Long-leg spica casts demonstrate superior outcomes in developmental dysplasia of the hip: a multi-center retrospective analysis of failure risks and protective factors.

OBJECTIVES

While both short- and long-leg spica casts present viable options after closed reduction (CR) in developmental dysplasia of the hip (DDH), comprehensive comparative studies are needed to guide clinical practices. This multi-center retrospective study aimed to evaluate their effectiveness in treating DDH and identify predictors of treatment failure.

METHODS

This retrospective study analyzed 146 DDH patients (0-18 months) treated with closed reduction and spica casts (70 short-leg vs. 76 long-leg) at two tertiary centers (2005-2024). Incident-free survival (time from casting to failure: re-dislocation, imaging-confirmed reduction loss, or surgical conversion) was analyzed via Kaplan-Meier/Log-rank tests. A multivariable Cox model evaluated eight variables: cast type, age (>6 vs. ≤6 months), sex, laterality (bilateral/unilateral), IHDI grade (IV/III), birth presentation, delivery mode, and family history, allowing quantification of independent predictors associated with treatment failure risks.

RESULTS

The analysis of 146 DDH cases (70 short-leg vs. 76 long-leg casts) revealed significant outcome differences between cast types. Patients receiving long-leg spica casts demonstrated substantially higher 6-month incident-free survival rates (84% vs. 68%, Log-rank p < 0.05), with multivariable Cox regression confirming long-leg casting as an independent protective factor (HR = 0.45, 95% CI 0.32-0.64, p < 0.001). The analysis identified three significant risk predictors: older age (>6 months) increased failure risk by 89% (HR = 1.89, 95% CI 1.02-3.51), bilateral involvement elevated risk by 78% (HR = 1.78, 95% CI 1.25-2.54), and IHDI IV dysplasia doubled failure likelihood (HR = 2.15, 95% CI 1.45-3.18). Notably, cephalic presentation showed a protective trend (HR = 0.67, 95% CI 0.48-0.93), while delivery mode and family history did not reach statistical significance.

CONCLUSIONS

Long-leg spica casting shows superior biomechanical stability in DDH management post-CR, particularly for high-risk patients. These findings support its preferential use in patients with bilateral involvement, advanced dysplasia, or older age (>6 months).