Final Paper - Biodegradable Bone Cement

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Information about Final Paper - Biodegradable Bone Cement

Published on January 6, 2017

Author: ShreyasSriram2


1. Introduction: Our “scientists” are currently in the process of developing an artificial knee joint which can be used instantly after surgery and will last a lifetime. We have approached this challenge by combining the pros of both the cemented and uncemented knee joint replacement techniques. We hope that our intensive research will bring forth a new era to orthopedic surgery, improving the lives of many young and old athletes. By using autologous stem cells and microsphere scaffolding we have developed the Orthogenua Joint Replacement. The design of our product is to insure the permanency of the artificial joint, for most artificial joints wear down with use over the years. The Orthogenua Joint Replacement will allow for increased mobility, flexibility, and longer lasting product. Background Information: The joints are considered part of the skeletal system. The skeleton is made up of over two hundred bones; The twomain bones this study will focus on are the tibia and the femur. Bones have several functions including: creation of new blood cells, mineral storage, protection of vital organs, assisting with movement, and maintaining the structure of the body (Class Powerpoints 2014). The joints play a major part in assisting with movement. The muscles contract and pull on the bones, causing them to move. The knee joint supports your entire body weight and is subject to constant and immense stress. Pathologies:

2. There are many reasons why someone may want or need an artificial knee joint replacement. Some might be athletes who have suffered sports accidents or people suffering from cartilage pathologies. Some examples of cartilage pathologies are arthritis, which is the chronic inflammation of articular cartilage, and osteoarthritis, which is when cartilage around the bone wears down over time. A total joint replacement is the best treatment for both osteoarthritis and arthritis. Unfortunately there are some cartilage pathologies that are incredibly hard to treat such as rheumatoid arthritis. Rheumatoid arthritis is the chronic inflammation of all the connective tissue; every joint. This disease affects the knees most. After time the joints become to get distorted which can be very painful. Current Technology: In the world of an orthopedic surgeon there are many decisions that must be made before, during and even after the surgery to ensure their patient recovers and heals properly. One of the big decisions before surgery is whether to use a cemented joint, an uncemented joint, or microfractures which are all current methods in treating both osteoarthritis and arthritis. Cemented and uncemented joints have the same function but are attached differently to the knee, resulting in differing recovery rates and longevity. Joints that are attached using bone cement are ready to use very soon after surgery since the cement adheres quickly and efficiently; however, cemented joints wear down in a span of 10-15 years and may need to be replaced at some point. Cemented joints are usually put in more elderly patients because they do not want to take the time to recover and since the joint is only going to be used for about 10-15 years. Even though the recovery time for a cemented joint is rapid, the range of motion is limited because

3. the bone cement is rigid limiting the motion of the knee. This side effect is counter productive because most who choose to have a cemented knee replacement are athletes who want to recover quickly to get back into training. In the non-cemented joints use a precisely textured rod that fits into a carved out portion of the bone marrow in the themer and tibia. This texturing allows cells to grow into the rods and secure it permanently. Although these joint replacements take a longer period of time to heal they are permanent and erode with time. Due to the endurance of this joint replacement, it is put in younger people such as teens or early adults. This joint is used for younger patients since they can recover faster and so that they do not have to return for future surgery. The third method available to surgeons for treating cartilage pathologies is microfractures. The process or creating microfractures creates tiny fractures in the cartilage and bone of the knee. These fractures tap into the bone marrow which yields stem cells which are released into the bone and cartilage. The stem cells form new bone and new cartilage; however, the cartilage formed is weaker than the original and will wear away faster than normal cartilage. The side effect may lead to multiple surgeries in the future which costs time and money for the patient.

4. "Cemented and Uncemented Prosthetics." WebMD. WebMD, n.d. Web. 10 July 2014. The Status Quo: Diseases, like arthritis, or injuries can damage knee joints. Knee joints are replaced with a prosthetic joint that is held in place by bone cement. Modern knee joint replacements are perfect in most categories: They relieve pain and most people don’t need any extra help after the surgery. However, the modern method doesn’t account for the fact that an artificial knee joint can’t replace the full functionality and biocompatibility of a knee joint made out of a patient’s own cells. They also don’t last a lifetime. “An increasing number of younger people are also replacing their knees because of injury from high-impact sports and activities that wear out their knees early” ( 2014). The average knee joint replacement lasts about 10-15 years ( 2011). If a teen receives a joint replacement they will have to have at least four more surgeries during their lifetime, if they live to the U.S. average life expectancy. If a professional sports player receives a joint replacement at any point in their career then they would at least three more surgeries during their lifetime if the live to the U.S. average life expectancy. Full recovery can take an additional three months and rehab is

5. Figure 1: X-ray (lateral View) of Knee Joint Replacement Manhattan Orthopedic & Sports Medicine Group 2012 Figure 2: X-ray (lateral View) of Knee Joint Showing Posterior Dislocation Villanueva – Indian Journal of Orthopaedics 2010 sometimes necessary. In some cases, recovery can take a full year. Having to waste years of one’s life recovering after multiple joint surgeries can be a grueling process. In addition to time spent, the efficiency of the new joint may not always match that of the replaced joint. Joint dislocation is possible. When joint dislocation occurs a new surgery is necessary. This again aggregates to the fact that the current method of joint repair can be a long and arduous process. Anoth er key issue with the current method of knee joint repair is the cost. The average cost for one surgery is about $50,000 ( 2014). If you include the cost of recovery, rehabilitation, and check-ups the numbers start piling up. Then you have to multiply that cost by the numerous surgeries that are necessary because the joint repair only lasts 10-15 years. Athletes, who may want joint repair faster so they don’t have to wait until the joint wears out, will have to pay even more. What is even more startling about the cost of joint replacements is that they cost more than the average annual income in 18 U.S. states ( 2014).

6. In addition to cost, join replacements are becoming increasingly common. “More than 1 million Americans have a hip or knee replaced each year” ( 2012). If a teen has a joint replacement surgery and has replacements across their lifetime, the cost could spiral into the hundreds of thousands of dollars. Multiply that by the million Americans who are getting replacements each year and you have a multi-hundred- billion-dollar problem. Materials and Methods: Our product is an improvement on joint replacements, mainly in the knee. The joint replacement will be made from Trabecular Metal and adhered to that metal using a biodegradable and biocompatible gecko-inspired tissue adhesive is a highly porous layer of microsphere scaffolding that is engineered to release the necessary growth factors. Both the Trabecular Metal and microsphere scaffold will be seeded with mesenchymal stem cells from the patient’s removed bone marrow. The joint replacement will be held in place by biodegradable calcium sulfate bone cement. Eventually that bone cement will disappear completely and the joint replacement will be held in place by the newly grown osteocytes. Trabecular Metal is made of tantalum, a highly biocompatible and corrosion resistant material that causes little to no adverse biological response (Harling 2002) (Zimmer 2013). “Many studies demonstrate [tantalum’s] excellent biocompatibility in a variety of situations including, those applications involving bone surgery” (Robert J Harling 2002). Trabecular Metal was developed and patented by Zimmer Dental. It has many properties that mimic those of cancellous bone, including interconnected pores, a maximum of 80% porosity, and a low modulus of elasticity similar to cancellous bone

7. Image From: http://www.zimmerde orporation/osseoincor poration.aspx: (Zimmer 2013). It has also exhibited high ductility without mechanical failure in compression testing (Zimmer 2013). Because of its interconnected porosity, Trabecular Metal allows for cell ingrowth of osteocytes and fibroblasts that will eventually hold the joint replacement in place. The Trabecular Metal can be shaped into any desirable shape, including ball and socket joints, hinge joints, and more. Trabecular Metal is manufactured by “utilizing a thermal deposition process, elemental tantalum is deposited onto a substrate, creating a textured surface topography to build Trabecular Metal Material, one atom at a time” (Zimmer 2013). To affix the Trabecular Metal to the microsphere scaffold, a biodegradable and biocompatible gecko-inspired tissue adhesive is used. This adhesive is created using nano-patterned polymers and was inspired by the adhering abilities of the feet of geckos (Kumar 2009). This adhesive meets the requirements of biocompatibility and biodegradability, so as the osteocytes and fibroblasts grow into the joint replacement the adhesive will degrade along with the polymeric scaffold with hydrogel porogens and eventually the newly formed bone will be all that is left. This adhesive is made of polymeric, conical pillars developed using a silicon template. The

8. surfaces of the pillars are then nano-patterned to increase the adhesion to flat surfaces almost two times more (Kumar 2009). Using the adhesive described above, a layer of a biodegradable microsphere scaffold is attached to the Trabecular Metal joint replacement. Microsphere scaffolds can be engineered and adjusted to release drug or growth factors at any desired rate. In this case the microsphere scaffold would be developed using polymers with a high molecular weight, due to the polymer’s high density the growth factors would be released at a slower rate (Dhandayuthapani et al 2011). Microsphere scaffolds have interconnecting pores which will allow for the ingrowth of cells. The microsphere scaffold is also biodegradable so they will disappear as the osteocytes and fibroblasts grow into the region. These microsphere scaffolds are manufactured using a process called solvent/non-solvent sintering (Laurencin et al 2011). Sintering is joining polymeric microspheres, placing them in a mold of the desired shape and size of the scaffold (Laurencin et al 2011). Then the solvent/non solvent liquid is poured into the mold and that liquid is allowed to evaporate (Laurencin et al 2011). The proportion of liquids and the diameters of the microspheres can then be adjusted (Laurencin et al 2011). Mesenchymal stem cells are found in bone marrow and are multipotent; they have the ability to differentiate into several different cell types, including bone and fat cells (Nombela-Arrieta et al 2011). To insert the joint replacement the bone must be cut and the bone marrow inside must be removed to make room for the replacement. Using stem cells that are isolated from this leftover bone marrow has several benefits. The stem cells don’t need to be taken from another part of the patient; the bone marrow is

9. "GEN | Insight & Intelligence": Osiris' Race to Market an FDA-Approved Stem Cell Product." GEN. N.p., n.d. Web. 10 July 2014. just being ‘recycled’. The cells taken from the bone marrow will easily form more bone cells, so there is very little uncertainty on how the stem cells will differentiate. The cells are autologous so they will not trigger any immune responses. These stem cells will be seeded into the microsphere scaffold and the Trabecular Metal just before insertion into the bone, and then those stem cells will differentiate and proliferate after implantation. Mesenchymal stem cells are isolated using a centrifuge, placed in vitro, then seeded into the joint replacement to grow after implantation. While the osteocytes and fibroblasts are growing into the joint replacement, biodegradable calcium sulfate bone cement will hold it in place. Tests have shown that calcium sulfate bone cement was completely reabsorbed and replaced by a large amount of new bone in around two months (Rechenberg et al. 2013). One example of calcium sulfate based bone cement is BoneSource®, a biocompatible, durable, osteoconductive, and easily sculptable material (Stryker 2004). The bone cement is manufactured as calcium phosphate powders that would then be mixed with a liquid solution to form a paste or cement. The growth factors that are to be inserted into the dense microsphere scaffold and slowly released over time are: IGF-1, BMP-2, and TGF beta. IGF-1 (insulin like growth factor) stimulates an increase in hypertrophy and hyperplasia of many tissues, including bone tissue (Utiger). The addition of this growth factor would encourage cell proliferation and the increased cell size of cells in the joint replacement. BMP-2 has a “pivotal role in the regulation of bone induction, maintenance and repair” (Sykaras

10. 2003). TGF beta is a “stimulator of osteoblastic bone formation, causing chemotaxis, proliferation and differentiation in committed osteoblasts” (Mundy 1991). IGF, BMP, and TGF beta are all naturally present in bones and affect the proliferation and differentiation of osteoblasts (Linkhart 1996). The combination of these three main growth factors demonstrate high applicability to increasing bone formation, promoting healing of bone fractures, and inducing bone growth around implants (Linkhart 1996); For these reasons IGF, BMP, and TGF beta especially applicable to joint replacements. This unique combination of cells, scaffolds, and growth factors should result in a flexible, biocompatible, and well integrated joint replacement. After the hydrogel scaffold and tissue adhesive have fully degraded, all that will remain is the Trabecular Metal scaffold that is being held in place by mature osteocytes and fibroblasts. This design creates the perfect balance of natural and artificial materials for the optimal performance of the new joint. Device Testing:

11. Image From: http://madsculp m/2011/01/saty r-legs-day- 60.html When testing this device our primary concern is bone ingrowth and the effects that stem cells seeded in an artificial joint have on it. We are also concerned with the strength of short-term bone cement as we do not want it to fail while the bone is still growing into the metal implant. The joint replacement should be able to withstand the rigors and stresses of movement, have sufficient mobility, and integrate into the natural tissues of the organism. To test this, we are going to implant this device in several goats, which can be used for testing orthopedic prosthesis due to similarities in joint structure. The joint will be X-rayed to check for any loosening and bone ingrowth two weeks after implantation. It will be checked again every month after implantation for a year, and then once a year after that. The joint will be tested for range of movement, flexibility, and ability to withstand the stresses of movement once each week. The goats will be observed and any handicaps of movement will be recorded and its progress will be closely monitored. All of this data will be compared to a healthy goat as a control to see how well it mimics a natural, healthy joint. Because the basic structure of the joint mechanism is not changing, we are not looking for anything involving the joint itself, instead only looking at how well the prosthesis integrates with the bone and how durable that integration is. The results will then be analyzed and the applicability of the Orthogenua Joint Replacement in humans. How We Change the Status Quo:

12. In modern times, joints last a minimal period of time, and specifically in the knee, last between 10-15 years. This time span is further shortened by the fact that athletes often require knee joint replacements, and they apply added stress to these joints. While we don’t change the type of replacement, we change the cement to offer a longer lasting joint, because the better material offers more resilience and naturally blends with the tissue over time because of our use of the autologous cells. Therefore our project does improve the “Status Quo”, and we have achieved something that can truly change joint replacement. Conclusion: Overall, with our use of the joint replacement made from Trabecular Metal and adhered to that metal using a biodegradable and biocompatible gecko-inspired tissue adhesive is a highly porous layer of microsphere scaffolding that is engineered to release the growth factors. Also, Future Developments: While our method for implanting artificial joints is an improvement upon already existing techniques, it still has the disadvantages associated with the use of non- biological components such as metals and plastics, which will wear down over time and will not be repaired by the body. To completely negate these effects we would need to design a joint that is completely made of the patient’s tissue, potentially allowing it to be repaired by the body in the event of damage or wear. However, we do not currently have the techniques to reliably and completely remake hard tissue suitable for use in the body, and joints are further complicated as they require tendons, ligaments, and

13. cartilage to function and these cannot be reliably produced with the correct mechanical properties. Despite these difficulties, our developments regarding bone regrowth into artificial joints should help further research into orthopaedic scaffolds and ingrowth, potentially allowing someone to completely recreate bones. While many of potential uses of this device are academic in nature, it does present immediate solutions to many problems. The most obvious of these is that it can be adapted for use in other joints besides the knee, but there are other uses as well. One example is traumatic injuries, which, in more severe cases, can leave people missing sections of bone. In the event of such an injury the trabecular metal and microsphere scaffold, once properly shaped and seeded with mesenchymal stem cells, could be used to replace the missing section of bone. If adhered with calcium sulfate bone cement the bone would grow into the trabecular metal relatively quickly, leaving a naturally attached section of bone and metal to replace what had to be removed. Works Cited: MacShane, Benjamin. "Knee Joint Replacement." MedlinePlus. U.S. National Library of Medicine, 22 Sept. 2011. Web. 08 July 2014. Renaud. "Knee Replacement Complications." Knee Replacement., 13 May 2014. Web. 08 July 2014.

14. Villanueva, Manuel. X-ray (lateral View) of Knee Joint Showing Posterior Dislocation. Digital image. Dislocation following Total Knee Arthroplasty: A Report of Six Cases. Indian Journal of Orthopaedics, 14 Sept. 2010. Web. 8 July 2014. Pratini, Napala. "Joint Replacements Cost More Than Annual Income in 18 States." The Huffington Post., 23 Apr. 2014. Web. 09 July 2014. Manhattan Orthopedic & Sports Medicine. JPG. New York City: Manhattan Orthopedic & Sports Medicine Group, P.C., 2012. McClanahan, Julia. "Arthritis." Joint Replacement Surgery and You. National Institute of Arthritis and Musculoskeletal and Skin Diseases, Oct. 2012. Web. 10 July 2014. Sechrest, Randale. "Artificial Knee Replacement." YouTube. YouTube, 10 Nov. 2013. Web. 10 July 2014. Beyer, N. B., and L. M. Da Silva. "Mesenchymal Stem Cells: Isolation, in Vitro Expansion and Characterization." National Center for Biotechnology Information. U.S. National Library of Medicine, 2006. Web. 10 July 2014. <>. "BoneSource® BVF Osteoconductive HA Bone Paste." Stryker, n.d. Web. 10 July 2014. <BoneSource® BVF Osteoconductive HA Bone Paste>. Dhandayuthapani, Brahatheeswaran, Yasuhiko Yoshida, Toru Maekawa, and D. Sakthi Kumar. "Polymeric Scaffolds in Tissue Engineering Application: A Review." Polymeric Scaffolds in Tissue Engineering Application: A Review. Hindawi

15. Publishing Corporation, 2001. Web. 10 July 2014. <>. Harding, Robert J. "Biocompatibility of Tantalum ." Tantalum Biocompatibility. Literature Review on Tantalum in Medical Applications. Danfoss Tantalum Technologies, Apr. 2002. Web. 10 July 2014. <http://www.x->. Kumar, A. J Et Al. "A Biodegradable and Biocompatible Gecko-Inspired Tissue Adhesive." SoftMatter RSS. N.p., 2009. Web. 10 July 2014. <http://soft- -Inspired_Tissue_Adhesive>. Laurencin, Cato T., Justin L. Brown, and Lakshmi Nair. "Solvent/Non-Solvent Sintering ToMake Microsphere Scaffolds." Solvent/Non-Solvent Sintering To Make Microsphere Scaffolds (2011): n. pag. NASA, Aug. 2011. Web. 10 July 2014. <>. Mohan, S., TA Linkhart, and DJ Baylink. "Result Filters." National Center for Biotechnology Information. U.S. National Library of Medicine, July 1996. Web. 10 July 2014. <>. Mundy, GR. "The Effects of TGF-beta on Bone." PubMed. U.S. National Library of Medicine, 1991. Web. 10 July 2014. Nillson, M., E. Fernandez, S. Sarda, L. Lidgren, and J. A. Planell. "Characterization of a Novel Calcium Phosphate/sulphate Bone Cement." Wiley Online Library. N.p., 4 June 2002. Web. 10 July 2014. <>.

16. Nombela-Arrieta, César, and Leslie E. Silberstein. "The Identity and Properties of Mesenchymal Stem Cells." Nature Publishing Group, Feb. 2011. Web. 10 July 2014. <>. Sykaras, N., and LA. Opperman. "Bone Morphogenetic Proteins (BMPs): How Do They Function and What Can They Offer the Clinician?" PubMed. U.S. National Library of Medicine, June 2003. Web. 10 July 2014. <>. Utiger, Robert D. "Insulin-like Growth Factor." Encyclopedia Britannican. N.p., 2014. Web. 10 July 2014. < factor-IGF>. Von Rechenberg, Brigitte Et Al. "Evaluation of Four Biodegradable, Injectable Bone Cements in an Experimental Drill Hole Model in Sheep." Science DIrect. N.p., Sept. 2013. Web. 10 July 2014. <>. "Zimmer Dental - Trabecular Metal." Zimmer Dental - Trabecular Metal. Zimmer Dental, 2013. Web. 10 July 2014. <>. Beane, Olivia, Manisha Kanthila, and Bryan Sutermaster. "Class Powerpoints." July 2014. Lecture.

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