Design and Mechanical Evaluation of a Polymer Keel SACH Foot Using Finite Element Analysis and Experimental Validation

Agus Setyo Nugroho; Kazuhiko Sasaki; Muhammad  Nouman; Rifky Ismail

doi:10.35882/jeeemi.v8i3.1807

Agus Setyo Nugroho Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand https://orcid.org/0009-0004-9313-8216
Kazuhiko Sasaki Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand https://orcid.org/0000-0002-1778-6308
Muhammad Nouman Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand https://orcid.org/0000-0001-5747-6518
Rifky Ismail Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia https://orcid.org/0000-0003-0445-3405

DOI: https://doi.org/10.35882/jeeemi.v8i3.1807

Keywords: SACH foot; polymer keel; finite element analysis; prosthetic foot; mechanical testing; lower limb prosthesis; experimental validation; biomechanical performance

Abstract

Conventional Solid Ankle Cushion Heel (SACH) foot commonly uses wooden keels, which may exhibit variability in mechanical properties and limited long-term durability. This study aimed to develop and evaluate a polymer-based keel SACH foot as a low-cost alternative with improved mechanical performance. An integrated methodology combining finite element analysis (FEA) and experimental validation was employed. Three polymer keel SACH foot configurations were designed and analyzed under loading conditions that represent heel strike, mid-stance, and terminal stance, in accordance with ISO 10328. The optimal design was subsequently fabricated and tested under static loading conditions to validate the numerical model. The models utilized ABS for the keel, HDPE for the footplate, and vulcanized rubber for the foot body. Mechanical performance was assessed through total deformation, von Mises stress, strain, and safety factor analysis. Among the three configurations, Model A demonstrated the best mechanical performance, with the lowest average deformation (20.12 mm), the lowest stress concentration (12.67 MPa), and the highest safety factor (1.59). The selected design was subsequently fabricated and validated experimentally under static loading conditions up to 1176.78 N. Experimental validation showed strong agreement with FEA predictions, with deviations below 5% across all gait phases, confirming the accuracy of the FEA model. Comparative testing against a conventional wooden-keel SACH foot revealed significantly lower deformation values for the polymer-based keel SACH foot (p < 0.05), indicating improved structural stiffness and more efficient load distribution during loading process. These findings suggest that replacing conventional wooden keels with polymer-based structures can enhance mechanical consistency and structural reliability, while maintaining manufacturability and cost-effectiveness. The proposed design offers a promising approach to developing an affordable and durable prosthetic foot, particularly for use in low- and middle-income countries

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Author Biographies

Kazuhiko Sasaki, Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand

Kazuhiko Sasaki has been an Assistant Professor at the Faculty of Medicine, Siriraj Hospital, Mahidol University, Thailand, since 2018. He received a Bachelor of Science in Physics from Tokyo University of Science in Japan in 1999. He received a Master of Engineering in Bio-Applications and Systems Engineering in March 2002 from Tokyo University of Agriculture and Technology, Japan. And a Ph.D. in Engineering in Electronic and Information Engineering, June 29, 2005, from Tokyo University of Agriculture and Technology, Japan. He worked in the Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand, from 2011 until now

Muhammad Nouman, Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand

Muhammad Nouman April 2014. He received a Bachelor of Prosthetics and Orthotics from Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand. In March 2017, he received an M.Sc. in Biomedical Engineering from the Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand, and in April 2021, he received a Ph.D. In Biomedical Engineering, Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand. Hingga saat ini beliau bekerja sebagai Lecturer di Sirindhorn School of Prosthetics and Orthotics, Faculty of Medicine, Mahidol University, Bangkok, Thailand

Rifky Ismail, Department of Mechanical Engineering, Diponegoro University, Semarang, Indonesia

Rifky Ismail is a Professor and Head of the Bachelor Program of Mechanical Engineering at Diponegoro University, Semarang, Indonesia. He obtained his Bachelor of Engineering degree in 2003 from the Department of Mechanical Engineering, Diponegoro University. He earned his Master of Engineering in 2007 from the Department of Mechanical and Industrial Engineering, Gadjah Mada University, Yogyakarta, Indonesia. In 2013, he earned a Doctor of Engineering degree from the Department of Mechanical Engineering at the University of Twente, The Netherlands. He is also active in research and development in prosthetics and orthotics through the Center of Excellence (COE) for Health Technology, CBIOM3S, UNDIP

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