Efficacy of Intra-Articular OnabotulinumtoxinA and Sodium Chloride Injections in Base-of-Thumb Osteoarthritis: A Randomized Double-Blind Controlled Trial

The primary objective of this study is to evaluate the efficacy of two **intra-articular** injections of onabotulinumtoxinA compared to one injection of onabotulinumtoxinA combined with one injection of normal saline, and two injections of normal saline, in reducing base-of-thumb pain at six months post-initial injection in adults with painful base-of-thumb **osteoarthritis**. This is clinically relevant as it aims to determine the most effective treatment regimen for managing pain associated with this common form of osteoarthritis, potentially improving patient outcomes and quality of life.

Secondary objectives include comparing the effects of the aforementioned injection regimens on: - Base-of-thumb pain during follow-up - Hand-specific activity limitations - Patient global assessment - Health-related quality of life - Osteoarthritis Research Society International-Outcome Measures in Rheumatology response - Economic evaluation

The clinical trial involves **adults aged at least 18 years** diagnosed with painful base-of-thumb **osteoarthritis**. The study population includes both male and female participants, with no specific gender restrictions. Participants are required to have a pain intensity of at least 30 on a self-administered 11-point pain numeric rating scale, and X-ray evidence of trapezometacarpial osteoarthritis. The trial population was selected based on specific inclusion criteria, including the presence of osteophytes, joint space narrowing, subchondral bone sclerosis, or subchondral cysts, as well as meeting the 1990 ACR classification criteria for hand osteoarthritis adapted to trapezometacarpial osteoarthritis. The study does not provide information on the total number of participants, as the sponsor has not disclosed this data. Participants must be affiliated with a mode of social security and women of childbearing potential are required to have a negative pregnancy test. The trial does not specify any particular lifestyle considerations such as diet or physical activity. The study includes a vulnerable population, although specific details regarding this aspect are not provided.

The clinical trial is designed to evaluate the **efficacy** of two ultrasound-guided intra-articular injections of **onabotulinumtoxinA** in combination with custom-made rigid splinting for the treatment of painful base-of-thumb **osteoarthritis**. This study is structured as a randomized, double-blind, controlled trial with three parallel arms. The trial will compare the effects of two intra-articular injections of onabotulinumtoxinA, one injection of onabotulinumtoxinA combined with one of normal saline, and two injections of normal saline. The primary endpoint is the mean change from baseline in base-of-thumb pain at six months post-initial injection, assessed using a self-administered 11-point numeric rating scale.

Participants will be involved in the study for a maximum of three months, with the trial estimated to conclude by December 2027. The study will commence recruitment in December 2024. The sequence of study visits includes an initial screening visit to confirm eligibility based on criteria such as age, pain intensity, and radiographic evidence of trapezometacarpial osteoarthritis. Follow-up visits will be scheduled to monitor the participants' response to treatment and to ensure adherence to the study protocol. The end-of-study visit will assess the primary endpoint and gather final data for analysis.

Inclusion criteria require participants to be adults aged 18 years or older with a pain intensity of at least 30 on the numeric rating scale, and evidence of trapezometacarpial osteoarthritis. Exclusion criteria are not specified in the provided data. Participants may be withdrawn from the study if they fail to adhere to the protocol, experience adverse effects, or choose to withdraw consent. The trial is not classified as low intervention and is categorized as a Phase III study, indicating its focus on assessing the treatment's efficacy and safety in a larger population.

The clinical trial involves the administration of **onabotulinumtoxinA**, commercially known as BOTOX 50 UNITÉS ALLERGAN, which is provided in the form of a **poudre pour solution injectable**. This experimental medication is prepared as a **solution for injection** and is administered via the **intraarticular route**. The active substance, **botulinum toxin type A**, is a protein of non-human origin. The trial protocol specifies a maximum treatment period of 3 months, with the dosing schedule involving two intra-articular injections. The precise dosage in units is not specified, and the administration is conducted under ultrasound guidance to ensure accuracy. Participant compliance is monitored through scheduled follow-up visits and assessments.

The comparator treatment in this study is **sodium chloride**, which serves as a placebo. It is also provided as a **solution for injection** and administered via the **intraarticular route**. Sodium chloride is a chemical substance, and its use in the trial is to evaluate the placebo effect in comparison to the active treatment. The administration schedule mirrors that of the experimental treatment, with two intra-articular injections over a 3-month period. The trial is designed as a randomized double-blind controlled study, ensuring that neither the participants nor the investigators are aware of the treatment allocations, thus maintaining the integrity of the trial results.

Efficacy in this clinical trial will be assessed by evaluating the primary endpoint, which is the mean change from baseline in base-of-thumb pain on the painful side, either left or right. This will be measured using a self-administered 11-point numeric rating scale, where 0 indicates no pain and 100 indicates maximal pain. The assessment will occur at 6 months following the first intra-articular injection. The analysis will be conducted by intention to treat, ensuring that all participants are included in the group to which they were originally assigned, regardless of whether they completed the treatment as per the protocol.