A team of students from Purdue University, West Lafayette, Indiana, has designed a new type of prosthetic leg for a five-year-old boy who was born with proximal femoral focal deficiency (PFFD). The leg uses a gearbox design that enables the prosthesis to move like a real leg.
The boy, Lucas Resch, was born with only a fraction of his left femur, making his left leg far shorter than his right. Conventional prostheses do not give Lucas the ability to run and ride a bicycle or play like his friends do, his parents, Ned and Melissa Resch of Providence, Rhode Island, told Purdue News. He is active, and his parents have been searching for ways to allow him to retain that level of activity as he grows.
“He has a traditional prosthesis that basically just makes his legs the same length, but does very little for his mobility,” said Purdue doctoral student Anne Zakrajsek.
The prosthesis was created by Purdue mechanical engineering seniors Sajed Dosenbach, Ted Kramer, and James Vandewalle and Purdue biomedical engineering seniors Alex Guerra and Ben Zakhary. Zakrajsek developed this assistive-technology senior design as part of a fellowship she received.
Barring a new type of prosthetic leg, the family was told that the child’s best hope was to undergo rotationplasty; then a traditional prosthesis could be used. While seeking a different solution, the Resches learned about a 2009 Purdue mechanical engineering senior design project to create a prosthesis for an Indiana boy with PFFD. Eventually, Ned Resch found a group of students in a senior design class at Purdue who were willing to take on the project for Lucas.
The prosthesis uses a gearbox to produce a knee’s range of motion; whereas an ankle joint swivels about 40 degrees, a knee joint moves about 90 degrees. The new design hinges on the innovative gearbox that converts the ankle’s limited movement to the motion of a knee, providing greater mobility.
Fitting of the new leg began November 2. The Purdue students created a mold of Lucas’s shin to make a better fit, and he and his family will return later this year to receive the form-fitted leg. The leg will be adjusted as Lucas grows.
Editor’s note: This story is adapted from materials provided by Purdue University.