Teacher Notes

Broken Bones

Flinn STEM Design Challenge™

Materials Included In Kit

(for 8 student groups)
Cardboard tube with foam insert, 9", 8
Foam sheets, peel and stick, 8
Plastic yarn needles, 8
Polyurethane foam pieces, 8" x 10", 8
Rubber bands, 20
Scalpels, disposable, 8
Yarn, 364 yards

Additional Materials Required

(for each lab group, optional)
Hand saw (Prelab Preparation)
Nails, 1" or smaller
Screws, 1" or less
Screw drivers

Prelab Preparation

  1. This kit includes four oblique fractues and four transverse fractures. To create other fractures see Teaching Tips.
  1. Place a precut, cardboard tube with foam insert onto a 8" x 10" piece of polyurethane foam and roll. Place a rubber band at each end to hold the foam and cardboard tube in place.
  2. Remove the backing from a sticky foam sheet. Roll the polyurethane foam and cardboard tube in the sticky foam sheet so the open ends are aligned (the portions that overlap should be considered the back of the leg—opposite where the students will make their incisions). 

Safety Precautions

Ensure students have experience and/or direction on working with sharps. Discuss which tools are allowed to be used in the classroom. Have students wear protective eyewear and follow all laboratory guidelines during the activity. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory.


All materials are considered nonhazardous and can be disposed of in the regular trash. The scalpel is disposable and should be discarded in a sharps container.

Lab Hints

  • Enough materials are provided in this kit for 8 groups of students. Each part of the lab can reasonably be completed in one 50-minute class period each (totaling 4 days).
  • Students design their medical implantation device and will need to bring in their own materials to create and install the device. Discuss with students that the materials used to create their medical device do not need to be sophisticated. Materials can be creative and from around the house.
  • Surgeons will usually avoid cutting through muscle tissue to repair fractures due to increased recovery time. However, the design of the femur for this lab uses foam; therefore, students will need to cut through muscle rather than separate or shift the tissue.
  • X-ray fractures: 1 Transverse Fracture, 2 Oblique Fracture, 3 Spiral Fracture and 4 Comminuted Fracture.
  • This kit includes four x-rays, groups can share the x-rays or photocopies can be made for each group.

Teacher Tips

  • This STEM activity incorporates the engineering design process into a life or biomedical science activity. It can be used during an anatomy or human body unit or in a health class.
  • This kit comes with 8, precut, femure models. There are four oblique fractures and four transverse fractures. If a comminuted fracture is desired, using an oblique fracture cut a third peice of the bone (see Figure 4).
    The foam insert will need to be glued to the small peice of cardboard tube to maintain its placement.
  • The instructor must decide what types of equipment/tools students will be allowed to use. Power tools are not necessary. A 1-inch screw can be screwed into the cardboard tube with foam insert with a screwdriver.
  • Be sure to discuss safety and use of scalpels, including disposal in a sharps container.
  • Place a time constraint on the actual surgical procedure (Part IV) to relate to the use of anesthesia or patient tolerance.
  • It is reasonable to allot extra time for the design and testing of the prototype (Part III).
  • For Part III. Prototype, have students bring in paper towel rolls filled with paper towel, newspaper, etc. to test their prototypes prior to the final design and Part IV. Surgery and Implanation.
  • Extensions to the activity can include adding additional characteristics to the thigh, complicating surgery. Ideas include veins and arteries, blood or connective tissue. Long thin balloons can be filled with fluid and placed inside the foam for blood vessels, ketchup can be used as blood, and rubber bands can be included as connective tissue (tendons and ligaments). Other possible extensions include students assembling the broken femurs and trading with another group or the inclusion of muscles (drawn onto the polyurethane foam) that groups would need to avoid during surgery to minimize tissue damage.

Answers to Prelab Questions

  1. What is a biomedical-engineered device? Give two examples.

    A biomedical engineered device does not include pharmaceutical (drug) or biological (vaccine) treatment methods, rather it combines engineering with medical science to advance healthcare treatment. Examples include a pacemaker, mircrokeratome and excimer lasers, and projection radiography (X-ray).

  2. Look at the X-ray in Figure 2 and determine which type of femoral shaft fracture is shown.

    Oblique femoral shaft fracture.

  3. What type of medical devices designed by biomedical engineers would be utilized to diagnose and surgically repair a femoral shaft fracture?

    Answers may vary but can include implants and medical imaging. Medical imaging would be a device designed by biomedical engineers that would be useful in diagnosing the type of fracture the patient endured. These devices give doctors the ability to “see” what is not visible directly. Most likely an X-ray would be utilized, however if the fracture was very thin, a CT scan may be used. Implants are devices placed inside the body to provide support to the organ/tissue. Many are made of metal or plastic.

Answers to Questions

  1. What is the problem being addressed in this activity?

The problem in this activity is designing a medical device that will repair a broken femur. Identification of the type of femoral shaft fracture is based on the X-ray and teacher-created femoral shaft fracture. The femoral shaft fracture is either oblique, transverse, spiral or comminuted.

  1. Record the research that was discovered as potential solutions to the problem.

Typical types of medical devices used to fix femoral shaft fractures include external fixation (pins and screws attached to bar or plate outside the leg), intramedullary nailing (titanium rod through marrow canal and screwed into hip and knee), or plates and screws (metal plates that are screwed into bone to hold bone fragments together). Most students will design an intramedullary nail (if the marrow canal is drilled out by the teacher) or plates and screws.

  1. Develop a step-by-step procedure of how the surgery will be performed. Include a description and sketch of the possible device(s) that will be used to correct the problem and how it will work.

Student answers will vary. Students must include the type of femoral shaft fracture, a sketch of the implant device they intend to use (plate, screws, intramedullary nail), the equipment required to install the implant device (screwdriver, metal rod, screws) and the dimensions of the implant device. Discussion of the surgical process should include making the incision through the skin and muscle, holding the tissue off the bone while affixing the implant device, how the implant device will be attached, whether it will be on one side or both, and the process of stitching the skin and muscle back together.



—Oblique femoral fracture
—Implant device: plates with screws
—Equipment needed:

Large binder clips, 2
Permanent marker
Phillips screwdriver 
Screws, 1", 4 
Tongue depressors (5 cm L x 2 cm W), 2


    1. Determine the location of the break by feeling along the skin.
    2. Mark the skin where the incision will be made.
    3. Make incision through the skin.
    4. Make incision through the muscle.
    5. Secure the skin and muscle away from the bone using the binder clips.
    6. Stabilize the bone and affix the plate by screwing one tongue depressor to the left side of the bone using two screws, one above the fracture and one below the fracture.
    7. Screw the second plate (tongue depressor) to the right side of the bone using two screws, one above the fracture and one below the fracture.
    8. Remove binder clips and pull muscle over bone.
    9. Pull skin over muscle.
    10. Suture the skin and muscle using yarn and needle.
  1. After discussing and refining the individual designs, collaborate with your group to design the final implant device and develop detailed procedural steps for performing the surgery.

Student answers will vary. This will be similar to Question 3, but will also include the names of group members and their responsibilities and roles during the lab activity.

  1. Construct a prototype—a preliminary model—of the implantation device that will repair the femoral shaft fracture. Record the strengths and weaknesses of the prototype and any changes that were made for the final design.

Student answers will vary. Strengths may include the ease of affixing the implant device to the “bone” and how secure the bone is held together. Weaknesses may include cracking or breaking of device while affixing the device to the bone, length of the device, ability to screw into the “bone” and how secure the bone is held together post-operation.

  1. Perform the surgery, which includes incision, implantation of the device and suturing the tissue, to repair the broken bone. Record each step with great detail. Upon completion of the surgery, evaluate the effectiveness by examining the femur by checking for strength and stability, feeling the skin for abnormalities and the cleanliness of the sutures (scar).

Student answers will vary but must include precise details. Step-by-step notes should be taken during the surgery by the recorder and copied by the remaining group members. Evaluation of the procedure should be discussed here. It should include the secure placement of the bone, the length of time to complete the surgery, the look of the stitches, and overall group work.

  1. In paragraph form, write a post-operation summary about the surgical procedure to the patient and their family explaining what was performed and the success of the surgery.

Student answers will vary. The summary should include all the steps from the Engineering Design Process graphic organizer that is on the first page of the Broken Bones Worksheet.

  1. Discuss what changes you would make to your biomedical device and surgical procedures for the future.

Student answers will vary based on effectiveness of their device.


Sakakeeny, J. Repairing Femoral Fractures. Integrating Engineering and Science in Your Classroom; Brunsell, E.; NSTAPress: Arlington, VA, 2012.

Student Pages

Broken Bones


Have you ever broken a bone that required surgery to fix? Biomedical engineers are responsible for designing, testing and manufacturing medical devices intended for curing, alleviating, treating and preventing disease. These devices include CT scans, titanium plates, artificial limbs and much more.


  • Biomedical engineering
  • Engineering design
  • Human anatomy


Medical Devices

Biomedical engineering combines the design and problem-solving skills of engineering with medical and biological sciences to advance healthcare treatment. Prominent biomedical engineering applications include biocompatible prostheses, diagnostic equipment and medical devices for home or clinical use. A medical device is any kind of healthcare product that does not achieve results via pharmaceutical (drug) or biological (vaccine) methods, but rather is intended to diagnose, cure, treat or prevent disease. Some common medical devices include:

  • Pacemaker—A pacemaker is a small device that is placed under the skin, near the heart to help control the heartbeat and correct problems with the sinoatrial (SA) node. The device includes a small metal container that houses a battery and electric circuitry that regulates the rate of electrical impulses sent to the heart (pulse generator). Insulated wires or leads are placed in a chamber of the heart and deliver the electrical pulses that adjust the heart rate.
  • Microkeratome and Excimer Lasers—LASIK surgery is a vision correction procedure that uses these two biomedical devices. The microkeratome is a mechanical “shaver” with a sharp blade that is guided across the eye and cuts thin layers off the cornea. The excimer laser then reshapes the exposed cornea, resulting in clear vision.
  • Implants and Prosthetics—These are devices or tissue placed inside or on the surface of the body to replace missing body parts, deliver medication, monitor body functions or provide support to organs and tissues. Implants and prosthetics can be made from skin, bone or body tissue as well as metal, plastic or ceramic materials. Implants and prosthetics can be permanent, such as stents or hip implants, or temporary, such as chemotherapy ports or titanium screws.
  • Medical Imaging—Medical imaging devices give clinicians the ability to “view” things, directly or indirectly, that are not visible due to size or location. Examples include: magnetic resonance imaging (MRI), positron emission tomography (PET scan) and projection radiography (X-ray, CT scan or ultrasound).

The Femur Bone

The femur is the longest and strongest bone in the human body (see Figure 1). The long, straight part of the bone is referred to as the femoral shaft, and a break anywhere along this portion of the bone is known as a femoral shaft fracture. A bone fracture can be closed or open. Closed fractures are contained within the skin. Open, or compound fractures, occur when the bone punctures the skin, causing a more severe injury due to the extensive damage to surrounding muscle and tissue and increased susceptibility to infection or complications. Breaks are further classified by the location of the fracture, pattern of the fracture (direction the bone breaks), and whether the skin and muscle around the fracture is torn. Some of the most common femoral shaft fractures are listed. 

  • Transverse fracture—straight, horizontal line across the femoral shaft
  • Oblique fracture—angle line across the femoral shaft
  • Spiral fracture—fracture line encircles the femoral shaft like stripes on a candy cane
  • Comminuted fracture—bone broken in three or more pieces

When a person breaks the femur, the doctor will usually discuss the accident and medical history and conduct a visual inspection. The doctor will look for obvious deformities, breaks in the skin, bruises or bony pieces pushing on the skin during the visual inspection. Next, the doctor will feel along the thigh for abnormalities, tightness of the skin and muscle, pulses, sensation and movement in the leg and/or foot. Typically, femoral shaft fractures require an X-ray or CT scan (Computed Tomography). X-rays give a clear image of the bone to help determine the type of fracture and location. The CT scan can give more precise information about the severity of the fracture, as thin fractures can be difficult to see in a traditional X-ray.

Treatment of a femoral shaft fracture typically requires surgery. The timing for the surgery will depend on the type of break. If the break is closed, the medical team will wait until the patient is stable. The broken femur will either be put into a long-leg splint or skeletal traction (pulley system) to keep the bone aligned and maintain leg length. An open fracture will be operated on immediately to prevent infection. Common surgical treatments include the following:

  • External Fixation—temporary treatment; pins/screws are placed into the bone above and below the fracture and then attached to a bar outside the skin.
  • Intramedullary Nailing—most common treatment; a titanium metal rod (“nail”) is placed into the marrow canal of the femur and screwed into the hip and knee through small incisions.
  • Plates and Screws—used when intramedullary nailing is not possible; bone fragments are repositioned into proper alignment and special metal plates and screws are attached to outer bone surfaces.

Experiment Overview

The purpose of this activity is to apply the process of engineering to medicine. Your task will be to evaluate a broken femur from a model and an X-ray, design a procedure and medical device to repair the broken bone, and perform surgery to repair a model femur.


Broken femur model
Medical device (student provided)
Plastic needle
Scalpel, disposable

Prelab Questions

  1. What is a biomedical-engineered device? Give two examples.
  2. Look at the X-ray in Figure 2 and determine which type of femoral shaft fracture is shown.
  1. What type of medical devices designed by biomedical engineers would be utilized to diagnose and surgically repair a femoral shaft fracture?

Safety Precautions

Protective eyewear is a necessity when working with scalpels. These instruments are extremely sharp and must be used with extreme caution. Do not use excessive force when working with or cleaning sharp instruments. Proper usage and disposal of sharps should be discussed prior to the lab activity. Wash hands thoroughly with soap and water before leaving the laboratory. Please follow all laboratory safety guidelines.


Part I. Independent Design Solution

  1. After being assigned to your group, obtain the assigned broken leg model and corresponding X-ray. Each student must independently observe the X-ray and broken femur.
  2. Determine the type of femoral shaft fracture (use the Background for help). Record your observations under Question 1 on the Broken Bones Worksheet.
  3. Research treatment methods that are most common for the type of femoral shaft fracture. Record this information under Question 2 on the worksheet.
  4. Develop a detailed solution to repair the broken bone. Include sketches and explanations. Record your procedure under Question 3 on the Broken Bones Worksheet.
Part II. Group Design Solution
  1. Return to your group. One by one, group members should describe their independent design solutions. As a group, while discussing each individual design solution, create a list of strengths and weaknesses of that design by offering constructive criticism. Fill in the Independent Design Evaluation graphic organizer on the worksheet for each group member.
  2. After all group members have presented their design solutions, determine a final group design solution for repairing the femoral shaft fracture.
  3. Develop a detailed procedure to repair the broken bone. Include sketches and explanations. Record this procedure under Question 4 on the Broken Bones Worksheet.
Part III. Prototype
  1. With the group, gather materials and practice the procedure. Use the materials to create a prototype—a preliminary model.
  2. Make adjustments to the final design procedure based on the prototype. Record effectiveness under Question 5 on the Broken Bones Worksheet.
Part IV. Surgery and Implantation
  1. Obtain the following materials:
    • Broken femur
    • Scalpel
    • Yarn
    • Medical device (finalized prototype from Part III)
    • Needle
    • Tools
  1. Perform implantation of the created medical device to repair the femoral shaft fracture. Begin with an initial incision and finish with suturing the incision.
  2. Record each step of the surgical procedure, beginning with “Make the initial incision, _____ centimeters in length.”
  3. The instructor will evaluate the effectiveness of the medical device and implantation design solution and execution.
  4. Complete questions 6–8 on the Broken Bones Worksheet.
  5. Consult your instructor for appropriate disposal procedures.

Student Worksheet PDF


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