After spending a good deal of time at home for holidays, I am finally back to working on these legs. Since going back to work on January 5th, I have been in contact with an orthotist/prosthetist from Union Orthotics and Prosthetics. I and a few of my peers visited his facilities and observed the process and materials used to make orthoses and prostheses. This visit was incredibly helpful in directing my design focus.
At the moment, what currently exists for sockets is well developed and, with regard to the focus of my project, does not need improvement. In fact, it would be best to retro-fit my current design based on current socket models at the junction of the socket and shank. I did not see enough of what currently exists for youth foot prostheses to assess whether that prosthesis component should be addressed and made to simulate growth.
The other benefit of having visited the facilities is here the prosthetist concerns regarding prostheses. The process of making prostheses has been long-tested and refined over centuries, but even he said that there is a problem with current prostheses for children because of how fast they grow. I was extremely pleased to hear that my research earlier in my project was accurate and my rationale holds valid.
On 1/12/15, a design was decided for a straight, cylindrical shank composed of modular components:
By the end of the week, several pieces will be printed to test to potential for a modular design.
Log (12/15-12/19)
Goals Status:
- Draft a test to test perpendicular shin (i.e. a kick to the shin) and test the current 20 cm bio-mimic and elliptic shanks
- Several types of tests were considered, and a final test design was chosen. However, time did not permit completion of the test. Such a set up would take several hours to complete, and on the day I planned on performing the test, there was an event scheduled making it impossible to start and finish.
- Print bio-mimic and elliptic straight shank designs at 15 cm, plus the design for the circular shank.
- Did not happen. Although, looking back on it, this goal seems unnecessary anyway. The point of this goal was to produce shanks closer to the size of children; however, a smaller shank is proportionally stronger due to there being less in-fill. Plus, there may be an opportunity to get real measurements of children soon, so waiting until after that might be ideal.
- Contact expert at Union Orthotics and Prosthetics to arrange meeting.
- An email has been sent with a set of proposed times. My adviser and I are waiting to hear back from him.
- Create on Solidworks one design for a modular shank (create one piece)
- Incomplete; this goal is being extended into the holidays.
Work on a shank-socket leg took up a large amount of time that would've been spent on testing. This design is closer to usage than the shank alone in that this has a place in which to put the point of amputation. There are two designs, both of which are based on the bio-mimic design. One has the bands strictly on the shank with the socket appearing to be placed on top; it looks to have two distinctly separate parts that are fused together. The other has the bands attached to the top of the socket, which looks like a more continuous design.
It should be noted that there were several mechanical issues this week. Of four attempts to print, not one worked. Two times were due to attempts to print a faulty design; while the solid part was being made in Solidworks, two parts (a socket file and a shank file) were brought into one file. When the parts were put on top of each, wherever there was overlap, the part was hollowed out. I didn't know why Solidworks was making the overlapped portions hollow, so it was printed once at small scale (approximately %15), and that failed at the point of hollowness. Due to how small it was and how it appeared to print, it was unclear if it was an issue with the printer or the design. The design was then printed at 62.5%, and it was very clear that the part was in fact hollow. Another design without this fault was printed, but mechanically issues (filament replacement and filament overlap/knotting) made the prints fail early in the process.
Log (12/9-12/14)
Since the last post, some progress, although not a lot, has been made. A second straight elliptical shank was printed at 20 cm, 20% in-fill. This is almost the same as the other existing straight elliptical shank, but that one was at 10% in-fill while the new one is 20% in-fill. The reason for this second printing was to have a straight elliptical shank comparable to the existing 20 cm, 20% in-fill bio-mimic shank. The past three shanks have been particularly cumbersome to print because, from what I recall, they each failed to print at least once, so three shanks required six or seven prints; each of them takes between four and eight hours to print, as well.
A second advancement, and set back, was the beginning of the next set of tests: perpendicular shank impact. A sustained weight test was started, but it was realized that the test wouldn't sufficiently test the limits of the shank due to how small the weight applied could be and the test wouldn't simulate normal stress and wear due to, once again, how small the weight applied could be. Other setups were considered, but so far, no test has been determined to give accurate, repeatedly results and usable, meaningful results.
Log (11/7-12/8/14)
A lot has happened since the last log; sorry for not keeping you updated. I already posted the details of the past few weeks in a post named "Research Update (12/8/14): New Designs (some, even printed!)". Check it out!
The only thing not mentioned in that post is that I will be contacting an expert at Union Orthotics and Prosthetics within the next week or the week after that.
Log (10/30-11/6)
Almost back on schedule! The review for "Limb Prosthetics Services and Devices: Critical Unmet Need: Market Analysis" (check it out! It has a lot of valuable content) has been posted; this article is going to be crucial for the steps ahead. "Proof of Problem" has yet to be publish, but you can expect that tonight (11/7) or early tomorrow. I have one more article to read about below-knee amputations; this should give a solid foundation on the mechanics of below-knee amputations, their causes, and their effects on patient lives.
A question that hasn't been answered in my research so far, and maybe not be for a while if at all due to the nature of my project, is: what matters to the patients beyond simply having a prosthesis? What I mean by this is do the patients care more about comfort or aesthetics, or does functionality win out always. Those are very black and white phrasing of complex questions that are specific to each patient. Every amputee will have a different set of specifications, and this question should be considered once the simple prosthesis is made. Some research paths to consider after the initial prosthesis is made is whether to improve on the "growing" mechanism further or to consider other aspect of prostheses.
Initial background research on the mechanisms of below-knee prostheses has started. Along with that, I am looking at diagrams of healthy limbs so that l can consider that range of motion a child may want in a prosthesis. The schedule for next week:
- To be published (tonight) 11/7: Proof of Problem
- Due 11/7-11/8: Review of "Prosthetic Management of Children with Limb Deficiencies"
- 11/7-11/9: Further research on below-knee prostheses (mechanics/physics/schematics)
- Due 11/9: Decide route/concept to follow
- Due 11/10: Research proposal
- Due 11/14: Rough draft of prosthesis
I fell behind in work due to illness, but I'll be back on schedule next week!
Check out the day to day goals to stay up-to-date next week:
- Due 11/5: Proof of Problem
- Due 11/7: Background Research on Below Knee Prosthetics (mechanics/physics/schematics)
- Due 11/11: Decide route/concept to follow
- Due 11/14: Rough draft of prosthesis
Preliminary background research has demonstrated proof of problem: Children have limited access to prosthetics limbs due to their especially large rate of growth. The two articles read this cycle ("Traumatic amputations in children and adolescent" and "Limb Prosthetics Services and Devices: Critical Unmet Need: Market Analysis" (review not yet published)) have both shown that there is great financial burden on those who require limb prosthetics; in addition to this observation, "Traumatic amputations in children and adolescent" showed that below-knee amputations are extremely common in adolescent, and "Limb Prosthetics Services and Devices: Critical Unmet Need: Market Analysis" showed that there is a need for lower cost, adolescent limbs due to restrictions on third party reimbursement.
Other concepts to consider are some type of utilitarian leg with different attachments for different purpose or a modular leg in which a child can attach more pieces as they grow to lengthen the prosthetic.
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