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The knee joint is the strongest and the largest joint of the human body. It consists of the lower end of the thighbone, upper end of the shin bone, and the knee cap. The three bones are connected to each other with articular and meniscal cartilages that act as shock absorbers and help protect and cushion the joint. Degeneration of the knee joint due to age and overuse can cause unwanted friction and bone spurs. The condition, also known as osteoarthritis, is the most prevalent form of arthritis and is often seen in individuals over 50 years of age. Osteoarthritis develops slowly and leads to worsening pain and stiffness of the knee joint, grinding or clicking noise during movement, and weakness in the knee. Treatment involves lifestyle changes, physical therapy, and viscosupplementation injections. Patients with severe form of the disease may require a surgical intervention. During the process, the doctor may remove cartilage from another part of the body and place it in the knee or may replace the damaged cartilage with plastic and metal implants. Researchers across the globe are now looking at three-dimensional (3D) medical printing and bioprinting technologies to create highly compatible, patient-specific knee implants that will increase the success rates of total knee arthroplasty by improving patient outcomes and lowering the risks of a revision surgery. Unlike traditional implants that come in a few specific shapes and sizes, 3D printed cartilages can be customized as per the needs of the patient. Surgeons can use the additive printing technology to print larger cartilages as well. The Biopen: A Handheld Bioprinter Used During Operations A team of researchers and surgeons from St. Vincent’s Hospital, Melbourne, developed the Biopen, a type of 3D printer that helps doctors create cartilaginous tissue fragments during the actual surgical intervention. The surgeon can customize the size and the shape of the tissue as per the needs of the patient. Researchers predict that the medical-grade plastic and titanium Biopen will lead to 97 percent survival of the cells and will transform knee surgeries forever. This technology may, however, have some drawbacks. The human cartilage is made of only one type of cell. Scientists, therefore, tried to grow the tissue by embedding specific cells in a hydrogel but the liquid medium may restrict cell growth and intercellular communication. Consequently, the new implant may not have the desired mechanical integrity. Additionally, the degradation of the hydrogel may lead to the formation of toxins that would inhibit cell growth. Hence, researchers began looking for other materials to create cartilage implants. A New Bio-ink Holds Promise for Printing Cartilage Scientists at Penn State, under the supervision of Dr. Ibrahim T. Ozbolat, created tiny tubes from algae extracts, injected cow cartilage cells into them, and allowed the tubes to grow for a week to create tiny cartilage strands. A bio-ink made from these strands was fed into a specially designed nozzle of a 3D printer to develop cartilage tissues of the desired size. Although this 3D printed cow cartilage is weaker than its natural counterpart, it is definitely better than the hydrogel version. Dr. Ozbolat believes that the implants will strengthen once they get exposed to the pressure from the joints. His team also hopes to mimic the entire process using human cartilage cells. The Center for Disease Control and Prevention (CDC) estimates that one in two Americans will be diagnosed with osteoarthritis by the age of 85. An estimated 249,000 children under the age of 18 also suffer from some form of arthritis. Additive printing technology is offering hope to millions of individuals looking to overcome pain and improve quality of life. While most of these products are still at an inceptive stage, researchers are trying to start clinical trials at the earliest and get the required approvals in the not-so-distant future. Sources: https://www.engadget.com/2016/04/04/biopen-lets-doctors-3d-print-cartilage-during-surgery/ https://www.sciencedaily.com/releases/2016/06/160627094828.htm

Organ transplantations and surgical reconstructions using autografts and allografts have always been challenging. Apart from the complexity of the procedure, healthcare professionals also have difficulty finding compatible donors. Autografts derived from one part of the body may not fit in completely at the new location causing instability and discomfort. As per the U.S. Department of Health and Human Services, about 22 people die each day due to a shortage of transplantable organs. Creating more awareness about organ donation is only part of the solution. Researchers have to look for other alternatives, and this is where technologies such as three-dimensional medical printing and bioprinting are making an impact. Integrated Tissue-Organ Printing System (ITOP) Millions of dollars are being invested to develop technologies that will help healthcare professionals print muscles, bones and cartilages using a printer and transplant them directly into patients. The ITOP system is a big step in that direction. It was developed by researchers at Wake Forest Institute for Regenerative Medicine. They used a special biodegradable plastic material to form the tissue shape, a water-based gel to contain the cells, and a temporary outer structure to maintain shape during the actual printing process. The scientists extracted a small part of tissue from the human body and allowed its cells to replicate in vitro before placing them in the bioprinter to generate bigger structures. Unlike other 3-D printers, the ITOP system can print large tissues with an internal latticework of valleys that allows the flow nutrients and fluids. As a result, the tissue can survive for months in a nutrient medium prior to implantation. Researchers have used this technology to develop mandible and calvarial bones, cartilages and skeletal muscles. The goal is to create more complex replacement tissues and organs to offset the shortage of transplantable body parts. Polylaprocaptone Bone Scaffolds Researchers at John Hopkins are also developing 3-D printable bone scaffolds that can be placed in the human body. Their ingredients include a biodegradable polyester, known as Polylaprocaptone, and pulverized natural bone material. Polylaprocaptone has already been approved by the Food and Drug Administration (FDA) for other clinical applications. Researchers combined it with natural bone powder and special nutritional broth for cell development. The cells were added to a 3-D printer to generate bone scaffolds, which have been successfully implanted into animal models. Researchers at John Hopkins are now looking for the perfect ratio of Polylaprocaptone and bone powder that will produce consistent results. They will subsequently test their scaffolds in humans as well. More studies are being done as we speak. Many surgeons have also started using 3-D printed tissues and bones to help their patients. In the next few years, this technology will become more accessible, affordable and effective and may change medicine forever. Sources: Photo Credit: Wake Forest Institute for Regenerative Medicine Scientists 3D Print Transplantable Human Bone