This is an open access article under the CC BY license: An Improved Prosthesis for Through Ankle Joint Amputation 2Yassr Y. Kahtan ,*1 Noon Kadhim Rasheed 1,2 Department of Prosthetics and Orthotics Engineering, College of Engineering, Al-Nahrain University, Baghdad,Iraq *Corresponding Author’s E-mail: Noonkadom96@gmail.com (Received 9 April 2023; Revised 29 September 2023; Accepted 4 October 2023; Published 1 December 2024) https://doi.org/10.22153/kej.2024.10.006 Abstract Prosthetics through the ankle joint are prescribed to patients with a Symes amputation after rehabilitation. Energy can be stored and discharged from the flexible parts, such as the foot, leg and joints of the prostheses. This work improves the prosthetics for amputation through the ankle joint by providing the prosthetics with a movable ankle joint. The most important achievement of the ankle joint is that it performs important walking movements, the most important being planter flexion, dorsiflexion, inversion and eversion. A movable ankle joint was suggested and modelled in the SOLIDWORK program, and it was analysed using the finite element method to evaluate stresses and deformations. This model was used to improve a patient’s gait and reduce exertion. The suggested ankle joint was evaluated through several experimental tests, such as the ground reaction force (GRF) test, 6 min walking test and range of motion test. All the results indicate an improvement in gait parameters and patient adaptation to the suggested ankle-joint prosthetic. The GRF test showed the behaviour of the normal state approaches when using the suggested ankle-joint prosthetic. The results of the GRF test illustrate the percentage difference in the forces for the healthy limb from the suggested movable prosthetic and thetraditional one, with approximate values of 10.96% and 38.88%, respectively. Calculation revealed that the weight of the movable prosthetic with the suggested ankle joint was reduced by 32.69% compared with traditional prosthetic. In addition, a questionnaire was conducted to determine the extent of patient satisfaction when the moving prosthetic was used for a certain period. The questionnaire presented a considerable improvement in patient comfort and other aspects compared with the traditional prosthetic. Keywords: prosthetic, amputation, eversion, inversion, ankle joint, solid work, suggested prosthetic 1. Introduction Prostheses restore body parts lost due to trauma, genetic defects or other causes [1]. These parts allow amputees to have a normal work and social life [2]. Amputation changes a person, from being a healthy individual into one with a disabled body and hurt. This condition causes sadness, pain and poor energy when interacting with the society, which causes difficulty in adaption [3]. Walking is one of the basics of daily life necessary for everyone. However, this movement is a complex functional process that involves the combination of muscles and tendons. A person can move from one place to another while keeping his body image balanced and stable. Walking is difficult for those with amputated lower limbs. The development of the lower extremities is aimed at improving the image of walking through modern and advanced innovative mechanisms [4]. Comprehending the functioning of prostheses is necessary to identify foot movements: eversion (EV)–inversion (IN), dorsiflexion (DF) and plantar flexion (PF) [5] (Figure 1). Al-Khwarizmi Engineering Journal Al-Khwarizmi Engineering Journal ISSN (printed): 1818 – 1171, ISSN (online): 2312 – 0789 Vol. 20, No. 4, December (2024), pp. 13-24 mailto:Noonkadom96@gmail.com https://doi.org/10.22153/kej.2024.10.006 Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 14 Fig. 1. Different foot movements [6] Ruben C. Martinez, et al. (2014) [7] designed an ankle joint for BK amputation with a one-way spring. This spring is meant to store and release energy to aid in toe movement. The weight of the joint can be reduced by changing its component materials. Positive results were obtained in walking while using the joint, but difficulty in standing, sitting and ascending and descending stairs remained. These issues will all be fixed in the future. Eric Nickel et al. (2014) [8] developed a foot-and-ankle model by making a flat foot plate with a thickness of 10 mm from nylon 6/6 with a black crepe layer for cushioning and a rubber layer for guaranteed high stability while walking on sloping ground. In addition, the foot was provided with an annular bottom arch to form a natural rocking shape for the ankle to walk at ground level. The low rigidity of the PF and neutralisation were achieved using a polyurethane rubber bumper (compensating absorber) placed inside the keel ring. According to the initial mechanical test, this stiffness was sufficient to reduce the PF velocity (reducing foot slap), with which positive results were obtained in downhill walking. Pierre Cherelle et al. (2017) [9] proposed an ankle joint design with an mechanism of locking and unlocking four columns by pushing them out of position against the mechanical stop. At this point, the necessary torque is produced during the early stopping phase when the leg’s action compresses the PF springs. To recover the maximum amount of energy from walking, scholars have added additional locking mechanisms to AMP-Foot 3, such as the natural capability to adapt to different walking speeds and incline and improved energy storage during early standing. Experiments involving climbing hills and walking on flat ground were conducted. Dianbiao Dong, et al. (2017) [10] designed a new energy mechanical ankle joint using a five-bar spring mechanism due to its flexibility during various special foot movements in walking. The most important of these movements include PF and DF without restriction. In the future, the act of walking on various terrains must be developed. The ankle joint was suggested due to its importance in performing the crucial movements used for walking. This work aimed to design an ankle joint that is suitable for ankle joint amputation, comfortable while walking, low cost and easy to use and maintain and provides important walking movements (PF, DF, IN and EV). 2. Numerical Analysis Modelling of Ankle Joint using SOLIDWORKS Program An ankle joint design consisting of two pieces, with one attached to the foot and the other to the socket, was proposed. The first model was designed for the ankle joint, and the lateral opening was oval to perform movements (IN and EV). The joint was designed and manufactured using the Solid Work 2018 program. The design failed because it did not activate these movements, which when applied realistically failed to meet the requirements. The function appeared in walking. Figure 2 shows the upper part and Figure 3, the lower part. All the dimensions are in millimeters (mm). Fig. 2. Upper part of the suggested ankle joint Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 15 Fig. 3. Lower part of the ankle joint Another two-piece ankle joint design with a ball end bolt was proposed (Figure 4). The lateral holes assume a circular shape to allow movements of DF and the plantar muscles (Figure 5). The upper hole connected to the socket of the prosthesis has an oval shape with a bolt fixation, and the middle oval hole promotes lateral movements (Figure 6). Fig. 4. Beam for the ankle joint design Fig. 5. Lower part of the ankle joint Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 16 Fig. 6. Upper part of the ankle joint The final form of the suggested ankle joint was manufactured from aluminum in CNC Vector 610 at the University of Technology (Figure 7). Figure 8 shows the final assembly for the suggested ankle joint and foot. Fig. 7. Assembly of the designed suggested ankle joint Fig. 8. Final assembly for the suggested ankle joint with foot 3. Finite Element Analysis (FEA) Often substantive in the phrasing of formulated equations is the use of mechanics samples to solve the command equation of a known phenomena and the capability to predict deterministic and various phenomena in the fields of science and engineering. Numerical styles have been adopted to remove difficult-to-eliminate sacrificial solutions from equations. Among these numerical styles, FEA approximates continuity with an infinite degree of freedom by a discrete body. The finite element method has become a powerful instrument for finding numerical solutions of a vast range of engineering problems [11]. ANSYS–19 was adopted to generate the finite element model (Figure 9). Table 1. Mechanical properties of the parts of movable prosthetic (the suggested ankle joint). Mechanical properties Bolt Ankle joint Foot Material Stainless steel Aluminum alloy Carbon fibre Tensile Ultimate Strength (MPa) 586 310 345 Tensile Yield Strength (MPa) 207 280 230 Young modulus (GPa) 193 71 395 Passion ratio 0.31 0.33 0.2 Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 17 Fig. 9. Ankle joint in ANSYS-19 software 4. Design and Manufacture of the Ankle Joint After designing the joint in the Solid Work program, it was implemented in real life. A piece of aluminum 7075 metal was purchased (20 * 25 cm2), and an X-ray fluorescence test was carried out to determine its material contents and the percentage of each. The joint was manufactured at the University of Technology, in the Laboratories and Workshops section, Turning Department (in a machine; Vector 610) (Figures 10 and11). Fig. 10. CNC machine vector 610 and aluminum block Fig. 11. Final design shape of the ankle joint The ankle joint was assembled using screws, with the addition of springs and a piece of rubber, to enable the necessary movements and absorbance of energy (storage and waste of energy) during the stance phase and push off (Figures 12 and 13). Fig. 12. Ankle joint components Fig. 13. Bolts; the first is half tooth and the other is smooth Figure 14 shows the connection of the joint with the foot and socket. Fig. 14. Final shape of the prosthetic The bolt nut connects every two parts with each other. However, the nut was dispensed in a manner that made the bolt half smooth and half serrated (Figure 15), with the teeth of the pieces to which it was attached to making it like a nut to prevent the addition extra weight when adding nuts. The mathematical equations below were applied: Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 18 Fig. 15. Bolts The tension stress (Figure 16), and stress bearing can be calculated using the following: σ = F A where σ: stress bearing (Pa), F: tensile Load in the axial direction (N) and A: sectional area= 2td (mm) The bolt shear (Figure 17) can be calculated as follows: τ = F A where τ: shear stress (Pa), F: shear load (N) and A: sectional area = πd²/4 (mm) Fig. 16. Tension load of bolt Fig. 17. Bearing joint 5. Results and Discussions 5.1 Numerical Simulation conducted using FEA Results Numerical analysis was carried out using the workbench ANSYS-19 software to determine stress analysis results, deformation and safety factors. Force (900 N) was applied on the bolt and surface of the upper part of the suggested ankle joint (Figure 18). Fig. 18. Applied force in ANSYS software The following steps were suitable for the FEA when using the ANSYS program. The ankle joint was analysed in the static structure by applying load on the top of the ankle joint for two cases (heel strike and toe off), by making the fixation the base for the entire foot in one and by making the fixation only with the heel and toes in another. Heel-Strike Phase ANSYS Analysis Numerical analysis was conducted to determine the stresses and deformations expected to occur during heel strike. When fixation was at the base of the entire foot, and the angle of force was 20°, the von Mises stress reached 17.292 MPa, and the total deformation was 0.015158 mm (Figures 19 and 20, respectively). On the other hand, when the fixation was only at the foot heel, the von Mises stress reached 26.49 MPa, and the total deformation was 0.057475 mm (Figures 21 and 22, respectively). Fig. 19. Von Mises stress in heel strike of the whole- foot fixed support Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 19 Fig. 20. Total deformation in heel strike of the whole-foot fixed support Fig. 21. Von Mises stress in heel strike and heel fixed support Fig. 22. Total deformation in heel strike and heel fixed support Toe-Off Phase ANSYS Analysis Numerical analysis was conducted to determine the stresses and deformations expected to occur during toe off. When fixation was at the base of the whole foot, and the angle of force was 40.5°, the von Mises stress reached 21.326 MPa, and the total deformation was 0.015172 mm (Figures 23 and 24, respectively). On the other hand, when fixation was only at the front of the foot, the von Mises stress reached 38.62 MPa, and the total deformation was 0.063299 mm (Figures 25 and 26, respectively). Fig. 23. Von Mises stress in toe off for the whole-foot fixed support Fig. 24. Total deformation in toe off for the whole- foot fixed support Fig. 25. Von Mises stress in toe off for front-foot fixed support Fig. 26. Total deformation in toe off for front-foot fixed support Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 20 The safety factor for all phases was 15 (Figure 27). Table 2. ANSYS program results Fig. 27. Safety factor Table 2 contains the von Mises stresses and total deformations for all phases. The minimum von mises stress applied was approximately 5 MPa, which was obtained in the standing phase. The highest von Mises stress was approximately 38 MPa, which was obtained in the toe-off phase. This finding indicates that the stronger the movement, the higher the increase in the von Mises stress values. 5.2 Prosthetics Weight The weight of the foot is approximately 23% of the foot length [12]. The weight of a traditional prosthetic for an amputation through the ankle is approximately 1.3 kg. The weight of the movable prosthetic with the suggested ankle joint is 875 g, with the weight of the socket at 500 g. The suggested ankle joint has a weight of 375 g (Figure 28). Fig. 28. a) Weight of the movable prosthetic; b) weight of a traditional prosthetic The difference between the weight of the movable prosthetic with the suggested ankle joint and that of a traditional prosthetic was calculated as follows: ( 1.3 − 0.875 1.3 ) × 100 = 32.69 The weight of the movable prosthetic with the suggested ankle joint was reduced by 32.69% compared with that of the traditional prosthetic, which indicates an increase in patient comfort. 5.3 Ground Reaction Force (GRF) Test Results The GRF test was conducted by a patient walking on the strength board in the rehabilitation laboratory at the Department of Orthotic and Prosthetic Engineering, Al-Nahrain University, once while wearing the traditional prosthesis with a fixed joint (Figure 29) and then while wearing the prosthesis with a movable joint (Figure 30). The test was performed thrice, and the patient rested for 2 min between each attempt. Fixed support Von Mises stress (MPa) Total deformation (mm) Heel Strike Total Foot 17.292 0.015158 Heel Strike Heel 26.49 0.057475 Toe Off Total Foot 21.326 0.015172 Toe Off Front Foot 38.62 0.063299 a b Amputee Side sound Side Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 21 Fig. 29. GRF curve results obtained when using the traditional prosthetic Fig. 30. GRF curves results obtained when using the movable prosthetic The results of the GRF test for the first case (which is the traditional limb) were obtained. The force was higher in the amputated part than in the healthy ones, which shows the extent of the patient’s confusion in using the limb. The patient was attempting to reach the ground at a high speed due to fear of falling. The findings of the GRF test for the second (which is the limb with a movable joint)were acquired. A convergence was observed in the peak force reached by the amputated and healthy parts, which indicates the extent of the patient’s comfort, balance and confidence when walking while wearing the limb with a movable ankle joint (Table 3). Table 3, Maximum forces observed for both prosthetics. Traditional prosthetic test Moveable prosthetic test Max. forces amputee side, N Max. forces sound side, N Max. forces amputee side, N Max. forces sound side, N 1 472.76 336.5 6 417.55 453.29 2 468.90 286.5 7 317.14 356.19 3 464.68 264.7 5 405.62 449.92 Amputee Side sound Side Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 22 Table 3 shows the ratio of the change in the curve in relation to the sound and amputated sides. The results were compared with those observed when using the traditional prosthetic and the prosthetic limb with the suggested ankle joint (Table 4). Table 4, Force ratio of traditional and moveable prosthetics Type of prosthetic The force ratio % Traditional prosthetic 38.88 Movable prosthetic 10.96 The results of the GRF test reveal that the percentage differences in the forces of the healthy limb from the (suggested) movable prosthetic and traditional prosthetics were approximately 10.96% and 38.88%, respectively. 5.4 Results of Ankle Joint Angle Measurement The range of motion of the patient’s ankle joint was measured while wearing the prosthesis with the movable joint while walking and measured again in the standing phase (Figure 31). Fig. 31. Ankle range of motion Table 5 shows the degrees of special movements necessary for walking. Table 5. Ranges of motion of the manufactured ankle joint Motion DF PF IN/EV Normal range limits 20 deg. 20 deg. 5 deg. Range limits for patient 20 deg. 50 deg. 12 deg. This indicates a closeness in the values of normal ankle joint motions compared with those of the manufactured ankle joint and fixed joint. 6. Conclusions A two-piece ankle joint was suggested to provide important movements for walking (PF, DF, IN and EV). One of the pieces is attached to the foot and the other to the socket. Bolts connect the pieces to each other. The upper hole of the piece connected to the socket is characterised by an oval shape for performing IN and EV movements. The movable ankle joint was modelled using the SOLIDWORK program and analysed with the FEA program. Experimental tests were carried out to evaluate the acceptability of the prosthesis for the patient, and the following were observed: 1 . The designed prosthetic with a movable ankle joint is the best for performing movements necessary for walking functions because it was made to be lightweight (the weight of the movable prosthetic was 32.69% lower than that of a traditional prosthetic), inexpensive and small in size compared with a traditional prosthetic limb. The ankle joint was designed using the SolidWork program, analysed with the FEA program and then manufactured using a CNC machine. 2. The results obtained from the FEA program indicate that the highest stress was 38 MPa in the toe-off phase, but it was obtained only when the front of the foot was connected to the ground. The least amount of stress (5 MPa) was reached in the standing phase. The whole-foot fixed support and safety factors in all cases were equal to 15. 3. From the GRF test, when using the traditional prosthetic, instability was observed in the gait compared with the moving limb, which is close to a sound foot. According to the results of the GRF test, the percentage difference in the forces for the sound limb from the (suggested) movable and traditional prosthetics were approximately 10.96% and 38.88%, respectively. The extent of the amputee’s comfort and satisfaction with the movable prosthesis was observed in the 6 min walking test with the prosthetic limb with a movable ankle joint and by measuring the stride length, step length and step width. 4. In general, the patient felt more satisfied while using the prosthesis with a movable ankle joint. Abbreviations: PF Planter flexion, DF Dorsiflexion, IN Inversion, EV Eversion, ROM Range of Motion, 6MWT Six Minute Walking Test, GRF Ground Reaction Force, FEM Finite Element Method Noon Kadhim Al-Khwarizmi Engineering Journal, Vol. 20, No.4, P.P. 13- 24 (2024) 23 7. References [1] Mohsin J. Jweeg and Jana S. Jaffar, “Vibration Analysis of Prosthesis for the through knee Amputation”, Al-Nahrain University, College of Engineering Journal (NUCEJ) Vol.91 No.1, 2016. [2] Stefano Alleva, Michele Gabrio Antonelli, Pierluigi Beomonte Zobel and Francesco Durante, “Biomechanical Design and Prototyping of a Powered Ankle-Foot Prosthesis”, Materials Journal, Vol.13, 5806 ,doi:10.3390/ma13245806 , 2020. [3] Anila Viran, Carol Ewashen, Jane Werunga and Teri Green, “Caring for Patients with Limb Amputation”, Nursing Standard, Vol.30, NO.6 ,2015. [4] Huong Thi Thu Vu , Dianbiao Dong , Hoang- Long Cao, Tom Verstraten , Dirk Lefeber , Bram Vanderborght and Joost Geeroms , “A Review of Gait Phase Detection Algorithms for Lower Limb Prostheses” , Sensors journal, 20, 3972, doi:10.3390/s20143972, 2020. [5] Joel Zagoya-López, Luis Adrián Zúñiga- Avilés, Adriana H. Vilchis-González and Juan Carlos Ávila-Vilchis, “Review Foot/Ankle Prostheses Design Approach Based on Scientometric and Patentometric Analyses”, Appl. Sci. Journal, Vol.11, 5591, https://doi.org/10.3390/app11125591, 2021. [6] Claire L. Brockett and Graham J. Chapman, “Biomechanics of the ankle”, National Library Medicine Journal, Vol.30(3):232-238 , 2016. [7] Ruben C. Martinez, Roberto L. Avitia, Miguel E. Bravo and Marco A. Reyna, “A Low Cost Design of Powered Ankle-Knee Prosthesis for Lower Limb Amputees - Preliminary Results”, International Conference on Biomedical Electronics and Devices, dio:10.5220/0004914402530258, 2014. [8] Eric Nickel, Jonathon Sensinger and Andrew Hansen, “Passive prosthetic ankle-foot mechanism for automatic adaptation to sloped surface”, Journal of Rehabilitation & Development, Vol. 51, NO. 5, 2014. [9] Pierre Cherelle, Victor Grosu, Louis Flynn, Karen Junius, Marta Moltedo, Bram Vanderborght and Dirk Lefeber, “The Ankle Mimicking Prosthetic Foot 3 -Locking Mechanisms, Actuator Design, Control and Experiments with an Amputee”, Journal of Robotics and Autonomous Systems, Vol.91, 2017. [10] Dianbiao Dong, Wenjie Ge, Shumin Liu, Fan Xia and Yuanxi Sun, “Design and optimization of a powered ankle-foot prosthesis using a geared five-bar spring mechanism”, International Journal of Advanced Robotic Systems, Vol.10, dio: 10.1177/1729881417704545, 2017. [11] Muslim Muhsin Ali, “Design and Analysis of a Non-Articulated Prosthetic Foot for People of Special Needs”, MSc.Thesis, Nahrain University, 2010. [12] Carina Price and Christopher Nester, “Foot dimensions and morphology in healthy weight, overweight and obese males Clinical Biomechanics”, Centre for Health Science Research, University of Salford, Salford, England, United Kingdom, 2016. (2024) 13-24، صفحة 4، العدد20مجلة الخوارزمي الهندسية المجلدنون كاظم رشيد 24 تحسين الطرف الصناعي لبتر خالل مفصل الكاحل 2ياسر يعرب قحطان ،*1نون كاظم رشيد قسم هندسة االطراف والمساند الصناعية، كلية الهندسة، جامعة النهرين 2،1 Noonkadom96@gmail.com: البريد اإللكتروني* المستخلص ( بعد عملية إعادة التأهي . يمكن تخزين الخاقة Symesيعانون من بتر )يتم وصفففففر ا طراف االصفففففخناعية من لكا م صففففف الكا للمر ففففف ال ين للبتر من لكا وت ريغها من ا جزاء المرنة مث القدم والسفا وم اصف ا طراف االصفخناعية. وتتمث دا دة ه ا العم دي نح ي سفن ا طراف االصفخناعية لم صف الكا هو نح يدد ركا مهمة دي الميفي همها )انثناء م صف الكا من لكا تزويد ا طراف االصفخناعية بم صف كا مت رأ. هم إن ا وت ليلح باسفففتخدام SOLIDWORKالمصفففي ، عخر يهر ، انقكل للدال ، انقكل للخا. (. تم اقترات وتصفففميم م صففف الكا المت رأ دي برنام ين ميية المريض وتقلي ال هد المب وا. يتم تقييم م ص الكا المقترت من طريقة العناصر الم دودة لتقييم الضغوط والتيوها . يستخدم ه ا النموذ لت س ت سفففن دي لكا عدة التبا.ا ت ريبية مث التبا. قوة .د ال ع اال. فففي والتبا. سفففق دقا م ميفففي مسفففتمر والتبا. مدي ال ركة. تيفففير جمي النتا إل المقترت ، ويظهر التبا. قوة .د ال ع اال. ففي ن سففلوأ م صفف الكا يقترل من ال الة معايير الميففية وتكير المريض م م صفف الكا االصففخناعي وي للخرف الخبيعية عند اسفففتخدام م صففف الكا االصفففخناعي المقترت . و ففف ق نتا التبا. قوة .د ال ع اال. فففي ن النسفففبة الم وية لكلتكف دي الق ٪ عل التوالي. عند سفففال الو ن ، تيفففير ٣٨‚٨٨٪ ، ١٠‚٩٦والخرف االصفففخناعي التقليد والي السفففليم من الخرف االصفففخناعي المت رأ )المقترت( ٪ مقا.نةً با طراف الصففناعية التقليدية. باإل ففادة إل ٣٢‚٦٩النتا إل ن و ن الخرف االصففخناعي المت رأ م م صفف الكا المقترت انخ ض بنسففبة المريض عند اسففففتخدام الخرف االصففففخناعي المت رأ ل ترة من الزمن. قدم االسففففتبيان ت سففففنا كبيرا دي .ا ة ذلك ، تم إجراء اسففففتبيان لمعردة مدي . ففففا .ناعية التقليديةالمريض وال وانب ا لري لكستبيان بالمقا.نة م ا طراف الص mailto:Noonkadom96@gmail.com https://doi.org/10.22153/kej.2024.10.006 3. Finite Element Analysis (FEA)