Individuals with upper limb functional impairments, such as those resulting from stroke, spinal cord injury, musculoskeletal disorders, or degenerative joint disease, often experience difficulties operating smartphones. Standard devices typically require bilateral, precise fine motor control, which can limit independence, participation, and access to digital communication for this population. Although assistive products such as phone stands, straps, or styluses are available, they are often designed as "one-size-fits-all," lack individualization, and may not be well integrated into daily life.

Three-dimensional (3D) printing offers advantages of customization, modularity, low cost, and rapid production, and may support better matching between users and assistive devices. However, in clinical practice, the use of 3D-printed assistive technology is constrained by the lack of an integrated resource platform and standardized fitting procedures.

This exploratory intervention study aims to develop a 3D assistive device selection interface and a standardized fitting process for smartphone-related devices targeting adults with upper limb dysfunction. Approximately 30 outpatients will be recruited from a regional teaching hospital in northern Taiwan and will receive a 1-week intervention using a 3D-printed mobile phone holder or related assistive device, with occupational therapist support. Pre- and post-intervention assessments will examine smartphone task performance and satisfaction with the assistive technology. Feasibility, usability, and preliminary effectiveness will be evaluated to inform the development of a sustainable clinical service model.

Upper limb dysfunction due to neurological, musculoskeletal, or degenerative conditions frequently interferes with the performance of fine motor tasks, including smartphone operation. Many individuals with unilateral weakness, limited range of motion, pain, or grip instability find it difficult to hold a phone securely, touch the screen accurately, or perform multi-step operations such as dialing, messaging, or taking photos. As smartphones have become central tools for communication, information access, and social participation, these limitations can widen the "digital divide" and negatively affect independence and quality of life.

Although a variety of commercial assistive devices exist (e.g., generic phone stands, straps, styluses, and gripping aids), they are often designed for the "average user" and may not accommodate severe deformities, contractures, or complex motor coordination problems. Many users and clinicians must improvise or modify existing devices, which is time-consuming and may compromise stability and safety. Clinical decision-making regarding assistive device selection frequently relies on individual therapist experience rather than standardized procedures or objective criteria, and patients often lack access to systematic information about available options, features, and indications.

Three-dimensional (3D) printing provides a promising avenue for developing lightweight, modular, and customizable assistive devices that can be tailored to each user's anatomy and functional needs. Prior research has demonstrated that 3D-printed assistive devices can improve functional performance, reduce pain, and increase satisfaction in populations with upper limb impairments. However, in routine rehabilitation practice, the implementation of 3D-printed assistive technology is hindered by (1) the absence of an integrated platform that consolidates design models, indications, and material/safety guidance, and (2) the lack of standardized fitting workflows and validated evaluation tools, which limits reproducibility and wider adoption across therapists and settings.

Objectives

This study is designed as an exploratory intervention to:

Develop an internal 3D assistive device selection interface (menu system) that consolidates smartphone-related assistive resources suitable for individuals with upper limb movement difficulties.

Establish a standardized fitting process (SOP) for smartphone operation supports (e.g., single-hand or bilateral phone holders).

Modify and modularize 5-8 commonly used smartphone assistive devices (e.g., holders, straps, desk or forearm-mounted supports) to enhance functional usability and convenience.

Evaluate the clinical feasibility and preliminary effectiveness of these devices in terms of functional performance, user satisfaction, and efficiency, and use these findings to inform a sustainable service model.

Study Design and Setting

The study adopts a single-group, pre-post exploratory intervention design. Participants will be recruited from the outpatient rehabilitation department of a regional teaching hospital in northern Taiwan. Eligible participants will be adults with upper limb functional impairments who experience difficulties using a smartphone and are able to follow instructions and provide informed consent.

Intervention

After baseline assessment, each participant will undergo a structured selection and fitting process using a 3D-printed smartphone assistive device (e.g., custom mobile phone holder or related support). An internal 3D device menu/interface will support therapist-patient joint decision-making based on functional needs and hand function status.

Participants will be instructed to use the assigned 3D-printed assistive device for at least 10 minutes per day over 1 week in their daily environment. During the intervention period, an occupational therapist will provide two individual follow-up sessions (approximately 15 minutes each) to:

Review the participant's functional abilities and goals.

Explain and demonstrate correct device use and recommended practice activities.

Monitor compensatory patterns, provide posture and movement corrections, and adjust the device or training tasks as needed.

Participants will be asked to complete a brief daily log documenting device usage (e.g., whether used, duration), activity examples, and any discomfort or adverse events.

Outcome Measures

Assessments will be conducted at baseline (pre-intervention) and at the end of the 1-week intervention (post-intervention) by trained occupational therapists who are not involved in the fitting process.

Primary outcomes will include:

Smartphone operation task performance, assessed through standardized tasks such as:

Searching the contact list and making a call

Dialing a phone number using the keypad

Answering a call

Sending a text or instant message

Taking a photo Performance metrics will include completion time, observable errors, and task completion.

Secondary outcomes will include:

User satisfaction with the assistive device, measured using the Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST).

Feasibility indicators, such as adherence to daily device use (from logs), therapist-rated fitting feasibility, and the occurrence and nature of adverse events.

Data Analysis

Descriptive statistics will be used to summarize participant characteristics, device use patterns, and feasibility indicators. Non-parametric tests will compare pre- and post-intervention functional performance and satisfaction scores. Adverse event rates will be calculated to describe safety and tolerability. Linear regression and general linear model-based univariate analyses may be used to explore associations between baseline factors and changes in functional outcomes, where appropriate. Statistical analyses will be performed using SPSS 26.0, with the significance level set at α < 0.05.

The findings of this exploratory trial will inform the refinement of the 3D-printed device library, the standardized fitting process, and the clinical workflow, with the long-term goal of developing a scalable and sustainable 3D-printed assistive technology service model for individuals with upper limb functional impairments.

Inclusion Criteria:

• Currently receiving occupational therapy in the Department of Physical Medicine and Rehabilitation.
• Onset of condition > 3 months.
• Presence of upper-limb functional impairment that causes difficulty or limitations in smartphone use.
• Able to understand instructions for using the assistive device.
• Montreal Cognitive Assessment (MoCA) score > 24.

Exclusion Criteria:

• Age younger than 18 years.
• Severe visual or hearing impairments that would affect the ability to perform smartphone tasks.
• Unstable medical condition that may interfere with participation in the study.

This study will recruit adults with upper limb functional impairments who are currently receiving occupational therapy in the Department of Physical Medicine and Rehabilitation. Eligible participants must have an onset of more than three months, report difficulties or functional needs related to smartphone use due to upper limb impairment, and demonstrate adequate cognitive ability to follow instructions (Montreal Cognitive Assessment [MoCA] score > 24). Individuals younger than 18 years, those with severe visual or hearing impairments, or those with unstable medical conditions that may interfere with participation will be excluded.