## 1 Introduction  
Spinal cord injury (SCI), particularly cervical injury, is a major disorder that causes sensory, motor, and autonomic dysfunctions in different body parts served by the spinal cord below the level of injury [1]. It often leads to permanent sequelae and eventually results in extensive physical and emotional disabilities among patients, families, and society [1]. However, currently, there is no treatment that can promote the complete recovery of functional status in patients with SCI [2]. In particular, patients with tetraplegia cannot perform all the activities of daily living (ADL) due to arm and hand dysfunction. Hence, they require assistance from others. ADL assistive devices can improve the independence of patients with cervical SCI and reduce caregiver burden. Therefore, it is important to prescribe an assistive device for cervical SCI with consideration of the person's muscle strength, residual function, and individual circumstances [3]. However, an assistive device made from ready-made products is manufactured in a batch shape and size. Hence, it is difficult to match to the individual characteristics of patients. Prefabricated aids and splints can be uncomfortable and unsuitable. Thus, they can cause different conditions such as pain, edema, pressure, and perspiration, and they cannot maximize patient function. Therefore, patients with cervical SCI cannot gain maximum independence.  
[PERSON] et al. investigated the self-reported availability and the unmet needs of 150 patients with tetraplegia who had impaired hand function and who used 18 different assistive devices [4]. In this study, 67.3% of patients with tetraplegia did not use any assistive device to compensate for impaired hand function. One or two devices were available for 10.0% and 10.7%, respectively [4]. The writing and typing devices were only available in 10.6% and 14.1% of patients, respectively [4]. Therefore, there is a need for a writing and typing devices customized according to SCI severity. In the rehabilitative fields, there is a growing interest in the development of customized assistive devices to accommodate the body's interpersonal anatomical transformation [5]. Three-dimensional (3D) printing offers an innovative method for therapists or physicians to conveniently make customized assistive devices for special use in clinical settings. Three-dimensional printing is a computer-aided manufacturing method that can create 3D objects using different materials such as plastic, metal, liquids, and even living cells [6; 7]. Recently, there is a tendency to make the lower limb aesthetic covers, insoles, silicone liners, wheelchair control devices, and spinal orthoses to suit disability characteristics and individual body shape by using 3D design and scanning. This technology is beneficial as it is cost-effective, can be customized, and has enhanced productivity. Hence, it has attracted significant attention in the biomedical field [8; 9].  
The current study aimed to evaluate the effects of customized 3D-printed writing and typing assistive devices in patients with cervical SCI who presented with severe hand dysfunction. Accordingly, it was applied to patients with chronic SCI, and its effects on hand function were evaluated via clinical tests. The device aims to improve the quality of life and self-esteem of patients with cervical SCI.