Structural integrity of polypropylene prosthetic sockets manufactured using the polymer deposition technique

Abstract

Rapid prototyping (RP) technology has been used recently as a means for automated socket fabrication. Although the technology has proven to be promising and has truly automated the socket fabrication process, the structural integrity of RP sockets remains questionable. For the long term, unsupervised use of these 'unconventional' sockets, their material properties and structural integrity must be determined. This study investigated the structural integrity of polypropylene sockets manufactured using a polymer deposition technique, in which a socket is formed by a continuous strand of partially melted polypropylene that is spirally deposited according to the socket's cross-sectional contour. To investigate the problem of delamination of the socket, the tensile properties of the socket material were determined according to ASTM D638-99. The ultimate tensile strength was found to be approximately 13-23 per cent lower than that of polypropylene sheets that are at present normally used for socket fabrication. In order to improve the load-bearing capacity of the socket, it was reinforced using a double-wall arrangement at the distal region, where failure normally occurs. The structural integrity of the complete prosthesis was then investigated according to ISO 10328 (loading condition II). The prosthesis passed the static loading test registering only 12 mm permanent deformation, and it successfully completed a preliminary cyclic test of 250,000 cycles with no observable failure.

Additive manufacturing of custom orthoses and prostheses—A review

“…12(a)) [36,37]. The material strengths of PP fabricated by RSMM had 12-23% lower ultimate tensile strength when compared to that of regular PP [36].…”

“…12(a)) [36,37]. The material strengths of PP fabricated by RSMM had 12-23% lower ultimate tensile strength when compared to that of regular PP [36]. The structural integrity of PP sockets with reinforced double-wall structure made by RSMM had good static loading strength and passed a cyclic test of 250,000 cycles with no observable failure [36].…”

Innovations With 3‐Dimensional Printing in Physical Medicine and Rehabilitation: A Review of the Literature

“…In the traditional fabrication method for prostheses, the highly unique geometry of a person's residual limb requires manual molding techniques using casting materials such as fiberglass or plaster [27,28,40]. Hsu et al provided a visual comparison of traditional versus CAD/ CAM prosthetic fabrication processes [28].…”

“…Plastics are the most often used material in 3DP. Warping and brittleness are 2 problems with many of the currently available plastics [40,49]. Such characteristics are not desirable in the fabrication of devices for persons with disabilities.…”

Strength evaluation of prosthetic check sockets, copolymer sockets, and definitive laminated sockets

“…Applying the standard used to evaluate nearly all of the components to which a socket is attached was a natural choice. Further, there is some historical precedent for the use of ISO 10328 [4,6,[11][12] and continuing with this trend allows for comparisons between this study and those that preceded it.…”