Prosthetic Leg Breakthrough Boosts Mobility

A prosthetic leg option from Europe delivers exceptional mobility. Keck Medicine of USC is one of only a few places in the United States to offer it.

For Robert Johnson, the ability to pick up his young daughter and go for walks around the neighborhood with his wife means everything. But it was not long ago that this simple activity posed a major challenge.

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Robert had his right leg amputated above the knee in 2019 after a cancer diagnosis. He relied on a traditional prosthetic, a socket that fits atop the residual limb and connects to an artificial leg. But the Mid-City resident constantly felt off balance and afraid to hold his baby girl.

“When I had a socket on, it wouldn’t ‘stick’ on to me,” Robert says, “so I was always scared the leg would fall off and I would fall and drop her.”

Thanks to an innovative procedure offered at Keck Medicine of USC called osseointegration — where a metal implant inserted into the bone of the remaining limb is attached directly to a prosthesis — Robert has gained better mobility and the confidence to experience life with his family.

And the surgery, performed for more than two decades in Europe, now has the potential to help many other patients with prosthetic legs.

Preventing cancer spread through amputation

In 2016, Robert started to experience chronic pain in his right leg. A bump formed above his knee and continued to grow, but multiple physicians sent him away without a diagnosis.

“I went to different doctors and hospitals for about a year, and they all told me it was nothing,” Robert says. “At one hospital, they did an X-ray, decided it wasn’t cancerous, and just sent me home with pain medication.”

The turning point finally came after Robert was referred to Lawrence Menendez, MD, an orthopaedic oncologist with Keck Medicine. After performing a biopsy, he diagnosed Robert with osteosarcoma, an invasive form of bone cancer, and performed surgery to remove the mass from the patient’s leg.

To prevent the cancer from spreading further, Dr. Menendez and his team needed to amputate his right leg above the knee.

Robert Johnson in his Mid-City neighborhood (Photos by Kremer Johnson Photography)

The news came while Robert’s wife was pregnant with their daughter.

“I just went for it because I didn’t want the worst outcome that could happen from cancer,” Robert says. “I was thinking long term, being able to be there for my daughter.”

After the wound healed and six months of chemotherapy, Robert was cancer-free and fitted with a socket prosthesis. But walking with it was challenging, and the onset of the COVID-19 pandemic kept him from regular physical therapy appointments.

Unhappy with his limitations, Robert began researching other options.

“I watched an interview with a woman who had been struggling to get around, but after the osseointegration procedure, she could walk and even go hiking,” he says. “I really wanted that.”

What is osseointegration? Procedure enhances stability and balance

The timing was ideal. The U.S. Food and Drug Administration had approved osseointegration for above-knee amputations in December 2020, and Dr. Menendez was one of just a handful of surgeons in the country with the training and expertise to perform it.

“Robert was a good candidate,” says Dr. Menendez. “He’s a young guy and otherwise healthy, and I thought he would benefit greatly from this type of prosthetic management.”

Osseointegration is a two-part procedure in which a metal implant is inserted into the bone of the residual limb after the amputation. Over the course of about three months, the bone grows into the implant until it is secure and fully integrated.

Being one of the first centers in the U.S. to perform osseointegration, we’ve established a solid track record here at Keck Medicine and we’re ahead of the game.

Lawrence Menendez, MD, orthopaedic oncologist, Keck Medicine of USC

Next, an additional device is attached to the implant, which protrudes from the skin and attaches to the prosthesis. Patients take up to a year to heal and require physical therapy.

The primary benefit of osseointegration is that it dramatically enhances the patient’s stability and balance.

“With osseointegration, the prosthesis is connected directly to the femur bone, so patients really feel like it’s just their leg,” Dr. Menendez says. “Patients are much more comfortable walking — especially walking uphill, downhill and even backward.”

Osseointegration in the U.S. offers ‘remarkable’ potential

Dr. Menendez performed the first surgery on Robert in March 2021. Robert says he relied on crutches to get around while he waited for the bone to grow into the implant. The second surgery took place three months later.

Robert started weight-bearing training about six weeks after that to learn to walk on the new prosthetic, with physical therapists gradually increasing the amount until he was comfortable placing his entire body weight on the prosthetic.

Today, the 28-year-old no longer worries about the leg coming loose.

“I just screw the prosthetic onto my leg, and it doesn’t come off,” he says. “I’m never scared to hold my daughter anymore.”

Osseointegration typically involves two surgeries, but Robert has a third scheduled due to the size of his thigh. A plastic surgeon will contour Robert’s thigh and remove extra tissue and muscle surrounding the implant.

His quality of life, meanwhile, is forever changed.

“When I put my prosthetic on the floor, I can feel the different sensations,” Robert says. “I can feel the grass, I can feel sand, I can feel soft surfaces. It feels completely different from having a socket.”

Robert’s journey is poised to be one of many stateside success stories, Dr. Menendez says.

“Being one of the first centers in the U.S. to perform osseointegration, we’ve established a solid track record here at Keck Medicine and we’re ahead of the game,” he says.

“It’s been remarkable to see what patients can do with this type of prosthetic management.”

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Our nationally recognized USC Orthopaedic Surgery doctors treat a wide range of conditions. From minimally invasive options to robotic surgery to physical therapy, our mission is to help you recover and get back to the activities and lifestyle you love.

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Erin Laviola

Erin Laviola is a freelance writer for Keck Medicine of USC.

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Millions of people in the United States are currently living with limb loss. This number is expected to grow as the population ages and rates of diseases such as diabetes that can cause dysvascularity (poor blood circulation in the legs) increase.

For people with limb loss, prosthetic devices improve quality of life by providing movement and independence. Early prosthetics were uncomfortable to wear, but they may have helped people return to work and feel accepted in their daily lives. We’ll explore how these devices have changed over time, from clunky, early designs and materials to modern innovations—some of which NIH-supported researchers are developing.

When were prosthetics invented, and what were they used for?

Historians don’t know for certain if the first prosthetics were functional or for appearances. According to Katherine Ott, Ph.D., curator for the Division of Medicine and Science at the Smithsonian Institution’s National Museum of American History, this is partly because different cultures have their own ideas about what makes a person whole.

The oldest known prosthetics are two different artificial toes from ancient Egypt. One prosthetic toe, known as the “Greville Chester toe,” was made from cartonnage, which is a kind of papier-mâché made from glue, linen, and plaster. It is thought to be between 2,600 and 3,400 years old, though its exact age is unknown. Because it doesn’t bend, researchers believe it was cosmetic.

The other prosthetic, a wooden and leather toe known as the “Cairo toe,” is estimated to be between 2,700 and 3,000 years old. It is thought to be the earliest known practical artificial limb due to its flexibility and because it was refitted for the wearer multiple times.

Approximately 300 years later—300 B.C.—in Italy, an ancient Roman nobleman used a prosthetic leg known as the “Capua leg.” The leg was made of bronze and hollowed-out wood and was held up with leather straps.

Other known early prosthetics include artificial feet from Switzerland and Germany, crafted between the 5th and 8th centuries. These were made from wood, iron, or bronze and may have been strapped to the amputee’s remaining limb.

 

 A wood and aluminum prosthetic arm invented by William Robert Grossmith in the mid-19th century.

How war—and the U.S. military—inspired prosthetic advances

Soldiers who lost their limbs in battle often used early artificial limbs made of wood or iron. For example, about 2,200 years ago, the Roman general Marcus Sergius Silus lost his right hand during the Second Punic War. He had it replaced with an iron one that was designed to hold his shield. Knights of the Middle Ages sometimes used wooden limbs for battle or to ride a horse. And in the 16th century, the French surgeon Ambroise Paré designed some of the first purely functional prosthetics for soldiers coming off the battlefield. He also published the earliest written reference to prosthetics.

Then came the American Civil War in 1860. The record number of amputees from the war caused the number of patents for prosthetics to almost quadruple. One of these patents was for a wooden leg called the “Hanger limb.” It was the first to use rubber in the ankle and cushioning in the heel, showing that inventors understood they needed to make prosthetics less painful for amputees to wear.

 

 An artificial leg from the American Civil War.

Today, the U.S. Department of Veterans Affairs is a major provider of prosthetics and a leader in rehabilitation treatments for veterans who lose their limbs during their service. These patients are at risk for polytrauma, meaning they have injuries on multiple body parts, usually from blast-related events.

When this happens, these veterans need multifaceted clinical care and a support network. The Rehabilitation Medicine division at the NIH Clinical Center and the National Center for Medical Rehabilitation Research at the Eunice Kennedy Shriver National Institute of Child Health and Human Development help treat prosthetic users and conduct research about limb loss.

Improvements in design

While prosthetics were still made of combinations of wood, metal, glue, and leather even up to the 20th century, they were becoming more functional. From the late 15th century to the 19th century, France and Switzerland were making artificial limbs that could rotate and bend using cables, gears, cranks, and springs. However, these devices still needed to be adjusted manually. For example, an artificial hand could be cranked shut around a fork, but the person still needed another hand to operate the crank.

During the 1900s, manufacturers started to build more functional prosthetics by swapping wood and leather for plastics and other artificial materials. Still, some of the best prosthetics were out of reach for most people, including veterans. Many of these devices were only designed for specific tasks such as piano playing. They would not become more accessible to veterans until World War I, when prosthetic manufacturing for soldiers with limb loss increased in Great Britain. According to Jeffrey S. Reznick, Ph.D., Chief of the National Library of Medicine History of Medicine Division, such wartime manufacturing (and repair) sometimes occurred in military hospitals. Soldiers recovering in those facilities were fitted with artificial limbs as part of their care.

Today’s prosthetics look and work very differently from those made before the late 20th century. More lightweight and durable materials such as plastic, aluminum, titanium, and silicone are common in today’s prosthetic devices. They also fit closer to the user’s remaining limb. The Walter Reed National Military Medical Center will even tattoo service members’ prosthetics to help them look and feel more natural.

But what if a prosthetic could move without the user consciously controlling it? That is what the next generation of artificial limb technology aims to do.

 

 An example of a modern bionic prosthetic arm.

NIH-supported innovations in prosthetics

Scientists are developing robotics, 3D printing, artificial intelligence, virtual reality, and motion-sensing technologies for prosthetics. Over the last decade, NIH has funded several projects that harness the brain’s electrical activity to move prosthetic limbs using electrodes implanted in a person’s remaining muscles. These electrodes send signals to the brain and allow the prosthetic limbs to move more freely.

One example of research funded by the National Institute of Biomedical Imaging and Bioengineering is a robotic lower leg prosthesis that creates a more natural walking motion. Researchers at Vanderbilt University created the device with powered knee and ankle joints and with software that can anticipate how the user wants to move.

In addition to these technological advances, it’s also important to track how many people use prosthetics and what treatments work best for these patients. That’s why NIH, together with the U.S. Department of Defense and the Mayo Clinic, helped create the Limb Loss and Preservation Registry in 2020. This registry uses electronic health records to measure how many people in the United States have limb loss and understand the costs and treatment outcomes for these patients.

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