RESUMO
BACKGROUND: Lateral epicondylitis is a common condition for which botulinum toxin has been reported to have a therapeutic role in uncontrolled studies. OBJECTIVE: To determine if an injection of botulinum toxin is more effective than placebo for reducing pain in adults with lateral epicondylitis. DESIGN: Randomized, double-blind, placebo-controlled trial conducted from September 2002 to December 2004. SETTING: Outpatient clinics at a university hospital and a district hospital in Hong Kong. PARTICIPANTS: 60 patients with lateral epicondylitis. MEASUREMENTS: The 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. INTERVENTIONS: A single injection of 60 units of botulinum toxin type A or normal saline placebo. RESULTS: Mean 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. LIMITATIONS: The 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. CONCLUSIONS: Botulinum 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.