Local anesthetic selection for spine and large joint radiofrequency ablation: a practical review for the musculoskeletal radiologist.

Abstract

Local anesthetic (LA) selection for radiofrequency ablation (RFA) of spinal medial branch nerves, sacroiliac joint lateral branches, and large peripheral joint articular branches has not been addressed by any dedicated document. The concentration, class, and sequencing of agents used during needle placement, stimulation testing, and pre-lesioning injection have plausible implications for procedural accuracy and post-procedural analgesia. This review synthesizes pharmacological data and adjacent procedural literature into practice considerations for the musculoskeletal radiologist. No randomized or prospective comparative trial has evaluated LA agents, concentrations, or sequencing within an RFA procedure; every statement therefore rests on indirect evidence, mechanistic reasoning, or the authors' practice, and each is labeled accordingly. Lidocaine 1% is a reasonable default for skin, subcutaneous, and deep track anesthesia. Where sensory and/or motor stimulation testing is performed, there is a mechanistic argument for avoiding lidocaine 2% close to the target nerve, since selectivity between fiber classes falls as concentration rises; that argument derives from epidural quantitative sensory testing and rodent electrophysiology, has not been tested in RFA, and no study has shown that lidocaine 2% impairs stimulation testing or procedural outcome. Bupivacaine 0.25% or ropivacaine 0.2% is a reasonable choice for perineural injection before lesioning. Premixing lidocaine and bupivacaine has no demonstrated advantage: across five randomized trials, all outside interventional pain settings and heterogeneous in design, mixtures did not accelerate onset relative to bupivacaine alone and in several curtailed its duration; two also found same-site sequential injection no better than premixing. Ropivacaine is a reasonable preference in cardiac conduction disease or multi-level procedures. A structured allergy substitution pathway is provided with formal allergist evaluation as the central step. These considerations are offered to inform practice and to prompt the prospective studies the field lacks.