O2124: Kicking the Can in DDH: The Impact of Age on Outcomes Following Secondary Reconstructive Surgery for Residual Dysplasia

Background: Following closed reduction of developmental hip dislocations, residual dysplasia is common with rates of secondary reconstructive surgery with pelvic osteotomy approaching 50-60%. The determination and timing of when to proceed with surgery is difficult as acetabular remodeling occurs gradually over the first years following closed reduction. The purpose of this study was to evaluate how age at secondary reconstructive surgery influences the clinical and radiographic outcomes following pelvic osteotomy for residual dysplasia.

Methods: Following IRB approval, we retrospectively reviewed all Salter or Pemberton pelvic osteotomies performed for residual dysplasia following an index closed reduction performed at a single institution between 1983-2020. Patients with concurrent femoral osteotomy, femoral head deformity from avascular necrosis on follow-up radiographs, or patients with < 2 years radiographic follow-up were excluded. Radiographic outcomes included markers of acetabular dysplasia. Acetabular index (AI) and migration index (MI) were measured on pre-operative, immediate post-operative, and 2-year follow-up radiographs. Following triradiate cartilage closure, anterior-posterior pelvis radiographs were measured for lateral center-edge angle (LCEA), Tönnis angle, MI, and lateralization ratio (LR) (Figure 1). Univariate and multivariate analysis and Spearman’s correlation coefficients were used to evaluate outcomes based on age at time of surgery. Significance was set at p< 0.05.

Results: 84 hips from 77 patients were included. 52 Salter (62%) and 32 Pemberton osteotomies (38%) were performed with mean age at surgery of 5.19±1.57 years. There was no significant difference in acetabular dysplasia at 2 years postop or after triradiate closure between those hips treated before or after 5 years of age (all p>0.05). A higher-than-expected number of patients (41/84, 49%) across both treatment groups were noted to have residual dysplasia at final follow up (FFU) with LCEA of < 25 (Figure 2). However, there was no difference in the rate of residual dysplasia at triradiate closure between those hips treated before or after age 5 (48% vs 51%, p=0.19). There was a weak negative linear correlation between the age at pelvic osteotomy and the FFU LCEA (-0.23, p=0.04) across both treatment groups. However, there was no correlation between age at surgery and Tönnis angle, MI, or LR (all p>0.05). On multivariate analysis, age at surgery was not a significant predictor of LCEA (p=0.16).

Conclusion: We found high rates of residual dysplasia at skeletal maturity following closed reduction and subsequent pelvic osteotomy. However, the age at secondary reconstructive surgery for residual dysplasia does not significantly influence the radiographic markers of dysplasia at triradiate closure. These findings may guide preoperative counseling for families and suggest that there is no opportunity cost to short-term continued observation while monitoring for acetabular remodeling.