In the FPS group , the average actual wear rate for months 1 , 2 , and 3 were 91.7 % ( 15 patients ; 72.7 % to 97.0 % ) , 86.8 % ( 9 patients ; 60.5 % to 96.3 % ) , and 77.1 % ( 7 patients ; 52.6 % to 95.8 % ) , respectively .