Patients in the intervention group were nearly twice as likely to report at least a 30 % improvement in their pain score by 12 months ( 51.7 % vs 27.1 % ; relative risk , 1.9 [ 95 % CI , 1.4 to 2.7 ] ) , with a number needed to treat of 4.1 ( 95 % CI , 3.0 to 6.4 ) for a 30 % improvement .