We’ve already discussed about the importance of cartilages in the human body. Two examples are the knee menisci and the thyroid cartilage that origins the Adam’s apple. We’ve also understood that 3D printing would probably represent a great revolution in the world of medicine, with the possibility of reproducing human body parts or fabricating new-generation assistive tools. Put the two things together and you’ll be able to print human cartilage by means of a 3D printer. I simply copy-paste here the content of this interesting webpage (to which all rights belong).
Dr. Darryl D’Lima and the members of his team at the Scripps Clinic in La Jolla, California, say they’ve unlocked the secrets of bioprinting human cartilage. That’s big news as the current best practice medical technique to replace lost cartilage is implantation of an artificial joint. Even though that sort of operation is painful, requires a long stretch of rehabilitation and artificial joints can often need replacement as time goes on, such procedures are the industry standard.
The global market for knee replacements amounts to nearly $7 billion annually, and experts say it will climb to nearly $11 billion within the next few years. Somewhere around 773,000 Americans have a hip or knee replaced each year. That’s big business and a lot of pain. But D’Lima says the design of his latest prototype bioprinter will print living cartilage, and that would mark a great leap forward for those suffering from painful knee and joint damage. Taking a Hewlett-Packard inkjet printer as his starting point, D’Lima says his bioprinter uses cartilage progenitor cells suspended in a biocompatible liquid. Once the solution is exposed to ultraviolet light, it takes a permanent shape.
The extremely tiny drops of material provide other benefits as well. Measuring just one picoliter in diameter (or one-billionth of a liter), the droplets output by the bioprinter are compact enough to fill microscopic pits on the surface of cartilage or bone. “It would be the equivalent of filling a pothole,” D’Lima says. “It would automatically fill the defect as you’re printing it. You’re getting a fairly good mechanical integration into the tissue, which is very difficult for us to do when we do traditional transplants.”
Patients suffering with arthritis or knee injuries are often plagued by a lack of cartilage. That means bones begin to grind against bones, and that means extreme pain and constant discomfort for patients. Using D’Lima’s bioprinting method, cartilage can be applied directly into the knee joint to provide a custom fit impossible to achieve by cutting pre-made cartilage to the particular patient. And one day, D’Lima says he’s confident that the process will involve printing the cartilage material directly onto a patient on the operating table. “We wouldn’t have to prepare (material) in advance,” D’Lima said. “All of this would be done on the day of surgery, on demand.”
The major hurdle, according to D’Lima, is that as there’s currently no printer which can print directly onto a patient. His technique needs some refining. D’Lima says he’s working on those tweaks now with biotech firms Invetech and Organovo. And D’Lima also says he’s certain the method will work in practice as cartilage, due to its simpler cellular structure and lack of a complicated network of blood vessels, will be less challenging to create than some other tissues. Cartilage, flexible connective tissue found in various areas of the body, is not as rigid as bone but can be stiffer and less flexible than muscle. Composed of specialized cells called Chondrocytes, cartilage (unlike other connective tissues) doesn’t contain blood vessels. The chondrocytes are supplied with nutrients by diffusion as a result of the pumping action generated by compression, so in comparison with other connective tissues, cartilage grows and repairs much more slowly. “(Cartilage) is complex enough that you need technology like 3D printing, but at the same time, it’s not so complex that it’s extremely challenging,” he said. “We’ve gotten interest from other researchers, wanting to print retinal cells. The retina has some similarities to cartilage in that the photoreceptors and the neural cells of the retina don’t require a blood supply, so we don’t have to print microvasculature. And the retina is a mature tissue in that if you lose a photoreceptor, that’s it. You don’t grow a new one. So it’s fairly attractive for 3D printing.”
There are many different types of implants. When Knee Replacement is found to be necessary, the surgeon discusses with the patient about the clinical needs and all the possible implants. The basic principle is to reduce as much as possible the bone volume interested by the bone cut stage. Some people can benefit from just a partial (or unicompartmental) knee replacement, that is when the prosthesis replaces only one knee compartment (medial or lateral).
In normal conditions, knee implants ensure a 15-20 years lifespan. When pathologies or suboptimal balance conditions occur on a prosthetic knee, this value is no longer ensured and risks being strongly reduced. In such cases, the only solution is represented by revision surgery. The patient undergoes a second Knee Replacement surgery in order to remove the suboptimal prosthesis and install a new one. This leads to a new hospitalisation period, a further bone cut procedure (revision components usually have longer stems that insert into the bones, as shown by the figure) and, of course, to a second rehabilitation period. Revision surgery always turns out to be more stressful than the first one: human body doesn’t appreciate when someone is playing with its parts, thus the probability of rejection increases and the recovery period gets harder.
andreacollo 