With the proliferation of improvised explosive devices (IEDs), used by insurgents in Iraq and Afghanistan, many soldiers are returning home with severe trauma injuries. Advances in battlefield medicine also mean that soldiers who may have died in combat in another era will live. Doctors are turning to a new generation of medical techniques and devices, including advanced prosthetics, to help soldiers recuperate and maintain mobility. An essential part of this science is the bone graft, using bone from another source to fill in gaps where bone has been damaged, destroyed or removed.
Sometimes a bone graft can mean the difference between amputation and saving a limb. Bone grafts aren’t just for battlefield injuries -- they're a vitally important procedure used to treat many conditions and injuries, including serious accidents, broken bones, birth defects, degenerative bone disorders, bone loss due to removal of tumors or intensive dental surgery.
Currently bone grafts can be performed with a small piece of bone, either from another part of the patient’s body or a cadaver, or with metallic inserts. However, there are drawbacks to each of these methods. Taking bone from another part of a patient’s body requires additional incisions, which means more pain and recovery time. It also presents the potential for complications such as infection or weakening of the bone. Bone from cadavers is generally considered less effective because it doesn’t develop as well as natural bone, and metallic inserts have to be replaced over time.
Enter artificial bones, a concept that contains enormous potential but one that has until recently been fraught with difficulties. Bones made from biological materials are generally too fragile to support weight. Artificial bones made from ceramics have limited use and are best used in conjunction with a bone graft anyway. But an ingenious new method may present new possibilities for bone grafts and artificial bones, and surprisingly, it makes use of something many people have in their home: an inkjet printer.
Of course, this is not a typical inkjet printer -- it is heavily modified and quite a bit bigger. But the technology is quite similar to a conventional inkjet printer, and the process could potentially revolutionize bone graft surgery. Scientists at McGill University in Montreal, Canada, are using their printer to create perfect replicas of damaged bones by “printing” new bones, layer by layer.
See the next page to learn more about bone making.
Making Artifical Bone
Describing the process to the "Daily Mail" Professor Jake Barralet from McGill University said, "The 'paper' in our printer is a thin bed of cement-like powder. The inkjet sprays the cement with an acid which reacts with it and goes hard. That deals with one layer. Then new layers of fresh powder are sprayed on top and the layers build up to the shape we need" [Daily Mail].
The entire process takes only 10 minutes to print most grafts. What further differentiates this method from other types of grafts and artificial inserts is that the compounds in the printer contain the same building blocks found in human bones. The grafts can also eventually dissolve into the human body, allowing natural bone to take its place.
The printer's sophisticated design means that precise "holes" can be left in the graft to encourage the body's own tissue to regrow and rejuvenate the area. This ability allows very specific grafts to be made for sensitive areas or for bones to grow in a specific manner to affect tissue repair, which can also be useful in reconstructive surgery where a doctor is trying to allow an area to both heal and maintain a certain appearance.
Professor Barralet says that inkjet-produced bone grafts are "a long way" from being used in hospitals, but the project appears to have tremendous potential.
Professor Barralet's team is not the only group employing inkjet technology to develop new bone graft techniques. A company called Advance Ceramics Research Inc., in Tucson, Arizona, has developed a technology called "Plasti-Bone." Like inkjet-produced bones, Plasti-Bone is strong enough to act as a graft but also porous to encourage bone regeneration and allow blood to flow through the bone. Plasti-Bone is made from a biologically friendly plastic with a ceramic coating, and natural bone begins bonding to Plasti-Bone after about eight weeks. The artificial bone eventually dissolves harmlessly into the body.
In order to create their Plasti-Bones, ACR designs them on computers and then produces them through rapid prototyping fabrication. Rapid prototyping builds layer upon layer, similar to inkjet technology, and allows scientists to control how long the bone remains in the body before dissolving by altering porosity and the thickness of the ceramic coating.
Like the technology being developed at McGill University, Plasti-Bone will likely be first used in place of small, natural bone grafts and it will be years before entire bones are replaced through this process.
Inkjet Technology Applications
Inkjet-produced bones and rapid prototyping are part of a wider effort to use these technologies to make precise, custom-designed implants for medical use. Scientists at Manchester University in the United Kingdom are working on a technique to print artificial skin, which could similarly revolutionize the skin graft process. That technology may be ready for clinical trials in five years [Live Science].
“Bio-inks” also exist in the form of proteins or individual cells arranged in patterns. These inks can be adapted for a variety of purposes. In December 2006, researchers at Carnegie Mellon University announced that they had used a custom-designed inkjet printer to develop bone and muscle cells from mice stem cells [Technology Review]. Stem cells have scientists particularly excited because they have the ability to grow into any type of cell, though they remain a contentious topic. (To learn about the controversy surrounding stem cells, read How Stem Cells Work.) The Carnegie Mellon team uses growth factors -- solutions that direct stem cells to grow into a specific type of cell -- in combination with adult mice stem cells and a material that binds to growth factors. Through continued research, combining stem cells with bio-inks may allow scientists to create not only “printed,” natural bones but also tendons, ligaments, blood vessels and other needed tissues.
Inkjet technology improved document printing long ago, but it seems that the real revolution may be in how it changes medicine. A decade from now, a car accident victim or a grandmother suffering from osteoarthritis may simply receive a customized, natural, printed piece of bone rather than facing amputation, painful grafts or metal inserts. In fact, scientists dream that one day they will be able to print whole bones, tissues or even organs, making loss of limb, mobility or vital organs a thing of the past.
For more information about artificial bones, the various applications of inkjet technology and related topics, please consult the following links:
Related HowStuffWorks Articles
More Great Links
- Bjorn, Carey. “Printable Skin: 'Inkjet' Breakthrough Makes Human Tissue.” Feb. 1, 2005.http://www.livescience.com/technology/050201_skin_printing.html
- Chu, Jennifer. ”Printing Muscle and Bone.” Technology Review. Dec. 19, 2006.http://www.technologyreview.com/Biotech/17913/
- Fields, Scott. “Growing Bones: New Technique Proves Promising.” Live Science. May 9, 2006. http://www.livescience.com/humanbiology/060509_growing_bones.html
- Mayne, Eleanor. “The artificial bones made from an inkjet.” Daily Mail. Apr. 14, 2007.http://www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_id=448654
- Wichner, David. “Bones of invention.” Arizona Daily Star. July 17, 2003.http://www.azstarnet.com/clips/bones071703.html