Differences within and between groups in pain and disability
disability, pain
There were no differences over time between surgical groups in pain (p = .951) or disability (p = .688). There was a significant main effect over time in pain F(1.59, 68.41) = 78.92, p < .001, Cohen’s d > 1.0. Post hoc analyses showed significant improvements from baseline to 10 years as well as from 10 to 20 years after surgery in both groups (CP, p < .001 – .007, CIFC, p < .001 – .013). There was a significant main effect in disability over time F(2,80) = 9.30, p < .001, Cohen’s d = 0.96. Post-hoc analyses showed significant improvements from baseline to 20-year follow-up in the CP group (p = .014), but not in the CIFC group (p = .066). Analyses showed no improvements from 10 to 20 years in either group (CP, p = .41, CIFC, p = 1.00).Descriptive data on pain divided by fusion status at 2-year follow-up show that non-fused individuals had smaller reductions in pain over time than fused individuals. These reductions were not significantly different (p = .052) between groups based on fusion status. In NDI, the 2 individuals who had a non-fused CP surgery differed from the other by rating increased disability at 20-year follow-up. Analyses showed that individuals with a documented fusion (independent of type of surgery) had significantly larger improvements than those with non-fusion (mean difference: 13.4, 95% CI 1.3–25.6, p. = .031, Cohen’s d = 0.714) when adjusted for baseline NDI values.