Adjustable prosthetic sockets: a systematic review of industrial and research design characteristics and their justifications

Abstract

Background The prosthetic socket is a key component that influences prosthesis satisfaction, with a poorly fitting prosthetic socket linked to prosthesis abandonment and reduced community participation. This paper reviews adjustable socket designs, as they have the potential to improve prosthetic fit and comfort through accommodating residual limb volume fluctuations and alleviating undue socket pressure. Methods Systematic literature and patent searches were conducted across multiple databases to identify articles and patents that discussed adjustable prosthetic sockets. The patents were used to find companies, organisations, and institutions who currently sell adjustable sockets or who are developing devices. Results 50 literature articles and 63 patents were identified for inclusion, representing 35 different designs used in literature and 16 commercially available products. Adjustable sockets are becoming more prevalent with 73% of publications (literature, patents, and news) occurring within the last ten years. Two key design characteristics were identified: principle of adjustability (inflatable bladders, moveable panels, circumferential adjustment, variable length), and surface form (conformable, rigid multi-DOF, and rigid single DOF). Inflatable bladders contributed to 40% of literature used designs with only one identified commercially available design (n = 16) using this approach. Whereas circumferential adjustment designs covered 75% of identified industry designs compared to only 36% of literature devices. Clinical studies were generally small in size and only 17.6% of them assessed a commercially available socket. Discussion There are clear differences in the design focus taken by industry and researchers, with justification for choice of design and range of adjustment often being unclear. Whilst comfort is often reported as improved with an adjustable socket, the rationale behind this is not often discussed, and small study sizes reduce the outcome viability. Many adjustable sockets lack appropriate safety features to limit over or under tightening, which may present a risk of tissue damage or provide inadequate coupling, affecting function and satisfaction. Furthermore, the relationship between design and comfort or function are rarely investigated and remain a significant gap in the literature. Finally, this review highlights the need for improved collaboration between academia and industry, with a strong disconnect observed between commercial devices and published research studies.

Walking with unilateral ankle-foot unloading: a comparative biomechanical analysis of three assistive devices

“…This suggests that the soft calf lacer of the ZG may be inadequate for complete unloading, whereby the entire GRF is transferred through the shank. Instead, a rigid brace, similar to an open transtibial prosthetic socket, may provide improved results [ 43 ]. However, a rigid brace must be custom-made and not prefabricated.…”

Identifying Users’ Needs to Design and Manufacture 3D-Printed Upper Limb Sockets: A Survey-Based Study

“…Thus, adjustable prosthetic socket designs [10,11] aim to address fitting issues and minimize the effect of slight residual limb volume loss that may occur during prosthetic use. Nevertheless, most lack appropriate safety features to limit over-or undertightening, which imply either a tissue damage risk or inadequate fixation [12].…”

“…Three-dimensionally printed prosthetics is an emerging field that would benefit from improved socket designs to fit users' anatomies because the current adjustable designs lack features to control tightening [12]. Socket fit has always been a problem in traditionally manufactured sockets, and it is a key factor for the acceptance of prosthetic devices [2][3][4].…”

“…Nevertheless, it is key to listen to users' experiences and perceptions to propose new socket designs because personal and contextual factors are critical determinants of prosthesis acceptance [38]. However, there is a gap in the studies that analyze functional [12] and esthetics-related aspects of upper limb sockets. In fact, no agreement between professionals and prosthesis users has been reached [39].…”

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“…One of the primary benefits of customization is the optimization of socket fit, which is crucial for ensuring comfort and stability during prosthetic use. Traditional socket-based prosthetics often encounter issues such as pressure sores, discomfort, and poor suspension due to ill-fitting sockets that fail to distribute load adequately and accommodate variations in residual limb shape [85]. However, through techniques such as 3D scanning and computer-aided design, prosthetists can now create custom-fitted sockets that closely conform to the user's residual limb, minimizing pressure points and enhancing overall comfort [86].…”