Clinical and technical factors associated with knee radiofrequency ablation outcomes: a multicenter analysis.

BACKGROUND: There has been a surge in interest in radiofrequency ablation (RFA) of the genicular nerves over the past decade, with wide variability in selection, technique and outcomes. The aim of this study is to determine factors associated with treatment outcome. METHODS: We retrospectively evaluated the effect of 23 demographic, clinical and technical variables on outcomes in 265 patients who underwent genicular nerve RFA for knee pain at 2 civilian and 1 military hospital. A primary outcome was designated as a > 30% decrease in average knee pain score lasting at least 3 months without cointerventions. RESULTS: The overall rate of a positive response was 61.1% (95% CI 55.2% to 67.0%). In univariable analysis, larger electrode size (p=0.01), repeated lesions (p=0.02), having>80% pain relief during the prognostic block (p=0.02), not being on opioids (p=0.04), having no coexisting psychiatric condition (p=0.02), having a lower baseline pain score (p=0.01) and having >3 nerves targeted (p=0.02) were associated with a positive outcome. In multivariate logistic analysis, being obese (OR 3.68, 95% CI 1.66 to 8.19, p=0.001), not using opioids (OR 0.35, 95% CI 0.16 to 0.77, p=0.009), not being depressed (OR 0.29, 95% CI 0.10 to 0.82, p=0.02), use of cooled RFA (OR 3.88, 95% CI 1.63 to 9.23, p=0.002) and performing multiple lesions at each neural target (OR 15.88, 95% CI 4.24 to 59.50, p<0.001) were associated with positive outcome. CONCLUSIONS: We identified multiple clinical and technical factors associated with treatment outcome, which should be considered when selecting patients for RFA treatment and in the design of clinical trials.

Current pharmacologic approaches to treating neuropathic pain.

Most neuropathic analgesic medications have been introduced initially for other medical conditions. Anticonvulsants, local anesthetics, and antidepressants later were found to be effective in the treatment of neuropathic pain. Carbamazepine and the newer anticonvulsants such as gabapentin, lamotrigine, topiramate, and oxcarbazepine are being used as first-line or adjunctive therapy. The newer agents have less potential for drug interactions and a more favorable side-effect profile. Lidocaine administered systemically or topically is useful for some peripheral and central neuropathic pain conditions. The tricyclic antidepressants amitriptyline, nortriptyline, and desipramine have been shown to be effective for the management of neuropathic pain, independent of their antidepressant property. All of the available analgesics have considerable side effects, which necessitate careful titration. Future drug research may focus on developing medications specifically for neuropathic pain. These designer agents may have more desirable action without the unwanted side effects.