Have you ever picked up a “universal remote” and have to study it for a minute before finding the power, channel, and volume buttons? Just as you settle in, a push of a wrong button puts up a panel that obscures the program, forcing another long look at the remote for the “exit” button to go back to the program. On the other hand, a tutorial was likely not needed to operate an iPhone. Why is that?
Historically, the upper limb is the most abandoned prosthesis. Yet, the October issue of IEEE Spectrum asked, “Do High-Tech Prosthetics Serve their Users?” with a picture of a person holding a below-elbow prosthetic forearm that should be attached on the other side. The November issue of Spectrum has “Rewiring the Brain to Smell Again” as its lead article, despite the fact that long, functional lives can be lived without that sense. That Engineering in Medicine and Biology topics were the cover issues of other journals and magazines demonstrate the desire to replace lost natural function. This begs the question: how much engineering is over-engineering? How does one go about finding the sweet spot where technology improves the life of its intended user, for the most part?
A good question might be, “Is there compatible technology that will support this space at this time?” Widespread adoption of any new technology occurs many times by a confluence of similar technologies with compatible features that make it easy (“intuitive”) to do/know/acquire. The next question might be, “Is there compatible technology that will support this space at this time?” It comes down to luck, oftentimes. For example, General Magic, a company made up of former Apple employees that failed but incubated eBay, LinkedIn, and Android, created the first smart device back in the early 90s. While its technology was sound, there was no context for it. What they created eventually became the “talk, text, and data” ubiquitous today, but the context did not support it at the time of its release. The universe of internet-adjacent information was not yet available. Something similar to this is occurring in the cuffless blood pressure sphere: The prevailing paradigm in our understanding of blood pressure has not caught up to the knowledge base that can be explored through continuous monitoring. The FDA and established practice guidelines are still very much stuck on a numerical standard to describe what is normal or not, rather than looking on other factors such as diurnal variation, paroxysmal spikes, and other biomarkers of autonomic instability. How can engineers provoke new ways of thinking about physiological “norms”? Even when using Ockham’s Razor, the simplest explanation might still be quite complex.
Streamlining for efficiency
In this age of smart devices that serve as our prosthetic brains, simpler ones still have market share. Many who own a smart device still limit their usage to “talk, text, and data.” Our bodies have redundancy and few of us use all of its functions. A peek through any AARP: The Magazine will have ads that limit a phone or a computer to the most commonly used functions. Engineers at these companies have removed functions to streamline the device for the user. It is nice to have the option to choose the buttons we want to use on the remote, and it is equally important not to waste too much time and effort finding those common functions.
Medicine has adopted this model somewhat organically. There are decision trees that are sensitive and specific to diagnoses with high morbidity and mortality. For example, “right lower quadrant (RLQ) pain with acute abdomen in a male is appendicitis until proven otherwise.” In women, it could be ovarian cyst, ectopic pregnancy, endometriosis, but appendicitis will still be front and center for the clinician. In fact, surgeons have historically strived to have a rate of “cold appendix” (normal appearing appendix upon removal) of around 3% in order to capture all of the “hot” (inflamed) ones. As endoscopy and robot surgery has become more widely available, “presumed (“Pre-Op”) diagnosis” and “actual (“Post Op”) diagnosis” after the exploratory endoscopy is performed is demonstrating both that appendicitis is still the top diagnosis and that other issues can also cause RLQ pain. While this might seem less specific despite its sensitivity, the adoption of endoscopy has improved diagnoses and treatment of pathologies by being able to look thoroughly within the abdomen.
Emotional rewards: “Love and logic”
Humans are both logical and emotional. Most “sticky” decisions have an emotional component to it. As such, perhaps the first question might be, “How do I want to feel doing X?” Engineering is largely logical. Perhaps one way to improve adoption is to consider rewards to the user. “Intuitive” is a loaded term that requires more unpacking than can be done in a short column. Yet, we have all had experiences that are more or less intuitive upon first experience. It implies there are consistencies in needs and wants. It implies that there are fundamental things important to persons in daily activities. Those activities that provide emotional rewards are generally the ones that are repeated. As errors arise, it should be obvious, as well as the way to return to the step prior to that error.
So, why is it that the upper limb prosthetic is frequently abandoned? Some of it is related to specialization. Humans have hand dominance and dexterity (“context”). Similar dominance is also in the lower limbs, as anyone who has played soccer/football will attest, but it’s not as obvious during locomotion. The time it takes to train a non-dominant hand to become dominant is much less than training and daily donning/doffing the prosthetic interface (“efficiency”). Furthermore, there is the tactile enjoyment of being able to feel the action at the fingertips (“emotional rewards”).
Example: Ambulation vs. locomotion
In clinical practice rehabilitating persons with spinal cord injury (SCI), it is not uncommon for the injured survivor’s first question to be, “Will I walk again?” There are several companies creating exoskeletons that attach to the lower limbs to train those with SCI to “walk.” However, most of these are cumbersome, taking an average of 10 or more minutes to don and doff. Gait speed is limited to less than 1 MPH for the most experienced. It requires hours of training to manage the orthostatic hypotension that ensues from blood pooling in the lower limbs without the ability to pump it back up to the heart. Having said this, there are some benefits to the standing exercise, such as improved bone density and/or satisfaction of simply standing to one’s full height. A few have adopted it for home use, and there are a handful of adaptive athletes who train and “race” with it. For the most part, the cost (well over $100,000 each) and functional limitations prevent widespread adoption. Why are there more than half a dozen companies in this space when very few of those injured continue to use it regularly after being trained in it?
By reframing the context to “locomotion,” the same person is generally content with their wheelchair a year after being in it. Other than challenges associated with rolling on carpet or going uphill, many SCI survivors revel in whizzing past others in unobstructed space. There is also opportunistic enhancement through technology. With minor modifications and accommodations to their equipment, para-athletes are able to compete at the highest levels. Oscar Pistorius of South Africa was able to run so efficiently with his bilateral lower limb prosthetics that able-bodied athletes complained about his mechanical advantage.
On the other hand, being able to manage bowel and bladder function is highly desired for most persons with SCI. Controlled elimination of waste significantly improves quality of life, especially for those whose mobility is limited either by injury, disease, or aging. For example, many women struggle with stress incontinence after pregnancy and/or with aging, due to loss of elasticity in the tissues around the perineum. Men who have had prostatectomies complain of “leakage.” Adaptive strategies are used, such as always being aware of the restroom location and sitting in aisle seats. There are medications to manage the condition, but side effects are common. Continence requires a coordination of being able to sense the fullness of the bladder, having an intent in the brain, and consciously triggering the micturition process. As such, engineering the sensors and triggers to coordinate this process requires the equivalent of creating an entire exogenous nervous system. It’s easier to wear a pad or perform “timed voids” (scheduled bathroom breaks).
There is the temptation to simplify this to, “Form vs. Function.” Yet, both of those terms are highly individualized. What is functional for the carpenter may not be for the artist. What form is acceptable for the athlete may not be manageable for a sedentary person who has deficits in coordination and strength. A sommelier would no longer be able to perform his/her profession without a sense of smell, but the loss of that sense might not be so bad for a pig farmer. It all comes down to the individual for whom the technology serves. To complicate things further, individuals may verbalize ideas about what they think they want, but live as if they desire something different. As such, the customization market is a costly one that can be somewhat wasteful.
As we engineer better living through technology, asking the questions that address function and emotional impact, streamlined for broadly adopted context, might be a good place to start.
Nancey Trevanian Tsai, MD FABPMR, is a practitioner representative for AdCom EMBS. She is a board-certified sports medicine physician, a clinical professor with the Department of Neurosurgery, Medical University of South Carolina, Charleston, SC, USA, and a medical technology innovator with an international patent for EyeStat. She is a Senior Member of IEEE.