Effectiveness of 3D-printed orthoses for traumatic and chronic hand conditions: A scoping review

Background In the field of orthotics, the use of three-dimensional (3D) technology as an alternative to the conventional production process of orthoses is growing. Purpose This scoping review aimed to systematically map and summarize studies assessing the effectiveness of 3D-printed orthoses for traumatic and chronic hand conditions, and to identify knowledge gaps. Methods The Cochrane Library, PubMed, EMBASE, CINAHL, Web of Science, IEEE, and PEDro were searched for studies of any type of 3D-printed orthoses for traumatic and chronic hand conditions. Any outcome related to the effectiveness of 3D-printed orthoses was considered. Two reviewers selected eligible studies, charted data on study characteristics by impairment type, and critically appraised the studies, except for case reports/series. Results Seventeen studies were included: four randomized controlled trials, four uncontrolled trials, four case series and five case reports. Only three studies had a sample size >20. Impairments described were forearm fractures (n = 5), spasticity (n = 5), muscle weakness (n = 4), joint contractures (n = 2) and pain (n = 1). Four poor to fair quality studies on forearm fractures supported the effectiveness of 3D-printed orthoses on hand function, functionality, and satisfaction. One good quality study on spasticity demonstrated the effectiveness of 3D-printed orthoses on hand function. One poor quality pain study reported limited positive effects on satisfaction. Studies on muscle weakness and joint contractures showed no benefits. Conclusion Current literature addressing the effectiveness of 3D-printed orthoses for traumatic and chronic hand conditions consists primarily of small and poor methodological quality studies. There is a need for well-designed controlled trials including patient-related outcomes, production time and cost analyses.


INTRODUCTION
Hand function is important for the performance of activities. An injury to the underlying structures of the hand (including the wrist and fingers), either due to trauma or caused by neuro-musculoskeletal disorders (i.e. traumatic and chronic hand conditions) may lead to hand impairments like bone discontinuity, joint deformity, contractures, muscle weakness, spasticity, loss of sensibility, and/or pain. [1][2][3][4] These impairments may limit a person's ability in performing activities of daily living like eating, dressing and writing, as well as work-and leisure-related activities. [3][4][5][6] Accordingly, this can seriously impact on participation and quality of life. 5,7,8 Orthoses, including casts, are commonly used in the treatment of traumatic and chronic hand conditions. [9][10][11] An orthosis is a rigid or semi rigid device used for the purpose of support, alignment, prevention or correction of joint deformities, or to improve function or restrict motion of a movable body part. 12 For many centuries, plaster casts and, more recently, fiberglass casts have been used in the treatment of traumatic hand conditions. 13,14 These casts are low cost, strong, and easy to apply 15 , and positive outcomes on pain, joint range of motion, and muscle strength have been shown in distal radius fractures and ligament injuries. 14,16 Chronic hand conditions are commonly treated with custom fabricated orthoses of sustainable materials such as resin, leather, silicone or polypropylene. 17 In people with arthritis and post stroke it has been shown that these orthoses can reduce impairments like pain, muscle weakness and spasticity, and increase the ability to use the affected hand in daily activities. 18,19 Despite the reported benefits of conventional casts and custom fabricated orthoses, complications and discomfort have also been reported, including skin lesions (e.g. pressure sores, blisters), improper fit, sweating due to low breathability, heavy weight, bulkiness, and not being waterproof. 11,15,19 Since casts and custom fabricated orthoses are handmade, the risks of complications and discomfort, especially skin lesions and improper fit largely depend on the practitioner's skills and experience. 11,20 Furthermore, the manufacturing of custom fabricated orthoses is a labor intensive and time consuming process. 21 In the last decade, the use of three-dimensional technology started to emerge in the field of orthotics, being a promising alternative to conventional orthoses. This technology involves three-dimensional scanning, modelling and printing, whereby materials are joined, layer by layer to manufacture 3D-printed orthoses. 20 So far, research into 3D-printed orthoses has mainly focused on the lower extremities, including two reviews on 3D-printed (ankle-)foot orthoses. 21,22 These reviews concluded that the use of 3D printing to manufacture (ankle-)foot orthoses seems to have many potential benefits over conventional methods, in terms of improved comfort, fit and function. Furthermore, three-dimensional technology allows to eliminate several steps from the conventional manufacturing process of custom fabricated orthoses, and may improve efficiency by a shorter production time and lower costs. 20,21,23 While previous studies on the effects of 3D-printed orthoses for the upper extremities also indicated some of these benefits, 24-26 a synthesis of the results on the effectiveness of 3D-printed orthoses for the upper extremities, specifically with traumatic and chronic hand conditions is currently lacking.
A preliminary literature search conducted on September 4, 2020, in PubMed, JBI Evidence Synthesis and Open Science Framework registries identified that to date, no scoping or systematic reviews on 3D-printed hand orthoses have been performed and that none are currently underway. Also, the Cochrane Database of Systematic Reviews and the PROSPERO database were searched, revealing no systematic reviews on this topic. Since the use of 3D printing in manufacturing hand orthoses is quite recent and the literature lacks high quality and homogeneous studies to perform a systematic review, we choose to perform a scoping review. The objective of this scoping review is to systematically map and summarize the research done on the effectiveness of 3D-printed orthoses for persons with traumatic and chronic hand conditions, as well as to identify any existing gaps in knowledge and needs for future research.
The scoping review will be conducted in accordance with the JBI methodology guidance for scoping reviews. 27

Eligibility criteria
Population Eligible studies will include participants of any age with hand (including wrist and fingers) conditions due to trauma or chronic neurological, neuromuscular or musculoskeletal disorders.

Interventions
As treatment with 3D-printed orthoses for hand conditions is a relatively new concept and not much research has been conducted, the scoping review will include all types of 3D-printed hand orthoses, whether as a single intervention or combined with other interventions. Studies using orthoses with only small 3D-printed parts, and studies on 3D-printed prostheses and myoelectric orthoses will be excluded. In order to be inclusive of any study that reports on 3D-printed hand orthoses, both studies involving any type of comparator and studies without a comparator will be included.

Outcome measures
Any outcome measure related to the effectiveness of 3D-printed hand orthoses, such as hand function, user satisfaction, adverse events, production time and costs will be included.

Types of studies
There will be no restrictions regarding publication year and study design, meaning that both RCTs and observational studies will be included. Studies will be restricted to the English language, and only full-text publications will be included. Ongoing studies, conference abstracts and posters will be excluded.

Search strategy
The first step will be to conduct a preliminary limited search of The Cochrane Library and PubMed databases, in order to identify the appropriate text words and index terms that will be used as keywords. A second literature search will be undertaken by one reviewer (EL) across the following electronic databases: The Cochrane Library (Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials), PubMed, EMBASE, Web of Science, IEEE, CINAHL and PEDro. The search strategy will be formulated by two reviewers (EL and TO), combining the identified keywords and medical subject headings (MeSH) related to three-dimensional technologies, anatomical body parts and interventions. No filters will be applied. The complete PubMed search strategy is outlined in the Appendix. This search strategy will be adapted for the other indexed databases. As a third step, the reference lists of the selected studies will be searched for additional relevant sources by the two reviewers.
If needed, the authors of eligible studies will be contacted to ask for further information and resolve any uncertainties.

Selection of studies
The search results will be imported into Rayyan, a web-based literature screening program. 28 One reviewer (EL) will remove duplicates and will lead the process of study screening and selection supported by a second reviewer (TO). The two reviewers will independently screen the title and abstract of the search results using the predetermined eligibility criteria to in-or exclude the studies. Each excluded article will be labelled with an exclusion reason in Rayyan. Full-texts will be retrieved and evaluated if it is unclear whether the study meets the eligibility criteria. Conflicts regarding inclusion status will be resolved by discussion. If no consensus is achieved, a third reviewer (MB) will be consulted.

Data extraction
Each study will be charted by one reviewer (EL) using a data extraction table designed in Microsoft Excel. The charted data will be verified by a second reviewer (TO). After discussion, the data extraction table will be eventually updated and refined. Any refinements will be explained in the scoping review report. The following key study characteristics will be extracted: study design, subjects (sample size, age, and diagnosis), intervention(s) (type of orthosis, frequency and duration of wearing, followup, and, if present, description of co-interventions). If disagreements will occur between reviewers, a third reviewer (MB) will be consulted.

Critical appraisal of studies
To provide a qualitative overview of the existing evidence, the randomized controlled trials and uncontrolled clinical trials included in this review will be critically appraised.
The Modified Downs and Black checklist is chosen since it can be used to assess the methodological quality of randomized controlled studies, as well as non-randomized studies. 29 Prior to the critical appraisal, the reviewers (EL, TO, MB) will discuss the checklist's items to ensure the same interpretation. Two reviewers (EL and TO) will independently assess the studies. Disagreements will be resolved through discussion and consensus, if necessary with a third reviewer (MB).

Analysis of the evidence
First, the study selection process will be described. Second, an overview of the characteristics of the included studies will be provided. Third, the results of the methodological quality assessment will be shown. To meet the objectives of the review, data concerning the identified outcome measures will be mapped, summarizing the existing research findings. Furthermore, research gaps in the existing literature will be identified and recommendations for future research in this field will be made.

Presentation of the results
The study selection process of search results will be shown in a PRISMA flow diagram.
The number of studies mapped to each characteristic will be summarized by numerical counts, and the data extraction table will be presented. Critical appraisal scores of the included studies will be tabulated. Outcome measure findings will be descriptively synthesised. If there will be availability of identical outcomes and sufficient homogeneity, data will be pooled and subgroup analysis will be carried out. Findings may be also mapped by a tabular presentation to provide an overview of the outcomes investigated in the included studies. Nevertheless, the development of the framework will be an iterative process that will be refined according to what will emerge while conducting the review.

Conflicts of interest
The contributors declare that there are no conflicts of interest.

Funding
The contributors receive no financial support for the research, future authorship, and/or publication of this scoping review.