A digital workflow for personalized design of the interface parts integrated in a powered ankle foot orthosis (PAFO).

The use of actuated exoskeletons in gait rehabilitation increased significantly in recent years. Although most of these exoskeletons are produced with a generic cuff, at the foot and ankle there are a lot of bony prominences and a limited amount of soft tissue, making it less comfortable . Furthermore, a proper alignment of the actuation systems is essential for the correct functioning of the exoskeleton. Therefore, we propose a digital workflow for the design of bespoke cuffs as interface parts of a powered ankle foot orthoses (PAFO). Moreover, this digital workflow permits the creation of axis and points of reference for the anatomical features which allows not only for the creation of custom-made cuffs but also for the integration and alignment of the PAFO mechanical components and actuation unit.

Using a texture analyser to objectively quantify foot orthoses.

BACKGROUND AND AIM: Foot orthoses alter the kinematics and kinetics in gait. With the increasing importance of evidence based practice and with the permanent development of subtractive manufacturing and introduction of additive manufacturing, there is a growing need for quantification of orthoses parameters. We describe a measurement method and protocol to quantify different parameters of a foot orthosis. TECHNIQUE: A texture analyser is used to impose a displacement of the surface of the orthosis, while the applied force is measured. The measured points are determined based on the location of anatomical landmarks on the foot. Out of the measured data, parameters are calculated representing the stiffness, compression set and shape. DISCUSSION: To illustrate the proposed technique, five different parameters are extracted from three example orthoses. Results show the added value of the proposed technique as the parameters are not only defined by the material but also by the shape.

Evaluation of the influence of cyclic loading on a laser sintered transtibial prosthetic socket using Digital Image Correlation (DIC).

People with a transtibial amputation worldwide rely on their prosthetic socket to regain their mobility. Patient comfort is largely affected by the weight and strength of these prosthetic sockets. The use of additive manufacturing could give the prosthetist a range of new design possibilities when designing a prosthetic socket. These new design possibilities can in turn lead to improved socket designs and more comfortable prosthetic sockets. This new way of designing and producing prosthetic sockets radically differs from the manual traditional production process. This makes it difficult for prosthetists to understand how all these new design possibilities influence the mechanical properties of the additive manufactured prosthetic socket. Therefore there is a growing need for a method to evaluate the strength and stiffness of newly developed socket designs.We propose a method to evaluate the strength and stiffness of prosthetic sockets. A robotic gait simulator is used to apply realistic kinetics of amputee gait to the tested socket. A Digital Image Correlation (DIC) system is then used to measure the deformation of a prosthetic socket under different loading conditions. This way it is possible to check if plastic deformation will occur in the designed transtibial socket. Furthermore it is possible to assess the effect of cyclic loading on the 3D printed socket.To illustrate the proposed method, a transtibial prosthetic socket was designed using CAD software and produced with laser sintering PA12. DIC measurements were performed on this transtibial socket both before and after it was subjected to a cyclic load of 1 million cycles (mimicking realistic amputee gait).

Assessment of transfemoral amputees using a passive microprocessor-controlled knee versus an active powered microprocessor-controlled knee for level walking.

BACKGROUND: In transfemoral (TF) amputees, the forward propulsion of the prosthetic leg in swing has to be mainly carried out by hip muscles. With hip strength being the strongest predictor to ambulation ability, an active powered knee joint could have a positive influence, lowering hip loading and contributing to ambulation mobility. To assess this, gait of four TF amputees was measured for level walking, first while using a passive microprocessor-controlled prosthetic knee (P-MPK), subsequently while using an active powered microprocessor-controlled prosthetic knee (A-MPK). Furthermore, to assess long-term effects of the use of an A-MPK, a 4-weeks follow-up case study was performed. METHODS: The kinetics and kinematics of the gait of four TF amputees were assessed while walking with subsequently the P-MPK and the A-MPK. For one amputee, a follow-up study was performed: he used the A-MPK for 4 weeks, his gait was measured weekly. RESULTS: The range of motion of the knee was higher on both the prosthetic and the sound leg in the A-MPK compared to the P-MPK. Maximum hip torque (HT) during early stance increased for the prosthetic leg and decreased for the sound leg with the A-MPK compared to the P-MPK. During late stance, the maximum HT decreased for the prosthetic leg. The difference between prosthetic and sound leg for HT disappeared when using the A-MPK. Also, an increase in stance phase duration was observed. The follow-up study showed an increase in confidence with the A-MPK over time. CONCLUSIONS: Results suggested that, partially due to an induced knee flexion during stance, HT can be diminished when walking with the A-MPK compared to the P-MPK. The single case follow-up study showed positive trends indicating that an adaptation time is beneficial for the A-MPK.

Gait assessment during the initial fitting of customized selective laser sintering ankle foot orthoses in subjects with drop foot.

BACKGROUND: Recently, additive fabrication has been proposed as a feasible engineering method for manufacturing of customized ankle foot orthoses (AFOs). Consequently, studies on safety, comfort and effectiveness are now carried out to assess the performance of such devices. OBJECTIVE: Evaluate the clinical performance of customized (selective laser sintering) SLS-AFOs on eight subjects with unilateral drop foot gait and compare to clinically accepted (polypropylene) PP-AFOs. STUDY DESIGN: Active control trial. METHODS: For each subject two customized AFOs were fabricated: one SLS-AFO manufactured following an additive fabrication framework and one thermoplastic PP-AFO manufactured according to the traditional handcraft method. Clinical performance of both AFOs was evaluated during gait analysis. RESULTS: A significant beneficial effect of both custom-moulded PP-AFO and customized SLS-AFO in terms of spatial temporal gait parameters and ankle kinematic parameters compared to barefoot gait of adults with drop foot gait are observed. No statistically significant difference between the effect of PP-AFO and of SLS-AFO was found in terms of spatial temporal gait parameters and ankle kinematic parameters. CONCLUSION: AFOs manufactured through the SLS technique show performances that are at least equivalent to the handcrafted PP-AFOs commonly prescribed in current clinical practice. Clinical relevance Manufacturing personalized AFOs with selective laser sintering (SLS) in an automated production process results in decreased production time and guarantees the consistency of shape and functional characteristics over different production time points compared to the traditional manufacturing process. Moreover, it reduces the dependency of the appliance on the experience and craftsmanship of the orthopaedic technician.