INNOVATIVE 3D-PRINTED INTERNAL STRUCTURE IN SILICONE PARTIAL-HAND PROSTHESES: ENHANCING FUNCTION AND MECHANICAL PERFORMANCE

BACKGROUND: Silicone cosmetic prostheses play a significant role in improving body image and reducing psychosocial issues among individuals with partial hand amputation; however, high weight and insufficient stiffness are their primary limitations. OBJECTIVES: To design a novel silicone cosmetic prosthesis with a lightweight and durable internal structure using 3D printing and to evaluate its impact on user satisfaction and functional ability scores. METHODOLOGY: This pilot semi-experimental pre–post study was conducted between February and September 2024 at a prosthetics and orthotics center in Tehran, on 7 individuals (4 males, 3 females; mean age 27.9 ± 7.6 years) with unilateral partial hand amputation. For each participant, a silicone cosmetic prosthesis with a 3D-printed internal thermoplastic polyurethane (TPU) structure was fabricated. User satisfaction was assessed using the TAPES questionnaire, and functional ability was evaluated using the DASH questionnaire. Prosthesis stiffness was measured using a force–displacement test, and fatigue resistance was assessed through a displacement-controlled cyclic loading test (25 mm) until failure. Outcomes were compared with participants’ existing conventional full-silicone prostheses. RESULTS: The results indicated that the TPU prosthesis was lighter than the full-silicone prosthesis (0.200 ± 0.05 vs. 0.29 ± 0.09 kg; p = 0.001), stiffer (81.43 ± 27.07 vs. 27.29 ± 10.83 N; p = 0.028), and more resistant to fatigue in the tested sample (36,500 vs. 13,800 cycles). The mean DASH score was lower for the TPU prosthesis (43.69 ± 11.67 vs. 53.09 ± 11.56; p = 0.012), indicating superior functional ability. Additionally, overall satisfaction (TAPES) and separately measured satisfaction with prosthesis stiffness were higher in the TPU prosthesis. Participants reported longer daily wear time with the TPU prosthesis. CONCLUSION: In this pilot sample, silicone prostheses incorporating a 3D-printed internal TPU structure demonstrated improved mechanical and functional outcomes compared to conventional full-silicone prostheses. Despite the limitation of small sample size, these preliminary findings highlight the potential value of integrating lightweight and durable materials through 3D printing in the design of cosmetic partial-hand prostheses. Future studies with larger sample sizes are necessary to confirm and generalize these results. Layman's Abstract Losing part of the hand can affect not only daily function but also self-confidence and quality of life. Many individuals with partial hand amputation use silicone cosmetic prostheses to restore the natural appearance of the hand. Although these prostheses look realistic, they are often heavy and may not provide enough stiffness to assist with daily activities. In this study, we designed a new type of silicone cosmetic prosthesis that includes a lightweight internal structure made from thermoplastic polyurethane (TPU) using 3D printing technology. Seven individuals with unilateral partial hand amputation tested both the conventional full-silicone prosthesis and the new TPU-based design. The results showed that the prosthesis with the 3D-printed TPU internal structure was lighter, stiffer, and more resistant to repeated bending over time compared to the conventional model. Participants reported better functional ability, higher overall satisfaction, and better satisfaction with stiffness when using the TPU prosthesis. They also reported longer daily use of the TPU prosthesis. These findings suggest that combining silicone with a lightweight 3D-printed internal structure may improve comfort, durability, and daily function for individuals with partial hand amputation. Larger studies are needed to confirm these results. Article PDF Link: https://jps.library.utoronto.ca/index.php/cpoj/article/view/47092/35110 How To Cite: Mohammad Zadeh M, Jalali M, Khaghani A. Innovative 3D-printed internal structure in silicone partial-hand prostheses: Enhancing function and mechanical performance. Can Prosthet Orthot J. 2026;9(1):10. https://doi.org/10.33137/cpoj.v9i1.47092  Corresponding Author: Alireza Khaghani, PhDAffiliation: Rehabilitation Research Center, Department of Orthotics and Prosthetics, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Iran.E-Mail: Khaghani.a@iums.ac.ir ORCID ID: https://orcid.org/0000-0002-7585-3062