3D-printed custom-designed prostheses for partial hand amputation: Mechanical challenges still exist.

STUDY DESIGN: This is a technical report involving evaluation of two 3D-printed custom-designed prosthetic prototypes for an adult male with partial amputation of his dominant hand. INTRODUCTION: Prosthetic solutions for partial hand amputations have progressed modestly in comparison with advances in full hands for transradial and higher amputations. 3D-printing technology allows Bespoke prosthetic design and rapid prototyping, but evidence regarding functional performance and consumer ratings of devices is lacking. PURPOSE OF THE STUDY: The purpose of this study was to compare grip strength, dexterity, and consumer perceptions for two novel 3D-printed devices with a myoelectric prosthesis. METHODS: This study involves a 2-year iterative design process with an input from the participant, engineers, a prosthetist, and a hand therapist. The evaluation involved standardized tests of grip/pinch strength and dexterity and participant ratings of key criteria. RESULTS: Both 3D-printed devices had very poor grip and pinch strength but comparable dexterity with the myoelectric prosthesis. The participant was more satisfied with the weight and thermal attributes of the 3D-printed devices. DISCUSSION: Aspects of both 3D-printed designs showed the potential for future refinements; however, the mechanical solutions to minimize force required at the wrist to activate grip are still required. CONCLUSION(S): Future design efforts should be client-centered and involve professionals with specialist prosthetic and engineering knowledge.

A Paediatric 3D-Printed Soft Robotic Hand Prosthesis for Children with Upper Limb Loss.

Designing prosthetic hands for children is challenging due to the limited space for electronics and the need of reducing the cost to cater for the constant growth of their hand. In this paper, we proposed an anthropomorphic hand prosthesis for children, using monolithic design and 3D printing of soft/compliant materials. The use of monolithic soft robotic structure provides a lightweight and compact design required in paediatric hand prostheses. The use of 3D printing also allows fabrication of customised products manufactured at low volumes in a cost-effective way which is of interest in prosthetic hand for children. The proposed hand/arm design has a total weight of 230gr including battery and actuation and control systems and a size similar to the biological hand of 5-7 years old children. The hand can provide two grasp types: pinch/tripod and power (cylindrical and spherical) and controlled by using two surface electromyography electrodes. The capability of the proposed hand prosthesis is demonstrated through grasping objects with different shapes and sizes.

A practical 3D-printed soft robotic prosthetic hand with multi-articulating capabilities.

Soft robotic hands with monolithic structure have shown great potential to be used as prostheses due to their advantages to yield light weight and compact designs as well as its ease of manufacture. However, existing soft prosthetic hands design were often not geared towards addressing some of the practical requirements highlighted in prosthetics research. The gap between the existing designs and the practical requirements significantly hampers the potential to transfer these designs to real-world applications. This work addressed these requirements with the consideration of the trade-off between practicality and performance. These requirements were achieved through exploiting the monolithic 3D printing of soft materials which incorporates membrane enclosed flexure joints in the finger designs, synergy-based thumb motion and cable-driven actuation system in the proposed hand prosthesis. Our systematic design (tentatively named X-Limb) achieves a weight of 253gr, three grasps types (with capability of individual finger movement), power-grip force of 21.5N, finger flexion speed of 1.3sec, a minimum grasping cycles of 45,000 (while maintaining its original functionality) and a bill of material cost of 200 USD (excluding quick disconnect wrist but without factoring in the cost reduction through mass production). A standard Activities Measure for Upper-Limb Amputees benchmark test was carried out to evaluate the capability of X-Limb in performing grasping task required for activities of daily living. The results show that all the practical design requirements are satisfied, and the proposed soft prosthetic hand is able to perform all the real-world grasping tasks of the benchmark tests, showing great potential in improving life quality of individuals with upper limb loss.

An Investigation of Pressure Profiles and Wearer Comfort During Walking With a Transtibial Hydrocast Socket.

OBJECTIVE: The aims of the study were to conduct an investigation of the transtibial hydrocast socket interface pressures during walking and to explore potential relationships between pressures experienced and resultant wearer comfort. DESIGN: In this cross-sectional study, pressure data at the limb and hydrocast socket interface during walking were collected from 16 users of hydrocast sockets. The pressures at this interface were described by location, magnitude, and duration for all participants and were compared between the most and least comfortable participants. RESULTS: High pressures were found about the bony prominences of the residual limb, especially the tibial crest of the anterior distal region. Factors identified as potentially causing discomfort (P < 0.1, d > 0.80) were high peak pressures at the anterior proximal region and longer durations of submaximal loading at the lateral proximal region and the anterior and medial distal regions. High pressure variability at the anterior proximal region may also contribute to discomfort (P = 0.106, d = 0.88). CONCLUSIONS: The hydrocast socket interface pressures have been described for a cohort of users. A number of differences were found in the pressure profiles of the most and least comfortable participants. These differences suggest trends between the identified pressure parameters and resultant wearer comfort. Future studies should confirm these exploratory results.

Flexo-glove: A 3D Printed Soft Exoskeleton Robotic Glove for Impaired Hand Rehabilitation and Assistance.

This paper presents a compact and streamlined design of a soft exoskeleton glove for assistance in activities of daily livings and also rehabilitation purposes of patients with hand function impairment. Most of the existing hand exoskeletons have focused on either providing a customizable and modular design or making it portable to be used outside the hospital environment. We have developed a design of an exoskeleton glove that combines both of these features in one compact design. This was achieved by using a parameterised CAD design of glove, 3D printing of soft (i.e., compliant) materials, design a bidirectional cable driven spooling system and integrating them together in a modular fashion. The overall weight of the Flexo-glove is 330g including battery and is able to provide 22N pinch force, 48N power grasp force and object grasp size of up to 81mm in diameter. The device has two control modes: intention-sensing via wireless sEMG for assistive mode and externally-directed via an accompanying smartphone application for rehabilitation (repetitive exercise) programs, both managed through Bluetooth communication. The effectiveness of the proposed design is evaluated in performing cylindrical, hook, and pinch grasps on various objects.

The functional, spatio-temporal and satisfaction outcomes of transtibial amputees with a hydrocast socket following an extended usage period in an under-resourced environment.

BACKGROUND: Transtibial hydrocast sockets have been shown to be a potential alternative to hand-cast patella-tendon bearing sockets, the use of which would have particular benefits in under-resourced environments. However, data concerning wearer outcomes of hard hydrocast sockets (i.e. those without silicone liners), especially over long-term usage periods, is scarce in the literature. RESEARCH QUESTIONS: Are there any changes in wearer functional, spatio-temporal or satisfaction outcomes over a long usage period with a hydrocast socket? And how do the post-usage period outcomes compare with those from the wearers original prostheses? METHODS: In this pre-post interventional study, the clinical outcomes of twenty-one experienced transtibial prostheses users were evaluated using widely-accepted and employed methods to assess wearer functional capacity, mobility, gait and satisfaction. The participants were fit with a hard hydrocast socket and the outcomes after an extensive usage period of 5 months were compared to the pre-usage period data following initial fitting and the data collected from the participants' original prosthetic limb. RESULTS: Significant differences were found in the temporal parameters of gait, all indicating decreased reliance on the intact limb and an increased loading of the prosthetic limb with the post-usage period hydrocast socket compared to both the pre-usage period socket and the participants' original limbs. No differences in the functional capacity, mobility, spatial gait parameters or satisfaction were found between the socket conditions. SIGNIFICANCE: This is the largest study to date of functional, spatio-temporal and satisfaction outcomes of hydrocast sockets following an extended usage period in an under-resourced environment.

Transtibial Prosthetic Socket Shape in a Developing Country: A study to compare initial outcomes in Pressure Cast hydrostatic and Patella Tendon Bearing designs.

This study compared the physical function and comfort level of patients with unilateral transtibial amputation after being fitted with a hand-cast Patella Tendon Bearing (PTB) socket and a pressure-cast (PCAST) hydrocast socket. The latter technique aims to reduce the skill dependency currently required for socket manufacture and fit. The study was conducted at the Vietnamese Training Centre for Orthopaedic Technologies and involved seventeen Vietnamese participants with unilateral transtibial amputation, all of whom were long term users of prosthetics. All participants were fitted with two sockets manufactured using both hand-cast and PCAST techniques with International Committee of the Red Cross components. Walking tests (timed up and go test and six-minute-walk-test), spatio-temporal gait analyses and subjective comfort assessments were completed after a short acclimatisation period with each socket. The participant-preferred socket was also noted. No significant differences were found for the measures of mobility, functional capacity, spatio-temporal gait parameters, gait symmetry, perceived comfort or participant socket preference. The results show the initial patient outcomes are similar when participants are fitted with a hand-cast PTB socket and a PCAST hydrocast sockets. Future work should confirm these findings in a longer trial.

Grasp specific and user friendly interface design for myoelectric hand prostheses.

This paper presents the design and characterisation of a hand prosthesis and its user interface, focusing on performing the most commonly used grasps in activities of daily living (ADLs). Since the operation of a multi-articulated powered hand prosthesis is difficult to learn and master, there is a significant rate of abandonment by amputees in preference for simpler devices. In choosing so, amputees chose to live with fewer features in their prosthesis that would more reliably perform the basic operations. In this paper, we look simultaneously at a hand prosthesis design method that aims for a small number of grasps, a low complexity user interface and an alternative method to the current use of EMG as a preshape selection method through the use of a simple button; to enable amputees to get to and execute the intended hand movements intuitively, quickly and reliably. An experiment is reported at the end of the paper comparing the speed and accuracy with which able-bodied naive subjects are able to select the intended preshapes through the use of a simplified EMG method and a simple button. It is shown that the button was significantly superior in the speed of successful task completion and marginally superior in accuracy (success of first attempt).