Treatment of graf type iIa hip dysplasia: a cut-off value for decision making

Abstract

Background: The rate of spontaneous normalization in type lla hips is reported to be high, whereas dysplsia persists or worsens in 5%-10% of cases. Aims: To evaluate the natural course of type Ila 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 reiew of all patients diagnosed with type Ha 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 alpha and beta angles, ultrasonography measurements were carried out on the same image individually by all observers. The alpha and beta 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 alpha and beta 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 1144-) (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 a angle was >55 degrees (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 a angle value of 55 degrees on initial ultrasonography should be considered to prevent future dysplasia. An a angle <55 degrees on the initial ultrasonography was an independent predictor of worsening sonographic findings.