|Year : 2020 | Volume
| Issue : 4 | Page : 332-336
Designing and evaluation of new dynamic prosthetic foot on transtibial amputees in a low resource setup
Achintya Prakash1, Ranjeet Kumar2, Pooja Kumari2
1 Department of Multiple Disabilities and Rehabilitation, Faculty of Special Education, DSMNR University, Lucknow, Uttar Pradesh, India
2 Department of Prosthetics and Orthotics, ISIC-Institute of Rehabilitation Sciences, New Delhi, India
|Date of Submission||25-Mar-2020|
|Date of Decision||22-May-2020|
|Date of Acceptance||20-Jul-2020|
|Date of Web Publication||15-Oct-2020|
Mr. Achintya Prakash
Room No. 108, A2 Block, DSMNR University, Mohaan Road, Lucknow - 226 017, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
BACKGROUND: Foot as an essential part in lower extremity, serves for variety of purposes in daily life. Complex anatomy and biomechanics of normal foot makes its prosthetic replacement quite challenging. Technological boom in prosthetic industries has somehow improved the performance of prosthetic foot but also hike the cost, resulting in limited accessibility to majority of prosthetic user. In this study, we have designed a new dynamic prosthetic foot at low cost and compare its efficacy from the traditional solid-ankle, cushion-heel (SACH) foot.
MATERIALS AND METHODS: The current prototype presented is a dynamic foot design consisting of commercially available thermoplastic materials that resembles a hybrid model with true ankle articulation and a flexible keel in order to mimic motion in all cardinal planes. A posttest experimental study has been conducted with fifteen individuals selected purposively. The gait parameters with current prototype and SACH foot were analyzed in conventional way by using 10 meter walk test and energy cost was estimated by calculating physiological cost index (PCI). The correlation between gait variables and PCI were analyzed through a paired t-test.
RESULTS: Data analysis shows significant differences in the gait characteristics as stride length (P = 0.000), cadence (P = 0.001), velocity (P = 0.000), and PCI (P value 0.001), comparing the SACH foot and current foot prototype.
CONCLUSION: The study outcome reveals the advantage of current prototype over conventional SACH foot in terms of gait characteristic and energy cost at self-selected walking speed.
Keywords: Dynamic prosthetic foot, energy cost, gait evaluation, low resource setup, transtibial amputee
|How to cite this article:|
Prakash A, Kumar R, Kumari P. Designing and evaluation of new dynamic prosthetic foot on transtibial amputees in a low resource setup. Int J Health Allied Sci 2020;9:332-6
|How to cite this URL:|
Prakash A, Kumar R, Kumari P. Designing and evaluation of new dynamic prosthetic foot on transtibial amputees in a low resource setup. Int J Health Allied Sci [serial online] 2020 [cited 2021 Jan 16];9:332-6. Available from: https://www.ijhas.in/text.asp?2020/9/4/332/298120
| Introduction|| |
Prosthetic foot are the paramount component of lower limb prosthesis, designed to restore the biomechanical role of the anatomical ankle-foot system. Normal human foot is strikingly perplexing that, it cannot be supplanted by any current mechanical substitute so as to imitate its job similarly. That is why the metabolic/energy cost while using prosthesis is much higher rather than a pair of intact limb. In previous studies, it has been estimated that the individuals with transtibial amputation expend energy at 25% greater rates than normal individuals to gain only 87% of normal velocity. Advancement in technology has brought immense transformation in terms of design and material used in the development of prosthetic foot. A prosthetic foot with capacity of storing and releasing energy during particular phases of gait are seen as helpful for the individual with lower limb amputation., Energy storing and release (ESR) or dynamic prosthetic foot comes under this category, which are designed to diminish the quadriceps demand during loading response just after initial contact through its deformation and to minimize the push-off work of prosthetic limb by releasing mechanical energy stored during mid to late stance, instead of wasting it as occurs with non-ESR prosthetic feet, through viscoelastic deformation.
Though many developments in prosthetic foot have taken place to provide sophisticated gait, but the cost is very high. Due to which the conventional solid-ankle, cushion-heel (SACH) foot and Jaipur foot holds their popularity among the lower-extremity prosthetic users in the entire world. As a consequence of their unique properties at relatively very low cost their dominance has never been dented.
The purpose of this study was to design a new dynamic prosthetic foot at a minimum cost and to compare its efficiency in terms of stride characteristics with conventional SACH foot and normal gait parameters.
This study likewise uncovers the distinctions in energy cost of amputee utilizing this new prosthetic feet and SACH foot.
| Materials and Methods|| |
Development of human body parts is extremely testing in prosthetic industry. Any attempt of duplicating the structure, motion and functionality of the most incredible machine existing in the universe is quite difficult. For designing bio-mechanical gadgets, two sorts of mechanical standards have been proposed. (1) Rigid body mechanism, the traditional unbending body system which is used most widely and involves associating inflexible linkage through joints. (2) Compliant Mechanism, constitute mechanical complex utilizing material flexibility over the use of joints connecting nonflexible rigid linkage mechanism. In the present scenario, the compliant mechanism is prioritized over rigid-body mechanisms as it is cost-effective, lightweight, resilient, simple mechanism, and easier manufacturing as a single unit.,
Current prototype description
The current prototype of dynamic (ESR) prosthetic foot [Figure 1] and [Figure 2] represents a hybrid model constituting partially a rigid-body mechanism and partially a compliant mechanism. Plantarflexion and dorsiflexion motions around ankle were simulated through a true hinge joint connecting upper and lower members and regulated through compressible material (rigid-body mechanism). The transverse and frontal plane motions were mimicked through elastic deformation of the same members and keel attached to the lower member (compliant mechanism). The complete prototype is mostly consists of commercially available high-density polymer with the upper member having the provision for the incorporation of pyramid adapter to receive the pylon.
|Figure 1: Simple computer added designing (CAD) model of the current prosthetic foot showing its parts as. upper member A, lower member B, adapter for pylon C, bumpers D and foot plate (elastic keel) E|
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During the analysis of temporal and distance variables with the current design and conventional SACH foot, unilateral transtibial amputees of age group 20–40 years and body mass index (BMI) 18.5–24.9 were selected purposively (nonprobability purposive sampling technique). Only traumatic group of individuals using SACH foot for >1 year and having a normal range of motion of intact joints have been included in this study. Individuals with any complicated stump conditions, cardio-vascular diseases, musculoskeletal diseases, and neurological/psychological disorders were not part of our study. All individuals were initially fitted with similar kind of endoskeletal patella tendon bearing prosthesis with SACH foot and a supracondylar cuff suspension.
The stride parameters were analyzed during a 10-meter walk test using a paper walkway marked with initial and final 2 meter considered for acceleration and deceleration, respectively and a portable stopwatch. This conventional procedure for measuring stride parameters is very economic, reliable, and valid method in modern practice to perform gait studies in a low resource set up. The energy cost was analyzed by calculating physiological cost index (PCI), as it is the simple indirect calorimetric method suitable for measuring gait efficiency. This method has been used by many authors as Lenka and Kumar and Nielsen et al. earlier for energy comparison among individuals using various categories of prosthetic foot, either conventional or dynamic prosthetic foot.
For PCI estimation, resting heart rate of participants were taken following 30 min of rest, and strolling pulse were estimated following 5 min of strolling by the people with a self-selected speed by utilizing pulse oximeter. Similar procedures were applied for each individual while using their prosthesis with the SACH foot and the new dynamic foot alternatively after giving 15 min of adaptation period with each foot (to omit the carryover effect) before proceeding for the data collection procedure. The stride data and heart rate for both prosthetic feet (new prototype foot and SACH foot) were collected with the same individual wearing it on an alternate basis; however, the normal values of gait parameters were taken from the available literature. All the linear measurement, durations and heart rates were recorded and compiled within individual data collection form.
Obtained data were managed in an excel sheet and analyzed using the statistical tool (IBM Corp. Released 2015. IBM SPSS statistics for Windows, Version 23.0. Armonk, NY: IBM). Descriptive statistics (mean and standard deviation) were processed for each contemplated variable. A paired t-test was utilized to observe the distinction between SACH foot and current prototype with respect to stride characteristics and PCI. Speculation was tested at a significant level of P < 0.05.
| Results|| |
A total of fifteen subjects participated in the evaluation procedure with a mean age of 33.27 ± 5.47 and BMI 22.91 ± 1.42; arithmetical description has been provided [Table 1]. Variables considered for investigation were stride length, cadence velocity and PCI [Table 2]. Data analysis reflects a remarkable difference in the stride parameters and PCI between the SACH foot and new dynamic prosthetic foot. There was a significant difference in stride length (P = 0.000), cadence (P = 0.001), velocity (P = 0.000), and PCI (P = 0.001) [[Figure 3], [Figure 4], [Figure 5], [Figure 6], respectively].
|Table 1: Descriptive characteristics of subjects participated (n=15) in the study, mean, ±standard deviation, maximum, and minimum limits|
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|Table 2: Outcome of gait variables during self-selected walking, means and standard deviation while using SACH foot and current prototype with normal values|
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|Figure 3: Stride length, mean ± standard deviation with solid-ankle, cushion-heel foot (blue) and new dynamic foot (red). STLWSF = Stride length with SACH foot, STLWNDF = Stride length with new dynamic foot, SACH = Solid-ankle, cushion-heel|
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|Figure 4: Cadence, mean ± standard deviation with SACH foot (blue) and new dynamic foot (red). SACH = Solid-ankle, cushion-heel, CWSF = Cadence with SACH foot, CWNDF = Cadence with new dynamic foot|
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|Figure 5: Velocity, mean ± standard deviation with SACH foot (blue) and new dynamic foot (red). VWSF = Velocity with SACH foot, VWNDF = Velocity with new dynamic foot, SACH = Solid-ankle, cushion-heel|
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|Figure 6: Physiological cost index, mean ± standard deviation with SACH foot (blue) and new dynamic foot (red). PCIWSF = PCI with SACH foot, PCIWNDF = PCI with new dynamic foot, PCI = Physiological cost index, SACH = Solid-ankle, cushion-heel|
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| Discussion|| |
Analysis of the design and functionality of a prosthetic foot has been always a popular area of interest among the developers, scholars, and professionals in the field of engineering, rehabilitation and allied health sciences. Rolfe et al. structured a multi-segment rigid-body foot prototype by applying the approach of shape-changing kinematic synthesis, to coordinate the dynamic change in the shape of a human foot during gait. Resan et al. designed a prototype of compliant mechanism and presented its static and fatigue analysis by using numerical and experimental methods. Rigid body foot is generally oversimplified and to a great extent, unequipped for precisely matching to the geometry of the human foot, in the other hand compliant mechanisms replicate the physiological change in foot shape during ambulation due to the resiliency of material used in most of the current prosthetic foot accessible. Multi-segment rigid-body models bring a few advantages, including the capacity to hold up the greater load, and to acquire extraordinary shape-change taking into account practical usefulness. In this way, a prosthetic foot with a hybrid mechanism provides more appropriate geometry and replication of physiological change in shape as a normal foot while walking. The efficacy of prosthetic foot based on hybrid mechanism over the prosthetic foot with either rigid or compliant mechanism has been well described in many studies. Apart from numerical and mechanical analysis, clinical or experimental gait studies were found beneficial to observe the performance of prosthetic foot directly on individuals who are in need.
There are many literatures available regarding gait studies performed among the various class of prosthetic foot on individuals. The estimation of spatial-temporal parameters is necessary for the investigation of prosthetic parts as it gives basic knowledge of gait. Among various gait parameters, velocity is the most indicative measurement in selecting prosthetic foot, as it better describes the person's ability to walk. The normal walking velocity, as reported in many studies, ranges between 1.16 and 1.5 m/s. It has been also reported that the self-selected walking velocity while using any kind of prosthetic foot is always lower than the normal values. We also found similar results in our study, where the mean walking velocity of individuals using SACH foot and new dynamic foot were 70% and 85% of the normal velocity, respectively, which has been reported 80% and 90% of normal values in other studies respectively. The current dynamic foot design was also found significantly efficient in terms of velocity than the traditional SACH foot, supporting the outcomes of previous studies performed by Linde et al., indicating the advantage of other dynamic prosthetic foot over SACH foot in terms of velocity.
This study also corroborates a remarkable difference in cadence between the current dynamic foot and conventional SACH foot, which were found to be 87% and 80% of the normal cadence, respectively. This is similar to the outcomes of the study performed by Lenka and Kumar where dynamic prosthetic foot was more efficient in terms of cadence than the SACH foot. In contrast, few studies also endorse no significant differences or decreased cadence during a similar type of comparison. This dissimilarity in outcome may have been occurred due to variation in foot material, sample size, or demographic variation in the population of participants. The other gait parameters have also indicated significant statistical differences in the paired t-test as step length and stride length with the current dynamic foot were higher than that of the conventional SACH foot.
The PCI outcome in this study for the individuals while using SACH foot and current dynamic foot prototype reveals the advantage of the current prosthetic foot over SACH foot in terms of energy efficiency. Similar outcomes have been experienced in the studies of Lenka and Kumar and other investigators. This could be due to decreased quadriceps demand during loading response of the foot after initial contact and minimized push-off work of prosthetic limb due to released mechanical energy stored during mid to late stance.
| Conclusion|| |
Findings of this study reveal that the current dynamic prosthetic foot with a hybrid mechanism has shown better stride characteristics in terms of stride length, cadence, and velocity over SACH foot. The current dynamic foot was also more energy-efficient than the SACH foot as there was a significant difference in PCI have been observed during self-selected walking speed, proving the experimental hypothesis true. Finally, we can conclude that the ESR characteristics in the prosthetic foot for improved and efficient gait can be achieved in an economical way by appropriate design and material selection. The current prototype could be further optimized to achieve more natural results in terms of gait variables and energy cost. Gait analysis with other parameters can also be done.
This study is an original work performed in the Department of Prosthetics and Orthotics at Indian Spinal Injuries Centre, New Delhi. It has been done after approval from the Research Review Committee and Indian Ethical Committee. We are very thankful to the institute for providing the laboratory, technical support, and subjects who participated in this study. We are also thankful to the Medical Director, Northern Railway Central Hospital (NRCH), New Delhi, for permission of data collection and Mr. M C Dash, In-charge of Prosthetic and Orthotic Clinic (NRCH), for his support.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2]