Medical Electronics
The Cambrian explosion of medical robotics
By Stan Schneider, CEO of RTI A
bout 500 million years ago, all major types of animals on earth appeared over a period of only 25 million years or so. This event, known as
the Cambrian explosion, occurred because all the preconditions were right for animals to diversify. Simple organisms had many years to mature before the event. The explosion happened because multicellular structures, circulation systems, sensing, motor control and more were available for the first time.
A similar thing is going on in medical robotics today. The pioneering teleoperated robotic surgery system, Intuitive Surgical’s DaVinci, has been operating for over 20 years. It works with end effectors that look like sticks, and is used in only a few types of procedures, mostly in the urology and gynaecology areas. But now, computing, sensing, motor control, data flow architecture, and more are finally capable of powering a new generation of medical robots. Operating rooms are transforming into digital surgery platforms. These systems will take on almost every type of surgical procedure. This robotic explosion will change surgery more than anything in the last hundred years. For instance, imagine you are an orthopaedic surgeon specializing in knee replacements. The preconditions are there for robotic assistance. Compared to only a few years ago, prosthetic knees are commonplace these days. In fact, it’s become so common that efficiency is critical; surgeons handle almost one million operations in the U.S. each year. Robotic technology, including sensing, control, data flow, and intelligence, is ready for application. Specialised robotic systems will soon change both the process and economics of these procedures.
Your manual process looks like this:
Prepare Get X-ray or CT images of the knee Design how the new joint will work. This is
20 November 2024
complex, balancing positioning, alignment, laxity (play) and more. The biomechanics have to be right. You can use computer aided design (CAD) tools to plan exactly how it will work.
Choose a prosthesis: metal and plastic joint components designed to work together as a “new knee”. Most today are standard parts that come in various sizes. There’s one for the end of each bone in the joint.
Plan where you will cut and install the new joint.
Operate While the patient is anesthetized, you need to cut away the damaged bone, shape the
remaining bone to fit the prosthetic, and install the prosthetic.
But it’s not that simple. It’s hard to tell exactly where you are cutting and how to make it fit the prosthetic. Sometimes, you can use a real-time imaging system to track your cuts, but mostly this is a trial-and-error process where you cut, temporarily install the device, test motion and more. You
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may have guides, alignment jigs, and test instruments. But there’s a lot of experience required.
Despite all that, you can’t cut perfectly, so in the end you cement the prosthetic to close the gaps.
Then you restore the soft tissues (ligaments, tendons, etc.)
Recovery Take more images to ensure it works well. Put the patient into physical therapy.
Of all these steps, making accurate cuts is by far the hardest and most important. Setting up the table and patient to ensure cut alignment is the most expensive part. It can take two to three hours to correctly position all the things required for the surgery. Much of this has to be done with the patient on the table. Together, setup and cut planning and evaluation drive much of the cost and risk. Still, in the end, humans aren’t good at precision angle cuts. Even trained surgeons can’t make perfect cuts. And adapting the variety of human bones to standard parts means most
patients don’t get an optimal result. Robotics can help this. Robots can follow extremely precise cut paths generated by the imaging and CAD plans. The resulting precision angles and ultra-smooth surfaces are so clean that many operations don’t require cement; the part is press fit and the bone grows into the part like your natural joint. With robotic accuracy and flexibility, custom joints become realistic to install. Instead of adapting the patient to a standard part, a custom part can be 3D printed from the imaging information. Manually adapting procedures to install these unique parts is impractical for humans. It’s entirely possible for a robot.
Of course, it’s not quite that simple. Importantly, the robot has to know exactly where the bone is, a process called “registration”. That’s done with an imaging system that can track something that looks like an antenna with reflective targets on it. This is attached (screwed into) the bone, and then another probe with targets on it is used
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