Thumb osteoarthritis or trapeziometacarpal osteoarthritis (TMO) is a common and painful form of hand arthritis that limits thumb mobility and hand function, affecting patients' quality of life. Although corticosteroids injections are a typical treatment, their effectiveness has been challenged, and side effects have been reported. Recent studies suggest that saline injections, usually considered inactive, might be a viable treatment option. The primary goal of this study is to compare the effectiveness of saline injections versus corticosteroids injections in reducing TMO-related pain and improving hand function. In this study, 40 people with TMO will be randomly assigned to receive either a corticosteroids or a saline injection, without them or the doctors performing the injection knowing which one was administered (double blind). If saline injections prove more effective, they could provide a less harmful and cheaper therapeutic alternative for TMO patients.

Trapeziometacarpal osteoarthritis (TMO) is one of the most painful, disabling and prevalent hand osteoarthritis. One of the most common treatments for TMO is an intra-articular corticosteroids injection. However, non-superiority of corticosteroids injection over placebo to reduce pain has also been reported for TMO and other types of osteoarthritis (knee, hip, or shoulder). Furthermore, adverse effects of corticosteroids injection such as subcutaneous atrophy, tendon ruptures, and articular cartilage damage have been reported. Given the uncertain relevance of corticosteroids injection as a therapeutic agent, it becomes imperative to consider alternative options. In fact, three systematic reviews suggest that saline injections may be a viable option for TMO or knee pain.

To investigate the hypothesis that saline injection is a more effective modality than corticosteroids injection for the treatment of TMO in terms of reducing TMO pain and improving hand function, we must undertake a large, randomized trial in real clinical settings to ensure the acquisition of high-quality evidence. This pilot project is a preparatory phase for a larger study aimed at comparing the effectiveness of saline and corticosteroids injections in treating TMO, focusing on pain reduction and functional improvements. The study design is a pragmatic, double-blind randomized trial, adhering to PRECIS-2 guidelines.

The pilot randomized controlled trial will assess the feasibility of a study by evaluating aspects such as recruitment capabilities, treatment adherence, and the success of blinding techniques for participants and clinicians. It will also identify potential challenges and gather preliminary data to support a funding application for the full-scale study. Recruitment and data collection are planned over a 12-month period, targeting 40 participants initially to refine procedures and validate the study's feasibility. Participants will be randomly assigned to treatment, and the clinicians delivering the intervention will be blinded to the content of the injections. The study's primary outcome will measure pain intensity using a numeric scale at multiple time points, while secondary outcomes include upper limb functional limitations using the QuickDASH scale. These will be measured at baseline, before treatment, and at follow-up, 1, 3, and 6 months after treatment.

Inclusion Criteria:

• aged ≥18 years;
• diagnosis of TMO was confirmed by X-ray interpreted by a radiologist;
• suffering from pain at the base of the thumb;
• the attending physician deems that an intra-articular corticosteroid injection would be beneficial, rather than opting for other types of intervention such as surgery
• can read, understand and answer in either French or English.

Exclusion Criteria:

• having received one or more corticosteroid injections in the last 12 months or surgery on the affected thumb;
• suffering from painful thumb caused by a trauma (e.g., fracture, sprain), rheumatoid arthritis, or De Quervain's tendonitis; and
• being pregnant or breastfeeding; and
• known allergies to any components of the solutions (triamcinolone acetonide, benzyl alcohol, carboxymethylcellulose sodium, hydrochloric acid, polysorbate, sodium chloride, or sodium hydroxide) or to iodinated contrast media.

IPD will be shared by the investigators upon reasonable request

Undecided yet

IPD will be shared by the investigators upon reasonable request

Participants will be randomly assigned in a 1:1 ratio to receive either the saline injection or the corticosteroid injection. Opaque syringes will be used to mask the content to both participants and clinicians. The study will use computer-generated randomization to prepare and distribute sealed, opaque envelopes. These envelopes, indicating whether saline or corticosteroids should be injected, will be randomly sent to the healthcare facilities of the doctors involved in the study.