Robots are taking over the world, anyone who's paying attention will attest. What with robotic manufacturing, robotic pilots, even solar-powered robotic lawnmowers (!), it's a short philosophical step to the speculation that humans will soon be outmoded. But lest we go too far in that direction, this week's New England Journal of Medicine describes a robot that exists solely to serve a human, and while it's the stuff of science fiction, as Rick and I agree on PodMed, it's quite exciting and life-altering for this person. Rick also reveals that in almost eight years of recording the podcast, this is the first time we've ever talked about a study with an n of 1!
The subject in this study was a 31 year old man whose leg was amputated at the knee in 2009, following a motorcycle accident. At the time of the amputation the surgeons retained the major nerves serving those muscles in the lower leg and reimplanted them in muscles in the thigh. The reason they did this was to prevent the formation of neuromas, really painful collections of severed nerve ends that often proliferate after their target muscle has been removed, and also with an eye toward a unique prosthesis. The surgeons relied on their previous experience in arm amputations to accomplish this; they call the strategy 'targeted muscle reinnervation' or TMR and have shown that it ultimately improves the control of motorized arm prostheses.
Subsequent to the amputation investigators used electromyography (EMG) to assess the quality of signals from the nerves that were reimplanted. A grid of EMG signals from both muscles that had had the lower leg nerves reimplanted into them as well as those that had not was developed for use in robotic prosthesis control. As expected, the reimplanted muscles generated robust EMG signals, particularly when attempts to move the already amputated lower leg were made. Attempted motions had distinct EMG patterns which simplified the algorithm development for ultimate control of the prosthesis. Prosthesis control using just mechanical sensors versus the TMR enhanced system revealed the superiority of the latter, with no 'critical errors' occurring with the TMR system, which would be much more likely to result in a fall or injury. Using this system allowed the patient to climb and descend stairs, and walk outdoors on uneven surfaces. There's also a really cool video showing the subject kicking a soccer ball!
The TMR enhanced system was clearly superior to even the most sophisticated prostheses being used right now, with the patient reporting much better control and confidence as well as ability to transition between activities easily. Investigators suggest that further development of the grid implementing EMG signals as well as lighter, smaller and quieter robotic prosthetic limb are all improvements they're after, but everyone is feeling optimistic. I wonder if I could place my order for a robotic housekeeper? Specter of Hal notwithstanding.
Other topics this week include guidelines for medical breast cancer prophylaxis and arsenic and cardiovascular disease in Annals of Internal Medicine, and an effective drug to prevent cyctomegalovirus reactivation in people who've had bone marrow transplants, also in NEJM. Until next week, y'all live well.