This study will investigate the effectiveness of 3D-printed splints for treating thumb osteoarthritis (CMC OA). These splints are made by Occupational Therapists and Physical Therapists out of low-temperature plastic and formed on the patient's hand. 3D printed splints involve photographing the hand and creating a digital file of the splint. This is then printed and fit on the patient.

The goal of this cross-over clinical trial is to compare the effectiveness of 3D-printed splints versus thermoplastic splints for treating thumb osteoarthritis (CMC OA).

The main question[s] it aims to answer are:

Primary objective:

• Evaluate the general useability and possible benefits of splint production by 3D printing in a clinical setting

Secondary objectives:

• Compare the effectiveness of 3D printed orthosis and the low-temperature plastic fabrication manual method in pain reduction
• Compare the effectiveness of 3D printed orthosis and the low-temperature plastic fabrication manual method in improving the function.
• Compare the satisfaction of patients with the 3D printed orthosis and low-temperature plastic fabrication manual method.
• Compare the length of time needed to fabricate each orthosis
• Compare the weight of orthosis

Participants will provide with two splints (traditional orthosis and 3D-printed orthoses). Participants will use the first orthosis for three weeks, be given a week for washout, and then cross over to the second orthosis.

Non-surgical treatment is the initial consideration for symptomatic carpometacarpal (CMC) osteoarthritis (OA). Immobilization with orthosis (splint) is one of the methods of non-surgical treatment. The evidence is mounting regarding the effectiveness of orthosis in OA of the thumb. A recent systematic review indicated that splinting causes a moderate to large effect on pain. However, a recent network meta-analysis showed that a short thermoplastic CMC splint is the best treatment to increase function.

The variations of the recommended orthosis for immobilization of the CMC are varied from the neoprene splints to the rigid thermoplastic material. However, the patient's satisfaction with these materials is different. Patients reported more satisfaction with neoprene thumb splints but found custom-made splints more functional.

Hand therapists typically use low-temperature thermoplastic materials (LTTP) for orthosis fabrication.

3D-printed orthoses are emerging as an alternative for immobilizing joints. Different studies tried to compare the two methods of the 3D printed orthosis with a thermoplastic orthosis and reported some advantages for a 3D printed orthosis. These studies reported advantages including being lighter in weight, producing less incidence of skin irritation, offering better hygiene with less odour and perspiration, appealing and custom-tailored aesthetic design, and the ability to use recycled affordable materials. Furthermore, the fabrication of thermoplastic orthosis needs expertise and knowledge, which require specialized training to fabricate and are time-consuming, expensive, difficult to keep clean, bulky, cumbersome, and unable to tolerate moisture at high temperatures. Also, the thermoplastic material is subject to cracking, requiring the patient to go through the healthcare system again and return to the clinic just for a therapist to make another splint. Off-the-shelf splints have better breathability and longevity but cost more and are often less form-fitting or stabilizing than a therapist-made splint. Despite the numerous advantages of the 3D printed splint listed in the literature, the high cost of equipment, lack of training and skill of clinicians and the long time required for production limited their use in hand therapy.

Progress has been made in developing the 3D of orthoses. Potential advantages include comfort, well-fitting, adequate ventilation in the splint and a clean production process. However, there are challenges in reducing the reliance on the in-person evaluation given the complex geometries of the hand, unavailability of high-resolution scanners, fabrication time that may require multiple visits and cost, equipment materials and expertise. Accurate and high-resolution 3D scanners are available on the market and are currently used in research studies. Different scanners are being used in the literature to scan the hand. Different steps are required to fabricate a 3D printed orthosis, including scanning the body segment with a 3D scanner, CT scan or MRI; transferring the scanned data to a computer modelling software program; printing the orthosis; and finishing/adjusting the final product. The time needed to scan the affected upper limb ranged from 1 to 3 minutes. The time needed to modify the scanned digital file in a computer-aided design software program to be ready for 3D printing was reported to take approximately 1 hour. Only one study reported a 53% reduction in total fabrication time with a 3D-printed orthosis compared with a traditional orthosis.

Few studies compared 3D-printed orthosis with traditional orthosis fabrication in the clinical setting. The reported outcome measures are Outcome measures pain, overall satisfaction, and function. More satisfaction, less skin irritation, itchiness and odour; however, none utilize patients with CMC OA as participants. Chu et al. used 3D hand parametric modelling techniques to create customized designs of short thumb orthoses in healthy adults. They reported that the 3D-printed orthosis provided greater flexibility of hand movement and stronger support than the traditional, manually formed orthosis.

There is a gap in evidence regarding the clinical utility and feasibility of using 3D printing versus traditional orthosis in patients with CMC joint OA.

Patients would be eligible to participate in our study :

• At least 18 years old,
• able to provide written informed consent
• indicating immobilization of CMC as part of their therapy. The orthosis treatment can be in any part of their treatment (first users or the patients with experience of using orthosis).

Patients will be excluded if

• have skin irritation, blister, or wound.
• have neurologic conditions affecting their pain perception in the upper limb.