New stance-control device may increase mobility

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January 2007

Biomechanics Magazine

http://www.biomech.com/showArticle.jhtml?articleID=196900348

New stance-control device may increase mobility

By: Lori Rochelle Roniger

A new stance-control knee ankle foot orthosis (SCKAFO) allows users

to walk with more natural gait kinematics than their regular knee

ankle foot orthoses do, according to a preliminary study published

in Clinical Biomechanics in December.

The new SCKAFO was designed and the study performed by researchers

at the University of Ottawa, the Ottawa Hospital Rehabilitation

Centre, and the University of Waterloo, all in Ontario.

Although older SCKAFO designs can also improve mobility and gait

kinematics, they may have drawbacks, such as a limited number of

locking positions or requiring full knee extension to engage the

knee-joint lock. Or they may be noisy, heavy, bulky, or expensive,

according to the study's researchers. They developed the new device

to address these problems. It allows free rotation in swing,

stability in stance at any knee or ankle angle, and knee extension

at any time.

The new SCKAFO, the development of which was discussed in detail in

a study published in IEEE Transactions on Neural Systems and

Rehabilitation Engineering in September, is 30% thinner and 25%

lighter than commercially available SCKAFOs, its developers said. It

is designed with a friction-based belt-clamping mechanism that

resists knee flexion when clamped.

" Unlike some commercial SCKAFOs, the new SCKAFO knee joint resists

knee flexion at any knee angle in stance, permitting a greater level

of support, " said Terris Yakimovich, MME, a project engineer at the

Institute for Rehabilitation Research and Development at the Ottawa

Hospital Rehabilitation Centre and the study's primary author.

The SCKAFO's knee flexion resistance may help users perform

activities that place relatively heavy loads on the limb, such as

descending stairs or a ramp.

The researchers studied the kinematic gait analyses of three male

KAFO users. Subjects ranged in age from 52 to 60 and had knee

extensor weakness in at least one limb.

They were each fit with a customized version of the new SCKAFO by a

certified orthotist and orthotic technician and practiced walking in

it for approximately 20 minutes. Three trials were then conducted

during which they walked down an 8-m walkway at a natural pace. Each

subject participated in another three trials while wearing his

regular KAFO.

All three subjects increased their knee flexion while walking with

the SCKAFO compared with their regular KAFOs, the researchers

reported, and the mean knee range of motion increased for the group.

However, the 32 degrees average range of knee motion for the SCKAFO

was lower than the range reported in studies of other SCKAFOs. All

subjects had difficulty providing the brief extension moment

required to unlock the knee joint, though this ability increased

during the laboratory session. Two of the three subjects said they

preferred the new SCKAFO to their regular KAFOs after the session.

Mean walking speed was 32% slower with the SCKAFO than with the

KAFOs, which may have been because wearing the SCKAFO required more

concentration. This may also have caused stride length to be

shorter, stride time longer, and walking pace slower than when

wearing the regular KAFOs, the researchers reported.

Using of the SCKAFO affected hip and pelvis motion. Hip abduction

decreased in one subject and another had an improved pelvic

obliquity pattern, but the changes were not uniform between

subjects. The researchers said this area required further study with

more subjects.

The SCKAFO has undergone some redesign since the study was

conducted. Yakimovich said that a clinical study with more subjects,

bilateral gait analysis, and a longer accommodation period is

planned.

" Our intent is to commercialize the technology with an industrial

partner, " he said.