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proliferation of osteoclasts. Osteoclasts cause loosen- ing of the implant by resorbing the bone around it. 37 3. Implant allergies. This is a controversial issue that has not yet been unanimously supported. Studies have found a small percentage of patients with implant fail- ure showing signs of contact dermatitis. Tissue inflam- mation around the implant, which causes loosening of the implant, and skin lesions one year after the surgery have been observed. Some researchers agree that there is a need for presurgical screening for allergies. Oth- ers believe that the population of patients manifesting allergic reactions to the implant is so small that it does not justify regular screening. 38 C. Enhancing bone healing. Implant osteointegration is a process that requires the right conditions in order to occur. The first few weeks following the surgery is the most critical time; when the implant is most prone to failure as integration is just starting to take place. Stabili- zation highly depends on osteointegration; therefore, the faster it occurs the lower the chance of implant failure. Bone healing enhancers catalyze integration by provid- ing the necessary elements needed for bone healing. 1. Growth factors, hormones and other osteogen- ic compounds. Growth factors are signal mol- ecules that stimulate the prol iferation, recruit- ment and differentiation of mesenchymal cells into osteogenic cells. 39 Growth factors also stimulate angiogenesis and granulation tissue formation. 40 Parathyroid hormone (PTH) is another protein that has been used as a bone healing enhancer. PTH controls calcium homeostasis by regulating the osteo- blast-osteoclast activity in bone. This type of hormone therapy is especially used in osteoporotic patients, for which fast fracture healing is paramount. 41 There are many other products in the market that promote osteogenesis such as bone morphogenic proteins, which is a family of proteins commonly used in spi- nal fusion due to their osteoinductive properties, and oxysterols, which are a group of osteogenic and anti- adipogenic compounds. 42 2. Bone-marrow-derived mesenchymal cells. Bone-mar- row-derived mesenchymal cell therapy is frequently used in cases with non or delayed union. Randomized studies have shown the significant benefits of stem cell therapy, such as a reduction of up to half the healing time com- pared to control. One of the technical issues regarding the studies on bone-marrow-derived mesenchymal cells as a therapy option is the certainty with which it can be determined that the osteogenic cells involved on the healing process are derived from the therapeutic agent and not from the patient’s bone marrow. 43 C O N C L U S I O N The nature of bone, as both a composite and a dynamic living structure, dictates its mechanical properties and its behavior in response to injury. However, many injuries and/or conditions require a surgical approach in order to promote correct bone remodeling. The experimental study of the structure and composition of bone has led to the development of orthopedic implants that allow osteoin- tegration to otherwise irreparable injuries. The surgical technologist should become proficient in the areas of bone biology, orthopedic biomechanics and orthopedic bioma- terials in order to identify the appropriate prosthetic mate- rials and healing enhancers for the surgical patient. A B O U T T H E A U T H O R Pamela Benavidez, CST, was born in Venezuela and graduated from ERWIN Technical Center in Tampa Bay, Flori- da. She currently works as a CST in the Tampa Bay area and holds a bachelor’s degree in integrative animal biology from the University of South Florida (USF). During her bachelor’s studies, she joined two research projects, one of which was presented during the 2014 USF Undergraduate Research Colloqui- um. Benavidez is also a member of the Corpus Christi Medical Mission, where she has had the opportunity to help the underserved community of Dilaire, Haiti. She is currently pursuing her goal of becoming a doctor. R E F E R E N C E S 1. Fleet ME. Carbonated Hydroxyapatite: Materials, Synthesis and Applica- tions . Singapore: Pan Stanford Publishing. 2015. 2. Veis, A. Collagen fibrillar structure in mineralized and nonmineralized tissues. Current Opinion in Solid State & Materials Science . 1997; 2 (3), 370-378. doi:10.1016/S1359-0286(97)80130-1. 3. Davies E, Muller K, Wong W, Pickard C, Reid D, Skepper J, and Duer M. Citrate bridges between mineral platelets in bone. Proceedings of the National Academy of Sciences of the United States of America . 2014; 111 (14), E1354-E1363. PNAS Online website. www.pnas.org/cgi/ doi/10.1073/pnas.1315080111. Accessed Jan. 19, 2015. 4. Sampath, KT and Vukicevic S, eds. Bone morphogenetic proteins: from local to systemic therapeutics . Basel, Switzerland: Birkhauser. Progress in Inflammation Research; 2008. doi:10.1007/978-3-7643-8552-1. 5. Zhao Q, Gautieri A, Nair AK, Inbar H, and Buehler M. Thickness of hydroxyapatite nanocrystal controls mechanical properties of the col- lagen−hydroxyapatite interface. Langmuir . 2011;28(4): 1982-1992. ACS Publications Website. http://pubs.acs.org/doi/abs/10.1021/la204052a. Published Dec. 31, 2011. Accessed Jan. 19, 2016. doi:10.1021/la204052a. MARCH 2016 | The Surgical Technologist | 119