The fusion rate was similar between groups : fusion occurred in 84.6 % ( 33/39 ) in group A and 85.7 % ( 36/42 ) in group B at 1 year after surgery ( P = 0.86 ) , and 89.7 % ( 35/39 ) in group A and 90.4 % ( 38/42 ) in group B at 2 years after surgery ( P = 0.93 ) .