Follow-up Value of Hip Medial Ultrasound in Infants and Children With Developmental Dysplasia of the Hip Treated With Reduction and Spica Casting

Abstract

Objective: Closed or open reduction and spica casting are common treatments for children aged 6 to 18 months, as well as infants aged 0 to 6 months whose harness treatment for developmental dysplasia of the hip (DDH) was unsuccessful. The study aimed to quantify the distance between the femoral head and the acetabulum after closed or open reduction and evaluate the dynamic docking progression of the femoral head using serial hip medical ultrasound. Methods: We retrospectively reviewed the medical records and hip medial ultrasound images of a consecutive series of patients with DDH who underwent spica casting after reduction and compared images obtained immediately after reduction and at follow-up. The first cast (stage I) was maintained for 2 to 3 months and scheduled for outpatient repeat ultrasound in 4 to 8 weeks. Then the second cast was placed (stage II), lasting for another 2 to 3 months. The triradiate cartilage-femoral head distance (TFD) was measured in the acetabulum coronal mid-sectional plane. The Wilcoxon signed-rank test was used to compare the TFD values. Results: This study included 49 patients. All patients underwent hip medial ultrasound 0 to 3 days after stage I (time 1) and 4 to 8 weeks (time 2) postoperatively, with 24 patients reviewed again 0 to 7 days after stage II. The TFD values in time 1 and time 2 were 6.0 (5.0, 9.0) mm and 5.0 (3.6, 7.0) mm, respectively. There was a statistically significant difference between times 1 and 2 regarding TFD values in 49 close-reduction hips (6.0 vs 5.0 mm, P < 0.001). Similar findings were also observed in 13 open-reduction hips (6.0 vs 5.0 mm, P = 0.023). Conclusions: Hip medial ultrasonography during the period of cast immobilization after reduction in children with DDH can objectively and quantitatively show the dynamic change of the distance between the femoral head and the acetabulum, and can be used to assess reduction of the hip and progression of femoral head docking. Level of Evidence: Level II—prognostic study.