A digital process to replicate the socket-foot alignment in below-knee running specific prostheses.

A well-fitting socket and a fine-tuned foot alignment are crucial elements in a running-specific prosthesis to allow Paralympic athletes with below-knee amputation to express their full competitive potential. For this reason, once a satisfactory socket-foot configuration is established after dynamic alignment, it is fundamental to reproduce the same conditions when constructing the definitive carbon fiber socket, and when renewing or constructing a back-up prosthesis, without dismantling the original. In addition, to cope with emerging needs of the athlete, it would be beneficial to implement fine-tuning adjustments of the alignment in a very controlled manner. At present, this requires elaborate bench procedures, which tend to be expensive, time consuming, prone to manual errors, cumbersome in use and most often require damaging or disposing of the current socket. In this study, we propose an original CAD/CAM workflow that allows replicating the desired socket-foot configuration for below-knee sprinting prostheses, as well as performing socket adaptations and introducing fine-tuning adjustments to the alignments. The workflow is exemplified with reference to two case studies involving elite Paralympic runners with transtibial and partial foot amputations, respectively.

A Workflow for Studying the Stump-Socket Interface in Persons with Transtibial Amputation through 3D Thermographic Mapping.

The design and fitting of prosthetic sockets can significantly affect the acceptance of an artificial limb by persons with lower limb amputations. Clinical fitting is typically an iterative process, which requires patients' feedback and professional assessment. When feedback is unreliable due to the patient's physical or psychological conditions, quantitative measures can support decision-making. Specifically, monitoring the skin temperature of the residual limb can provide valuable information regarding unwanted mechanical stresses and reduced vascularization, which can lead to inflammation, skin sores and ulcerations. Multiple 2D images to examine a real-life 3D limb can be cumbersome and might only offer a partial assessment of critical areas. To overcome these issues, we developed a workflow for integrating thermographic information on the 3D scan of a residual limb, with intrinsic reconstruction quality measures. Specifically, workflow allows us to calculate a 3D thermal map of the skin of the stump at rest and after walking, and summarize this information with a single 3D differential map. The workflow was tested on a person with transtibial amputation, with a reconstruction accuracy lower than 3 mm, which is adequate for socket adaptation. We expect the workflow to improve socket acceptance and patients' quality of life.

Static strength of lower-limb prosthetic sockets: An exploratory study on the influence of stratigraphy, distal adapter and lamination resin.

Knowledge about the mechanical properties of lower-limb prosthetic sockets fabricated with resin infusion lamination and composite materials is limited. Therefore, sockets can be subject to mechanical failure and over-dimensioning, both of which can have severe consequences for patients. For this reason, an exploratory study was conducted to analyze the effect of stratigraphy (layup and fibers), matrix (resin) and mechanical connection (socket distal adapter) on socket static strength, with the objectives of: 1) implementing a mechanical testing system for lower-limb prosthetic sockets based on ISO 10328:2016 and provide the mechanical design of the loading plates, 2) apply the testing system to a series of laminated sockets, and 3) for each type of distal adapter, identify the combinations of stratigraphy and matrix with acceptable strength and minimum weight. Twenty-three laminated sockets were produced and tested. Sixteen met the required strength, with ten exhibiting an excessive weight. Among the remaining six, four combinations of stratigraphy and resin were identified as best option, as they all overcame ISO 10328 P6 loading level and weighted less than 600 g. The selected stratigraphies had limited or absent amount of Perlon stockinettes, which seems to increase weight without enhancing the mechanical strength. Sockets based on Ossur MSS braids and connector show the best compromise between strength and weight when the amount of carbon braids is halved.

Mechanical testing of transtibial prosthetic sockets: A discussion paper from the American Orthotic and Prosthetic Association Socket Guidance Workgroup.

BACKGROUND: The advent of novel manufacturing technologies, materials, and socket design concepts could introduce risks to prosthetic limb users, as the existing knowledge base for safe fabrication may not apply. Moreover, although structural test standards exist for mass-produced prosthetic components, they are not applicable to prosthetic sockets. METHODS: The "AOPA Socket Guidance Workgroup" was formed in 2020 to provide the prosthetic community with evidence-based clinical best practices and methods in the field of prosthetic socket structural analysis. This multidisciplinary expert workgroup undertook a critical analysis of the knowledge gaps regarding the requirements for mechanical testing of lower limb prosthetic sockets. RESULTS: The Workgroup identified knowledge gaps in 4 domains. Domain 1 describes the shape and composition of a mock residual limb, required to support and generate in vivo representative loading within the socket. Domain 2 concerns prosthetic socket coordinate systems and alignment. Domain 3 regards the components and requirements of test specimens. Finally, Domain 4 considers test conditions, loading parameters, and acceptance criteria. CONCLUSIONS: This paper describes these knowledge gaps in detail and recommends potential solution approaches based on literature review, group consensus around existing knowledge, or the formation of new study groups to fill each knowledge gap. Our intent is for the recommendations arising from this paper to support the community (e.g., researchers in the clinic, academia, industry, and funders) in addressing these knowledge gaps.

Structural testing of lower-limb prosthetic sockets: A systematic review.

A lower-limb prosthetic socket is the custom-made structural element interfacing the residual limb of a person with an amputation to their prosthetic leg comprising off-the-shelf componentry. The socket can be subject to mechanical failure, especially when new fabrication methods and materials are introduced (e.g. 3D printing). Failures can have severe consequences for patients. A systematic review was conducted to collect information about available socket mechanical testing methods, to support the definition of widely accepted guidelines. To this aim the structural testing methods were reviewed, but not the results of the individual studies. 729 records were retrieved, of which 16 articles were included. No articles addressed transfemoral socket testing, as all focused on transtibial sockets. Thirteen articles used some sort of adaptation of ISO 10328, and all of them simulated the toe-off instant of gait, with load level acceptable for patients from 100 to 125 kg of weight. Ten considered a rigid limb dummy. Overall, ISO 10328 appears as a viable starting point for defining a testing guideline, but a considerable number of details has to be agreed upon, starting from clear definitions of anatomical landmarks and socket axes, which are required to implement a representative and repeatable test method.