An evaluation of 3D printable elastics for post stroke dynamic hand bracing: a pilot study

Figures & data

Table 1. Participant demographics.

	Participants (n = 5)
Age, years (mean, SD)	50 (18)
Gender (male/female)	5/0
Dominant hand, prestroke (right/left)	5/0
Stroke-affected side (right/left)	3/2
Time since stroke, months (mean, SD)	38 (72)
SISHand (mean, SD)	37 (27)

Abbreviations: SD, standard deviation; SIS_Hand, hand function subscore of Stroke Impact Scale.

Figure 1. Dynamic wrist–hand–finger orthosis. Rendering of prototype orthosis on the left and fabrications of orthosis on the right with five different finger-extension components fabricated using 3DP elastic materials from commercial vendors: (i) thermoplastic polyurethane by Shapeways Holdings, Inc.; (ii) elastomeric polyurethane by Shapeways Holdings, inc.; (iii) thermoplastic polyurethane by Sculpteo; (iv) elastomeric polyurethane by Sculpteo; and (v) thermoplastic polyurethane by i.Materialize N.V.

Table 2. Commercial 3DP elastic materials for the dynamic WHFO.

Components		Material	Vendor (location)	3D printing method	Modulus of elasticity (MPa)
Base wrist component		TPU	Shapeways Holding, Inc. (New York, NY, USA)	SLS	45.80
Finger-extension components	BC #1	TPU	Shapeways Holdings, Inc. (New York, NY, USA)	SLS	45.80
	BC #2	EPU	Shapeways Holdings, Inc. (New York, NY, USA)	CLIP	3.33
	BC #3	TPU	Sculpteo (Paris, France)	MJP	39.90
	BC #4	EPU	Sculpteo (Paris, France)	CLIP	3.24
	BC #5	TPU	i.Materialize N.V. (Leuven, Belgium)	MJP	43.10

Abbreviations: BC, brace condition; MPa, megapascals; TPU, thermoplastic polyurethane; SLS, selective laser sinter; EPU, elastomeric polyurethane; CLIP, continuous liquid interphase production; MJP, multi-jet print.

Figure 2. An exemplary setup of the in-house tensile test of one material along with the representative stress-strain curves for the five dogbone specimens tested for that material.

Figure 3. Test apparatuses used to acquire metrics of hand biomechanics and upper extremity function including: (a) maximum pincer force; (b) pincer aperture; and (c) box and block test.

Table 3. Usability survey results for the dynamic WHFO.

Likert-scale question	Prototype	Commercial	Prototype - Commercial
(lower scores being more positive)	Median (range)		p-value*
Ease of use?	2 (1–8)	3 (1–8)	0.500
Likelihood you would use?	8 (2–10)	4 (1–8)	0.380
How intuitive?	3 (1–10)	3 (1–10)	1.000
How comfortable?	4 (1–7)	3 (1–8)	1.000
How appealing to look at and wear?	2 (1–8)	3 (1–6)	1.000

*Based on the Wilcoxon signed-rank testing difference between prototype and commercial = 0.

Abbreviations: WHFO, wrist–hand–finger orthosis.

Figure 4. Maximum pincer force for each participant and orthosis condition. Note baseline on the left and commercial brace on the right and 3DP prototype brace listed in order of increasing stiffness.

Figure 5. Box and block test scores for each participant and orthosis condition. Note baseline on the left and commercial brace on the right and 3DP prototype brace listed in order of increasing stiffness.

Data availability statement

The datasets generated and analyzed during current study are available from the corresponding author upon reasonable request.