Prevalence and Risk Factors for Acetabular Rim Irregularities in Infants with Hip Dysplasia: A Cohort Study

Background/Objectives: Hip ultrasound is the standard screening method for developmental dysplasia of the hip (DDH) in infants, yet sonographic acetabular rim irregularities (SARIs) remain understudied regarding their prevalence and clinical associations. Methods: A total of 1010 infants within the first four months of life, referred to a specialized pediatric orthopedic hip clinic between 2014 and 2019 for suspected or confirmed DDH, were included in this retrospective cohort study. Hip ultrasound was performed using the standardized Graf technique. Clinical, demographic, and sonographic data were extracted from patient records. Two pediatric orthopedic specialists assessed all ultrasound hip images for the presence of an SARI and measured its relative size (d/D). Associations among SARI, patient characteristics, and sonographic parameters were analyzed using appropriate univariate and multivariable statistical methods (p < 0.05). Results: We identified SARI in 9.11% of all hips and in 13.07% of all infants, with many developing during Pavlik harness treatment. Univariate and multivariate analyses revealed cesarean delivery as an independent factor associated with SARI occurrence. SARIs that developed over time had a significantly larger d/D ratio compared with those that were visible from the very beginning (p = 0.04). Conclusions: These findings establish a baseline prevalence and highlight potential risk markers for SARI in a dysplasia-enriched cohort. Further prospective studies are warranted to elucidate the clinical significance of SARI and its impact on treatment outcomes and hip development.