Measuring Balance Abilities of Transtibial Amputees Using Multiattribute Utility Theory

Background. Berg Balance Scale (BBS) can be considered the standard for assessment of functional balance but has a noted ceiling effect in active transtibial amputees (TTAs). Development of ceiling-free measures based on quantitative measurement techniques that is suitable for patients in any experience levels, yet sensitive enough to capture improvements in any stage of prosthetic rehabilitation, is needed. Research Question. Does a scoring scheme based on Multiattribute Utility (MAU) theory assess balance abilities of multileveled TTAs comparable to BBS? Methods. A case-control study including 28 participants (8 novice TTAs, 10 experienced TTAs, and 10 healthy controls) was conducted. Guided by MAU theory, a novel balance model was developed and initially validated by Spearman correlation between index-generated scores and expert assigned scores, providing preliminary evidence of validity. Floor/ceiling effects were tested, and between-group comparisons of static/dynamic balance were conducted by paired t -test or Wilcoxon signed-rank test depending on data distribution normality. Results. BBS score was correlated with computed balance index ( r = 0.847 , p < 0.001 ). The BBS score of novice/experienced TTAs was 39/54, and the computed balance index was 38/75. A ceiling effect of BBS (30%) was observed in the experienced TTA group, whereas no ceiling effects were found for the computed index in any combination of TTA groups. Group differences between novice and experienced TTAs were observed in center of pressure (COP) ellipse shift area, COP path length, COP average velocity, gait speed, and cadence (all p < 0.05 ). Significance. Evidence from first stage validation of the proposed MAU balance model indicated that the model performed well. This proposed method can monitor the progress of balance for varied experience-leveled TTAs and provide clinicians with useful information for assessing the rehabilitation training.

Dynamic balancing responses in unilateral transtibial amputees following outward-directed perturbations during slow treadmill walking differ considerably for amputated and non-amputated side

Background Due to disrupted motor and proprioceptive function, lower limb amputation imposes considerable challenges associated with balance and greatly increases risk of falling in presence of perturbations during walking. The aim of this study was to investigate dynamic balancing responses in unilateral transtibial amputees when they were subjected to perturbing pushes to the pelvis in outward direction at the time of foot strike on their non-amputated and amputated side during slow walking. Methods Fourteen subjects with unilateral transtibial amputation and nine control subjects participated in the study. They were subjected to perturbations that were delivered to the pelvis at the time of foot strike of either the left or right leg. We recorded trajectories of center of pressure and center of mass, durations of in-stance and stepping periods as well as ground reaction forces. Statistical analysis was performed to determine significant differences in dynamic balancing responses between control subjects and subjects with amputation when subjected to outward-directed perturbation upon entering stance phases on their non-amputated or amputated sides. Results When outward-directed perturbations were delivered at the time of foot strike of the non-amputated leg, subjects with amputation were able to modulate center of pressure and ground reaction force similarly as control subjects which indicates application of in-stance balancing strategies. On the other hand, there was a complete lack of in-stance response when perturbations were delivered when the amputated leg entered the stance phase. Subjects with amputations instead used the stepping strategy and adjusted placement of the non-amputated leg in the ensuing stance phase to make a cross-step. Such response resulted in significantly larger displacement of center of mass. Conclusions Results of this study suggest that due to the absence of the COP modulation mechanism, which is normally supplied by ankle motor function, people with unilateral transtibial amputation are compelled to choose the stepping strategy over in-stance strategy when they are subjected to outward-directed perturbation on the amputated side. However, the stepping response is less efficient than in-stance response.

Simulating the Effects of Anthropometry on the Contralateral Limb of Transtibial Amputees

Gait analysis is a clinically relevant method to assess walking patterns in rehabilitating patients, especially transtibial amputees. Prior work in biomechanics has detailed the impacts of below-the-knee amputation and anthropometric characteristics on patient gait, but little work has been done in the intersection of these fields, particularly with consideration towards the contralateral (intact) limb. This study utilizes OpenSim, a biomechanics simulation package, to investigate the impact of anthropometry on the stresses and response behavior of the hip, knee, and ankle joints in the contralateral limb of transtibial amputees. Musculoskeletal geometry, gait, and ground reaction force data for models were sourced from a healthy subject and appropriately adjusted based on amputation status and anthropometry. Inverse dynamics operations were performed on each model. Results indicate the need for special clinical focus on the ankle of heavier, taller amputees, along with the prescription of appropriate prosthetic componentry with a sufficient range of motion, to prevent long-term joint damage within the lower extremities. Initial data is preliminary, but serves as a foundation for additional simulations and related work in biomechanics simulations.

Dynamic Balancing Responses in Unilateral Transtibial Amputees Following Outward-Directed Perturbations During Slow Treadmill Walking Differ Considerably for Amputated and Non-Amputated Side

BackgroundDue to disrupted motor and proprioceptive function lower limb amputation imposes considerable challenges associated with balance and greatly increases risk of falling in case of perturbations during walking. The aim of this study was to investigate dynamic balancing responses in unilateral transtibial amputees when they were subjected to perturbing pushes to the pelvis in outward direction at the time of foot strike on non-amputated and amputated side during slow walking.MethodsFourteen subjects with unilateral transtibial amputation and nine control subjects participated in the study. They were subjected to perturbations that were delivered to the pelvis at the time of foot strike of either the left or right leg. We recorded trajectories of center of pressure and center of mass, durations of in-stance and stepping periods as well as ground reaction forces. Statistical analysis was performed to determine significant differences in dynamic balancing responses between control subjects and subjects with amputation when subjected to outward-directed perturbation upon entering stance phases with non-amputated or amputated side.ResultsWhen outward-directed perturbations were delivered at the time of foot strike of the non-amputated leg, subjects with amputation were able to modulate center of pressure and ground reaction force similarly as control subjects which indicates application of in-stance balancing strategies. On the other hand, there was a complete lack of in-stance response when perturbations were delivered when the amputated leg entered the stance phase. Subjects with amputations instead used the stepping strategy and adjusted placement of the non-amputated leg in the ensuing stance phase to make a cross-step. Such response resulted in significantly higher displacement of center of mass. ConclusionsResults of this study suggest that due to the absence of the COP modulation mechanism, which is normally supplied by ankle motor function, people with unilateral transtibial amputation are compelled to choose the stepping strategy over in-stance strategy when they are subjected to outward-directed perturbation on the amputated side. However, the stepping response is less efficient than in-stance response. To improve their balancing responses to unexpected balance perturbation people fitted with passive transtibial prostheses should undergo perturbation-based balance training during clinical rehabilitation.

Design of a Single Layer Metamaterial for Pressure Offloading of Transtibial Amputees

While using a prosthesis, transtibial amputees can experience pain and discomfort brought on by large pressure gradients at the interface between the residual limb and prosthetic socket. Current prosthetic interface solutions attempt to alleviate these pressure gradients by using soft homogenous liners to reduce and distribute pressures. This research investigates an additively manufactured metamaterial inlay with a tailored mechanical response to reduce peak pressure gradients around the limb. The inlay uses a hyperelastic behaving metamaterial (US10244818) comprised of triangular pattern unit cells which can be 3D printed with walls of various thicknesses controlled by draft angles. The hyperelastic material properties are modeled using a Yeoh 3rd order model. The 3rd order coefficients can be adjusted and optimized, which corresponds to a change in the unit cell wall thickness to create an inlay that can meet the unique offloading needs of an amputee. Finite element analysis simulations evaluated the pressure gradient reduction from: 1) a common homogenous silicone liner, 2) a prosthetist's inlay prescription that utilizes three variations of the metamaterial, and 3) a metamaterial solution with optimized Yeoh 3rd order coefficients. When compared to a traditional homogenous silicone liner for two unique limb loading scenarios, the prosthetist prescribed inlay and the optimized material inlay can achieve equal or greater pressure gradient reduction capabilities. These results show the potential feasibility of implementing this metamaterial as a method of personalized medicine for transtibial amputees by creating a customizable interface solution to meet the unique performance needs of an individual patient.

Classification and Comparison of Mechanical Design of Powered Ankle–Foot Prostheses for Transtibial Amputees Developed in the 21st Century: A Systematic Review

A systematic review of the mechanical design of powered ankle-foot prostheses developed from 2000 to 2019 was conducted through database and manual searches. A total of 10 English and two Chinese databases were searched using the same keywords. Moreover, information on commercialized prostheses was collected through a manual search. A total of 8,729 publications were obtained from the database search, and 83 supplementary publications and 49 online product introductions were accumulated through the manual search. A total of 91 powered ankle-foot prostheses were extracted from 159 publications and online information after exclusion. The mechanical design characteristics of the prostheses were described briefly and compared after they were categorized into 11 subclassifications. This review revealed that a considerable number of powered ankle-foot prostheses were developed in the last 20 years. The development of such prostheses was characterized by alternative modes, that is, from pneumatic or hydraulic drivers to motorized drivers and from rigid transmissions to elastic actuators. This review contributes to the comprehensive understanding of current designs, which can benefit the combination of the advantages of and redundancy avoidance in future powered ankle-food protheses.