Cumulative rates for surgery at the index level were lower ( p < 0.001 ) in the investigational group ( 11 [ 4.8 % ] of 276 ) when compared with the control group ( 29 [ 13.7 % ] of 265 ) ( based on life-table method ) , and there were statistical differences between the investigational and control groups with specific regard to the rate of subsequent revision and supplemental fixation surgical procedures .