Comparisons of the reductions achieved with posterior Harrington instrumentation of 21 type A and 26 type B burst fractures revealed that the percent correction of angular deformity at surgery was significantly higher (type A, 52% versus type B, 65%) and was better maintained at 6 (type A, 13% versus type B, 36%) and 12 months (type A, 0% versus type B, 28%) after surgery in type B fractures (p < 0.05). Percent correction of anterior compression achieved at surgery was similar for both groups (type A, 33% versus type B, 37%), but maintenance of correction 6 (type A, 9% versus type B, 23%) and 12 months after surgery (type A, 3% versus type B, 23%) also was significantly better in type B fractures (p < 0.05). Percent correction of sagittal plane displacement immediately following surgery (type A, 71% versus type B, 73%), and 6 (type A, 62% versus type B, 61%) and 12 months after surgery (type A, 60% versus type B, 56%) was the same in both groups. Results of posterior instrumentation of burst fractures appears to be dependent upon the type of burst injury; significantly better reductions were achieved and maintained in Denis type B fractures.