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.