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Vol. LIX, No. 12
June 15, 2007

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'Do Tread on Me'
Unique Floor Aids Mobility Research, Rehab

On the front page...

The same technology that lets you wield Tiger Woods's golf swing in a video game is what researchers are using to address mobility problems at the Clinical Center. Take homegrown software, several infrared cameras and a one-of-a-kind floor, and suddenly an individual's strides come alive on computer screen.

"We can measure how much joints can move and how strong muscles are," said Karen Siegel, a physical therapist in the Physical Disabilities Branch, a collaboration between the CC and the National Institute of Child Health and Human Development. "The forces we can measure tell how a person controls his or her movements. We can sometimes give patients-and their doctors and physical therapists-additional information to help with decisions about treatments."


  Physical therapist Karen Siegel shows lab components.  
  Physical therapist Karen Siegel shows lab components.  
Consider a woman in her 50s who underwent partial amputation of her foot due to cancer. "Doctors had amputated the three toes on the outside of her foot, and the long bones in her foot that the toes are attached to," Siegel recalled. "The part of her foot that remained was her heel and a very narrow forefoot that was only a few inches wide. She tended to roll off the outside of her residual foot and it was very difficult for her to transfer weight to the front part of her foot for push-off when she walked."

The woman was fitted with a foot orthotic/insole, a filler for the inside of her shoe to compensate for the missing foot and some modifications to the outside of her shoe to improve her gait, but "still walked with a noticeable limp. The limp was giving her hip and back pain," Siegel said.

'May the Force[s] Be With You'

Several years after the initial surgery, the woman returned to NIH for a follow-up visit. Her physical therapist referred her to PDB for a gait study. "I traced the outline of her bare foot, her foot in the orthotic and her shoe onto a piece of paper and then marked where we put the targets on her foot for the study," Siegel explained. "We used the force platforms [three-dimensional scales that are part of the floor] with information from the cameras to track how she transferred her weight through her foot while she walked. We discovered that she kept her weight on her heel the whole time. She never transferred her weight forward and never used the modifications the orthotist had made to her insole or her shoe to assist her."

At left, Karen Siegel applies reflective targets to a research volunteer      Cameras track motion of the targets in 3-dimensional space. The projected image on the wall shows what Siegel sees on her desktop monitor. Custom software measures movement of the targets.
At left, Karen Siegel applies reflective targets to a research volunteer     Cameras track motion of the targets in 3-dimensional space. The projected image on the wall shows what Siegel sees on her desktop monitor. Custom software measures movement of the targets.

Siegel and the woman's physical therapist used the information from the study to design a new sole for the patient's shoe with a special curve on the bottom. Siegel said when the woman put the shoe on for the first time and walked down the hall, "she said 'This is the most natural my walking has felt in 5 years!' When she came back for her next follow- up visit several months later, she reported that her hip and back pain also had decreased because her walking was more symmetrical. This is a case of where the forces were the most important part of the story. [They] also had a big clinical impact on the patient."

A recycling box marks the level flood water reached.  
Ceiling tile debris lies atop a work station.
Siegel shows how easy it is to move the force platforms to accommodate different patients. She uses suction-equipped handles to grip the panels.  

Walking problems are common in people with such disorders as dystonia, which causes involuntary muscle contractions; osteogenesis imperfecta, in which bones break easily for no apparent reason; and myositis, which causes muscle weakness. Other people, as in the case Siegel described, need rehabilitation from amputation or recommendations for prostheses. With its high-tech Clinical Movement Analysis Laboratory, PDB helps with all of these.

Don't Try This at Home

"The floor is state-of-the-art," Siegel said. "There's no other floor like this one." If you put the same equipment in an average room with regular flooring and tried similar gait tests, she explained, "it would be like putting your bathroom scale on a trampoline and trying to measure your body weight."

Although you don't notice, regular floors have too much vibration to get accurate measurements. Before constructing the new lab, "CRC architects talked to vibrational engineers," Siegel said. The floor was built on footings separate from the rest of the building. Its foundation was poured 6 feet thick, using special concrete that dampens vibrations. Resin was used to level the floor completely flat, followed by installation of stainless steel sheets. "The combination of construction and our ability to move the floor plates in different configurations as needed make this pretty unique," she said.

Besides the custom-built hardware, specialized software called Visual3d-designed by veteran NIH computer engineer Tom Kepple of PDB-helps capture movement data that are translated into the videos researchers use to analyze and diagnose gait problems.

  A recycling box marks the level flood water reached.
  Early stages of CRC construction. The large hole with the railing around it eventually became the floor of the laboratory. Separate footings and floor were built so vibrations in the rest of the building could not be transmitted to the lab floor and create errors in the force measurements. What is now known as the "pit" shown in the photo below is located within the center of this hole.
A lab view of all of the tiles that now fill in the pit.
  A lab view of all of the tiles that now fill in the pit.

"The software originally started as a program that I wrote for the [NIH] biomechanics lab called Move3d," Kepple said. "Move3d was used to compute the kinematics-positions, velocities, acceleration-of anatomical segments and joints as well as compute the net muscular forces and torques that produce the motions."

Move3d was first distributed around the world as freeware, he continued, and "at the height of its popularity it was the second-most-used movement analysis software."

In 1997, amid constant demand to support and upgrade the software, a technology transfer grant was arranged with Rockville-based C-Motion, Inc. For 4 years, Kepple worked with C-Motion to turn Move3d commercial. In mid- 2001, the resulting product-Visual3d-was released. Since then Visual3d has generated between $2 million and $3 million in revenue worldwide.

Putting 'Fun' in Functional

These were extremely rewarding results, considering Kepple virtually taught himself software design and was really just dabbling when he wrote the original program. "Fortuitous avocation is a good description of my time spent designing software," he admitted. "Although I enjoy programming, I enjoy the engineering and computer modeling aspects of my job more."

Kepple, Siegel and their branch chief Dr. Steven Stanhope all have published papers about their work. "I have used Visual3d to look at foot and ankle motion in normal subjects, analyze the contribution of various muscle groups to support forward progression in gait, test a variety of musculoskeletal models and generate computer simulations of walking," Kepple said, describing the lab studies that not only help put the spring back in many patients' step, but also provide extra enjoyment for researchers.

Ceiling tile debris lies atop a work station.
Siegel chats with patient testing the floor.  

Recent example: One of the lab's projects involves not golf, but another athletic pursuit. Although NIH does not usually study sports movement, PDB is examining one aspect of America's favorite pastime-the baseball pitch. "We saw it as a chance to further refine our analysis technique," Siegel said. "We looked at how each muscle in the body-not just arm, hand and shoulder muscles, but also leg and torso muscles-contributes to the ball's velocity."

Explaining that the project moves their research beyond the lower body, Kepple concluded, "The baseball pitch study is designed to expand and test our models on upper extremity tasks, but is turning out to be a fun little bit of work." NIH Record Icon

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