Dorsal root ganglion stimulation for the treatment of chronic neuropathic knee pain.

PURPOSE: To elucidate the efficacy of dorsal root ganglion stimulation in the treatment of chronic neuropathic pain confined to the knee. METHODS: Retrospective analysis of prospectively collected data of 14 consecutive patients undergoing dorsal root ganglion stimulation for chronic knee pain, in a single centre. The primary outcome measure was pain reduction assessed by numeric pain rating scale score pre-operatively and post-operatively. Secondary outcomes included quantification of percentage of pain area covered by stimulation, and reduction in usage of opioid medications. Responders were defined as patients that experienced a greater than or equal to 50% improvement in their pre-operative pain score. RESULTS: 14 patients were implanted with dorsal root ganglion stimulator (DRG) electrodes. 8 had a single L3 lead implanted, 1 patient had a single L4 lead implanted, and 3 patients had 2 leads implanted (L3 and L4). 2 patients had their leads explanted: 1 for non-efficacy, and 1 for repeated electrode displacement. The most common indication for surgery was type 2 complex regional pain syndrome (CRPS), secondary to either trauma or post-operative chronic pain (either knee replacement or arthroscopy). Median pre-op numeric rating scale score was 8.5, median post-op numeric rating scale score was 2 (p=0.002, Wilcoxon signed rank test). The median improvement in pain score was 80%. All 12 patients undergoing chronic stimulation were responders. Median coverage of pain area was 85%. All but 1 patient that was on opioid medication prior to surgery had reduced the dosage of regular opioid. CONCLUSION: In selected patients, dorsal root ganglion stimulation is an extremely efficacious means of treating otherwise refractory chronic knee pain.