Article
Courtesy of Derrick Campana/Bionic Pets
Math,

Lending a Limb

Engineer Derrick Campana builds prosthetic limbs to help animals with disabilities

By Jeanette Ferrara
From the March/April 2022 Issue

Learning Objective: Students will create a structure and test how much weight it can hold.

Lexile: 880L; 710L
Focus Area: Measurement and Data,
Standards
  • CCSS: 3.MD.A.2 TEKS: 3.7E

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Lexile® measure

  • 880L
  • 710L
cast

An object made by shaping material inside a mold
plaster

A soft material that can be spread over walls, ceilings, or other structures to form a smooth, hard surface when it dries
customizes

Builds or changes something to fit the exact needs of an individual
mobile

Able to move freely and easily

Courtesy of Derrick Campana/Bionic Pets 

Derrick Campana built a brace for an injured elephant in Botswana.

Derrick Campana designs prosthetic limbs for a living. These artificial devices replace missing arms and legs. Campana used to make prosthetic limbs for humans. But in 2004, a veterinarian asked him to design an artificial leg for a dog named Charles.

Like people, animals can lose limbs or be born without them. That can make certain movements difficult. At the time, no company was making prosthetic devices for animals. But Campana knew that he could make one for Charles. The experience inspired him to start a company called Bionic Pets. Since then, his team has created prosthetic limbs for more than 30,000 animals, from dogs to kangaroos!

Derrick Campana designs prosthetic limbs for a living. A prosthetic limb is a human-made replacement for a missing arm or leg. Campana used to make prosthetic limbs for humans. But in 2014, a veterinarian asked him to create a prosthetic leg for a dog named Charles.

Animals can lose limbs just like people can. They may also be born without them. It can be hard for an animal to move when it is missing a limb. No company was making prosthetic limbs for animals in 2014. But Campana knew that he could make one for Charles. The experience inspired him to start a company of his own. He called it Bionic Pets. His team has created prosthetic limbs for more than 30,000 animals so far. Those animals include dogs and kangaroos!

Prosthetic Process

Courtesy of Derrick Campana/Bionic Pets 

Campana customizes each prosthetic limb to fit the animal it’s designed for. To do that, he first creates a fiberglass cast. Fiberglass is a light, durable plastic that can be shaped around the remaining part of an animal’s missing limb. This is where the prosthetic that Campana designs will be attached.

After the cast is removed, Campana fills itwith plaster. The plaster hardens into a copy of the animal’s body part. Campana then uses soft plastic to build the prosthetic limb around the plaster. He adds bolts, gears, and other pieces to allow the device to move like a real limb.

Campana creates each prosthetic limb to fit the animal it is designed for. He first creates a fiberglass cast. Fiberglass is a type of plastic that is both light and strong. Campana shapes the cast around the remaining part of an animal’s missing limb. This is where Campana will attach the final prosthetic limb.

Campana removes the cast. Then he fills it with plaster. The plaster hardens. It creates a copy of the part of the body where the cast was wrapped. Campana then uses soft plastic to build the prosthetic limb around the plaster. He adds bolts and gears so that the limb can move like a real limb.

Courtesy of Derrick Campana/Bionic Pets 

Fresh Foot Forward

Fitting the patient with the new device is the final step—and Campana’s favorite! That’s when he puts the prosthetic limb on the animal for the first time. He tests whether it fits properly and keeps the animal stable. If it doesn’t fit well, he and his team keep adjusting and testing the prosthesis until it works just right.

Campana doesn’t give up until his patient has a fully functional prosthetic limb. “Watching the animals take their first steps and seeing them mobile again is the best part of the job,” he says.

The final step is putting the prosthetic limb on the animal for the first time. It’s Campana’s favorite part! He tests whether the limb fits properly. He checks that it can keep the animal stable. Sometimes the limb doesn’t fit at first. So Campana and his team keep adjusting and testing it until it works just right.

Campana doesn’t give up until his patient has a prosthetic limb that works perfectly. “Watching the animals take their first steps and seeing them mobile again is the best part of the job,” he says.

Math Talk

What types of measurements would be important when making a prosthetic limb?

Math Talk

What types of measurements would be important when making a prosthetic limb?

Hands-on Math: Build a Sturdy Structure

Derrick Campana designs prosthetic limbs to support animals as large as elephants! Can you create a structure strong enough to hold a heavy weight?

Materials

• 5-10 books weighing about 1 pound each • scale • tape • glue • rubber bands •  a variety of building materials, such as plastic cups, cardboard boxes, plastic straws, and paper plates

Procedure

STEP 1
Choose materials for your structure. Think about how to design it so it holds the most possible weight.

STEP 2
Build your structure. Make sure that your design has a flat top so that books can be placed on top of it.   

STEP 3
Test how much weight your structure can support. Place books on top of your structure one at a time until the structure collapses. Then use the scale to weigh the books your structure was strong enough to hold. Record the total weight.

STEP 4
Think and rebuild! Try to create a structure that will hold more weight than your first one. You can use different materials, a different design, or both.

STEP 5
Repeat Step 3 with your new structure.

Hands-on Math: Build a Sturdy Structure

Derrick Campana designs prosthetic limbs to support animals as large as elephants! Can you create a structure strong enough to hold a heavy weight?

Materials

• 5-10 books weighing about 1 pound each • scale • tape • glue • rubber bands •  a variety of building materials, such as plastic cups, cardboard boxes, plastic straws, and paper plates

Procedure

STEP 1
Choose materials for your structure. Think about how to design it so it holds the most possible weight.

STEP 2
Build your structure. Make sure that your design has a flat top so that books can be placed on top of it.   

STEP 3
Test how much weight your structure can support. Place books on top of your structure one at a time until the structure collapses. Then use the scale to weigh the books your structure was strong enough to hold. Record the total weight.

STEP 4
Think and rebuild! Try to create a structure that will hold more weight than your first one. You can use different materials, a different design, or both.

STEP 5
Repeat Step 3 with your new structure.

Analysis

Answer the following questions on a separate sheet of paper.

Answer the following questions on a separate sheet of paper.

How much weight did your first structure hold? Did it surprise you? Explain.

How much weight did your first structure hold? Did it surprise you? Explain.

What changed when you created your second structure? Why did you make those changes?

What changed when you created your second structure? Why did you make those changes?

Did your second structure support more weight than your first one? Why do you think that happened?

Did your second structure support more weight than your first one? Why do you think that happened?

Continue Your Learning

  • Rewatch the video “Derby the Dog” (above). What factors did the designer need to think about when creating Derby’s prosthetic legs? Write a list of at least 5 questions that people like Derrick Campana would need to ask when designing an artificial limb for an animal.
  • Play a weight guessing game! Gather 5 objects of varying sizes that you can easily carry (for example: a book, a notebook, a paperweight, a toy, and a bowl). Take turns with a partner holding each item and guessing its weight. Then use a scale to measure the exact weight of the object. For each object, the person whose estimate is closest to the actual weight wins a point!

Continue Your Learning

  • Rewatch the video “Derby the Dog” (above). What factors did the designer need to think about when creating Derby’s prosthetic legs? Write a list of at least 5 questions that people like Derrick Campana would need to ask when designing an artificial limb for an animal.
  • Play a weight guessing game! Gather 5 objects of varying sizes that you can easily carry (for example: a book, a notebook, a paperweight, a toy, and a bowl). Take turns with a partner holding each item and guessing its weight. Then use a scale to measure the exact weight of the object. For each object, the person whose estimate is closest to the actual weight wins a point!
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