Potential predictors of hip surgery following selective dorsal rhizotomy in children with cerebral palsy: Survival analysis of a retrospective cohort.

BACKGROUND

Neuromuscular hip dysplasia is a prevalent sequela in children with cerebral palsy (CP) that often requires orthopedic intervention. Selective dorsal rhizotomy (SDR) is a procedure that reduces spasticity with some suggesting protective benefits against future hip surgery. Still, some individuals require surgery following SDR and it is unclear what factors may contribute to this incidence.

OBJECTIVE

To determine what factors influenced the need for hip surgery following a SDR in children with CP.

METHODS

Retrospective sample of patients diagnosed with CP who had a SDR. The primary outcome was incidence of hip surgery. Clinical data included gender, age, CP distribution, Gross Motor Function Classification Scale level, hip surgery type, spinal levels of the SDR, and the percentage of rootlets cut during SDR. Migration index, acetabular index (AI), and neck shaft angle were calculated on preoperative SDR pelvis radiographs. A survival analysis using a multivariable Cox proportional hazard ratio was conducted to determine the effect of demographic, clinical, and radiographic measures on the incidence of hip surgery. Receiver operating characteristics analysis was conducted on significant variables to determine potential cutoff values for high and low risk.

RESULTS

Sixty-eight patient records (135 hips) were analyzed. Sixteen patients (30 hips) required hip surgery 3.0 ± 1.9 (range: 0.6-7.6) years after their SDR. When adjusting for gender and age at SDR, a high AI significantly increased the risk for hip surgery (hazard ratio = 1.36, 95% confidence interval [CI] 1.22-1.51, p < .001). An AI cutoff of 23° was determined to have 63.3% sensitivity and 80.0% specificity.

CONCLUSION

Children with CP who have an AI ≥23° at the time of SDR are more likely to require hip surgery regardless of gender or age. Thus, AI may be better factor to consider when advising patients on SDR and potential for future hip surgery as part of a shared decision-making process.