A single injection of intra-articular botulinum toxin Type A may significantly decrease pain and improve shoulder function in osteoarthritis sufferers, according to researches presented this week at the American College of Rheumatology Annual Scientific Meeting in Boston, Mass.
Osteoarthritis is the most common joint disease affecting middle-age and older people. It is characterized by progressive damage to the joint cartilage—the slippery material at the end of long bones—and causes changes in the structures around the joint. These changes can include fluid accumulation, bony overgrowth, and loosening and weakness of muscles and tendons, all of which may limit movement and cause pain and swelling.
Injection of botulinum neurotoxin (commonly referred to by the brand name Botox) into joints is a promising new approach for treating sustained shoulder pain brought on by arthritis. An injection of neurotoxin in the joint may work by decreasing the release of certain proteins from the nerves in the joints—thereby decreasing the pain sensation in the joint.
Researchers recently studied the effectiveness of intra-articular botulinum neurotoxin versus placebo in patients with chronic shoulder pain, due to osteoarthritis or rheumatoid arthritis, who did not respond to corticosteroids or pain medication. These patients also were not candidates for shoulder arthroplasty.
Forty-three patients with moderate to severe arthritis pain (categorized as greater than 4.5 on a scale of zero to 10 with zero as no pain and 10 as the worst pain) were randomly placed in two groups and assessed at one, three and six months. The first group received intra-articular neurotoxin and lidocaine, while the second group received saline and lidocaine.
By comparing pain levels before beginning treatment to pain levels 28 days after the treatment, researchers found that pain levels were significantly lower in the patients receiving neurotoxin compared to placebo. Thirty-eight percent of patients receiving the injection of botulinum neurotoxin into the joint had at least a 30 percent reduction in pain score compared to only nine percent of patients in the placebo group. There was a trend toward a greater improvement in shoulder function in the botulinum toxin group, as compared to the placebo group at 28 days.
"This study provides the initial 'proof of concept' of effectiveness of botulinum toxin injection for relief of shoulder joint pain," says investigator in the study, Jasvinder Singh, MBBS, MPH; staff physician, Minneapolis VA Medical Center; assistant professor of medicine, University of Minnesota; visiting scientist and K -12 scholar, Mayo Clinic School of Medicine. "A more sophisticated, larger, multicenter, randomized study is needed to assess efficacy, safety, mode of action, optimal dose and frequency of this novel treatment option."