After obtaining an informed consent , 25 patients with low back pain due to failed back syndrome were randomly assigned to receive a transforaminal epidural injection of hyaluronidase 1500 IU ( HYL ) or normal saline ( NSL ) to a mixture of bupivacaine 0.5 % ( 1 mL ) and triamcinolone 40 mg ( 1 mL ) in a double-blind fashion .