4. Discussion
Symptomatic osteoarthritis of the thumb saddle joint is prevalent in ageing populations. Since treatment options are limited, new therapeutic approaches should be considered. Leeches have been applied extensively to treat pain throughout medical history and recently have been found to effectively relieve pain and improve joint function in osteoarthritis of the knee.
In this randomized trial, patients with osteoarthritis of the first carpometacarpal joint who were treated with leech therapy experienced clinically significant improvements in self-perceptions of pain for a period of at least 2 months. Moreover, the single course of leech therapy improved joint function, quality of life, and grip strength when compared with the results of a course of topical diclofenac.
The observed improvements are in accordance with the results of leech therapy for osteoarthritis of the knee and suggest that leech therapy may effectively alleviate the symptoms of osteoarthritis in other types of joints. At the outset the patients in the leech therapy group had slightly higher symptom scores, which might bias the results. But with the exception of pain with motion, the baseline differences were not significant, and since the study was randomized, these differences must have occurred by chance. Moreover, all reported results have been statistically adjusted for baseline differences.
Different mechanisms may explain the observed effects. First, a variety of pharmacological active substances besides hirudin have been described in leech saliva, such as histamin-like vasodilators, kallikrein and tryptase inhibitors, a variety of other proteinase inhibitors and anaesthetics. Through the concomitant activity of a further leech saliva component, hyaluronidase these substances might reach deeper tissue zones, and, possibly, the joint space. Hirudin itself is a potent thrombin-inhibitor and has recently been found to have potent antiinflammatory effects in arthritis. In arthritis models, genes involved in coagulation showed enhanced expression, and arthritis was