4.4. Periradicular infiltration (IV and V)

Periradicular infiltration was performed by an experienced radiologist (M.K.) using conventional technique (Derby et al. 1992) under repeated fluoroscopic screening (C-arm) with a 22- to 25-G spinal needle. For the L4 and L5 roots the needle was advanced obliquely toward the base of the corresponding pedicle. For the S1 root the needle was aimed in a medial and cephalad direction relative to the corresponding sacral foramen. After the injection of 0.5 to 1 ml contrast medium to produce a neurogram that identified the nerve root in question, either Solomet (methylprednisolone 40 mg/ml)-bupivacaine (5 mg/ml) or isotonic (0.9%) sodium chloride solution was injected (Figure 3). The volume of the injection was 2 ml for L4 and L5 blocks and 3 ml for S1 based on anatomic differences.