My Propitious Perusers,
I've spent this evening sitting in the NAU library developing the next logical post and here it is! I think it's important to talk about the different subjects used in this study so you have a better frame of reference as to who wears the prosthesis. We're going to first talk, though, about a bunch of device/subject-related material.
First, we'll look at some stats. Currently, of the 1.2 million transtibial amputees in the United States, only 40,000 are capable of wearing the BiOM. And of the 40,000 amputees having surgeries in the last year, only 16,000 are BiOM capable. To be "BiOM capable", an amputee most meet requirements of a mobility assessment. Which is measured through something called a k-value: a system that ranks your range of motion (ROM) on a scale of 1-4. An acceptable ROM is a 3 or 4, meaning the amputee is "good enough" at walking. Sometimes, a 2 is acceptable but this varies from case-to-case. Additionally, only 900 people in the United States currently use the BiOM, most of which are ex-military personnel. This is for various reasons, some include personal preference of an active vs. passive device but it's safe to assume the main reason is cost, especially because in most studies subjects find the active device more comfortable and efficient. The cost for one BiOM is between $50,000 and $75,000. Due to this huge investment, many studies (including ours) are often limited to only using one BiOM which means subjects don't have much time to become accustomed to the device, something I'll talk about when referencing individual subjects.
Now for specific subjects, each subject uses the same BiOM and their own personal prosthetic device. The BiOM is altered through computer mechanisms to meet different standards for each wearer. Their individual passive prostheses are energy-return systems (ERS), which gives very little energy return, making it passive. Using this device, it's likely their self-selected speeds will probably be slower. Here, we find the problem referenced earlier: study limitations. Because our subjects can't each receive a BiOM months in advance, they can't easily lose what are called compensation mechanisms. Compensation mechanisms are mechanisms the body uses to compensate for the lag of the prosthesis. By wearing a passive device for at least 1.5 years or more, our subjects are losing those mechanisms with their passive devices but are unable to lose those mechanisms with the BiOM. This is because with every testing session, each subject is granted only one hour of time to grow used to the BiOM. This has many consequences, the most important is that it changes their self-selected gait speeds. Simply, because subjects are less comfortable in the BiOM, their speeds slow in comparison to when using the ERS, especially in backward walking (we'll talk a lot more about backward walking and its implications in another post).
Our first subject, subject one (S1) had a mechanized injury, meaning they didn't lose their limb to cancer or another disease that may affect neurological communication. This subject lost their limb in bike accident when they were 18. In my last post, I referenced a subject who's worn a passive device longer than their original limb, this is that subject. And because of this, the subject is bothered by the faint buzzing made by the motor of the BiOM, which affects them too much for them to be satisfied with the device. It bothers S1 because it impairs their ability to conceal the device easily, making it an abnormality to S1, whereas they're already accustomed to the passive device's properties, believing that it is a "part of them". So, if they did wear it, their quality of life would be lowered.
Our second subject, subject two (S2) also had a mechanized injury after suffering through a car accident. S2 has worn their device for 1.5+ years. This subject does believe the BiOM is more capable than the passive prosthesis.
Our third subject, subject three (S3) also had a mechanized injury through a hunting accident. S3 has worn their passive device for 1.5+ years. Specifically, S3 believes the device increases functionality.
Now, you may be wondering how the BiOM attaches to the amputated leg, which happens in two ways: 1. a vacuum pump or 2. a sling. One of our subjects uses the vacuum pump, and feels that the device is a part of him, and no longer seems to be hanging on, which is what is typically felt by sling users (our other two subjects).
Hope that wasn't a touchy subject,
Pooja
P.S. I'm sorry for all of the bad puns in this post.
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