What is the Correlation Between Facet Joint Radiofrequency Outcome and Response to Comparative Medial Branch Blocks?

BACKGROUND Facet joint pain is a common cause of low back pain. There are no physical exam findings that provide a reliable diagnosis. Diagnosis is made by medial branch block injections (MBB). Once the source of pain has been determined, radiofrequency neurotomy (RFN) can be performed. Previous studies have shown that RFN reduces level of pain and improves function. No study has tried to correlate MBB results with outcomes after RFN. OBJECTIVES (1) Estimate percentage decrease in pain, decrease in analgesic use, and increase in activity tolerance after facet joint radiofrequency neurotomy (2) Determine correlation between percentage pain relief or duration of pain relief after MBB and RFN outcomes. STUDY DESIGN Retrospective review of patients undergoing RFN, who had = 70% pain relief on 2 sets of MBB with 0.5 - 1 mL of 2% lidocaine (MBB 1) and 0.75% bupivacaine (MBB 2). IRB approval was obtained before data collection began. SETTING All patients undergoing RFN between 12/06-1/10 at University Spine and Pain clinics. METHODS Subgroup analysis was performed based on response to MBB, a)100% pain relief and <100% pain relief after MBB 1 and 2 and a) those with > 8 hours and = 8 hours pain relief after MBB 1 and 2. Correlational analysis was conducted to determine the correlation between a) percent pain relief after MBB1 and 2 and percent change in pain after RFN and b) duration of pain relief after MBB 1 and 2 and percent change in pain relief after RFN. OUTCOME MEASURES Pain intensity, disability index, analgesic use, and patient perception of benefit. RESULTS Mean improvement of Disability scores at 3 months was 12.63 (P = 0.001), percent pain relief was 47.68% (P = 0.001). Patients with 100% pain relief after MBB 1 had greater improvement of disability scores (P = 0.008). Those with > 8 hours pain relief after MBB 1 had greater reduction in pain (P = 0.014). Pearson correlation analysis showed no correlation between percent pain relief or duration of pain relief after MBB and percent pain relief after RFN. LIMITATIONS This was a small observational study with short-term follow up. CONCLUSION Patients had improved disability scores and decreased pain after RFN. No correlation was seen between results on MBB and pain relief after RFN. It is still unclear how many medial branch blocks are needed and the criteria for MBB results before proceeding to RFN.