Lesson: Bone Fractures and EngineeringContributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Educational Standards :
Pre-Req Knowledge (Return to Contents)
A basic understanding of bones, how they work and what they are made of. See the Our Amazing Skeleton lesson.
Learning Objectives (Return to Contents)
After this lesson, students should be able to:
Introduction/Motivation (Return to Contents)
(Have ready to show to the class the attached Bone Repair and Biomedical Engineering PowerPoint presentation, which contains information, explanations, drawings, photographs and examples of the subject matter covered in the Lesson Background & Concepts for Teachers section. Follow-up with a quiz, as described in the Assessment section.)
How many of you have had a broken bone? Or, know someone who has? What did the doctor do to fix it? (Expect "Put a cast on it" to be a common answer.) Do any of you know of other steps doctors take to fix more serious breaks? (Take suggestions from students.) That's correct, doctors use rods, pins, plates and screws to help repair broken bones. Do you think doctors design, create and use pins, plates and rods by themselves? Biomechanical engineers and materials science engineers help doctors develop and design bone-fixing devices. These engineers play important roles in making sure the materials will be accepted by the body and not lead to other complications. They design special surgical stainless steel, titanium alloys and polymers especially for medical implants. They also make sure that the devices can be inserted in a way that supports the body in repairing the bone, and not weaken it.
Engineers must consider many things when designing devices to repair broken bones. Some important things to consider are:
Engineers want devices to be strong enough to support the body, match the properties of bone well, and not be rejected by the body. Doctors desire devices that are easy to implant, inexpensive, and minimally invasive for the patient. All of these factors have been considered and have influenced current bone repair devices and techniques. Next, let's learn more about how engineers aid doctors in repairing serious bone fractures.
(Show the class the attached Bone Repair and Biomedical Engineering PowerPoint presentation, and follow-up with a quiz as described in the Assessment section. Then conduct the associated activity)
Lesson Background & Concepts for Teachers (Return to Contents)
When a bone breaks it immediately begins to heal itself. When minor fractures occur, doctors cast the broken region so it will not move while healing. Figure 1 illustrates the steps of this healing process. Problems occur, however, when bones are not able to heal correctly on their own. In these cases, doctors and engineers are needed.
(See the attached Bone Repair and Biomedical Engineering PowerPoint presentation.) When severe fractures occur, doctors and engineers help the body repair broken bones for certain reasons:
The two categories of bone repair are internal and external fixation. Internal fixation is temporary or permanent fixtures directly attached to the bone under the skin, for alignment and support. Internal fixation includes pins, rods, plates, screws, wires and bone grafting.
External fixation is temporary repair supports outside of the skin that stabilizes and aligns bone while the body heals. External fixation includes screws in the bone to hold it in place, and metal braces or casts; these can be externally adjusted.
Internal fixation is recognized for providing increased patient mobility and quicker healing time.
Materials science engineers play important roles in designing devices and technologies to help heal fractured bones; they continually seek and concoct materials that closely match bone properties and are biocompatible. This is challenging! Bone is incredibly strong while also being fairly flexible, while most strong materials are brittle and unable to flex like bone.
Commonly used implant material for orthopedic devices include surgical stainless steel, titanium alloys and polymers. Stainless steels are made from nickel, chrome and molybdenum, combined into endless combinations for characteristics that are desired for different applications (strength, flexibility, biocompatibility, etc.). While the "surgical" versions are designed to be easy to sterilize, strong, and corrosion-resistant, sometimes the human immune system reacts to the nickel component. Titanium is a reactive metal and its surface quickly oxidizes upon exposure to air, which provides an excellent surface on which bone grows and strongly adheres. Advances are being made in the uses of polymers that are designed to degrade in the body. Sometimes a fractured bone that is supported by a steel plate can be re-fractured, damaged, or opened to risk of infection upon removal of the device. But, the same device made of a polymer can be engineered to degrade at a rate that slowly transfers load to the healing bone and does not require another surgical procedure to remove.
Vocabulary/Definitions (Return to Contents)
Associated Activities (Return to Contents)
Lesson Closure (Return to Contents)
What are some of the current devices and techniques designed by engineers to help doctors repair severely broken bones? (Answer: Pins, rods, plates, screws, wires, bone grafting, metal braces, casts, slings.) Which of these are used temporarily? Which might be used permanently? What's a difference between internal and external fixation? (Answer: Repair work that is attached directly to the bone [under the skin] is internal fixation; repair supports outside of the skin are external fixation.)
While the current technology for bone repair has greatly increased the number of bones that are successfully healed each year, much improvement can still be made. Young engineers (like you!) still have work to do. As you saw in the presentation, some surgeries are intense and invasive, and can result in patients being in hospital for long periods of time.
What things might engineers take into consideration when designing devices to help heal fractured bones? (Answer: Strength, minimally invasive, biocompatibility, expense, ease of implementation.) Engineers play important roles in making sure the materials are accepted by the body, and that the devices can be inserted safely into the body. A commonly-used material, titanium alloy, is as strong but not as flexible as bone. Do you think engineers can still improve the implementation and materials used in bone repair?
Attachments (Return to Contents)
Assessment (Return to Contents)
Discussion Questions: Solicit, integrate and summarize student responses. Have students discuss the following questions together in small groups.
Lesson Summary Assessment
Device Design & Presentation: Have students imagine they are biomedical and materials science engineers. Challenge groups of 3-4 students to design on paper their own devices to repair fractured tibiae (shinbones). Then have the teams present their designs to the class. Ask the groups to consider the following in their design:
Additional Multimedia Support (Return to Contents)
Refer to an excellent four-part bone fracture repair series that includes drawings and summary explanation of the devices and surgical procedures involved in fracture repair. See the MedlinePlus Medical Encyclopedia website at http://www.nlm.nih.gov/medlineplus/ency/presentations/100077_4.htm
References (Return to Contents)
Bone fracture repair-series, Procedure. Last updated September 21, 2009. MedlinePlus Medical Encyclopedia, US National Library of Medicine, National Institutes of Health. Accessed October 29, 2009. http://www.nlm.nih.gov/medlineplus/ency/presentations/100077_3.htm
Internal Fixation for Fractures (wires, pins, plates, nails or rods, screws, etc.) Updated August 2007. Your Orthopaedic Connection, American Academy of Orthopaedic Surgeons. Accessed October 30, 2009. http://orthoinfo.aaos.org/topic.cfm?topic=A00196&return_link=0
Martini, Frederic H. Fundamentals of Anatomy & Physiology: Seventh Edition. San Francisco, CA: Pearson Education, Inc., 2006.
Middleton, John C. and Arthur J. Tipton. Synthetic Biodegradable Polymers as Medical Devices. Originally published March 1998. Medical Plastics and Biomaterials Magazine, Medical Device Link. http://www.devicelink.com/mpb/archive/98/03/002.html
Surgical Stainless Steel. Updated October 23, 2009. Wikipedia, The Free Encyclopedia. Accessed October 30, 2009. http://en.wikipedia.org/w/index.php?title=Surgical_stainless_steel&oldid=321664314
ContributorsTodd Curtis, Malinda Schaefer Zarske, Janet Yowell, Denise W. Carlson
Copyright© 2008 by Regents of the University of Colorado
Supporting Program (Return to Contents)Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Acknowledgements (Return to Contents)
This digital library content was developed by the Integrated Teaching and Learning Program under National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.