Intention-to-treat analysis found lower Neck Disability Index scores at @ months in the mechanical traction group compared to the exercise group ( mean difference between groups , @ ; @ % confidence interval : @ , @ ) and over-door traction group ( mean difference between groups , @ ; @ % confidence interval : @ , @ ) , and at @ months in the mechanical traction group compared to the exercise group ( mean difference between groups , @ ; @ % confidence interval : @ , @ ) .