Follow-up sonographic results for Graf type 2A hips: association with risk factors for developmental dysplasia of the hip and instability

The purpose of the study was to evaluate the association of sonographic worsening in type 2a hips with risk factors of developmental dysplasia of the hip, stability of the hip, and initial sonographic findings. Among infants who were referred for hip sonography between 2007 and 2009, 3450 were included in this study. Sonographic examinations were performed by combining the static Graf technique and the dynamic Harcke technique. The rate of sonographic worsening in type 2a hips and the relationship between sonographic worsening and risk factors for developmental dysplasia, instability of the hip, lateralization (right or left) of immaturity, and the presence of unilateral and bilateral immature hips were evaluated. Type 2a hips were observed in 529 infants (15.3%; 780 hips [11.3%]). Of these, in 36 cases (6.8%; 44 hips [5.6%]), the sonographic results worsened. Twenty-five of these 36 cases (32 of 44 hips) were diagnosed as type 2 b; in others, the dysplasia worsened, and 6 cases (7 hips) were classified as type 2 c, 3 cases (3 hips) as type D, and 2 cases (2 hips) as type 3. Instability, unilateral type 2a hips, and associated central nervous system anomalies were found to be independent predictors of sonographic worsening in type 2a hips. Type 2a hips may worsen sonographically at a rate of 5.6%; hence, sonographic follow-up is needed. Instability, central nervous system anomalies, and unilateral type 2a hips were found to be independent predictors of sonographic worsening. Our study shows that cases with these risk factors should be followed more carefully.