Abstract
Background
Recent evidence suggests an anti-nociceptive effect of botulinum toxin.
Objectives
To compare the efficacy and safety of botulinum toxin in comparison to placebo or other treatment options for shoulder pain.
Search methods
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), Ovid MEDLINE, CINAHL (via EBSCOhost), Ovid SPORTDiscus, EMBASE and Science Citation Index.
Selection criteria
Randomized controlled trials (RCTs) comparing botulinum toxin with placebo or active treatment in people with shoulder pain were included.
Data collection and analysis
For continuous measures we calculated mean difference (MD), and for categorical measures risk ratio (RR) (with 95% confidence interval (CI)).
Main results
Six RCTs with 164 patients were included. Five RCTs in participants with post-stroke shoulder pain indicated that compared with placebo, a single intramuscular injection of botulinum toxin A significantly reduced pain at three to six months post-injection (MD -1.2 points, 95% CI -2.4 to -0.07; 0 to 10 point scale) but not at one month (MD -1.1 points, 95% CI -2.9 to 0.7). Shoulder external rotation was increased at one month (MD 9.8°, 95% CI 0.2 to 19.4) but not at three to six months. Shoulder abduction, external rotation or spasticity did not differ between groups, nor did the number of adverse events (RR 1.46, 95% CI 0.6 to 24.3).
One RCT in arthritis-related shoulder pain indicated that botulinum toxin reduced pain severity (MD -2.0, 95% CI -3.7 to -0.3; 10 point scale) and shoulder disability with a reduction in Shoulder Pain and Disability Index score (MD -13.4, 95% CI -24.9 to -1.9; 100 point scale) when compared with placebo. Shoulder abduction was improved (MD 13.8 degrees, 95% CI 3.2 to 44.0). Serious adverse events did not differ between groups (RR 0.35, 95% CI: 0.11, 1.12).
Authors’ conclusions
The results should be interpreted with caution due to few studies with small sample sizes and high risk of bias. Botulinum toxin A injections seem to reduce pain severity and improve shoulder function and range of motion when compared with placebo in patients with shoulder pain due to spastic hemiplegia or arthritis. It is unclear if the benefit of pain relief in post-stroke shoulder pain at three to six months but not at one month is due to limitations of the evidence, which includes small sample sizes with imprecise estimates, or a delayed onset of action. More studies with safety data are needed.
Plain language summary
Botulinum toxin for shoulder pain
This summary of a Cochrane review presents what we know from research about the effects of botulinum toxin on shoulder pain.
The review shows that in people with shoulder pain and muscle spasms, botulinum toxin:
-may improve pain;
-may lead to slightly more adverse events;
-effects on physical function and disability were not reported.
We often do not have precise information about side effects and complications. This is particularly true for rare but serious side effects of botulinum toxin injections such as difficulty swallowing, muscle soreness, respiratory infections, or a rash.
What is botulinum toxin and what is shoulder pain?
Shoulder pain is a common disorder affecting adults around the world. It can be caused by several conditions such as rotator cuff tendinitis, adhesive capsulitis, osteoarthritis of the shoulder and acromio-clavicular joint disease. Although shoulder pain can often go away on its own, sometimes it can result in chronic pain and disability.
Botulinum toxin is produced by the bacteria, Clostridium botulinum. In people with pain and muscle spasms in their shoulder, it may work by blocking muscular nerve signals to the brain and consequently decrease the feeling of pain in the shoulder. Botulinum toxin is given as an injection in the doctor’s office or clinic.
Best estimate of what happens to people with shoulder pain and muscle spasms after 6 to 24 weeks
Pain (after 6 to 12 weeks)
-people who had botulinum toxin injections rated their pain to be 4 on a scale of 0 to 10;
-people who had a fake injection (placebo) rated their pain to be 5 on a scale of 0 to 10;
-people who had botulinum toxin injections rated their pain to be just over 1 point better after treatment (absolute difference: 12%).
Side effects (after 24 weeks)
-33 people out of 100 who had botulinum toxin injections had side effects;
-24 people out of 100 who had a fake injection (placebo) had side effects;
-9 more people out of 100 had side effects with botulinum toxin injections (9% absolute difference).
