Prosthetics and Orthotics International

Conventional methods for producing custom prosthetic fingers are time-consuming, can be uncomfortable for the patient, and require a skilled prosthetist. The subject was a 40-year-old male with congenital absence of the thumb and related metacarpal bone on the right non-dominant hand, anomaly of the lengths of individual upper limb segments, and contracture of the elbow joint. This hand presentation made it impossible for him to perform thumb opposition, which is a very important function for common daily activities.

The goal was to design an individual passive thumb prosthesis using free open-source software, 3D scanning technology, and additive manufacturing methods (i.e., fused filament fabrication).

Case report.

Artificial thumb prostheses with two types of bases and fastening interfaces were designed and manufactured. One combination was chosen as the best alternative.

The shape, positioning, firmness, and fastening of the prosthesis were compliant enough for the patient to be able to hold objects with his healthy fingers and artificial thumb. This innovative approach to fabrication of a custom thumb prosthesis provided considerable advantages in terms of custom sizing, manufacturing time, rapid production, iteration, comfort, and costs when compared to conventional methods of manufacturing a hand prosthesis.

The methodology of designing and manufacturing a prosthetic thumb using 3D scanning and additive manufacturing technologies have been demonstrated to be adequate from a practical point of view. These technologies show potential for use in the practice of prosthetics.

Although the incidence of major pediatric lower limb loss secondary to either congenital deficiencies or acquired amputations is relatively low, the prevalence of lower limb loss among children in the United States (US) remains unknown.

To estimate the prevalence of major lower limb loss, and the associated prosthetic services use and costs among commercially-insured children in the US.

Observational, retrospective, longitudinal cohort study.

The IBM MarketScan^® Commercial Database was used to identify children (<18 years) with major lower limb loss in the US between 2009 and 2015. Descriptive statistics were used to characterize pediatric cases according to sociodemographic and limb loss characteristics. Multivariate models assessed factors associated with annual prosthetic visits, prosthetic-related costs, and overall medical costs.

Of the 36.5 million children in the MarketScan database, 14,038 had a major lower limb loss, yielding a prevalence estimate of 38.5 cases per 100,000 commercially insured children in the US during the 7-year study period. Congenital deficiencies accounted for 84% of cases, followed by 13.5% from trauma. Only 10.1% had at least one prosthesis-related visit during any 12-month period following their cohort entry. Among those, the mean annual prosthetic-related costs ranged from $50 to $29,112 with a median annual cost of $2778 (interquartile range = $4567). Annual coinsurance and copays for prosthetic services accounted for nearly half of the overall annual out-of-pocket outlays with medical care for these children.

Pediatric lower limb loss results in lifelong prosthetic needs. This study informs insurers and policy-makers regarding the prevalence of these patients and the medical costs for their care.

Current body-powered hands have very low acceptance rates. They also require high activation forces. In the past, a high acceptance rate was reported for the then-available Hüfner hand, a hand which could be controlled by relatively low activation forces.

The aim of this study was to measure and quantify the mechanical performance of the Hüfner hand.

Mechanical evaluation.

Two versions of the Hüfner hand were tested using a mechanical test bench. Forces and displacements were measured under four different glove conditions (no glove, leather, polyvinyl chloride (PVC), silicone). The measured results were compared to data from currently available voluntary-closing hands.

The Hüfner hand required 132–170 Nmm of work and 78–104 N cable force to pinch 15 N. The overall mechanical performance of the Hüfner hands is better than currently available body-powered hands.

The mechanical performance of the Hüfner hand was measured and quantified. Mechanical testing results show that the Hüfner hand has better mechanical performance than current body-powered hands. This may have contributed to its reported high acceptance rates. The design of the Hüfner hand, combined with data presented in this study, can serve as guidelines for the design of a new generation of body-powered hands.

Until recently, no study had compared the quality of life of persons with transfemoral amputation treated with osseointegration to socket prosthesis users.

Comparison of quality of life in two types of prostheses users: a cohort of patients with osseointegration and patients equipped with a socket prosthesis who were group-matched for age, body mass index and mobility grade.

A cross-sectional study that compared

The quality of life of 39 participants (22 in the osseointegration group and 17 in the socket prosthesis group) was measured using the Questionnaire for Persons with Transfemoral Amputation (Q-TFA) and European Questionnaire 5-dimension 3-level (EQ-5D-3L) surveys.

Compared with the socket prosthesis group, the osseointegration group had a significantly higher ‘Global’ score (p = 0.022) and a significantly lower ‘Problem’ score (p < 0.001) of the Q-TFA. The ‘Mobility’ (p = 0.051) and ‘Use’ scores (p = 0.146) of the Q-TFA, the EQ-5D-3L index (p = 0.723), and EQ-5D visual analog scale (p = 0.497) showed no significant differences between groups.

Patients with osseointegration experienced less prosthesis-associated problems than socket prosthesis users and had a higher prosthesis-associated quality of life when assessed with the Q-TFA. General quality of life, as assessed with the EQ-5D-3L, was not different between groups.

Children with hemiparesis are commonly prescribed ankle foot orthoses to help improve gait; however, these orthoses often result in only small and variable changes in gait. Research with adult stroke survivors has suggested that orthoses that extend beyond the ankle using long, passive tendon-like structures (i.e. exotendons) can improve walking.

The aim of this study was to quantify the impact of an exotendon-based exoskeleton on pediatric gait.

Repeated-measures study.

Two typically-developing children and two children with hemiparesis completed a gait analysis, walking without and with the exoskeleton. The exotendon was tested at three stiffness levels.

All children were able to walk comfortably with the exoskeleton, with minimal changes in step width. Walking speed increased and lower limb joint symmetry improved for the children with hemiparesis with the exoskeleton. Each participant had changes in muscle activity while walking with the exoskeleton, although the impact on specific muscles and response to exotendon stiffness varied.

Exotendon-based exoskeletons may provide an alternative solution for optimizing gait in therapy and in the community for children with hemiparesis. Determining the optimal stiffness and configuration for each child is an important area of future research.

Little is known about the patterns of prosthesis use and satisfaction of those who cease use or begin to use upper limb prostheses.

Among a longitudinal sample of Veterans with upper limb amputation, (1) describe changes in prosthesis use over 1 year, (2) examine rates of receipt of new prostheses, and (3) compare prosthesis satisfaction in respondents who received a new prosthesis to those who did not.

Longitudinal survey.

808 Veterans who had participated in a baseline interview 1 year earlier were invited to participate in structured telephone interviews.

A total of 562 persons with unilateral and 23 with bilateral amputation participated in the interviews (Response rate = 72.4% and 85.2%, respectively). Prosthesis use, frequency and intensity of use, and types of prostheses used were stable over 1 year. About 24% reported using a different primary terminal device type at follow-up than baseline. Prosthesis use was less frequent/intense at baseline among those who discontinued use compared with those who did not (P < 0.05), and less frequent/intense for those who started compared with those who continued using a prosthesis (P < 0.0001). Rates of prosthetic training were higher among those who received a different prosthesis type compared with those using the same type (P = 0.06). Satisfaction scores were higher (P < 0.01) for new prosthesis recipients, and lower at baseline for prosthesis abandoners compared with continued users (P = 0.03).

Prosthesis abandonment appears to be predicated on dissatisfaction with the device, as well as less frequent/intense prosthesis use. These findings can be used to identify those at risk for prosthesis abandonment and improve their prosthesis experience.

Recommendations for the alignment of the socket and foot in the sprinting prosthesis of athletes with transfemoral amputation are either based on walking biomechanics or lack public scientific evidence.

To explore the biomechanical changes and the sensations of a gold medal Paralympic sprinter, while running with three bench alignments: a conventional reference (A0), an innovative alignment based on the biomechanics of elite able-bodied sprinters (A2), and an intermediate alignment (A1).

Single subject with repeated measures.

A1 and A2 feature a progressively greater socket tilt and a plantar-flexed foot compared to A0. The 30-year-old female athlete trained with three prostheses, one per alignment, for at least 2 months. We administered a questionnaire to collect her impressions. Then, she ran on a treadmill at full speed (5.5 m/s). We measured the kinematics and moments of the prosthetic side, and the ground reaction forces of both sides.

A2 reduced the prosthetic side hip extension at foot-off while preserving hip range of motion, decreased the impulse of the hip moment, and increased the horizontal propulsion, leaving sufficient margin to prevent knee buckling without increasing sound side braking forces. Biomechanical outcomes matched well with subjective impressions.

A2 appears promising to improve the performance and comfort of sprinters with transfemoral amputation, without compromising safety.

bservation of elite able-bodied sprinters led to the definition of a new specific alignment for the sprinting prosthesis of athletes with transfemoral amputation, which appears promising to improve performance and comfort, without compromising safety. This may constitute a major improvement compared to alignments based on walking biomechanics.

Information access is essential for quality healthcare provision and education. Despite technological advances, access to prosthetics and orthotics information in low- and middle-income countries is not ubiquitous. The current state of information access, availability, and exchange among prosthetics and orthotics faculty is unknown.

Describe information exchange networks and access at two prosthetics and orthotics programs in Ghana and the United States.

Cross-sectional survey, social network analysis.

An online survey of faculty at two prosthetics and orthotics programs using REDCap. The survey included a social network analysis, demographics, and prosthetics and orthotics information resources and frequency of use. Descriptive statistics were calculated.

Twenty-one faculty members completed the survey (84% response). Ghanaian faculty were on average younger (median Ghana: 27 years, United States: 43 years), had less teaching experience, and had less education than US faculty. Textbooks were the most commonly used resource at both programs. The Ghanaian network had more internal connections with few outside sources. The US network had fewer internal connections, relied heavily upon four key players, and had numerous outside contacts.

Ghana and US faculty have two distinct information exchange networks. These networks identify key players and barriers to dissemination among faculty to promote successful knowledge translation of current scientific literature and technology development. Social network analysis may be a useful method to explore information sharing among prosthetics and orthotics faculty, and identify areas for further study.

A variety of instruments exist to measure human factors for lower limb amputation and prosthesis research yet, there is no valid or reliable tool available that focuses on technical potentials.

This study aimed to validate and revise the Questionnaire to Explore Human Factors and their Technical Potential.

Cross-sectional study

A total of 150 persons with lower limb amputation from Germany participated in the study. Statistical properties, including Cronbach’s alpha, item difficulty, item-total correlation, and distribution of missing values were calculated. Thresholds for acceptable psychometric properties were defined, unsuitable items were removed, and problematic items were reviewed regarding formulation.

The Cronbach’s alpha for subscales within the Questionnaire to Explore Human Factors and their Technical Potential were between 0.72 and 0.89. A total of 56 items showed acceptability, and 14 items had problematic item property values. Four of those items were reformulated, five were excluded, six were left in the scale, and an additional one was added to the scale.

Evaluation of the Questionnaire to Explore Human Factors and their Technical Potential indicates it exhibits good internal consistency and acceptable psychometric properties. The scale was revised and is recommended to explore aspects of technical prosthesis development.

Our results show that the revised Questionnaire to Explore Human Factors and their Technical Potential may serve as a reliable and valid means, when designing prostheses, both during development and clinical evaluations and fittings, to assess the technical potential of lower limb prostheses directly according to the needs of users with lower-limb amputations.

The Comprehensive Lower limb Amputee Socket Survey (CLASS) is a self-reported measure developed to assess prosthetic socket fit in individuals with lower limb amputation.

To assess the reliability and validity of the Persian version of the CLASS.

Cross-sectional and repeated-measures.

We evaluated the translation and back translation of the CLASS and made the required changes according to expert committee feedback. Then, we recruited 124 participants with unilateral lower limb amputation (89.5% men). Internal consistency was analyzed with Cronbach’s alpha and test–retest reliability using intra-class correlation coefficients. Convergent construct validity was assessed by comparing the CLASS scores with the Persian version of the Trinity Amputation and Prosthesis Experience Scales (TAPES) scores. In addition, known groups construct validity was assessed by comparing CLASS scores between groups with different causes and levels of amputation.

Cronbach’s alpha coefficient represented a very good internal consistency for all domains of the Persian CLASS (ranged from 0.86 to 0.92). The intra-class correlation coefficient for test–retest reliability for the Persian CLASS was good to excellent (ranged from 0.73 to 0.97). There was a significant correlation between the subscales of the Persian CLASS and satisfaction subscales of the Persian TAPES (p < 0.001). There was no significant difference between the Persian CLASS scores by cause or level of amputation.

The Persian CLASS is a reliable and valid measure for evaluating prosthetic socket fit.

Reliable information on both global need for prosthetic services and the current prosthetist workforce is limited. Global burden of disease estimates can provide valuable insight into amputation prevalence due to traumatic causes and global prosthetists needed to treat traumatic amputations.

This study was conducted to quantify and interpret patterns in global distribution and prevalence of traumatic limb amputation by cause, region, and age within the context of prosthetic rehabilitation, prosthetist need, and prosthetist education.

A secondary database descriptive study.

Amputation prevalence and prevalence rate per 100,000 due to trauma were estimated using the 2017 global burden of disease results. Global burden of disease estimation utilizes a Bayesian metaregression and best available data to estimate the prevalence of diseases and injuries, such as amputation.

In 2017, 57.7 million people were living with limb amputation due to traumatic causes worldwide. Leading traumatic causes of limb amputation were falls (36.2%), road injuries (15.7%), other transportation injuries (11.2%), and mechanical forces (10.4%). The highest number of prevalent traumatic amputations was in East Asia and South Asia followed by Western Europe, North Africa, and the Middle East, high-income North America and Eastern Europe. Based on these prevalence estimates, approximately 75,850 prosthetists are needed globally to treat people with traumatic amputations.

Amputation prevalence estimates and patterns can inform prosthetic service provision, education and planning.

The extent to which current prosthetic health economic evaluations inform healthcare policy and investment decisions is unclear. To further the knowledge in this area, existing evidence gaps and method design issues must be identified, thereby informing the design of future research.

The aim of this systematic review was to identify evidence gaps, critical method design and reporting issues and determine the extent to which the literature informs a wide range of policy and investment decisions.

Systematic review.

A range of databases were searched using intervention- and health economic evaluation-related terms. Issues with methodological design and reporting were evaluated using the Consolidated Health Economic Checklist – Extended and the Checklist for Health Economic Evaluation Reporting Standards.

The existing health economic evaluation literature was narrowly focused on informing within-participant component decisions. There were common method design (e.g. time horizon too short) and reporting issues (e.g. competing intervention descriptions) that limit the extent to which this literature can inform policy and investment decisions.

There are opportunities to conduct a wider variety of health economic evaluations to support within- and across-sector policy and investment decisions. Changes to aspects of the method design and reporting are encouraged for future research in order to improve the rigour of the health economic evaluation evidence.

This systematic review will inform the clinical focus and method design of future prosthetic health economic evaluations. It will also guide readers and policy-makers in their interpretation of the current literature and their understanding of the extent to which the current literature can be used to inform policy and investment decisions.

Finite element modelling has long been proposed to support prosthetic socket design. However, there is minimal detail in the literature to inform practice in developing and interpreting these complex, highly nonlinear models.

To identify best practice recommendations for finite element modelling of lower limb prosthetics, considering key modelling approaches and inputs.

Computational modelling.

This study developed a parametric finite element model using magnetic resonance imaging data from a person with transtibial amputation. Comparative analyses were performed considering socket loading methods, socket–residuum interface parameters and soft tissue material models from the literature, to quantify their effect on the residuum’s biomechanical response to a range of parameterised socket designs.

These variables had a marked impact on the finite element model’s predictions for limb–socket interface pressure and soft tissue shear distribution.

All modelling decisions should be justified biomechanically and clinically. In order to represent the prosthetic loading scenario in silico, researchers should (1) consider the effects of donning and interface friction to capture the generated soft tissue shear stresses, (2) use representative stiffness hyperelastic material models for soft tissues when using strain to predict injury and (3) interrogate models comparatively, against a clinically-used control.

How Achilles tendon mechanics and plantar flexion strength and torque steadiness are altered in the intact leg of persons with trauma-related amputation is unknown. Understanding Achilles tendon mechanics following amputation will further inform rehabilitation approaches to enhance posture, balance, and force control.

Conduct a pilot study to quantify plantar flexion maximal voluntary contraction torque, torque steadiness, and Achilles tendon mechanics in persons with unilateral trauma-related transfemoral amputation and controls without amputation.

Cross-sectional study.

Isometric plantar flexion maximal voluntary contractions were performed with the intact leg of ten males with transfemoral amputation (48 ± 14 years) and the dominant leg of age-matched male controls without amputation. Torque steadiness was calculated as the coefficient of variation in torque over 6 s during submaximal tracking tasks (5%, 10%, 25%, 50%, and 75% maximal voluntary contraction). Achilles tendon elongation and cross-sectional area were recorded with ultrasound to calculate strain, stress, and stiffness.

Maximal voluntary contraction and torque steadiness did not differ between persons with amputation (90.6 ± 31.6 N m, 3.7 ± 2.0%) and controls (95.8 ± 26.8 N m, 2.9 ± 1.2%; p > 0.05). Tendon stiffness (21.1 ± 18.2 N/mm) and strain (5.2 ± 1.3%) did not differ between groups (p > 0.05). Tendon cross-sectional area was 10% greater in persons with amputation leading to 29% lower stress (p = 0.021). Maximal voluntary contraction was a predictor of a lower coefficient of variation in torque (R² = 0.11, p < 0.05).

Persons with trauma-related transfemoral amputation do not differ in plantar flexion maximal voluntary contraction and torque steadiness of the intact leg compared with controls without amputation. Larger tendon cross-sectional area reduces stress and enables distribution of force across a greater area.

Millions of people in low- and middle-income countries lack access to prosthetic care. A well-fitting, durable socket is important for prosthesis comfort and function, but conventional fabrication techniques require highly trained clinicians and specialized equipment.

To increase access to prosthetic care by developing a simple, low-cost socket fabrication method that does not require specialized equipment or electricity, and can be performed by persons with minimal prosthetic training.

Socket fabrication methods and socket function were evaluated in a pilot feasibility study.

We describe a rapid method for fabricating a rigid foam socket directly over the residual limb, with a mass producible, strong, cosmetically appealing plastic outer shell. We fabricated sockets for four individuals with unilateral transradial amputations and evaluated socket function.

An individual with no formal prosthetic training was able to fabricate sockets and assemble a functional, comfortable prosthesis system within 90 min. All necessary supplies can be provided in a kit for under US$100.

Further work is required to determine durability, assess comfort, refine suspension methods, and to develop instructional materials.

We developed a simplified, inexpensive method to fabricate sockets on the residual limb using expandable foam with an integrated cosmetic/structural covering (i.e. an exoskeletal system), for persons with transradial amputation. A transradial prosthesis socket can be fabricated in around 90 min. and all necessary materials, tools, and written instructions for fabrication and fitting can be provided in a kit. Specialized equipment and electricity are not required. Instructions for fabrication and fitting can be provided in multiple languages using online videos.

Powered hand exoskeletons are an emerging technology that have shown promise in assisting individuals with impaired hand function. A number of hand exoskeleton designs have been described in the literature; however, the majority have not been supported by patient-oriented criteria.

The aim of this study was to define preliminary end-user needs and expectations for an assistive hand exoskeleton.

Explorative interview and case series.

Six clinicians and eight individuals with impaired hand function were interviewed in small groups or individually. A standardized list of questions was used to elicit feedback on specific design criteria or promote the discovery of new criteria. In addition, three participants with impaired hand function returned for a second session where hand characteristics, such as range of motion and force required to flex/extend fingers, were recorded to further quantify design requirements.

Interview responses indicated that there was general consensus among participants on criteria relating to important grasp patterns, grip strength, wear time, and acceptable bulk/weight. However, interview responses and hand characteristics also revealed important differences between individuals with impaired hand function.

Qualitative and quantitative data were collected to develop an understanding of end-user design requirements for assistive hand exoskeletons. Although the data collected were helpful in identifying some preliminary criteria, differences between participants exist and identifying a universal set of criteria applicable across individuals with impaired hand function is challenging. This work reinforces the importance of involving users of rehabilitation technology in the device development process.

Mechanical behavior is difficult to monitor in experimental environments, usually because of geometric or technology implementation limitations. Nevertheless, thermography has been shown to overcome these issues.

The aim of this study was to evaluate four types of assemblies between a Jaipur foot and a polyethylene tube using infrared thermography in order to find the best mechanical configuration in terms of thermal behavior.

Mechanical testing.

An infrared camera captured short videos every 5 min over 10 h in six different positions (three in the back and three in front of the Jaipur foot) around a prosthesis subjected to repetitive stresses (axial force 980 N) simulating kinematic variables like joint angles. We established a region of interest around the foot–ankle assemblies and calculated maximum temperatures and thermographic indices.

In this study, the best foot–ankle assembly used epoxy adhesive because it presented the lowest temperature in the six positions and the lowest thermal index.

Thermographic techniques can be used to study mechanical behaviors in complex experimental situations.

Maintaining an optimal rolling of the foot over the ground is thought to increase the stability and efficiency of pathologic gait. Ankle-foot orthoses are often prescribed to improve gait mechanics in individuals with lower extremity injuries; however, their design may compromise how the foot rolls over the ground.

The aim of this study was to investigate the effects of the sagittal plane ankle-foot orthosis alignment on roll-over shape and center of pressure velocity in individuals with lower limb reconstructions.

Randomized cross-over study with a control group comparison.

In total, 12 individuals with lower limb reconstruction who used a custom carbon ankle-foot orthosis and 12 uninjured controls underwent gait analysis. Ankle-foot orthosis users were tested in their clinically-provided ankle-foot orthosis alignment, with an alignment that was 3° more plantarflexed, and with an alignment that was 3° more dorsiflexed. Components of roll-over shape and center of pressure velocity were calculated from heel strike on the ankle-foot orthosis limb to contralateral heel strike.

Roll-over shape radius was not affected by 3° changes to alignment and was not significantly different from controls. Aligning the ankle-foot orthosis in more dorsiflexion than clinically provided resulted in a smaller peak center of pressure velocity that occurred later in stance.

Individuals using custom carbon ankle-foot orthoses can accommodate 3° alterations in the dorsiflexion or plantarflexion alignment.