A study of Pain relief in Chronic Low Back Pain sufferers given radio frequency lesions to the medial branch nerves with patient selection based on local anaesthetic and placebo injections .

Phase 1: Medial Branch nerve block of lumbar zygoapophyseal joints with local anaesthetic Dose 0.5ml of bupivacaine 0.5% at each nerve block up to a maximum of 6 blocks equals 3ml in total. The number and location of blocks is decided by clinical and radiological correlation of pain area and pathological joints. A maximum of 2 joints bilaterally in the lumbar spine are to be blocked or 3 adjacent levels unilaterally. Duration : Single injection over 5 seconds Mode : Injection with needle under image guidance in operating theatre Description of intervention Participants attend hospital for clinical assessment and attend on a separate occasion for intervention. Patient information sheet and consent forms are provided to the participants Participants initially receive medial branch blocks in the lumbar spine by a pain management specialist. This is performed in an operating theatre and their skin is painted with antiseptic (chlorhexidine 2%) The participants also receive a small dose of radio-opaque dye during the injection (Isovue 300 total 3mls) If adequate pain relief is obtained ( 50% pain relief) they then proceed to Phase 2 after a minimum of 1 week. Duration of time between Phase 1 and Phase 2 - 1-4 weeks Phase 2 Radio frequency neurotomy of the lumbar zygoapophyseal joints. Participants have a radio frequency lesion to the medial branch nerves supplying the zygo-apophyeseal joints that have previously been blocked in phase 1 in hospital by the same medical team. Prior to this the participants discuss the procedure with the medical team. Their baseline pain levels are assessed. The participants enter the operating theatre. An intravenous cannula is inserted. Sedation is administered intravenously with fentanyl up to 100 microgrammes and midazolam up to 5 milligrammes. Sterile technique is used and antiseptic (povidone Iodine) is applied to the skin. Local anaesthetic is administered ( lidocaine 1% up to 20mls ) with a small needle (25g) . Under image guidance with X ray a sterile procedure is performed with needles (20g and 10 m long) and a radio frequency generator to heat the nerves supplying sensation to the zygo-apophyseal joints that have been previously blocked in phase 1. (radio frequency neurotomy). Pain relief response to the radio frequency neurotomy is assessed by the research assistant and the nursing staff immediately post procedure and at regular time points after the procedure up to and including 3 months.