Efficacy of Botulinum Toxin in Treating Lateral Epicondylitis-Does Injection Location Matter?: A Systematic Review.

[OBJECTIVE] Clinical trials assessing the efficacy of botulinum toxin in treating recalcitrant lateral epicondylitis have demonstrated varied results and differed greatly in methodology. The objective of this systematic review was to demonstrate injection location as a significant contributor to outcome heterogeneity.

[DESIGN] Two reviewers independently conducted a systematic review using Scopus, Embase, and PubMed for randomized controlled trials assessing botulinum toxin in the treatment of lateral epicondylitis. After applying inclusion/exclusion criteria to abstracts and reviewing the full-text articles, seven studies were found representing six separate injection locations. Reduction in visual analog scale pain and change in grip strength were the principal outcomes of interest.

[RESULTS] The largest reduction in pain was seen in injection at 1/3 of the length of the forearm from the lateral epicondyle at 16-wk follow-up, whereas the smallest reduction was seen at 12-wk follow-up after injection at the 0-cm mark. Differences were also identified in grip strength, although all studies reported return to baseline strength by weeks 12-18.

[CONCLUSIONS] This study demonstrates injection location as a potential source of heterogeneity. This clinical question warrants further evaluation with direct comparison of outcomes at different injection locations while controlling for dosage, toxin type, and ultrasound/electromyographic guidance.