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Chow, et al.
for the application . Once the silicone insert was printed unfavorable effects, we adopted 3D printing to fabricate
[47]
and cured on the fabric, it was ready for adherence to the a customized silicone elastomer so that it is the same
pressure sleeve. The sleeve pattern was created using size as the HS. The elastomer is directly attached to the
ExactFlat for Rhino 3D software based on the scanned pressure sleeve so that the debonding of the silicone sheet
geometry of the patient hand. The hand model was is remedied. Figure 2A shows the differences between a
separated at the radial and ulnar sides of the wrist with conventional silicone sheet and our 3D printed silicone
two patterns. Since the created patterns are based on the elastomer.
scanned image of the hand geometry, no pressure can be Another issue that we observed about the silicone
exerted onto an HS and inhibit its growth. Therefore, a sheet is that it may not adhere to skin with just any
reduction of the sleeve circumference is required to create type of scar treating gel. To further confirm this issue,
an effective level of pressure to treat the HS. In this study, we used ASTM D5169 to assess the adhesion between
a reduction factor of 10% was applied which is a common the silicone and skin under various conditions. The
value for pressure garments [48,49] . After the patterns were schematic of the test and photo of the sample are shown
reduced to the appropriate size, the patterns were stitched in Figures 2B and C, respectively. Figure 2D shows that
together in the fifth step of the workflow (Figure 1E). when any random type of scar treating gel is used, lower
shear forces results when compared to skin without the
(3) Finite element analysis for pressure optimization use of any treating gel. When comparing the effect of the
After the pressure sleeve was produced, sub-models of the three different types of gels, SILBIONE BLEND 4001
®
carpal bones, pressure sleeve, silicone elastomer, and hand has a small effect on the shear force, while Hiruscar has
were constructed using FEA software (MSC Marc/Mentat) the worst performance. The pigskin samples that used
®
(Figure 1F). The material properties of the hand, sleeve, Hiruscar showed an approximately 3-fold and 8-fold
and silicone were obtained with reference to the literature reduction of the maximum shear force with the CICA-
®
and the experimental results in Yu et al. and Wu et al. [50,51] . CARE and Mepiform silicone sheets, respectively. This
The material properties and parameters are listed in Table indicates that the application of scar treating gel can
S3. To validate the accuracy of the FE contact model, the further aggravate the problem of silicone sheet debonding.
subject was invited to participate in a wear trial to measure The poor adhesion of the silicone sheet to gel-coated
the interface pressure produced by the pressure garment skin might be a possible challenge, so HS therapy that
and silicone elastomer using the NOVEL Pliance X system combines the use of a silicone sheet and silicone gel, such
(Figure 1G). The system has been objectively evaluated as an onion extract gel, has been seldom discussed in the
and validated for accuracy by different scholars [52,53] . In literature. In our proposed therapy, the silicone elastomer
total, four positions were marked on the subject, including is attached to the pressure sleeve which is secured by the
the center of the HS, and the ulnar, radial, and back of corresponding pressure so that the adhesion of the silicone
the hand which are horizontally aligned with the HS to the skin with silicone gel is not a problematic issue.
landmark. Through the FEA, the pressure distribution on 3.2. Finite element model and validation of
the hand from the silicone elastomer samples with five simulated result
different thicknesses of 1, 2, 3, 4, and 5 mm (the smallest
thickness was considered) and two pressure sleeves Figure 3 illustrates the components of the developed
with circumference reduction factors of 5% and 10% FEM and the simulation process. The FEM simulates the
were systematically evaluated (Figure 1H). A pressure wear process of the hand sleeve. The silicone elastomer
threshold of 25 mmHg was exerted onto the hypertrophic was secured onto the model of the hand to prevent any
scarred area for effective treatment while preserving unanticipated movement during the simulation process.
the wear comfort with the least amount of pressure on Since the circumference of the pressure sleeve is smaller
the other parts of the hand; this is as the optimal design than that of the hand, a face load was applied on the shell
criterion of the pressure sleeve (Figure 1I). elements of the pressure sleeve so that it stretched to
fully fit and came into contact with the hand. During the
3. Results and discussion stretching of the pressure sleeve, the sleeve was shifted
3.1. Evaluation of current treatments toward the hand, and then the face load was applied.
The pressure sleeve then recovered to its original size
Conventionally, the silicone sheet applied onto an HSs and came into contact with the silicone elastomer and
is larger than the HS itself, especially with smaller scars. the hand to simulate the pressure applied by the pressure
Otherwise, the silicone sheet would easily debond, sleeve. In this study, the friction between the hand and
causing inconvenience to the patient. Moreover, there the fabric of the sleeve was neglected. The interface
are negative impacts, such as excessive sweating, when pressure produced by the pressure sleeve and silicone
the silicone covers the healthy skin . To minimize these elastomer was observed at the end of the simulation. The
[26]
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