Transfemoral Amputation Research Articles

Automatic Stub Avoidance for a Powered Prosthetic Leg Over Stairs and Obstacles.

Passive prosthetic legs require undesirable compensations from amputee users to avoid stubbing obstacles and stairsteps. Powered prostheses can reduce those compensations by restoring normative joint biomechanics, but the absence of user proprioception and volitional control combined with the absence of environmental awareness by the prosthesis increases the risk of collisions. This article presents a novel stub avoidance controller that automatically adjusts prosthetic knee/ankle kinematics based on suprasensory measurements of environmental distance from a small, lightweight, low-power, low-cost ultrasonic sensor mounted above the prosthetic ankle. In a case study with two transfemoral amputee participants, this control method reduced the stub rate during stair ascent by 89.95% and demonstrated an 87.50% avoidance rate for crossing different obstacles on level ground. No thigh kinematic compensation was required to achieve these results. These findings demonstrate a practical perception solution for powered prostheses to avoid collisions with stairs and obstacles while restoring normative biomechanics during daily activities.

Prosthetic Limb Attachment via Electromagnetic Attraction Through a Closed Skin Envelope.

Current socket-based methods of prosthetic limb attachment are responsible for many of the dominant problems reported by persons with amputation. In this work, we introduce a new paradigm for attachment via electromagnetic attraction between a bone-anchored ferromagnetic implant and an external electromagnet. Our objective was to develop a design framework for electromagnetic attachment, and to evaluate this framework in the context of transfemoral amputation. We first used inverse dynamics to calculate the forces required to suspend a knee-ankle-foot prosthesis during gait. We then conducted cadaveric dissections to inform implant geometry and design a surgical methodology for covering the implant. We also developed an in silico framework to investigate how electromagnet design affects system performance. Simulations were validated against benchtop testing of a custom-built electromagnet. The physical electromagnet matched simulations, with a root-mean-square percentage error of 4.2% between measured and predicted forces. Using this electromagnet, we estimate that suspension of a prosthesis during gait would require 33 W of average power. After 200 and 1000 steps of simulated walking, the temperature at the skin would increase 2.3 °C and 15.4 °C relative to ambient, respectively. Our design framework produced an implant and electromagnet that could feasibly suspend a knee-ankle-foot prosthesis during short walking bouts. Future work will focus on optimization of this system to reduce heating during longer bouts. This work demonstrates the initial feasibility of an electromagnetic prosthetic attachment paradigm that has the potential to increase comfort and improve residual limb health for persons with amputation.

Radiographic Evidence of Bone Changes Around Intraosseous Transcutaneous Amputation Prosthesis: An 11-Year Retrospective Cohort Study

ABSTRACT Introduction Percutaneous Osseointegrated Implants (POIs) influence the load transfer path to the host bone. In turn, mechano-regulatory processes (strain adaptive bone remodeling) drive periprosthetic bone changes that influence implant stability and fixation outcome. These bone changes have not yet been reported for the Intraosseous Transcutaneous Amputation Prosthesis (ITAP) clinical trial. Objectives This study will first standardize the zoning and reporting of periprosthetic bone change in POI radiographs. Second, it will retrospectively measure periprosthetic bone change from radiographs of 12 participants with an ITAP up to 11 years. Finally, the results will be qualitatively compared with those from participants with different POI designs. Materials and Methods Twenty participants with unilateral transfemoral amputations received an ITAP in a 2-center UK clinical trial in either 2008/09 or 2013/14. Participant radiographs from one center were available (n = 12) over 11 years and have been collated and processed in a repeatable way. Transverse plane periprosthetic bone change measurements at 3 equidistant points along the implant stem were measured in AP and ML. Results Total median bone growth in AP was double that in ML (57.6 mm and 31.12 mm, respectively). Median lateral and posterior bone change (1.44 mm and 1.09 mm) was greater than median medial and anterior (0.83 mm and −0.005 mm) bone changes, respectively. The greatest change in radial bone growth was observed distally and the least proximally. Conclusions Bone changes were similar to other collared pressfit POIs in the literature. We demonstrate the influence of stem design and mechano-regulatory remodeling in stable fixation; however, additional influences on periprosthetic bone change were inferred from the results and further investigations are necessary. Clinical Relevance To identify ITAP design features and fixations that minimize endosteal resorption, thus promoting implant stability and contributing to clinical guidelines for rehabilitation and future design and fixation choices.

Reducing Gait Asymmetry in Transfemoral Amputees — A Neural Network-Based Approach

Gait asymmetry between intact and prosthetic limbs is one of the factors that affect the long-term health of an amputee. Existing prosthetic devices have fixed controllers that cannot adapt to changes in user gait, thereby contributing to this asymmetry. In this paper, we use the stance period of both limbs to measure the asymmetry in gait. We propose a neural network-based control strategy that can adapt to changing gait in real time and help achieve near-natural gait.

Computational assessment of carbon fabric reinforced polymer made prosthetic knee: Mechanics, finite element simulations and experimental evaluation.

A prosthetic knee is designed to replace the functionality of an anatomical knee in transfemoral amputees. The purpose of a prosthetic knee is to restore mobility and compensate amputees for their impairment. In the present research numerical modelling and simulation of a carbon fabric reinforced polymer made polycentric prosthetic knee with four-bar mechanism was performed. Virtual prototyping with computer-aided design and computer-aided engineering software ensured geometric and structural stability of the knee design. The linkage mechanism, instantaneous centre's location and trajectory were investigated using multibody dynamics and analytical formulations. Computational simulations with a non-linear finite element model were employed with joints, contact formulations and an orthotropic material model to predict the displacement, stress formulated and life of the knee prosthesis under static and cyclic loading conditions. Finite element analysis assessed the strength and durability of knee in accordance to standards. Maximum Principal stress of 155 MPa and life expectancy of 3.1 × 106 cycles were determined for the composite knee through numerical simulations ensuring a safe design. Experimental testing was also conducted as per standards and the percentage error was estimated to be 2.52%, thereby establishing the validity of the finite element model deployed. This type of simulation-based approach can be implemented to efficiently and affordably design and prototype a prosthetic knee with desired functioning criteria.

Effect of the ischial support on muscle force estimation during transfemoral walking.

Transmission of loads between the prosthetic socket and the residual limb is critical for the comfort and walking ability of people with transfemoral amputation. This transmission is mainly determined by the socket tightening, muscle forces, and socket ischial support. However, numerical investigations of the amputated gait, using modeling approaches such as MusculoSkeletal (MSK) modeling, ignore the weight-bearing role of the ischial support. This simplification may lead to errors in the muscle force estimation. This study aims to propose a MSK model of the amputated gait that accounts for the interaction between the body and the ischial support for the estimation of the muscle forces of 13 subjects with unilateral transfemoral amputation. Contrary to previous studies on the amputated gait which ignored the interaction with the ischial support, here, the contact on the ischial support was included in the external loads acting on the pelvis in a MSK model of the amputated gait. Including the ischial support induced an increase in the activity of the main abductor muscles, while adductor muscles' activity was reduced. These results suggest that neglecting the interaction with the ischial support leads to erroneous muscle force distribution considering the gait of people with transfemoral amputation. Although subjects with various bone geometries, particularly femur lengths, were included in the study, similar results were obtained for all subjects. Eventually, the estimation of muscle forces from MSK models could be used in combination with finite element models to provide quantitative data for the design of prosthetic sockets.

Mobility Rates After Lower-Limb Amputation for Patients Treated with Physician-Led Collaborative Care Model

Clinical outcomes after major lower-limb amputation have been historically poor. The current care provided to most amputees is often disorganized and without physician supervision. The primary purpose of this study is to examine rates of postamputation mobility achieved with a prosthesis by patients with chronic limb-threatening ischemia and/or diabetes who required major lower-limb amputation and were treated under an established physician-led collaborative care pathway. The secondary purpose is to describe the structure and utilization of the care pathway by multiple independent vascular surgery practices in the United States to enable future exploration of its impact on key clinical outcomes within this patient population. Clinical records of 2,475 patients from 6 vascular practices that adopted this collaborative care pathway between 2017 and 2020 were retrospectively reviewed. Only records with sufficient documented histories of amputation surgeries, prosthetic services, and mobility status were included. Of 2,475 patient records reviewed, 1,787 patients (2,157 major amputations) were eligible for analysis. Sixty-two-point 2 percent (n=1,111) of patients achieved mobility with the collaborative care pathway. Mobility rate varied by amputation level in the study. Prosthetic mobility was achieved in 73.5% of transtibial amputations, 40.4% of transfemoral amputations, and 35.7% of through-knee amputations, regardless of patient laterality, which is superior or equivalent to the best published rates of mobility. The study describes the structure and utilization of a physician-led collaborative care pathway for treating patients who require lower-limb amputation that meets 5 of the 7 recommendations from the 2019 Global Vascular Guidelines on the Management of Chronic Limb Threatening Ischemia. Internal data analysis results suggest that patients treated via this care pathway can potentially achieve improved mobility rates with a prosthesis following amputation. This collaborative care pathway should be further evaluated for its ability to directly improve mobility and other clinically relevant amputation outcomes.

Exploration and demonstration of explainable machine learning models in prosthetic rehabilitation-based gait analysis.

Quantitative gait analysis is important for understanding the non-typical walking patterns associated with mobility impairments. Conventional linear statistical methods and machine learning (ML) models are commonly used to assess gait performance and related changes in the gait parameters. Nonetheless, explainable machine learning provides an alternative technique for distinguishing the significant and influential gait changes stemming from a given intervention. The goal of this work was to demonstrate the use of explainable ML models in gait analysis for prosthetic rehabilitation in both population- and sample-based interpretability analyses. Models were developed to classify amputee gait with two types of prosthetic knee joints. Sagittal plane gait patterns of 21 individuals with unilateral transfemoral amputations were video-recorded and 19 spatiotemporal and kinematic gait parameters were extracted and included in the models. Four ML models-logistic regression, support vector machine, random forest, and LightGBM-were assessed and tested for accuracy and precision. The Shapley Additive exPlanations (SHAP) framework was applied to examine global and local interpretability. Random Forest yielded the highest classification accuracy (98.3%). The SHAP framework quantified the level of influence of each gait parameter in the models where knee flexion-related parameters were found the most influential factors in yielding the outcomes of the models. The sample-based explainable ML provided additional insights over the population-based analyses, including an understanding of the effect of the knee type on the walking style of a specific sample, and whether or not it agreed with global interpretations. It was concluded that explainable ML models can be powerful tools for the assessment of gait-related clinical interventions, revealing important parameters that may be overlooked using conventional statistical methods.

A Novel Ligamentous Complex in the Anteromedial Region of the Knee: A Cadaveric Study.

The medial knee structures have a primary role in stabilizing valgus and rotational stress, which makes them important in assessing the ligament-injured knee globally and choosing the most adequate treatment. To conduct a layer-by-layer dissection of the knee's anteromedial side and provide a qualitative and quantitative description of the anatomy and histology of a ligament in the anteromedial region of the knee, which we have termed the anterior oblique ligament (AOL). Also, to describe the AOL relationship with what we have termed the medial cross-a ligament complex that stabilizes the medial pivot. Descriptive laboratory study. A total of 35 fresh-frozen knees from transfemoral amputations that were exclusively performed for vascular reasons were dissected. Structures were identified after meticulous dissection, respecting the same protocol, measured with a digital caliper rule, and histologically studied for data. The AOL was found in all dissected knees, with a mean length of 31.47 ± 5.06 mm. This structure presented a ligament histology with densely organized collagen fibrils. The medial cross was represented by the superficial medial collateral ligament, AOL (anterior region), and posterior oblique ligament. This study demonstrated the presence of a ligament in the anteromedial region of the knee, termed the AOL. This structure was in the anterior part of a ligament complex-the medial cross. Studying and revisiting the medial compartment can provide important information for understanding joint instability and promoting better results in ligament reconstructions.

Frequency of Low Back Pain and its Effect on Function and HealthRelated Quality of Life across Three Levels of Lower Limb Amputation: A Cross-Sectional Study

Background: Amputation is a profoundly life-altering event that can have both physical and psychological impacts on individuals. Objective: This study aimed to investigate the frequency of low back pain and its effect on function and health-related quality of life in individuals with various levels of lower limb amputation. Methods: It was a cross-sectional study at the Pakistan Institute of Prosthetic and Orthotics Peshawar (PIPOS) from May to September 2020, 264 participants were purposively selected. Inclusion criteria: males and females aged 18-65 with unilateral transfemoral, knee disarticulation, or transtibial amputations. Exclusion criteria: hearing/speech impairments, hip pathology, or bilateral lower limb amputation. Data collected via selfadministered questionnaires, including the Roland Morris Disability Questionnaire (RMDQ) and the Short Form 36 Health Survey (SF-36). Data analyzed using SPSS v.25. Results: Of the 264 participants, 219 were males (83%), and 45 were females (17%). There was significant connection between before and after amputation back pain (P < 0.05). However, no notable link was observed between low back pain and the three amputation levels (P > 0.05). Moreover, there was no statistical disparity in disability based on the level of amputation (P > 0.05). Significantly, low back pain differed across all quality of life domains (P < 0.05), except for mental and physical health. In contrast, no statistical variation was noted in the quality of life among the three amputation levels (P > 0.05). Conclusion: This study underscores the prevalence of low back pain in lower limb amputees. However, we did not find a clear association between low back pain and specific amputation levels (unilateral transfemoral, knee disarticulation, or transtibial amputation). Additionally, low back pain appears to impact disability and select aspects of quality of life, such as physical function, social function, and general health in individuals with lower limb amputation.

The Effect of Prosthetic Limb Sophistication and Amputation Level on Self-reported Mobility and Satisfaction With Mobility

ObjectiveTo determine if lower limb prosthesis (LLP) sophistication is associated with patient-reported mobility and/or mobility satisfaction, and if these associations differ by amputation level. DesignCohort study that identified participants through a large national database and prospectively collected self-reported patient outcomes. SettingThe Veterans Administration (VA) Corporate Data Warehouse, the National Prosthetics Patient Database, participant mailings, and phone calls. Participants347 Veterans who underwent an incident transtibial (TT) or transfemoral (TF) amputation due to diabetes and/or peripheral artery disease and received a qualifying LLP between March 1, 2018, and November 30, 2020. InterventionsBasic, intermediate, and advanced prosthesis sophistication was measured by the accurate and reliable PROClass system. Main Outcome MeasurePatient-reported mobility using the advanced mobility subscale of the Locomotor Capabilities Index-5; mobility satisfaction using a 0–10-point Likert scale. ResultsLower limb amputees who received intermediate or advanced prostheses were more likely to achieve advanced mobility than those who received basic prostheses, with intermediate nearing statistical significance at nearly twice the odds (adjusted odds ratio (aOR)=1.8, 95% confidence interval (CI), .98–3.3; P=.06). The association was strongest in TF amputees with over 10 times the odds (aOR=10.2, 95% CI, 1.1–96.8; P=.04). The use of an intermediate sophistication prosthesis relative to a basic prosthesis was significantly associated with mobility satisfaction (adjusted β coefficient (aβ)=.77, 95% CI, .11–1.4; P=.02). A statistically significant association was only observed in those who underwent a TT amputation (aβ=.79, 95% CI, .09–1.5; P=.03). ConclusionsProsthesis sophistication was not associated with achieving advanced mobility in TT amputees but was associated with greater mobility satisfaction. In contrast, prosthesis sophistication was associated with achieving advanced mobility in TF amputees but was not associated with an increase in mobility satisfaction.

Lifetime cost-effectiveness analysis osseointegrated transfemoral versus socket prosthesis using Markov modelling.

Prior cost-effectiveness analyses on osseointegrated prosthesis for transfemoral unilateral amputees have analyzed outcomes in non-USA countries using generic quality of life instruments, which may not be appropriate when evaluating disease-specific quality of life. These prior analyses have also focused only on patients who had failed a socket-based prosthesis. The aim of the current study is to use a disease-specific quality of life instrument, which can more accurately reflect a patient's quality of life with this condition in order to evaluate cost-effectiveness, examining both treatment-naïve and socket refractory patients. Lifetime Markov models were developed evaluating active healthy middle-aged male amputees. Costs of the prostheses, associated complications, use/non-use, and annual costs of arthroplasty parts and service for both a socket and osseointegrated (OPRA) prosthesis were included. Effectiveness was evaluated using the questionnaire for persons with a transfemoral amputation (Q-TFA) until death. All costs and Q-TFA were discounted at 3% annually. Sensitivity analyses on those cost variables which affected a change in treatment (OPRA to socket, or socket to OPRA) were evaluated to determine threshold values. Incremental cost-effectiveness ratios (ICERs) were calculated. For treatment-naïve patients, the lifetime ICER for OPRA was $279/quality-adjusted life-year (QALY). For treatment-refractory patients the ICER was $273/QALY. In sensitivity analysis, the variable thresholds that would affect a change in the course of treatment based on cost (from socket to OPRA), included the following for the treatment-naïve group: yearly replacement components for socket > $8,511; cost yearly replacement parts OPRA < $1,758; and for treatment-refractory group: yearly replacement component for socket of > $12,467. The use of the OPRA prosthesis in physically active transfemoral amputees should be considered as a cost-effective alternative in both treatment-naïve and treatment-refractory socket prosthesis patients. Disease-specific quality of life assessments such as Q-TFA are more sensitive when evaluating cost-effectiveness.

What are relevant predictors of physical activity in older adults with lower limb loss (LLL)? Results of a retrospective analysis.

People with lower limb loss (LLL) have reduced physical activity (PA). There is evidence of physical and psychosocial predictors of PA in older adults with limb loss. However, these 2 areas (physical/psychosocial) have not been evaluated in the same analysis. To describe and identify predictors of PA in individuals with LLL. Cross-sectional study. Secondary analysis of data from a multisite Canadian randomized control trial involving community-dwelling prosthetic ambulators with unilateral transtibial or transfemoral amputation (N = 72). The dependent variable was the Physical Activity Scale for the Elderly. Potential predictors were four step square test, 2-minute walk test, Short Physical Performance Battery, Life Space Assessment, walking while talking test, and Activities-specific Balance Confidence scale. Seventy-two community-dwelling lower limb prosthesis users were enrolled. The sample included 62 male participants (86%), and 58 participants (81%) had transtibial amputation. The average age of participants was 65 (8.9) years, and for 49 participants (70%), the amputation was over 24 months ago. The total mean Standard Deviation (SD) Physical Activity Scale for the Elderly score was 153.2 (88.3), with scores of 148.1 (11.4) and 184.5 (24.7) for male and female participants, respectively. Regression analysis identified Life Space Assessment (β = 1.15, p = 0.007) and Short Physical Performance Battery (β = 3.51, p = 0.043) as statistically significant predictors accounting for 25% of the variance in PA. Community mobility and physical performance are the most meaningful predictors of PA. Future research should examine additional factors (e.g., environment, motivation). Understanding the predictors for PA after LLL would improve clinical practice as clinicians would have increased knowledge to modify and improve training.

A qualitative study of clinicians’ and individuals’ with lower limb loss perspectives on the development of a novel online self-management program

Purpose To explore the rehabilitation preferences and experiences of clinicians and patients for education after lower limb loss to facilitate the development of an online self-management program. Methods A qualitative descriptive approach was used. Thirty-one clinicians (physiotherapists, occupational therapists, and prosthetists), and 26 patients with lower limb loss (transtibial and transfemoral amputation; mean age (SD) of 63.3 (9.1), years) were recruited. We used semi-structured focus groups and one-on-one interviews, and audio recorded the interviews. Data were analyzed using conventional content analysis. Results Three themes were identified: (1) Needing education in rehabilitation described the education in current practice as one-on-one discussion and booklets and highlighted the limitations of education such as its length, static nature, and inaccessible for patients living in remote areas. (2) Getting back to activities prior to amputation emphasized how goal setting and social support could assist patients and facilitate self-management. (3) Augmenting learning highlighted the need for an accessible complementary source for education and potential solutions to overcome the barriers of online delivery. Conclusions Our findings underscore the importance of education in the rehabilitation of patients to help them get back to their activities. An online accessible tool may improve education by providing information and peer support.

The influence of prosthetic suspension on gait and cortical modulations is persons with a transfemoral amputation: socket-suspended versus bone-anchored prosthesis

BackgroundPersons with a transfemoral amputation (TFA) often experience difficulties in daily-life ambulation, including an asymmetrical and less stable gait pattern and a greater cognitive demand of walking. However, it remains unclear whether this is effected by the prosthetic suspension, as eliminating the non-rigid prosthetic connection may influence stability and cortical activity during walking. Spatiotemporal and stability-related gait parameters, as well as cortical activity during walking, were evaluated between highly active individuals (MFC-level K3-4) with a TFA and able-bodied (AB) persons, and between persons with a bone-anchored prosthesis (BAP) and those with a socket-suspended prosthesis (SSP).Methods18 AB persons and 20 persons with a unilateral TFA (10 BAP-users, 10 SSP-users) walked on a treadmill at their preferred speed. Spatiotemporal and margin of stability parameters were extracted from three-dimensional movement recordings. In addition, 126-channel electroencephalogram (EEG) was recorded. Brain-related activity from several cortical areas was isolated using independent component analysis. Source-level data were divided into gait cycles and subjected to time–frequency analysis to determine gait-cycle dependent modulations of cortical activity.ResultsPersons with TFA walked with smaller and wider steps and with greater variability in mediolateral foot placement than AB subjects; no significant differences were found between BAP- and SSP-users. The EEG analysis yielded four cortical clusters in frontal, central (both hemispheres), and parietal areas. No statistically significant between-group differences were found in the mean power over the entire gait cycle. The event-related spectral perturbation maps revealed differences in power modulations (theta, alpha, and beta bands) between TFA and AB groups, and between BAP- and SSP-users, with largest differences observed around heel strike of either leg.ConclusionsThe anticipated differences in gait parameters in persons with TFA were confirmed, however no significant effect of the fixed suspension of a BAP was found. The preliminary EEG findings may indicate more active monitoring and control of stability in persons with TFA, which appeared to be timed differently in SSP than in BAP-users. Future studies may focus on walking tasks that challenge stability to further investigate differences related to prosthetic suspension.

Transfemoral Amputee Stumble Detection through Machine-Learning Classification: Initial Exploration with Three Subjects

Transfemoral Amputee Stumble Detection through Machine-Learning Classification: Initial Exploration with Three Subjects

Transfemoral prosthetic simulators versus amputees: ground reaction forces and spatio-temporal parameters in gait.

This study aimed to compare the ground reaction forces (GRFs) and spatio-temporal parameters as well as their asymmetry ratios in gait between individuals wearing a transfemoral prosthetic simulator (TFSim) and individuals with unilateral transfemoral amputation (TFAmp) across a range of walking speeds (2.0-5.5 km h-1). The study recruited 10 non-disabled individuals using TFSim and 10 individuals with unilateral TFAmp using a transfemoral prosthesis. Data were collected using an instrumented treadmill with built-in force plates, and subsequently, the GRFs and spatio-temporal parameters, as well as their asymmetry ratios, were analysed. When comparing the TFSim and TFAmp groups, no significant differences were found among the gait parameters and asymmetry ratios of all tested metrics except the vertical GRFs. The TFSim may not realistically reproduce the vertical GRFs during the weight acceptance and push-off phases. The structural and functional variations in prosthetic limbs and components between the TFSim and TFAmp groups may be primary contributors to the difference in the vertical GRFs. These results suggest that TFSim might be able to emulate the gait of individuals with TFAmp regarding the majority of spatio-temporal and GRF parameters. However, the vertical GRFs of TFSim should be interpreted with caution.

How Comprehensive and Efficient Are Patient-Reported Outcome Measures for Individuals with Lower Extremity Amputation Undergoing Implantation of Osseointegrated Bone Anchored Limbs?

» Patient-reported outcome measures (PROMs) are essential for measuring quality and functional outcomes after implantation of osseointegrated bone anchored limbs for patients with lower extremity amputation.» Using a novel assessment criterion with 8 domains, this study assessed all commonly used PROMs for their efficiency and comprehensiveness.» Comprehensiveness was scored according to the presence or absence of PROM questions related to these 8 domains (maximum score = 60): mobility (15 items), prosthesis (14 items), pain (10 items), psychosocial status (10 items), independence/self-care (4 items), quality of life/satisfaction (4 items), osseoperception (1 item), general information (1 item), and vitality (1 item).» The efficiency scores were calculated by dividing the comprehensiveness score by the total number of questions answered by the patients with higher scores being deemed more efficient.» The most comprehensive PROMs were Orthotics and Prosthetics User's Survey-Lower Extremity Functional Status (OPUS-LEFS) (score = 36), Prosthesis Evaluation Questionnaire (PEQ) (score = 31), and Questionnaire for Persons with a Transfemoral Amputation (score = 27).» The most efficient PROMs were the OPUS-LEFS (score = 1.8) and European Quality of Life (score = 1.4).

Low-profile prosthetic foot stiffness category and size, and shoes affect axial and torsional stiffness and hysteresis.

Passive-elastic prosthetic feet are manufactured with numerical stiffness categories and prescribed based on the user's body mass and activity level, but mechanical properties, such as stiffness values and hysteresis are not typically reported. Since the mechanical properties of passive-elastic prosthetic feet and footwear can affect walking biomechanics of people with transtibial or transfemoral amputation, characterizing these properties can provide objective metrics for comparison and aid prosthetic foot prescription and design. We characterized axial and torsional stiffness values, and hysteresis of 33 categories and sizes of a commercially available passive-elastic prosthetic foot model [Össur low-profile (LP) Vari-flex] with and without a shoe. We assumed a greater numerical stiffness category would result in greater axial and torsional stiffness values but would not affect hysteresis. We hypothesized that a greater prosthetic foot length would not affect axial stiffness values or hysteresis but would result in greater torsional stiffness values. We also hypothesized that including a shoe would result in decreased axial and torsional stiffness values and greater hysteresis. Prosthetic stiffness was better described by curvilinear than linear equations such that stiffness values increased with greater loads. In general, a greater numerical stiffness category resulted in increased heel, midfoot, and forefoot axial stiffness values, increased plantarflexion and dorsiflexion torsional stiffness values, and decreased heel, midfoot, and forefoot hysteresis. Moreover, for a given category, a longer prosthetic foot size resulted in decreased heel, midfoot, and forefoot axial stiffness values, increased plantarflexion and dorsiflexion torsional stiffness values, and decreased heel and midfoot hysteresis. In addition, adding a shoe to the prosthetic foot resulted in decreased heel and midfoot axial stiffness values, decreased plantarflexion torsional stiffness values, and increased heel, midfoot, and forefoot hysteresis. Our results suggest that manufacturers should adjust the design of each category to ensure the mechanical properties are consistent across different sizes and highlight the need for prosthetists and researchers to consider the effects of shoes in combination with prostheses. Our results can be used to objectively compare the LP Vari-flex prosthetic foot to other prosthetic feet to inform their prescription, design, and use for people with a transtibial or transfemoral amputation.

A scoring system to evaluate stability of percutaneous osseointegrated implants for transfemoral amputation with validation in the ITAP clinical trial.

Percutaneous osseointegrated implants for individuals with lower limb amputation can increase mobility, reduce socket related pain, and improve quality of life. It would be useful to have an evaluation method to assess the interface between bone and implant. We assessed outpatient radiographs from the Intraosseous Transcutaneous Amputation Prosthesis clinical trial using an interface scoring system which summed and weighted equally measures of implant collar cortical ongrowth and radiolucency along the implant stem/bone interface. Radiographs from 12 participants with unilateral transfemoral amputations (10 males, 2 females, mean age = 43.2, SD = 7.4 years) in the clinical trial from cohort I (implanted in 2008/09) or cohort II (implanted in 2013/14) were collated (mean image span = 7.2, SD = 2.4 years), scale normalised, zoned, and measured in a repeatable way. Interface scores were calculated and then compared to clinical outcomes. Explanted participants received the lowest interface scores. A higher ratio of stem to residuum and shorter residuum's produced better interface scores and there was an association (weak correlation) between participants with thin cortices and the lowest interface scores. A tapered, cemented, non curved stem may provide advantageous fixation while stem alignment did not appear critical. In summary, the interface score successfully demonstrated a non-invasive evaluation of percutaneous osseointegrated implants interfaces when applied to the Intraosseous Transcutaneous Amputation Prosthesis clinical trial. The clinical significance of this work is to identify events leading to aseptic or septic implant removal and contribute to clinical guidelines for monitoring rehabilitation, design and surgical fixation choices.