Residual Acetabular Dysplasia at Walking Age: A Study of 470 Hips Treated With Pavlik Harness.

BACKGROUND

This study aims to report on the acetabular indices of walking age children following successful DDH treatment with Pavlik harness and investigate risk factors for residual acetabular dysplasia (RAD).

METHODS

We retrospectively reviewed the data for children treated for DDH at a single centre between 2015 and 2020. Acetabular indices (AI) measured on pelvic radiographs taken at 2- and 4-year follow-up visits were referenced against age-matched and sex-matched normal data. Values ≥90th percentile were considered to represent RAD.

RESULTS

A total of 305 children with 470 hips were suitable for inclusion. The mean age at treatment initiation was 7.0±4.5 weeks and mean treatment duration was 15.9±4.3 weeks. Overall, 27% and 19% of hips were found to have RAD at 2- (n=448) and 4-year (n=206) follow-up, respectively. The χ 2 test for independence demonstrated that the difference in the proportion of hips with RAD at both time points was significant ( P =0.032). Patients with RAD at 2 years were found to have been treated for longer ( P =0.028) and had lower alpha angles on final ultrasound assessment ( P <0.001). Patients with RAD at 4 years were older at initiation of treatment ( P =0.041), had lower alpha angles on final ultrasound assessment ( P <0.001) and were more likely to have had RAD at 2 years ( P <0.001). Multivariate analysis identified lower alpha angles on final ultrasound to be predictive for RAD at 2 years ( P =0.011), and presence of RAD at 2 years to be predictive for RAD at 4 years ( P <0.001).

CONCLUSIONS

The risk of RAD beyond walking age in children successfully treated with Pavlik harness is not negligible. However, we observed that a significant proportion of children with RAD at 2-year follow-up had spontaneously improved without any intervention. This data suggests that routine long-term radiologic follow-up of children treated with Pavlik harness is necessary, and surgical intervention to address RAD should be delayed until at least 4 years of age.

LEVEL OF EVIDENCE: Level III-case-control study.