasound Angles, Static (Graf) Technique