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Joint research

Knee bone connects engineers to surgeons

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  • Story by Nancy Moen
  • Photos by Shane Epping
  • Published: April 21, 2011
A. Sherif El-Gizawy

Sherif El-Gizawy, a professor of engineering design and manufacturing, works with students to develop devices that improve precision and efficiency in orthopedic surgery.

Some intriguing challenges in the operating room have enticed an engineering professor to apply his skills in mechanical and aerospace technology to helping improve surgical procedure.

“Give me a problem; we’ll find a solution” is the prevailing attitude in the labs of A. Sherif El-Gizawy, professor of engineering design and manufacturing.

El-Gizawy involves undergraduate and graduate engineering students in designing, testing and building devices to repair bone fractures and deteriorating joints in the human body.

Getting off the ground

The crossover projects took off about 12 years ago when physicians in the Department of Orthopaedic Surgery – now located in the University of Missouri Orthopaedic Institute (MOI) – wanted improved methods and materials to replace knee and hip joints with prosthetic implants.

Armed with ideas, funding and a laboratory furnished by MU orthopaedic surgeon Sonny Bal, El-Gizawy and a graduate student began research to find the optimum angle of inserting implants into bones during hip and knee replacement. It’s the kind of work mechanical engineers thrive on. In his research, El-Gizawy develops mechanistic-based models to predict quality and damage management in materials. 

El-Gizawy knew that surgeons typically choose to perform minimally invasive surgery for bone replacements. And although those smaller incisions reduce recuperative time for patients, they also limit a surgeons’ vision, making alignment of prosthetic implants more difficult and increasing the risk of bone fracture.

El-Gizawy and his student tested hundreds of cases from medical-imaging scans of bone structure. Their resulting model showed surgeons the least-risky path of inserting implants, thus preventing the misalignment of prostheses.

It was El-Gizawy’s first foray into work with the human body and quite a change from designing aviation fuel systems and unmanned aircraft.

Instrumental invention

A. Sherif El-Gizawy

Sherif El-Gizawy has led student teams in the development of orthopedic surgical tools, an intramedullary nail and custom knee replacements, with some devices being produced for use in the operating room.

In 2003 El-Gizawy directed five seniors in designing a medical instrument that would help surgeons insert and remove implants during hip replacements. The device would replace an existing tool resembling a primitive screwdriver, which allowed only limited rotation and couldn’t be used for removing implants.

The students’ newly designed device — a stem inserter — featured a clamp to efficiently push, pull, rotate and retrieve an implant. As an added benefit, it could be disassembled and reassembled for sterilization.

El-Gizawy and students gave the design to Zimmer Inc., a medical equipment company that had helped test the instrument and had the capability to produce it. A Zimmer adviser who worked with the students told El-Gizawy he was impressed that “young brains” could develop such a product in one semester.

Wired up

“I believe in young people. I rely heavily on our students. I’ve worked at three universities, and the best students I’ve met are here,” El-Gizawy says.

In a project that ended in 2006, Bal asked El-Gizawy and students if they could help surgeons improve a procedure to reattach hipbones.

During hip replacement surgery, doctors cut off the top of the hipbone, insert the implant and then reattach the top of the bone by wrapping it with a composite wire material. The procedure, at that time, involved 14 to 15 instruments and numerous staff members. If the team could simplify the process, surgical costs would be reduced.

Within a year, El-Gizawy and his student team produced one tool with a small motor that could handle the entire procedure.

Bal says the most rewarding part of collaborating with graduate students is experiencing their innovative concepts. Equipment and procedures adapted in his clinical practice are still benefiting his patients and those of other surgeons. “The technology advancement was generic and was applied,” he says.

Nailing surgical solutions

A. Sherif El-Gizawy and students

Undergraduate researchers (from left) Shane Corl, Annemarie Hoyer and Stewart Mitchell Lloyd and graduate student James Berlin (right) work with El-Gizawy on materials characterization, biomechanics and design of smart devices for biomedical and aerospace applications.

Word of the students’ success in solving design problems continued to spread.

When Josh Arnone, El-Gizawy’s doctoral advisee, sought a research project, MOI physicians Brett Crist and Gregory Della Rocca, and Carol Ward, professor of pathology and anatomical science, presented two cases for his consideration.  

Arnone took on the challenge to design and build an improved intramedullary nail — a rod inserted into the cavity of long bones to repair fractures. Using a super-computer to simulate the surgical process, Arnone plotted stress data that allowed him to reshape the straight rods to match the typical curvature of femurs. The new shape makes insertion of the device more accurate and easier. 

In another project, and again with El-Gizawy’s guidance, Arnone developed methods to prevent the breakage of femur plates used to join fractured bone segments. He found the answers by analyzing shock loads on hips during walking and stumbling.

Arnone says medical applications in engineering are now his passion and that selecting El-Gizawy for his adviser was his best career decision. The appreciation is reciprocal because El-Gizawy ranks Arnone among his top students. 

In a current collaboration, El-Gizawy and Arnone have formed a company — Industrial Technology Development and Management, LLC — and are applying for a patent on a new tool that can insert and remove intramedullary nails.

The engineer-inventors plan to award two-thirds of their financial returns to the university. With advice from MU's Office of Technology Management and Industry Relations, El-Gizawy will approach companies about producing the instrument and will do the marketing by visiting prospective buyers. 

“This is not like previous products. We’re not giving them away anymore,” El-Gizawy says.

Custom-made capability

Biomedical research involves the same theory and techniques as aerospace engineering, just in a different environment, El-Gizawy says. “We have projects that make us very attractive to funding agencies.”

For years researchers have sought the right material and manufacturing method to produce a mechanically stable and bioresorbable material for artificial bone grafts.

As El-Gizawy and Arnone worked on a Boeing-funded project, they speculated that a plastic aviation material might also serve as a bone-graft substitute to fit patients’ specific fractures. They are now proposing the idea to the National Institutes of Health.

Another proposed project involves improving the conventional procedure for knee replacement. El-Gizawy says his team has the capability to design digital manufacturing methods to produce custom-made knee implants. In the standard procedure, surgeons “custom-make the patients to fit the implants,” he says.

The conceptualized machine for producing individualized knee-implants would cost just $500,000 and is the size of a large refrigerator. El-Gizawy says technicians could take a CT scan of the knee, send it to the machine to convert the scan to a design and in five hours have a finished custom-made implant.

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Last updated: Feb. 22, 2012