• Shiu Man Wong, Andrew C F Hui, Po-Yee Tong, Dawn W F Poon, Evelyn Yu, and Lawrence K S Wong.
• North District Hospital, The Chinese University of Hong Kong, and Prince of Wales Hospital, Hong Kong, China. jsmwong@hkstar.com
• Ann. Intern. Med. 2005 Dec 6;143(11):793-7.

BackgroundLateral epicondylitis is a common condition for which botulinum toxin has been reported to have a therapeutic role in uncontrolled studies.ObjectiveTo determine if an injection of botulinum toxin is more effective than placebo for reducing pain in adults with lateral epicondylitis.DesignRandomized, double-blind, placebo-controlled trial conducted from September 2002 to December 2004.SettingOutpatient clinics at a university hospital and a district hospital in Hong Kong.Participants60 patients with lateral epicondylitis.MeasurementsThe primary outcome was change in subjective pain as measured by a 100-mm visual analogue scale (VAS) ranging from 0 (no pain) to 10 (worst pain ever) at 4 weeks and 12 weeks. All patients completed post-treatment follow-up.InterventionsA single injection of 60 units of botulinum toxin type A or normal saline placebo.ResultsMean VAS scores for the botulinum group at baseline and at 4 weeks were 65.5 mm and 25.3 mm, respectively; respective scores for the placebo group were 66.2 mm and 50.5 mm (between-group difference of changes, 24.4 mm [95% CI, 13.0 to 35.8 mm]; P < 0.001). At week 12, mean VAS scores were 23.5 mm for the botulinum group and 43.5 mm for the placebo group (between-group difference of changes, 19.3 mm [CI, 5.6 to 32.9 mm]; P = 0.006). Grip strength was not statistically significantly different between groups at any time. Mild paresis of the fingers occurred in 4 patients in the botulinum group at 4 weeks. One patient's symptoms persisted until week 12, whereas none of the patients receiving placebo had the same complaint. At 4 weeks, 10 patients in the botulinum group and 6 patients in the placebo group experienced weak finger extension on the same side as the injection site.LimitationsThe trial was small, and most participants were women. The blinding protocol may have been ineffective because the 4 participants who experienced paresis of the fingers could have correctly assumed that they received an active treatment.ConclusionsBotulinum toxin injection may improve pain over a 3-month period in some patients with lateral epicondylitis, but injections may be associated with digit paresis and weakness of finger extension.

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