Risk factors for re-dislocation after closed reduction in children with developmental dysplasia of the hip.

OBJECTIVE

To investigate the risk factors for re-dislocation after the closed reduction in children with developmental dysplasia of the hip (DDH).

METHODS

The clinical data of 88 children aged ≤ 18 months with DDH (103 hips) who were treated with adductor muscle relaxation + closed reduction + plaster fixation at the Children's Hospital, Zhejiang University School of Medicine from January 2015 to December 2017, were retrospectively analyzed. According to the diagnostic criteria of hip dislocation, patients were divided into two groups: reduction group and re-dislocation group. The univariate and multivariate logistic regression analysis were applied to identify the risk factors for the re-dislocation of children.

RESULTS

Eighty-six patients (99 hips) successively underwent the treatment. 69 hips were fixed at the first intention, 9 hips at the second intention, and a total of 78 hips with no re-dislocation occurred till the last follow-up with a rate of 78.8%. The univariate analysis showed that preoperative acetabular index (AI), International Hip Dysplasia Institute (IHDI) grade, intraoperative hip flexion angle, and intraoperative head-socket spacing were significantly related to the occurrence of re-dislocation after closed-reduction. The multivariate logistic regression analysis showed that preoperative AI > 40.5° ( OR=5.57, P<0.01), flexion angle < 80.5° ( OR=4.93, P<0.01) and head-socket distance > 6.95 mm ( OR=8.42, P<0.01) were risk factors for the re-dislocation. The area under the receiver operator characteristic curve was 0.91 when preoperative AI > 40.5°, flexion angle < 80.5°, head-socket distance > 6.95 mm, and IHDI grade were used to predict the occurrence of re-dislocation, and the sensitivity and specificity were 0.72 and 0.87, respectively.

CONCLUSIONS

Preoperative AI > 40.5°, intraoperative hip flexion angle < 80.5°, and head-socket distance > 6.95 mm are risk factors for postoperative re-dislocation in children with DDH. These risk factors combining with the IHDI grade would be better to predict the occurrence of re-dislocation.