The Impact of Spinal Fusion on Hip Displacement in Cerebral Palsy

Background and study aims: The aims of this study were to determine the risk of progressive hip subluxation in children with CP after spinal fusion for scoliosis and how frequent the hips follow-up should be scheduled.

Patients and methods: Pelvis radiography [migration index (MI) and pelvic obliquity (PO)] of Gross Motor Function Classification System (GMFCS) levels IV and V children with CP who received spinal fusion and pelvic fixation were reviewed retrospectively. This population was categorized into three groups based on the MI at spinal fusion: G1 = 0-29%; G2 = 30-59%; and G3 = 60-100%.

Results: Fifty children (age 7.5-15.0 years) and categorized into 3 groups (G1 = 19, G2 = 23, G3 = 8; 100 hips in total). Preoperative and last follow-up MI were 22 ± 7% and 30 ± 20% (G1), 41 ± 9% and 43 ± 22% (G2), 92 ± 15% and 97 ± 10% (G3). The MIs at spinal fusion between groups were statistically different (p < 0.001). In G1, the mean MI progression was 5% and 25% at 12 months and 62 months, respectively. In G2, the mean MI progression was 9% and 25% at 12 months and 32 months, respectively. The progression more than 10% occurred within 2 years in G1 and within 1 year in G2. There was no difference between groups based on preoperative degree of PO (p = 0.653) and correction rate in PO (p = 0.421).

Conclusions: In GMFCS IV and V children with the highest risk for progression occurred with increasing preoperative MI, especially over 50%. Hips should be monitored continuously after spinal fusion until hip stability is documented.