Disclosures: Martin J. Manansala, MD: Nothing to disclose

Case Description: Patients with chronic knee pain (> 1 year) secondary to knee osteoarthritis underwent genicular nerve blocks.

Setting: Outpatient clinic

Patient: Patients aged 33 to 70 years old with history of chronic knee pain secondary to OA.

Assessment/Results: 12 patients underwent initial genicular nerve block in order to qualify for cooled radiofrequency ablation. Nerve block was deemed successful with > 50% pain relief for at least 24 hours. Lidocaine 1% was used for local anesthetic and 1 mL of lidocaine 2% was used for the nerve block using fluoroscopic x-ray guidance. We injected 4 different sites: superior medial, superior lateral, inferior lateral genicular nerves and suprapatellar branch of the tibial nerve. Results show 11 of 12 patients had a successful block with an average of 85% pain relief for an average of 6.92 days. 7 of 12 patients had at least 7 days of pain relief with the longest duration being 19 days.

Discussion: Many studies note the onset of action and duration of anesthetics (i.e., lidocaine, bupivacaine, ropivacaine) for various nerve blocks. Average duration of pain relief ranges from 60 minutes to several hours, based on lidocaine inhibiting Na+ channels which decreases conduction in the healthy nerve. Thus, expectation would be pain relief for 24 hours or more, but not for the 1 week seen in our patients. We hypothesize this was due to the anti-inflammatory effects of lidocaine seen in both rat and in vitro human models: decreased activation of platelets, decreased PMN (polymorphonuclear neutrophil)/macrophage chemotaxis and phagocytosis, and prevention of free radical release by superoxide.

Conclusion: This small patient series identified longer than anticipated pain relief with lidocaine nerve blocks for knee OA. Large randomized controlled trials are needed to confirm lidocaine to be an anti-inflammatory agent to be used in standard practice.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/extended-pain-relief-with-lidocaine-genicular-nerve-block-a-case-series/