Prosthetics and Orthotics International

Three-dimensional printing provides an exciting opportunity to customise upper-limb prostheses.

This review summarises the research that assesses the efficacy and effectiveness of three-dimensional printed upper-limb prostheses.

Systematic review.

PubMed, Web of Science and OVID were systematically searched for studies that reported human trials of three-dimensional printed upper-limb prostheses. The studies matching the language, peer-review and relevance criteria were ranked by level of evidence and critically appraised using the Downs and Black Quality Index.

After removing duplicates, 321 records were identified. Eight papers met the inclusion criteria. No studies used controls; five were case studies and three were small case-series studies. All studies showed promising results, but none demonstrated external validity, avoidance of bias or statistically significant improvements over conventional prostheses. The studies demonstrated proof-of-concept rather than assessing efficacy, and the devices were designed to prioritise reduction of manufacturing costs, not customisability for comfort and function.

The potential of three-dimensional printing for individual customisation has yet to be fully realised, and the efficacy and effectiveness to be rigorously assessed. Until randomised controlled trials with follow-up are performed, the comfort, functionality, durability and long-term effects on quality of life remain unknown.

Initial studies suggest that three-dimensional printing shows promise for customising low-cost upper-limb prosthetics. However, the efficacy and effectiveness of these devices have yet to be rigorously assessed. Until randomised controlled trials with follow-up are performed, the comfort, functionality, durability and long-term effects on patient quality of life remain unknown.

The International Classification of functioning, disability and health refers capacity to what an individual can do in a standardised environment and describes performance as what an individual really does and whether the individual encounters any difficulty in the real-life environment. Measures of capacity and performance can help to determine if there is any gap between them that may restrict participation. The aim of this study was to explore the relationship between capacity scores obtained in a standardised clinical setting and proportional ease of performance obtained from a real-life environment.

The Assessment of Capacity for Myoelectric Control and the Prosthetic Upper Extremity Functional Index were used to assess capacity and performance in 62 prosthetic users (age 3–17). Spearman coefficient and generalised linear model were used to examine the association between these measures.

A strong correlation (Spearman = 0.75) was found between the capacity scores and the ease of performance. In both unadjusted and adjusted models, capacity was significantly associated with proportional ease of performance. The adjusted model showed that, by 1 unit increase in the Assessment of Capacity for Myoelectric Control score, the ratio of proportional ease of performance increases by 45%.

This implies that Assessment of Capacity for Myoelectric Control can be a predictor for ease of performance in real-life environment.

The ACMC scores may serve as an indicator to predict the difficulties that the children may encounter in their home environment. This prediction can help the clinician to make decisions, such that if the child requires more control training or is ready to move on to learn more complex tasks.

In 1970, Mori hypothesised the existence of an ‘uncanny valley’, whereby stimuli falling short of being fully human are found to be creepy or eerie.

To investigate how eerie people find different prosthetic hands and whether perceptions of eeriness can be accounted for by categorical ambiguity.

Students participated in computerised experiments during which photographic images of hands were presented.

We compared photographs of prosthetic hands pre-selected as more (H+) or less human-like (H–), as well as mechanical and real hands. Participants rated the hands for eeriness and human-likeness, as well as performing a speeded classification (human/non-human) and location judgment (control) task.

The H– prosthetic hands were rated as more eerie than the H+ prosthetic, mechanical and real hands, and this was unaffected by hand orientation. Participants were significantly slower to categorise the H+ prosthetic hands compared to the H– prosthetic and real hands, which was not due to generally slower responses to the H+ prosthetic hands (control task).

People find prosthetic hands to be eerie, most consistently for less human-like prosthetic hands. This effect is not driven by ambiguity about whether to categorise the prosthetic hand as human or artificial.

More obviously artificial, less-realistic, prosthetic hands consistently generate a sense of eeriness, while more realistic prosthetic hands avoid the uncanny valley, at least on initial viewing. Thus, greater realism in prosthetic design may not always incur a cost, although the role of movement and cutaneous input requires further investigation.

Prostheses are used to varying degrees; however, little is known about how environmental aspects influence this use.

To describe users’ experiences of how environmental factors influence their use of a myoelectric arm prosthesis.

Qualitative and descriptive.

A total of 13 patients previously provided with a myoelectric prosthetic hand participated. Their age, sex, deficiency level, etiology, current prosthesis use, and experience varied. Semi-structured interviews were audiotaped, transcribed, and analyzed through inductive content analysis.

Four categories were created from the data: “Prosthesis function,” “Other people’s attitudes,” “Support from family and healthcare,” and “Individual’s attitude and strategies.” The overarching theme, “Various degrees of embodiment lead to different experiences of environmental barriers and facilitators,” emerged from differences in individual responses depending on whether the individual was a daily or a non-daily prosthesis user. Environmental facilitators such as support from family and healthcare and good function and fit of the prosthesis seemed to help the embodiment of the prosthesis, leading to daily use. This embodiment seemed to reduce the influence of environmental barriers, for example, climate, attitudes, and technical shortcomings.

Embodiment of prostheses seems to reduce the impact of environmental barriers. Support and training may facilitate the embodiment of myoelectric prosthesis use.

For successful prosthetic rehabilitation, environmental factors such as support and information to the patient and their social network about the benefits of prosthesis use are important. Local access to training in myoelectric control gives more people the opportunity to adapt to prosthesis use and experience less environmental barriers.

Current outcome measures used in upper limb myoelectric prosthesis studies include clinical tests of function and self-report questionnaires on real-world prosthesis use. Research in other cohorts has questioned both the validity of self-report as an activity assessment tool and the relationship between clinical functionality and real-world upper limb activity. Previously,¹ we reported the first results of monitoring upper limb prosthesis use. However, the data visualisation technique used was limited in scope.

Methodology development.

To introduce two new methods for the analysis and display of upper limb activity monitoring data and to demonstrate the potential value of the approach with example real-world data.

Upper limb activity monitors, worn on each wrist, recorded data on two anatomically intact participants and two prosthesis users over 1 week. Participants also filled in a diary to record upper limb activity. Data visualisation was carried out using histograms, and Archimedean spirals to illustrate temporal patterns of upper limb activity.

Anatomically intact participants’ activity was largely bilateral in nature, interspersed with frequent bursts of unilateral activity of each arm. At times when the prosthesis was worn prosthesis users showed very little unilateral use of the prosthesis (≈20–40 min/week compared to ≈350 min/week unilateral activity on each arm for anatomically intact participants), with consistent bias towards the intact arm throughout. The Archimedean spiral plots illustrated participant-specific patterns of non-use in prosthesis users.

The data visualisation techniques allow detailed and objective assessment of temporal patterns in the upper limb activity of prosthesis users.

Activity monitoring offers an objective method for the assessment of upper limb prosthesis users’ (PUs) activity outside of the clinic. By plotting data using Archimedean spirals, it is possible to visualise, in detail, the temporal patterns of upper limb activity. Further work is needed to explore the relationship between traditional functional outcome measures and real-world prosthesis activity.

The evolution of three-dimensional printing into prosthetics has opened conversations about the availability and cost of prostheses. This report will discuss how a prosthetic team incorporated additive manufacture techniques into the treatment of a patient with a partial hand amputation to create and test a unique assistive device which he could use to hold his French horn.

Using a process of shape capture, photogrammetry, computer-aided design and finite element analysis, a suitable assistive device was designed and tested. The design was fabricated using three-dimensional printing. Patient satisfaction was measured using a Pugh’s Matrix™, and a cost comparison was made between the process used and traditional manufacturing.

Patient satisfaction was high. The three-dimensional printed devices were 56% cheaper to fabricate than a similar laminated device.

Computer-aided design and three-dimensional printing proved to be an effective method for designing, testing and fabricating a unique assistive device.

CAD and 3D printing techniques can enable devices to be designed, tested and fabricated cheaper than when using traditional techniques. This may lead to improvements in quality and accessibility.

Patient-reported outcome measures are increasingly used to evaluate effectiveness of treatment. However, the use of ‘paper and pencil’ questionnaires is time-consuming for both patients and healthcare specialists. Therefore, the aim of this project was to develop a custom-built web-based monitoring system.

We incorporated reliable and valid questionnaires on all domains of human functioning as described in the World Health Organization’s Classification of Functioning, Disability and Health (ICF and ICF-CY). The method of remote follow-up enables long-term evaluation of PROMs. We specified monitoring protocols for both children and adults, split for different age groups with emphasis on health-related quality of life.

Time-efficient evaluation of PROMs may lead to higher compliance and an increase of client-centred practice. Moreover, evaluating PROMs facilitates patient empowerment and enables patients to make informed decisions about their treatment and healthcare needs.

We developed a web-based system for evaluation of PROMs. The system has enabled better informed decision-making for our clients.

In order to create more uniformity in the prescription of upper limb prostheses by Dutch rehabilitation teams, the development and implementation of a Prosthesis Prescription Protocol of the upper limb (PPP-Arm) was initiated. The aim was to create a national digital protocol to structure, underpin, and evaluate the prescription of upper limb prostheses for clients with acquired or congenital arm defects.

Prosthesis Prescription Protocol of the Arm (PPP-Arm) was developed on the basis of the International Classification of Functioning and consisted of several layers. All stakeholders (rehabilitation teams, orthopedic workshops, patients, and insurance companies) were involved in development and implementation. A national project coordinator and knowledge brokers in each team were essential for the project.

PPP-Arm was successfully developed and implemented in nine Dutch rehabilitation teams. The protocol improved team collaboration, structure, and completeness of prosthesis prescriptions and treatment uniformity and might be interesting for other countries as well.

A national protocol to prescribe upper limb prostheses can be helpful to create uniformity in treatment of patients with upper limb defects. Such a protocol improves quality of care for all patients in the country.

Our hands constantly handle objects throughout our lives, where a crucial component of this interaction is the detection of grasping (pressure) and slipping (shear) of the object. While there have been a large amount of studies using pressure sensors for grasping detection, synchronised pressure and shear detection at the finger/object interface is still needed.

This study aims to assess the feasibility of a sensor system designed to detect both pressure and shear at the fingertip/object interface via a single subject test.

Descriptive study, proof of concept.

One healthy subject participated in the study and was asked to perform a single finger test protocol and a simple hand test protocol. The corresponding multidirectional loads at the fingertip/object interface were measured in real time using a pressure and shear sensor system.

Results from the finger test protocol show peak values of up to approximately 50 kPa (5 N) and 30 kPa (3 N) of pressure for each test, respectively. Results from the hand test protocol show a pressure and shear profile that shows a large increase in grip force during the initial grasping of the object, with a peak pressure of approximately 50 kPa (5 N). The pressure and shear profile demonstrates that the load is not evenly distributed across all digits.

This study provides evidence that the reported sensor system has sufficient resolution, dynamic response and load capability to capture biomechanical information during basic protocols and hand-grasping tasks.

The presented sensor system could be potentially used as a tool for measuring and evaluating hand function and could be incorporated into a prosthetic hand as a tactile feedback system.

The group of passive prostheses consists of prosthetic hands and prosthetic tools. These can either be static or adjustable. Limited research and development on passive prostheses has been performed although many people use these prosthesis types. Although some publications describe passive prostheses, no recent review of the peer-reviewed literature on passive prostheses is available.

Review the peer-reviewed literature on passive prostheses for replacement of the hand.

Literature review.

Four electronic databases were searched using a Boolean combination of relevant keywords. English-language articles relevant to the objective were selected.

In all, 38 papers were included in the review. Publications on passive prosthetic hands describe their users, usage, functionality, and problems in activities of daily living. Publications on prosthetic tools mostly focus on sport, recreation, and vehicle driving.

Passive hand prostheses receive little attention in prosthetic research and literature. Yet one out of three people with a limb deficiency uses this type of prosthesis. Literature indicates that passive prostheses can be improved on pulling and grasping functions. In the literature, ambiguous names are used for different types of passive prostheses. This causes confusion. We present a new and clear classification of passive prostheses.

This review provides information on the users of passive prosthetic hands and tools, their usage and the functionality. Passive prostheses receive very little attention and low appreciation in literature. Passive prosthetic hands and tools show to be useful to many unilateral amputees and should receive more attention and higher acceptance.

Measures of activity performance for adults with upper limb amputation are needed. The purposes of this study were to evaluate the measurement properties of a new measure of activity performance for adults with upper limb amputation, which we call the Brief Activity Measure for Upper Limb Amputees (BAM-ULA) and to compare BAM-ULA scores for users of different types of prostheses.

In all, 35 persons with upper limb amputation were administered the BAM-ULA, twice within 1 week. Internal consistency and test–retest reliability were evaluated. Construct validity was examined by comparing scores by amputation level. Concurrent validity was evaluated by examining correlations with other measures. Exploratory analyses using linear regression compared sub-group scores for users of myoelectric and body-powered devices, and for users of single-degree-of-freedom and multi-articulating devices, controlling for amputation level.

The scale alpha was 0.83; intraclass correlation coefficient was 0.91. Item scores differed by amputation level and device type. Persons with transradial amputation completed more items than those with amputations at the transhumeral or shoulder level (p < 0.05). Users of myoelectric devices completed more items than users of body-powered devices (p < 0.05). The BAM-ULA strongly correlated with the Activities Measure for Upper Limb Amputees; R = 0.86) and three modified Jebsen–Taylor Hand Function Tests (R = 0.62–0.68) and moderately correlated with one Jebsen–Taylor Hand Function Test (R = 0.46) as well as with the Wong–Baker FACES Pain Rating Scale. No differences in scores were found by degree of freedom of the terminal device after controlling for amputation level.

Analyses support reliability, construct validity, and concurrent validity of the Brief Activity Measure for Upper Limb Amputees. This new briefer measure is easier to score than the Activities Measure for Upper Limb Amputees.

This article reported on the development and evaluation of a brief 10-item measure of activity performance for persons with upper limb impairment, the BAM-ULA. The BAM-ULA takes 10 min to administer and has a simple scoring method, which may facilitate its adoption by clinicians in the field.

Body-powered prostheses require cable operation forces between 33 and 131 N. The accepted upper limit for fatigue-free long-duration operation is 20% of a users’ maximum cable operation force. However, no information is available on users’ maximum force.

To quantify users’ maximum cable operation force and to relate this to the fatigue-free force range for the use of body-powered prostheses.

Experimental trial.

In total, 23 subjects with trans-radial deficiencies used a bypass prosthesis to exert maximum cable force three times during 3 s and reported discomfort or pain on a body map. Additionally, subjects’ anthropometric measures were taken to relate to maximum force.

Subjects generated forces ranging from 87 to 538 N. Of the 23 subjects, 12 generated insufficient maximum cable force to operate 8 of the 10 body-powered prostheses fatigue free. Discomfort or pain did not correlate with the magnitude of maximum force achieved by the subjects. Nine subjects indicated discomfort or pain. No relationships between anthropometry and maximal forces were found except for maximum cable forces and the affected upper-arm circumference for females.

For a majority of subjects, the maximal cable force was lower than acceptable for fatigue-free prosthesis use. Discomfort or pain occurred in ~40% of the subjects, suggesting a suboptimal force transmission mechanism.

The physical strength of users determines whether a body-powered prosthesis is suitable for comfortable, fatigue-free long-duration use on a daily basis. High cable operation forces can provoke discomfort and pain for some users, mainly in the armpit. Prediction of the users’ strength by anthropometric measures might assist the choice of a suitable prosthesis.

The stump–socket interface is of utmost importance for prosthetic function in transhumeral amputees. Stability of this connection may be improved using a newly designed subcutaneous implant.

The purpose was to determine the effect of the implant together with customized socket designs on the range of motion of the shoulder and the prosthetic function compared to conventional fitting.

Case series.

The range of motion was measured with scaled metrics and the prosthetic function evaluated with the Southampton Hand Assessment Procedure and the Box and Block Test. Maximal loading was measured in straight and 90° flexion of the elbow.

The restriction of range of motion after conventional fitting was decreased from 42.55% ± 6.56% to 9.23% ± 14.89% in Patient I and from 62.18% ± 15.19% to 2.51% ± 2.49% in Patient II using the implant with customized sockets compared to range of motion without prosthesis. Both patients showed improved prosthetic function with the new system compared to conventional fitting.

The presented subcutaneous humeral implant, together with customized socket designs without straps and harnesses to the contralateral shoulder, can maintain almost complete range of motion of the shoulder. This resulted in improved prosthetic function and comfort for the patient without constant risk of infection.

Discomfort and limited prosthetic function are the main reasons for abandonment especially in transhumeral amputees. Shoulder straps and harnesses within conventional socket designs may not only lead to pain and skin irritations at the contralateral shoulder but also limit the range of motion of the shoulder joint and therefore prosthetic function.

Body-powered prosthesis users frequently complain about the poor cosmesis and comfort of the traditional shoulder harness. The Ipsilateral Scapular Cutaneous Anchor System offers an alternative, but it remains unclear to what extent it affects the perception and control of cable operation forces compared to the traditional shoulder harness.

To compare cable force perception and control with the figure-of-nine harness versus the Ipsilateral Scapular Cutaneous Anchor System and to investigate force perception and control at different force levels.

Experimental trial.

Ten male able-bodied subjects completed a cable force reproduction task at four force levels in the range of 10–40 N using the figure-of-nine harness and the Anchor System. Perception and control of cable operating forces were quantified by the force reproduction error and the force variability.

In terms of force reproduction error and force variability, the subjects did not behave differently when using the two systems. The smallest force reproduction error and force variability were found at the smallest target force level of 10 N.

The Anchor System performs no differently than the traditional figure-of-nine harness in terms of force perception and control, making it a viable alternative. Furthermore, users perceive and control low operation forces better than high forces.

The Ipsilateral Scapular Cutaneous Anchor System offers an alternative for the traditional harness in terms of cable operation force perception and control and should therefore be considered for clinical use.

Low cable operation forces increase the perception and control abilities of users.

Three-dimensional printer is widely used in industry, biology, and medical fields. We report a finger prosthesis produced by a three-dimensional scanner and printer for a 67-year-old man with a right thumb amputation above the metacarpophalangeal joint.

His right amputated and left intact hands were scanned with a three-dimensional scanner, and the left-hand image was rotated to the right side to design the right thumb prosthesis. The designed prosthesis was printed with a three-dimensional printer using the fused filament fabrication output system.

The Jebsen–Taylor hand function test and Box and Block Test scores improved after application of the prosthesis. Most Quebec User Evaluation of Satisfaction with Assistive Technology results were “very satisfied,” and most Orthotics and Prosthetics Users’ Survey results were “very easy.” Preparing the prosthesis made by three-dimensional scanner and three-dimensional printer was faster and cheaper than preparing a conventional prosthesis.

Using three-dimensional scanning and printing technique, we can easily produce specifically shaped finger prostheses for specific movements in amputated patients with low cost.