may the DEKA be with you

DARPA handout image shows the DEKA Arm SystemAnd FDA (U.S. Food and Drug Administration) finally said Yes! The robotic arm developed at the the DEKA Research and Development Corp. (founded by Dean Kamen, the smart guy who invented the Segway) has finally been approved as the first prosthetic arm that can carry out multiple, simultaneous movements controlled by signals from electromyogram electrodes (as reported here). Along the lines of what we discussed in a previous post, the DEKA Arm System (codenamed Luke, after Luke Skywalker’s artificial hand) is a prosthetic arm for upper limb amputees (either from the elbow or the shoulder).

With respect to conventional artificial limbs, Luke mainly relies on myoelectricity: via specific electrodes, the electrical activity sent to muscle fibers (absent in case of amputations, but still seeked by firing nerves) is detected and converted into corresponding movements. Besides making the prosthetic control more natural and intuitive for the user, Luke can take advantage of one of the most advanced myoelectric techniques, Targeted Muscle Reinnervation (TMR). Basically, residual nerves from the lost limb can be transplanted and re-wired to the remaining muscular structures. As explained by Wiki, “the goal of TMR is to transfer multiple nerves into separate regions of the targeted muscle, record multiple yet independent signals from the muscle regions, and to use the EMG signals to control a motorized prosthesis sophisticated enough to process multiple control signals”. A Luke-bearing patient could actually feel actual sensations via the prosthetic limb! Luke’s control flexibility is clearly remarkable and is meant to address a wide range of needs from various amputees.

deka2Come on, no drawbacks? There must be an issue with this awesome product! Actually, as discussed on this site, “the real challenge for the Deka arm, as for many other types of sophisticated prostheses, is cost. A simple prosthestic arm (an essentially cosmetic device) can run $3000, while a sophisticated prosthesis can crack $50,000. In many cases, limbs have a relatively short lifespan; it’s not unusual to need a replacement every 3-4 years due to wear and tear on the device”. In any case, in order for Luke’s price to lower a bit, some wise character would say “patience you must have, my young padawan” !

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how many bottles..?

Once I wrote an awesome post listing some interesting numbers about the human brain. Today, I’ll try to gather curious information about the topic litres-human body.

Wikicestello_acqua says that “iphysiologybody water is the water content of an animal body, contained in the tissues, the blood, the bones, or elsewhere. In the case of the average human male, 60% of the body weight is water. Other sources propose a slightly higher percentage, like 72-75% … however, it’s a huge quantity! Let’s say I weigh 65 kg, in my body I’ll have approximately 42 litres of water: I could fill 28 bottles of one litre and a half each, the common bottle we usually have on the table for dinner. Keep that in mind, the next time you go for a run and sweat!

bloogWhat about blood? The body of a 70 kg adult male contains, on average, 5.6 litres of blood. Three and a half bottles! As you’ll surely know, if you are between 18 and 60 years old and you weigh more than 45 kg, you can safely go for blood donation. Besides the free breakfast with which you’ll be rewarded, you’ll be happy to give about 350-470 millilitres of your blood. More or less, one third of a bottle! It’s nice to point out that this blood volume, that our body loses in ten minutes while we squeeze a rubber ball, will be recovered within just 24 hours.

drop drinkOk, I’ll admit I googled something like “teardrops how many millilitres” too. Tears size varies among individuals, as well as the chemical composition of teardrops, which is strongly related to many physiological aspects. In terms of millilitres, there is obviously no standard in the wonderful world of tears… anyway, to get an idea about small volumes of water, a teaspoon contains 5 ml and a medicine dropper usually drops a volume of about 0.05 ml. Therefore, we can fill our beloved 1.5 l bottle of water with 300 teaspoons or, if we really have time to spend on that, something like 30 thousand drops via a medicine dropper. Any plans for tonight?

the toughest job ever

Nothing scientific this week, just a nice video that I’d like to share with you. The last months of a PhD thesis are usually characterized by the research of “something to do next”. We start planning our future work, postdoc/teaching position/job/whatever, and often we struggle for making “the right choice” for “the career”… we hesitate, or we’re stressed, we want to make the right choice for ourselves. I totally abide by such state of mind, of course, but I also try to analyse the situation from another point of view. Maybe it’s because of my nationality, but I think that we should always keep in mind that all the choices that we make have to be discussed with and supported by those who care for us the most: our parents. We are taking decisions for ourselves, but also for them, who chose to do the toughest job ever. As usual, it is a matter of equilibrium.

accepted for publication – Biorob 2014

referenceA bit later than expected 🙂 but the good news has arrived: the paper I submitted to Biorob 2014 has been accepted for publication! This work presents one of the two miniaturised actuation systems for an instrumented knee implant that I’ve conceived in the framework of my PhD thesis. The second model is described in another paper that is currently under review.

TitleAn Active Tibial Component for Postoperative Fine-Tuning Adjustment of Knee Ligament Imbalance

AuthorsA. Collo, P. Poignet, C. Hamitouche, S. Almouahed, and E. Stindel

Abstract: Ligament tensioning is a key step in Total Knee Arthroplasty surgery. The surgeon has to manually set proper tension conditions for the two lateral ligaments of the knee. Inaccuracies may lead to severe postoperative complications and, in the worst-case scenario, to revision surgery. Unfortunately, suboptimal balance conditions are unavoidable and no assistance tool has been developed up to now to help the surgeon during the surgery. The goal of this work is to propose an instrumented tibial component able to evaluate ligament balance conditions after surgery and to monitor their evolution in the postoperative period. Thanks to an embedded actuation system, optimal ligament tension values can be restored so as to improve the prosthesis lifespan and avoid the need for revision surgery.