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.