Treatment of Graf Type IIa Hip Dysplasia: A Cut-off Value for Decision Making

BACKGROUND: The rate of spontaneous normalization in type IIa hips is reported to be high, whereas dysplsia persists or worsens in 5%-10% of cases. AIMS: To evaluate the natural course of type IIa hips using Graf’s own perspective of physiological immaturity and maturational deficit. STUDY DESIGN: A single center, retrospective cohort study. METHODS: This was an institutional review board-approved retrospective review of all patients diagnosed with type IIa hip dysplasia at a single institution from 2012 to 2014. All patients included in the study had hip ultrasonography at about 6 weeks and 3 months of age. To assess reliability in α and β angles, ultrasonography measurements were carried out on the same image individually by all observers. The α and β angles were used as the main outcome measurements to evaluate hip maturation at the last follow-up. A receiver operating characteristics curve was drawn at the 3 month ultrasonography to evaluate the cut-off values for α and β angles for persistent dysplasia. RESULTS: Sixty-four patients and 88 affected hips (63% unilateral and 37% bilateral) were included. The mean age at diagnosis was 6.4±2.7 weeks. Fifty-four hips were type IIa(+) (physiologically immature) and 34 hips were type IIa(-) (maturational deficit) at the initial ultrasonography evaluation. Improvement to type I was seen in 52 type IIa(+) and 17 type IIa(-) hips. Receiver operating characteristic analyses showed that patients do well if the α angle was >55° (area under the curve: 0.86; p<0.001 for the left hip and area under the curve: 0.72; p=0.008 for the right hip). CONCLUSION: The cut-off α angle value of 55° on initial ultrasonography should be considered to prevent future dysplasia. An α angle <55° on the initial ultrasonography was an independent predictor of worsening sonographic findings.