A preliminary investigation into the development of 3-D printing of prosthetic sockets

DEVELOPMENT AND EVALUATION OF A CAD/3DP PROCESS FOR TRANSTIBIAL SOCKET FABRICATION

This paper describes a multidisciplinary project that applied the concept of reverse engineering using computer-aided design (CAD) tools to develop a three-dimensional printing (3DP)-based prosthetic socket for transtibial amputees by combining the concepts of patellar tendon-bearing (PTB) socket design principle and total surface-bearing (TSB) socket casting method. Using contemporary tools such as a handheld 3D scanner and an entry-level 3DP machine, together with an in-house prosthetic socket design system and a stump forming device, allowed us to fabricate prosthetic sockets with a consistent quality, and to shorten the learning process time-frame to fabricate them. The results of a case study of two participants demonstrated that the proposed CAD/3DP process of fabrication of transtibial sockets can be easily applied by an unskilled prosthetist to fabricate a socket with the required quality at the first fitting.

A Review of Additive Manufacturing

Additive manufacturing processes take the information from a computer-aided design (CAD) file that is later converted to a stereolithography (STL) file. In this process, the drawing made in the CAD software is approximated by triangles and sliced containing the information of each layer that is going to be printed. There is a discussion of the relevant additive manufacturing processes and their applications. The aerospace industry employs them because of the possibility of manufacturing lighter structures to reduce weight. Additive manufacturing is transforming the practice of medicine and making work easier for architects. In 2004, the Society of Manufacturing Engineers did a classification of the various technologies and there are at least four additional significant technologies in 2012. Studies are reviewed which were about the strength of products made in additive manufacturing processes. However, there is still a lot of work and research to be accomplished before additive manufacturing technologies become standard in the manufacturing industry because not every commonly used manufacturing material can be handled. The accuracy needs improvement to eliminate the necessity of a finishing process. The continuous and increasing growth experienced since the early days and the successful results up to the present time allow for optimism that additive manufacturing has a significant place in the future of manufacturing.

Patient specific ankle-foot orthoses using rapid prototyping

BACKGROUND

Prefabricated orthotic devices are currently designed to fit a range of patients and therefore they do not provide individualized comfort and function. Custom-fit orthoses are superior to prefabricated orthotic devices from both of the above-mentioned standpoints. However, creating a custom-fit orthosis is a laborious and time-intensive manual process performed by skilled orthotists. Besides, adjustments made to both prefabricated and custom-fit orthoses are carried out in a qualitative manner. So both comfort and function can potentially suffer considerably. A computerized technique for fabricating patient-specific orthotic devices has the potential to provide excellent comfort and allow for changes in the standard design to meet the specific needs of each patient.

METHODS

In this paper, 3D laser scanning is combined with rapid prototyping to create patient-specific orthoses. A novel process was engineered to utilize patient-specific surface data of the patient anatomy as a digital input, manipulate the surface data to an optimal form using Computer Aided Design (CAD) software, and then download the digital output from the CAD software to a rapid prototyping machine for fabrication.

RESULTS

Two AFOs were rapidly prototyped to demonstrate the proposed process. Gait analysis data of a subject wearing the AFOs indicated that the rapid prototyped AFOs performed comparably to the prefabricated polypropylene design.

CONCLUSIONS

The rapidly prototyped orthoses fabricated in this study provided good fit of the subject's anatomy compared to a prefabricated AFO while delivering comparable function (i.e. mechanical effect on the biomechanics of gait). The rapid fabrication capability is of interest because it has potential for decreasing fabrication time and cost especially when a replacement of the orthosis is required.

Upper limb prosthesis use and abandonment: a survey of the last 25 years

This review presents an analytical and comparative survey of upper limb prosthesis acceptance and abandonment as documented over the past 25 years, detailing areas of consumer dissatisfaction and ongoing technological advancements. English-language articles were identified in a search of Ovid, PubMed, and ISI Web of Science (1980 until February 2006) for key words upper limb and prosthesis. Articles focused on upper limb prostheses and addressing: (i) Factors associated with abandonment; (ii) Rejection rates; (iii) Functional analyses and patterns of wear; and (iv) Consumer satisfaction, were extracted with the exclusion of those detailing tools for outcome measurement, case studies, and medical procedures. Approximately 200 articles were included in the review process with 40 providing rates of prosthesis rejection. Quantitative measures of population characteristics, study methodology, and prostheses in use were extracted from each article. Mean rejection rates of 45% and 35% were observed in the literature for body-powered and electric prostheses respectively in pediatric populations. Significantly lower rates of rejection for both body-powered (26%) and electric (23%) devices were observed in adult populations while the average incidence of non-wear was similar for pediatric (16%) and adult (20%) populations. Documented rates of rejection exhibit a wide range of variance, possibly due to the heterogeneous samples involved and methodological differences between studies. Future research should comprise of controlled, multifactor studies adopting standardized outcome measures in order to promote comprehensive understanding of the factors affecting prosthesis use and abandonment. An enhanced understanding of these factors is needed to optimize prescription practices, guide design efforts, and satiate demand for evidence-based measures of intervention.

Advanced trans-tibial socket fabrication using selective laser sintering

There have been a variety of efforts demonstrating the use of solid freeform fabrication (SFF) for prosthetic socket fabrication though there has been little effort in leveraging the strengths of the technology. SFF encompasses a class of technologies that can create three dimensional objects directly from a geometric database without specific tooling or human intervention. A real strength of SFF is that cost of fabrication is related to the volume of the part, not the part's complexity. For prosthetic socket fabrication this means that a sophisticated socket can be fabricated at essentially the same cost as a simple socket. Adding new features to a socket design becomes a function of software. The work at The University of Texas Health Science Center at San Antonio (UTHSCSA) and University of Texas at Austin (UTA) has concentrated on developing advanced sockets that incorporate structural features to increase comfort as well as built in fixtures to accommodate industry standard hardware. Selective laser sintering (SLS) was chosen as the SFF technology to use for socket fabrication as it was capable of fabricating sockets using materials appropriate for prosthetics. This paper details the development of SLS prosthetic socket fabrication techniques at UTHSCSA/UTA over a six-year period.