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Waldburger, et al.
a member of the study group, and an occupational environmentally sustainable material that could be
therapist for hand positioning because of restricted printed within a few hours, as opposed to a ready-made
scanner access were necessary. This partially accounts splint off the shelf.
for the greater production time for 3D splints. For Third, although we gained important insights into
more production efficiency in future studies with issues that need improvement, our results do not confirm
larger patient series, the scanner would preferably be the hypothesized differences in patient comfort and
located in the occupational therapist’s treatment room. satisfaction. This may be partly due to the small sample
Nonetheless, the chosen scanner provided good-quality size, which is the major limitation of our study, as it was
3D surface scans with a single photoshoot, which was designed to accommodate a variety of hand surgical
extremely helpful for patients with pain or tremor, or patients and different splint designs. We are aware that
for whom keeping a certain hand or finger in a desired this leads to a selection bias in a small study group, as
position was difficult. The 3D surface scans provided illustrated by the uneven distribution of splint designs
static mesh images, whereas the estimation of soft- between the two groups. On the other hand, patients
tissue thickness over bony prominences was difficult. seemed to be already highly satisfied with the custom-
The accuracy of splint fit, therefore, depended on the made thermoplastic splints from our occupational
experience and anatomical knowledge of the splint therapists. The previously mentioned studies, which
designer. In our pilot study, only the first author designed showed superior patient satisfaction with 3D splints,
the splints. The learning curve remained steep despite drew their conclusions from a comparison of 3D-printed
previous instruction by the software provider and the splints to fiberglass casts rather than thermoplastic
help of occupational therapists. Designing time varied splints. We believe that in comparison with a rigid
enormously, depending on splint type and scan quality, cast that cannot be taken off, a removable lightweight
but an improvement in efficiency was clearly noticeable. splint model would always be favored. In our study,
For future trials, we propose addressing these issues by we minimized the design bias. Exploration of the full
developing algorithms that prepare the 3D data and potential of individualized design would probably have
produce a first virtual splint design that needs small led to larger differences between the two groups; at the
adjustments. This will potentially ease the design same time, it would have reduced their comparability. We
process so that occupational therapists could help not would need to perform a larger trial with a high number
only with hand positioning in the scanner but also with of participants to detect or rule out potential significant
the computer-aided splint design. differences between 3D and thermoplastic splints in our
Second, for the printing of splints, FDM was setting.
proposed as a potentially applicable technique . We Fourth, we are aware that the innovative character
[9]
chose this technique because of its wide availability, of 3D-printed splints and their so-called coolness factor
relatively quick production time, and cost-effectiveness, could have led to a response bias in our study. The nature of
also for low-and-middle-income countries. However, the intervention, however, makes blinding of participants
there was substantial time loss in post-processing the impossible. A further risk of bias lies in the monitored
prints. Furthermore, the FDM method revealed limitations answering of questionnaires during therapy sessions.
in material stability by splint breakage, occurring after To determine and compare satisfaction and wearing
heavier use of the splints. This could be improved with comfort, we had to use non-validated questionnaires,
printing methods that do not rely on layering, such as as, unfortunately, no suitable assessment tool was found
laser sintering. The method needs to be balanced against in literature for temporary splinting. Therefore, our
higher printing costs and further increases in production questionnaires are the only available critical assessment
time as a result of the need for periodic cooling. Regarding tool of splint quality that we are aware of, and no
the material, PLA is environmentally sustainable and has comparison to other groups was feasible. Our simple
the advantage of possible splint adjustment after printing questionnaires may not be able to satisfactorily detect
because of its thermoformability. Throughout our study, small differences in patient comfort and satisfaction, as
the likelihood of splint adjustments was similar in the we found generally high acceptance rates. Refinement of
two groups. In our opinion, material used for hand splints these questionnaires is, therefore, necessary for further
should, therefore, possess a minimum of formability to studies.
allow comfortable wearing and removal of the splint, 5. Conclusions
as well as modifications to accommodate swelling and
bony prominences. As many different printing methods Splint adjustment seems to be inevitable, even for
and materials are currently under investigation, we 3D-printed made-to-measure splints. In our opinion, the
are looking forward to further tests. We would prefer cost-effectiveness of 3D-printed splints can be superior
a moldable, adjustable, and lightweight yet rigid and to current standards only if multiple adjustments can

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