Journal of Pediatric Orthopaedics - 2026-03-26 - Journal Article
Age at Fusion of Ischiopubic Synchondrosis Is a Predictor for Residual Acetabular Dysplasia After Closed Reduction for Developmental Dysplasia of the Hip.
Liao W, Ma Y, Yang H, Zhang T, Lyu X
Topics
Key Takeaway
Ischiopubic synchondrosis fusion before age 5 years is associated with an 82.9% rate of residual acetabular dysplasia after closed reduction for DDH, versus 63.2% in those fusing at age 5 or older.
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Summary
This study asked whether age at ischiopubic synchondrosis fusion predicts residual acetabular dysplasia (RAD) after closed reduction for DDH, defined as Severin grade ≥3 or requirement for secondary reconstructive surgery. Among 187 hips followed a mean 7.6 years, 28.3% met Severin grade 3/4 criteria and 39% underwent secondary surgery; higher IHDI grade, larger pre-reduction acetabular index, and synchondrosis fusion before age 5 were each independently associated with RAD. AI cutoffs of 30° at 1 year and 27° at 2–3 years post-reduction were identified as thresholds warranting concern.
Key Limitation
RAD was defined by a composite endpoint combining Severin grade and secondary surgery, conflating radiographic and surgeon-decision outcomes without reporting how many hips met each criterion independently, which obscures the true radiographic failure rate.
Original Abstract
BACKGROUND
Previous studies have evaluated risk factors of residual acetabular dysplasia (RAD) following closed reduction (CR). However, none of them have focused on the association between the age at fusion of the ischiopubic synchondrosis and RAD. The objective of this study was to determine whether the age at fusion of the ischiopubic synchondrosis was associated with RAD after CR and to evaluate other predictors for RAD.
METHODS
We retrospectively reviewed children who underwent closed reduction for developmental dysplasia of the hip (DDH) between 2008 and 2018 and were followed for at least 5 years. Exclusion criteria included inadequate follow-up, a diagnosis of teratologic hip dislocation or the presence of other neuromusculoskeletal diseases, and inadequate radiographs and clinical records. RAD was defined as a Severin classification grade of3 at last follow-up or having undergone a secondary reconstructive surgery. The AP pelvis plain radiograph was used to identify the age at fusion of the ischiopubic synchondrosis, IHDI grade, avascular necrosis (AVN), and to measure the acetabular index (AI). Statistical analysis was performed.
RESULTS
A total of 150 children (187 hips) with an average age of 13.6 months (range: 4 to 22 mo) at closed reduction were included. For an average duration of 7.6±2.1 years (range: 5 to 14 y) of follow-up, 53 (28.3%) hips were classified in Severin grade 3/4, and 73 (39%) hips underwent a secondary procedure. There was a significant difference in AI pre-CR and post-CR between the non-RAD and RAD groups. Analysis of the groups showed that the RAD group had a higher IHDI grade than the non-RAD group (P<0.01). The incidence of RAD was significantly higher in children with ischiopubic synchondrosis fused younger than 5 years compared with those with ischiopubic synchondrosis fused 5 years and older (82.9% vs. 63.2%, respectively; P=0.02). The mean AI declined after a reduction in both groups, with the greatest fall occurring in the first year. Cutoff values of AI were 30 degrees at 1 year and 27 degrees at 2 to 3 years post-CR.
CONCLUSION
In patients with CR of DDH, higher IHDI grade and larger AI pre-CR were associated with increased RAD. Age at fusion of the ischiopubic synchondrosis is a predictor for RAD. The acetabulum continued to remodel for 5 years after CR, suggesting long-term observation to identify acetabular dysplasia.