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To compare gait biomechanics of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket to the ischial containment (IC) socket.Randomized crossover trial with 2, 7-week periods.Private prosthetic clinics and university research laboratory.A total of 30 enrolled (n=30); 25 participants completed the study with full (n=18) or partial data (n=7).Two custom-fabricated sockets (IC and NU-FlexSIV), worn full-time for 7 weeks, with testing at 1, 4, and 7 weeks after socket delivery.Gait analyses were conducted at 1, 4, and 7 weeks post socket delivery. Differences between sockets in selected gait variables related to hip motion and coronal plane socket stability were assessed.For participants with data for both sockets at week 7 (n=19), there were no significant differences in any gait variables between sockets at self-selected normal walking speed. However, when all participants and all study time points were assessed (n=25), there was a significant main effect of socket (P=.013), with prosthetic side sagittal plane hip range of motion being significantly greater for the NU-FlexSIV Socket at self-selected normal walking speed. There were no other significant effects.The results suggest that, compared to the IC socket, the NU-FlexSIV Socket did not alter gait biomechanics related to hip motion and coronal plane socket stability in people with unilateral transfemoral amputation.

Prosthesis design is complex and multiple appropriate options exist for any individual with lower-limb amputation. However, there is insufficient evidence for guiding decision-making. Shared decision-making (SDM) offers an opportunity to incorporate patient-specific values and preferences where evidence is lacking for prosthesis design decisions. To develop resources to facilitate SDM, and consistent with the International Patient Decision Aid Standards, it is necessary to identify the decisional needs of prosthetists and prosthesis users for prosthesis design decisions.To assess the needs of prosthetists and new prosthesis users for SDM about the first prosthesis design.Qualitative descriptive design.Six focus groups were conducted with 38 prosthetists. Individual semistructured interviews were conducted with 17 new prosthesis users. Transcripts were analyzed using directed content analysis, with codes defined a priori using existing frameworks for SDM: the Three Talk Model for SDM and the Ottawa Decision Support Framework.Four main themes were identified among prosthetists and prosthesis users: acknowledging complexity in communication, clarifying values, recognizing the role of experience to inform preferences, and understanding the prosthetic journey.Resources that support SDM for the first prosthesis design should consider methods for identifying individual communication needs, support with clarifying values, and resources such as experience for achieving informed preferences, within the context of the overall course of rehabilitation and recovery following lower-limb amputation. The themes identified in this work can inform SDM to promote collaborative discussion between prosthetists and new prosthesis users when making prosthesis design decisions.

Objectives We conducted 2 complementary scoping reviews to identify instruments that assess the experience and outcomes of custom ankle-foot orthosis (AFO) care in individuals with neurologic and traumatic conditions and to determine to what extent they might be psychometrically sound for AFO users. A stakeholder advisory committee considered to what extent the identified and psychometrically sound instruments might be feasible for use in developing quality measures for custom AFO users. Data Sources Both scoping reviews were conducted using PubMed, the Cumulative Index to Nursing and Allied Health Literature, Embase, and Cochrane Systematic Reviews. The following were used for the first scoping review only: Cochrane Central Register of Controlled Trials and the Physiotherapy Evidence Database. Study Selection The initial scoping review yielded 79 articles with 82 instruments, 16 of which were used in 4 or more studies. The second scoping review yielded 57 articles reporting psychometric properties. Data Extraction Psychometric properties for populations who use AFOs were summarized for 15 of the 16 instruments. The advisory committee eliminated 2 insrtruments, noted overlap between 4 instruments in terms of the constructs measured, and suggested 6 potential contemporary substitutes. Data Synthesis Most instruments assessed activity (specifically mobility) and pertained to the National Quality Forum domain of “Health-Related Quality of Life.” The 10-meter walk test, 6-minute walk test, Berg Balance Scale, Timed Up and Go, and Rivermead Mobility Index were reported to have adequate reliability and validity, and were considered feasible for administration in a clinical setting. Conclusions Complementary scoping reviews demonstrated that some instruments with reasonable psychometric properties are available that are feasible to use in developing quality measures for custom AFO care. However, experience of care instruments suitable for this population were not identified but are needed for a comprehensive evaluation of care quality for AFO users.

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INTRODUCTION: When studying the effect of ankle-foot orthoses (AFOs) on gait, it is important to know their sagittal plane stiffness. However, there are no established thresholds for stiffness of non-articulated AFOs designed to be rigid. If wanting to implement published algorithms for ankle-foot orthosis-footwear combinations (AFO-FCs), the AFOs must be equally as stiff as those of the developer of the published AFO-FC algorithms. Hence, the aim of this work was to compare the sagittal plane stiffness of AFOs designed to be rigid, made for a clinical trial in the USA, and following algorithms for AFO-FC designs, to those made and used clinically in the UK by the developer of the AFO-FC algorithms. MATERIALS AND METHODS: Stiffness of 9 pediatric polypropylene AFOs was tested (UK: 6; USA: 3). A computer-controlled motorized device was used in which all AFOs were clamped with the calf shell in a fixed vertical component and the foot section in a rotating plate. Each AFO was tested for 3 trials, loading the foot plate 30 Nm towards dorsiflexion and 20 Nm towards plantarflexion. Torque-angle graphs were plotted and deflection and stiffness compared descriptively across AFOs. RESULTS: Average deflection of AFOs was UK: 3.42±0.83° and USA: 4.81±1.05°. Average stiffness of AFOs was UK: 14.34±3.34 Nm/° and USA: 10.30±1.92 Nm/°. CONCLUSIONS: All tested AFOs deflected only a few degrees in either direction (range: 2.59° to 6.02°), providing the first information reported for the stiffness of rigid pediatric non-articulated AFOs. Overall, the UK AFOs were stiffer and deflected less than the USA study AFOs. AFO design features should be carefully considered as they likely influence sagittal plane stiffness and deflection under load.

Valid comparisons of muscle strength between individuals or legs that differ in size requires normalization, often by simple anthropometric variables. Few studies of muscle strength in lower-limb prosthesis users have normalized strength data by any anthropometric variable, potentially confounding our understanding of strength deficits in lower-limb prosthesis users. The objective of this pilot study was to determine the need for as well as effectiveness and impact of normalizing hip strength in lower-limb prosthesis users.Peak isometric hip extension and abduction torques were collected from 28 lower-limb prosthesis users. Allometric scaling was used to determine if hip torque values were significantly associated with, and therefore needed to be adjusted for, body mass, thigh length, or body mass x thigh length, and whether normalization was effective in reducing any associations. Between limb differences in peak hip torque, and correlations with balance ability, were inspected pre- and post-normalization.Hip torques were consistently and significantly associated with body-mass x thigh length. Associations between peak hip torque and body-mass x thigh length were reduced by normalization. After normalization by body-mass x thigh length, between limb differences in hip extension torque, as well as the correlation between hip abduction torque and balance ability, changed from non-significant to significant.In the absence of normalization, hip strength (i.e., peak torque) in lower-limb prosthesis users remains dependent on basic anthropometric variables, masking relationships between hip strength and balance ability, as well as between limb differences.

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Purpose: To describe the priorities of orthotists and physical therapists about quality measurement themes, and the feasibility and utility of collecting data from persons using custom AFOs that co...

Precise form-fitting of prosthetic sockets is important for the comfort and well-being of persons with limb amputations. Capabilities for continuous monitoring of pressure and temperature at the skin-prosthesis interface can be valuable in the fitting process and in monitoring for the development of dangerous regions of increased pressure and temperature as limb volume changes during daily activities. Conventional pressure transducers and temperature sensors cannot provide comfortable, irritation-free measurements because of their relatively rigid construction and requirements for wired interfaces to external data acquisition hardware. Here, we introduce a millimeter-scale pressure sensor that adopts a soft, three-dimensional design that integrates into a thin, flexible battery-free, wireless platform with a built-in temperature sensor to allow operation in a noninvasive, imperceptible fashion directly at the skin-prosthesis interface. The sensor system mounts on the surface of the skin of the residual limb, in single or multiple locations of interest. A wireless reader module attached to the outside of the prosthetic socket wirelessly provides power to the sensor and wirelessly receives data from it, for continuous long-range transmission to a standard consumer electronic device such as a smartphone or tablet computer. Characterization of both the sensor and the system, together with theoretical analysis of the key responses, illustrates linear, accurate responses and the ability to address the entire range of relevant pressures and to capture skin temperature accurately, both in a continuous mode. Clinical application in two prosthesis users demonstrates the functionality and feasibility of this soft, wireless system.

Creating a secure and comfortable linkage between the residual limb and prosthetic socket in persons with lower limb amputation is a critical factor for successful rehabilitation, including ambulation and other activities of daily living. Unwanted rotation within the socket can be a clinical problem for prosthesis users. One way of addressing issues experienced with transverse plane control of the socket may be through increased friction interface forces. It has been proposed that friction at the residual limb/socket interface may be increased by adding texture to interface components. Three-dimensional (3D) printing may be used to fabricate sockets with texture patterns added to the inner socket surface. Hence, the aim of this study was to investigate the effects of socket texturing on transverse plane rotation of the socket on a mock residual limb under two suspension conditions: passive suction and active vacuum. To conduct this study, we developed a mechanical testing protocol as no standardized tests currently exist to assess prosthetic sockets. Sockets with 14 different texture patterns were fabricated using the Squirt-Shape™ 3D printer. Textured sockets were compared to an Original Squirt-Shape (OSS) socket and a smooth thermoformed socket. Sockets were fitted with a mock residual limb and bi-axially loaded to 350 N compression with simultaneous rotation (2.5°, 5° and 7.5°) using a custom rotation assembly attached to a uniaxial hydraulic material testing system. There was a statistically significant three-way interaction between suspension, angle and texture (p < 0.0005). Torques between textured and reference sockets, for all rotation angles and both suspension conditions, were significantly different (p < 0.0005). Using newly developed testing protocols, it was demonstrated that some texture patterns significantly increased torque (i.e., resistance against unwanted rotation) in the transverse plane compared to both OSS and smooth sockets, especially for passive suction. Rotation testing of sockets may provide insight into socket design to improve suspension in the transverse plane.

When walking in footwear with a positive "heel sole differential", the sagittal kinematics of the base of the footwear appear to mimic normal barefoot foot kinematics, creating an "effective foot," yet sagittal shank, thigh, and trunk kinematics appear to remain unchanged. These observations have not been quantified.To quantify these observations by assessing the effect of different heel sole differentials on sagittal shank and foot segment kinematics of able-bodied walking.Cross-sectional study.Gait data from 10 nondisabled females were collected while they walked with no-heel (mean heel sole differential = 0 (standard deviation = 0) mm), mid-heel (mean heel sole differential = 37 (standard deviation = 10) mm), and high-heel shoes (mean heel sole differential = 71 (standard deviation = 17) mm) to calculate the shank-to-vertical angle and foot-to-horizontal angle.There were no significant differences between shoe conditions in stride lengths ( p = 0.056) or shank kinematics between 0% and 50% gait cycle ( p = 0.079). There were significant differences in foot kinematics ( p = 0.000), with foot segment angle increasing with increasing heel sole differential.The ankle joint and actual foot segment adapt their kinematics to maintain consistent shank kinematics. The finding that heel sole differential and foot segment angle can be varied without influencing shank segment kinematics has implications for orthotic and prosthetic practice. Clinical relevance Heel sole differentials of footwear can be varied without implications for shank kinematics, which is relevant for both orthotics and prosthetics. Assessments and interventions with varying heel sole differential footwear may be helpful in patients with short calf muscle or restricted ankle motion who may walk more normally if an appropriate heel sole differential were provided.

While Amputee Mobility Predictor scores differ between Medicare Functional Classification Levels (K-level), this does not demonstrate that the Amputee Mobility Predictor can accurately predict K-level.To determine how accurately K-level could be predicted using the Amputee Mobility Predictor in combination with patient characteristics for persons with transtibial and transfemoral amputation.Prediction.A cumulative odds ordinal logistic regression was built to determine the effect that the Amputee Mobility Predictor, in combination with patient characteristics, had on the odds of being assigned to a particular K-level in 198 people with transtibial or transfemoral amputation.For people assigned to the K2 or K3 level by their clinician, the Amputee Mobility Predictor predicted the clinician-assigned K-level more than 80% of the time. For people assigned to the K1 or K4 level by their clinician, the prediction of clinician-assigned K-level was less accurate. The odds of being in a higher K-level improved with younger age and transfemoral amputation.Ordinal logistic regression can be used to predict the odds of being assigned to a particular K-level using the Amputee Mobility Predictor and patient characteristics. This pilot study highlighted critical method design issues, such as potential predictor variables and sample size requirements for future prospective research. Clinical relevance This pilot study demonstrated that the odds of being assigned a particular K-level could be predicted using the Amputee Mobility Predictor score and patient characteristics. While the model seemed sufficiently accurate to predict clinician assignment to the K2 or K3 level, further work is needed in larger and more representative samples, particularly for people with low (K1) and high (K4) levels of mobility, to be confident in the model's predictive value prior to use in clinical practice.

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To compare comfort and functional performance of the Northwestern University Flexible Subischial Vacuum (NU-FlexSIV) Socket with the ischial containment (IC) socket in persons with unilateral transfemoral amputation.Randomized crossover trial with two 7-week periods.Private prosthetic clinics and university research laboratory.A total of 30 enrolled (N=30); 25 participants completed the study with full (n=18) or partial data (n=7).Two custom-fabricated sockets (IC and NU-FlexSIV), worn full-time for 7 weeks, with testing at 1, 4, and 7 weeks after socket delivery.The primary outcome was change in Socket Comfort Score (SCS) at 7 weeks. Secondary outcomes at 7 weeks included the Orthotic and Prosthetic Users' Survey (OPUS) to assess lower extremity functional status, health-related quality of life, and satisfaction with device, as well as the 5-Times Rapid Sit-to-Stand Test, Four Square Step Test, and T-Test of Agility to assess functional performance.At 7 weeks, the mean SCS for IC (7.0±1.7) and NU-FlexSIV (8.4±1.1) Sockets were significantly different (P.001; 95% confidence interval, 0.8-2.3). Results from a linear mixed-effects model, accounting for data from all time points, indicated that the SCS was 1.7 (SE=0.45) points higher for the NU-FlexSIV Socket (P.001). For the secondary outcomes, only OPUS satisfaction with device was significantly better in the NU-FlexSIV Socket after accounting for all data points.The results suggest that after 7 weeks' accommodation, the NU-FlexSIV Socket was more comfortable and led to greater satisfaction with device than the IC socket in persons with unilateral transfemoral amputation and K3/K4 mobility. Other patient-reported outcomes and function were no different between sockets.

Background: Current transfemoral prosthetic sockets are problematic as they restrict function, lack comfort, and cause residual limb problems. Development of a subischial socket with lower proximal trim lines is an appealing way to address this problem and may contribute to improving quality of life of persons with transfemoral amputation. Objectives: The purpose of this study was to illustrate the use of a new subischial socket in two subjects. Study design: Case series. Methods: Two unilateral transfemoral prosthesis users participated in preliminary socket evaluations comparing functional performance of the new subischial socket to ischial containment sockets. Testing included gait analysis, socket comfort score, and performance-based clinical outcome measures (Rapid-Sit-To-Stand, Four-Square-Step-Test, and Agility T-Test). Results: For both subjects, comfort was better in the subischial socket, while gait and clinical outcomes were generally comparable between sockets. Conclusion: While these evaluations are promising regarding the ability to function in this new socket design, more definitive evaluation is needed. Clinical relevance Using gait analysis, socket comfort score and performance-based outcome measures, use of the Northwestern University Flexible Subischial Vaccum Socket was evaluated in two transfemoral prosthesis users. Socket comfort improved for both subjects with comparable function compared to ischial containment sockets.

The fit and function of a prosthetic socket depend on the prosthetist's ability to design the socket's shape to distribute load comfortably over the residual limb. We recently developed a sub-ischial socket for persons with transfemoral amputation: the Northwestern University Flexible Sub-Ischial Vacuum Socket.This study aimed to quantify the rectifications required to fit the Northwestern University Flexible Sub-Ischial Vacuum Socket to teach the technique to prosthetists as well as provide a computer-aided design-computer-aided manufacturing option.Development project.A program was used to align scans of unrectified and rectified negative molds and calculate shape change as a result of rectification. Averaged rectifications were used to create a socket template, which was shared with a central fabrication facility engaged in provision of Northwestern University Flexible Sub-Ischial Vacuum Sockets to early clinical adopters. Feedback regarding quality of fitting was obtained.Rectification maps created from 30 cast pairs of successfully fit Northwestern University Flexible Sub-Ischial Vacuum Sockets confirmed that material was primarily removed from the positive mold in the proximal-lateral and posterior regions. The template was used to fabricate check sockets for 15 persons with transfemoral amputation. Feedback suggested that the template provided a reasonable initial fit with only minor adjustments.Rectification maps and template were used to facilitate teaching and central fabrication of the Northwestern University Flexible Sub-Ischial Vacuum Socket. Minor issues with quality of initial fit achieved with the template may be due to inability to adjust the template to patient characteristics (e.g. tissue type, limb shape) and/or the degree to which it represented a fully mature version of the technique. Clinical relevance Rectification maps help communicate an important step in the fabrication of the Northwestern University Flexible Sub-Ischial Vacuum Socket facilitating dissemination of the technique, while the average template provides an alternative fabrication option via computer-aided design-computer-aided manufacturing and central fabrication.

Prosthetic clinics in the United States must attain accreditation in order to receive reimbursement from Medicare. The accreditation process requires clinics to establish and implement performance management plans and quality improvement activities. This report describes the experience of seven prosthetic clinics in collecting patient-reported outcome data and using it to improve quality of services.To describe the experience of prosthetic clinics implementing outcome monitoring and quality improvement activities as part of routine patient care.Qualitative, ethnographic design.Clinics incorporated the Orthotics Prosthetics Users' Survey into routine care for patients aged 18 years and older who received a new lower limb prosthesis or socket. Orthotics Prosthetics Users' Survey measures lower extremity functional status, quality of life, and satisfaction with device and services. Clinics selected Orthotics Prosthetics Users' Survey-derived indicators on which to implement quality improvement action plans.Seven clinics participated, but only three were able to sustain data collection. Two clinics initiated quality improvement activities focused on improving declining satisfaction or functional scores.Quality improvement activities based on patient-reported outcomes require a high degree of organizational commitment and support. External facilitation can support clinics' quality improvement activities. Clinical relevance This project illustrates the challenges of sustaining quality improvement activities using patient-reported outcome data in prosthetic clinics.

Objective As in all healthcare areas, there is a need to improve quality relevant to orthotic practice, but we lack information as to what aspects of healthcare quality are meaningful to measure. Thus, the objective was to identify issues that are important to the quality-of-care for people who use custom ankle-foot orthoses as identified by ankle-foot orthosis users, orthotists, and physical therapists. Design We conducted focus groups with custom ankle-foot orthosis users, orthotists, and physical therapists. A stenographer took verbatim notes and provided transcripts. Research staff members assessed the transcripts using thematic analysis. Results Participants included 5 ankle-foot orthosis users (1 focus group), 17 orthotists (2 focus groups), and 7 physical therapists (1 focus group). They discussed domains of quality-of-care relevant for people with ankle-foot orthoses. We identified 28 thematic codes addressing 10 broad themes of quality-of-care. Six of the broad themes (organizational characteristics, patient-clinician communication, care coordination, device fit and comfort, body function, activity, and participation) mapped to the National Quality Forum's person- and family-centered care concepts. Environment of care, clinician competencies, and device characteristics and usage were important to orthotic practice but do not map to any National Quality Forum concept. Participants did not mention the National Quality Forum concept of shared decision-making. Conclusions The quality themes provide information as to what aspects of healthcare quality are meaningful to measure with respect to orthotic care, thus providing guidance on how to measure and improve ankle-foot orthosis service delivery.

To function effectively, a lower limb prosthetic socket must remain securely coupled to the residual limb during walking, running and other activities of daily living; this coupling is referred to as suspension. When this coupling is insufficient longitudinal pistoning of the socket relative to the residual limb occurs. Increasing friction of the socket/liner interface may improve socket suspension and textured sockets may be fabricated relatively easily with 3D printing. The aim of this study was to investigate longitudinal displacement of sockets with different types of textures under two suspension conditions: passive suction and active vacuum. In order to do this, we developed a mock residual limb and mechanical testing protocol. Prosthetic sockets, 14 textured sockets and an Original Squirt-Shape (OSS) Socket, were fabricated from polypropylene copolymer using the Squirt-Shape™ 3D Printer and compared to a smooth socket thermoformed from polypropylene copolymer. Sockets were mounted onto a dual durometer mock residual limb and subjected to four levels of distraction forces (100 N, 250 N, 500 N and 650 N) using a hydraulic material testing system. There was a statistically significant three-way interaction between suspension, force level and texture (p < 0.0005). Longitudinal displacements between textured and reference sockets, for all force levels and both suspension conditions, were significantly different (p < 0.0005). Using these newly developed mechanical testing protocols, it was demonstrated that texturing of polypropylene copolymer sockets fabricated using Squirt-Shape significantly decreased longitudinal displacements compared to a smooth socket. However, none of the novel textured sockets significantly reduced longitudinal displacement compared to the OSS socket under passive suction suspension.

Background Upper limb motor deficits following traumatic brain injury are prevalent and effective therapies are needed. The purpose of this case report was to illustrate response to a novel therapy using a myoelectric orthosis in a person with TBI. Case description: A 42-year-old female, 29.5 years post-traumatic brain injury with diminished motor control/coordination, and learned nonuse of the right arm. She also had cognitive deficits and did not spontaneously use her right arm functionally. Intervention Study included three phases: baseline data collection/device fabrication (five weeks); in-clinic training (2×/week for nine weeks); and home-use phase (nine weeks). The orthosis was incorporated into motor learning-based therapy. Outcomes: During in-clinic training, active range of motion, tone, muscle power, Fugl-Meyer, box and blocks test, and Chedoke assessment score improved. During the home-use phase, decrease in tone was maintained and all other outcomes declined but were still better upon study completion than baseline. The participant trained with the orthosis 70.12 h, logging over 13,000 repetitions of elbow flexion/extension and hand open/close. Discussion Despite long-standing traumatic brain injury, meaningful improvements in motor function were observed and were likely the results of high repetition practice of functional movement delivered over a long duration. Further assessment in a larger cohort is warranted.

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Ischial containment sockets are the current standard of care for military service members with transfemoral amputation. However, they fit intimately with the ischium, which may limit hip motion and contribute to proximal socket discomfort, a common complaint among prosthesis users. Subischial sockets, such as the newly described Northwestern University Flexible Subischial Vacuum (NU-FlexSIV) Socket technique, do not interact with the ischium, potentially increasing hip motion and improving comfort.To transfer the NU-FlexSIV Socket technique to military prosthetists and evaluate performance among military service members with transfemoral amputation.case series.Four of the 11 enrolled subjects completed the study protocol comparing the NU-FlexSIV Socket to the ischial containment socket. Gait kinematics (over ground and on stairs), physical performance measures (Four-Square Step Test, T-test of Agility, and an obstacle course), limb-socket motion, and socket comfort were assessed after accommodation time in each socket.While wearing the NU-FlexSIV Socket, sagittal plane hip motion generally increased while coronal plane trunk motion and walking speed remained largely unaffected during over ground walking. During stair ascent, sagittal plane hip motion increased while wearing the NU-FlexSIV Socket, with minimal changes in walking speed for all subjects. Pre- and post-walking fluoroscopy measures suggest fit of the NU-FlexSIV Socket was less affected by activity. Most subjects reported that the NU-FlexSIV Socket was more comfortable for sitting but some found it less comfortable for walking and running. Performance measure results were mixed. Although attempts were made to consistently implement the NU-FlexSIV Socket technique, some challenges were experienced.The NU-FlexSIV Socket provided greater hip motion across a variety of tasks without adversely affecting other movement mechanics but did not consistently improve socket comfort. Variability in the liners and socket materials used may have contributed to variability in results. Overall, the design was a viable alternative to traditional ischial containment sockets for some individuals with transfemoral amputation.

Misaligning the mechanical axes of Ankle-Foot Orthoses with the ankle axis may lead to tissue damage, reduced gait efficiency, and mechanical wear on the orthosis. Previous models developed to describe the consequences of joint misalignments have only been applied to the sagittal plane. In this study, a previously developed three-dimensional model of the Ankle-Foot Orthosis/leg system was used to determine the effects of misalignments in the frontal and transverse planes and how they interact with misalignments in the sagittal plane.The motion of two corresponding points on the leg and Ankle-Foot Orthosis was calculated for different binary combinations of translational and rotational misalignments of the mechanical axis, and the resulting displacements between those points recorded.Misaligning the mechanical joint axis of the Ankle-Foot Orthosis in the transverse plane led to much greater displacements than other misalignments. Results from the model suggest the importance of prioritizing transverse plane alignment by appropriately accounting for tibial rotation.Misalignments in the transverse plane had a dominating effect on relative motion between the Ankle-Foot Orthosis and leg emphasizing the importance of including the third dimension in the model and prioritizing accuracy of alignment in the transverse plane.

Background: Misalignment of an articulated ankle-foot orthosis joint axis with the anatomic joint axis may lead to discomfort, alterations in gait, and tissue damage. Theoretical, two-dimensional models describe the consequences of misalignments, but cannot capture the three-dimensional behavior of ankle-foot orthosis use. Objectives: The purpose of this project was to develop a model to describe the effects of ankle-foot orthosis ankle joint misalignment in three dimensions. Study design: Computational simulation. Methods: Three-dimensional scans of a leg and ankle-foot orthosis were incorporated into a link segment model where the ankle-foot orthosis joint axis could be misaligned with the anatomic ankle joint axis. The leg/ankle-foot orthosis interface was modeled as a network of nodes connected by springs to estimate interface pressure. Motion between the leg and ankle-foot orthosis was calculated as the ankle joint moved through a gait cycle. Results: While the three-dimensional model corroborated predictions of the previously published two-dimensional model that misalignments in the anterior -posterior direction would result in greater relative motion compared to misalignments in the proximal -distal direction, it provided greater insight showing that misalignments have asymmetrical effects. Conclusions: The three-dimensional model has been incorporated into a freely available computer program to assist others in understanding the consequences of joint misalignments. Clinical relevance Models and simulations can be used to gain insight into functioning of systems of interest. We have developed a three- dimensional model to assess the effect of ankle joint axis misalignments in ankle-foot orthoses. The model has been incorporated into a freely available computer program to assist understanding of trainees and others interested in orthotics.

Although there is strong evidence to show that the risk of dying after transtibial amputation is higher than partial foot amputation, we are concerned by the implication that amputation level influences mortality, and that such interpretations of the evidence may be used to inform decisions about the choice of amputation level. We argue that the choice of partial foot or transtibial amputation does not influence the risk of mortality. The highest mortality rates are observed in studies with older people with more advanced systemic disease and multiple comorbidities. Studies that control for the confounding influence of these factors have shown no differences in mortality rates by amputation level. These insights have important implications in terms of how we help inform difficult decisions about amputation at either the partial foot or transtibial level, given a more thoughtful interpretation of the published mortality rates.