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.

Keywords: Adjustable socket; Adjustable-volume; Artificial limb; Prosthesis design; Prosthetic; Prosthetic interface; Prosthetic socket; Residual limb; Socket; Systematic review.

Fig. 1

PRISMA [19] flow diagrams detailing the systematic search processes; a literature search, b industry search

Fig. 2

Number of patents, literature papers, and news articles published each year from the search results

Fig. 3

Example of a prosthetic socket including the inflatable bladder principle of adjustability by Carrigan et al. [78]

Fig. 4

Examples of socket designs incorporating the moveable panel principle of adjustability. A A floating panel design by McLean et al. [35]. B A hinged panel design

Fig. 5

Examples of socket designs incorporating the circumferential adjustment principles of adjustability. A A strut design by Terrazas Quezada [46]. B An Overlap design by iFIT Prosthetics LLC [44], images from Kenia et al. [41]

Fig. 6

Example of a prosthetic socket including the Variable Length principle of adjustability. This socket is made by Ottobock [45], image from Nia et al. [42]

Fig. 7

Examples of control mechanisms, a micro-adjustment dial, b Straps and Buckle [41], c motor [35]

Fig. 8

Plots indicating a lack of collaboration between research institutions and industry