Prediction Model for Contralateral Hip Dislocation in Cerebral Palsy Patients with Unilateral Hip Dislocation: A Scoring System to Guide Decision Making

BACKGROUND: Cerebral palsy (CP) patients commonly present with unilateral hip dislocation. However, the decision for concurrent prophylaxis surgery on the contralateral hip in this condition is still controversial. AIM: This study aims to explore the prognostic factors for contralateral hip dislocation and develop a scoring system. MATERIALS AND METHODS: Data on CP patients with unilateral hip dislocation between January 2005 to January 2019 were reviewed. We explored the difference of preoperative parameters between the group in which the contralateral hip is eventually dislocated or remains stable. A multivariable logistic regression analysis was performed to develop a model for predicting contralateral hip dislocation. RESULTS: Seven of included 30 patients (23.3%) developed contralateral hip dislocation. Pre-operative contralateral hips Reimers Migration Index (RMI), Acetabular Index (AI), Lateral Center Edge Angle of Wiberg (CEA), and Pelvic obliquity (PO) were significantly different (p = 0.049, 0.019, 0.030 and 0.038 respectively). The multivariable logistic regression analysis reveals that RMI 25% (mOR 36.66, 95% CI 1.131185.50, p = 0.042) and age 9 years old (mOR = 22.55, 95% CI 0.76665.37, p = 0.071) are significant predictors. Both parameters were included in the model, which revealed an AuROC of 0.84 (95% CI 0.690.99). Each factor was assigned a score of 1. There was no contralateral hip displacement in patients with a score of 0. Two out of 15 patients (28.6%) with a score of one developed contralateral hip displacement. Five out of eight (71.4%) patients with a score of 2 developed contralateral hip dislocation. CONCLUSIONS. Significant predictors for contralateral hip dislocation in CP patients are RMI 25% and age 9 years old. The proposed scoring system might help guide the surgeons decision to perform contralateral prophylactic surgery.