A prospective study of the natural outcome and treatment indications of infant GrafIIa hip dysplasia

Objective To observe the natural outcomes of Graf typeⅡa hip dysplasia aged 6 weeks to 3 months, and to explore the indications of treatment. Methods A prospective study was conducted to collect children aged from 6 to 12 weeks with Graf typeⅡa dysplasia (50°≤α angle<60°) but clinically stable hips according to the Early Screening of Developmental Dysplasia of the Hip in Tianjin project from July 2012 to July 2014. Those hips with history of treatment or neuromuscular disorders were excluded. All infants had no treatment initially following with ultrasound surveillance each 2 weeks and radiograph evaluation each at 3, 4.5 and 6 months of age. Patients received Pavlik harness or abduction brace treatment if hip dysplasia turned to be type GrafⅡc or worse, or clinical unstable before 6 months; also if hip dysplasia was persistent in radiograph at 6 months. All infants were routinely followed up at 12 and 24 months of age to detect the late cases. The difference of initial α angle, hip abduction, acetabulum index and acetabulum margin morphology (sharp, round or defect) in the pelvic radiograph at 3 month were compared between the treated and untreated groups. Results A total of 238 children (285 hips) were enrolled in the present study, of which there were 25 males and 213 females, 193 left and 92 right hips. The average age was 9 weeks (range 6 to 12 weeks). No hip turned to be typeⅡc or worse, or clinically unstable. One hundred patients (120 hips) received treatment for persistent dysplasia at 6 months. There had statistically significant difference in initial α angle between the treated and untreated groups (respectively 54.5°±3.3° and 55.6°±2.9°, t=-2.749, P=0.004). In the treated group, there were 47 hips (39.2%, 47/120) with limited abduction initially, and 52 hips (43.3%, 52/120) with poor acetabular morphology at 3 months. The differences were statistically significant comparing with the untreated group (χ2=4.010, P=0.045; χ2=14.143, P=0.000). Logistic multivariate regression analysis showed that patients with GrafⅡa-hips (OR=2.908) and poor acetabular morphology hips (OR=2.822) were more likely to receive treatment. Thirty-eight patients (47 hips) received treatment among GrafⅡa+ hips (α angle ≥55°), of which 21 hips (44.7%, 21/47) had limited abduction and 31 hips (66.0%, 31/47) poor acetabular morphology. The differences were statistically significant comparing with untreated cases (χ2=12.073, P=0.001; χ2=35.879, P=0.000). Logistic multivariate regression analysis showed that Graf Ⅱa+ hips with limited hip abduction (OR=4.145) and poor acetabular morphology (OR=10.117) were more likely to receive treatment. Conclusion GrafⅡa dysplasia with clinically stable hips should be treated if α angle <55° at 6 weeks or if α angle ≥55° with limited hip abduction or poor acetabular morphology (round or defect) at 3 months. Key words: Hip dislocation, congenital; Infant; Ultrasonography; Prospective studies