The Impact of Spinal Fusion on Hip Displacement in Cerebral Palsy

Background and study aimsThe 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 methodsPelvis 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%.ResultsFifty 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).ConclusionsIn 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.