Thumb Base Osteoarthritis: Ultrasound-guided Platelet-rich Plasma Versus Placebo Injection

The goal of this clinical trial is to evaluate whether platelet-rich plasma (PRP) injections improve pain and function in adults with thumb base osteoarthritis (CMC-I OA). The main questions it aims to answer are: Does a PRP injection reduce pain compared to a placebo (saline) injection? Does PRP improve hand function, strength, and thumb mobility? What adverse events occur following PRP treatment? Researchers will compare PRP injections to a placebo injection (saline solution) to determine whether PRP is an effective treatment for CMC-I osteoarthritis. Participants will: Receive a single ultrasound-guided injection of PRP or placebo (saline) in the CMC-I joint. Attend follow-up visits at 3, 6, 9, and 12 months for clinical assessments. Complete questionnaires on pain (VAS) and hand function (MHQ-DLV) at multiple time points. Undergo physical examinations (grip strength, pinch strength, thumb motion). Undergo ultrasound evaluations to assess joint characteristics.

Inclusion Criteria: * Age 18 or older * Patients with an Eaton-littler score of I, II or III * Patients with uni- or bilateral CMC-I osteoarthritis * Non-responders to conservative therapy i.e., hand therapy and immobilisation after 3 months Exclusion Criteria: * Aged below 18 * Patients with an Eaton-littler score of IV (STT arthrosis) * Surgical interventions of the CMC-I joint * A known articular systemic disease (e.g. rheumatoid arthritis) or additional hand osteoarthritis/ tenosynovitis or metabolic disease like diabetes mellitus * Patients with an infectious arthritis of CMC-I joint * A known psychiatric condition * Neuropathic chronic pain syndrome * Intra articular injection 6 months prior to inclusion * Smoking * Active use of statins