Effectiveness and Safety of Breeded Leech for Symptomatic Primary Arthrosis of the First Carpometacarpal Joint

Inclusion Criteria: * Male and female patients aged 35 to 85 years * Pain intensity in the region of the thumb base in pain phases ≥ 40 mm on the VAS of 0 to 100 mm (relative to the last 24 hours) * Complaints for at least 3 months * X-ray Stadium Eaton I-IV at least once secured Exclusion Criteria: * Anticoagulation (Marcumar, Heparin) * Haemophilia, V. Willebrandt Jürgens syndrome, thrombocytopathy and other blood anomalies * Combination therapy of ASA and thienopyridines * Pain medication with opioid analgesics * Systemic medication with corticoids or immunosuppressants * Intraarterticular injections or RSO within the last 3 months * Past or planned surgery on the affected joint in the next 2 months * Pregnancy, lactation * Insulin-dependent type I diabetes mellitus * Acute psychotic disorders * Severe comorbidity