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Project 4 -- Development of Next-Generation Knee-Ankle-Foot-Orthosis Technology Project Staff |
Summary Knee-ankle-foot orthoses (KAFOs) for children can be greatly improved with technology that is available today. They can be made lighter, thinner, and more comfortable through the use of pre-impregnated composite materials, titanium hinges and better interface materials. These materials will be used in this project to fabricate KAFOs for children with myelomeningocele and other orthopedic disabilities such as cerebral palsy and spinal cord injury. New composite materials that can be postformed (see Project 5) and dynamic knee hinges currently under development will be incorporated into the KAFOs when they become available. Children will be fitted with prototype models throughout the project to test design features and foster communication between staff and users.
Progress Our First
KAFO systems used a posterior AFO with different Stiffness in plantar-flexion
and dorsi-flexion with ability to adjust length as the child grows. We
obtained and evaluated the Horton automatic knee-locking unit and found
several problems with the design, especially as it applies to children.
Then preliminary pediatric design appeared much too bulky and medicinally
complex for the pediatric population. We designed an actuation system
that with an adjustable amount of dorsiflexion or plantar flexion of the
food and weight shifting. The knee automatically locks in full stance
and posterior leaning motions, but releases with forward lean so the knee
automatically unlock to swing or go from standing to sitting. We maintain
our working relationship with Horton’s Orthotic Lab, Inc. to develop
a new dynamic-knee control system for a pediatric population. A prototype
of this system was built and fitted to a volunteer subject for evaluation
and verified to a volunteer subject for evaluation and verified the need
for a very low profile for evaluation and verified the need for a very
low profile knee joint. Prototypes continue to be lased on the previous
work using a composite, graphite strut (thermoset composite technology)
and posterior leaf AFO design(PLAFO). The previously developed titanium
posterior ankle joint is also used to give strength and lightweight. These
form a custom core to which metallic components as a modular system in
which minimal individual custom fitting is needed. The second
model developed evaluated the use of a low profile knee joint and breathable
supra-condular cuff. Thin, strong ankle joints used in AFO applications
where fitted medial-laterally at the knee. The key features evaluated
on this prototype are its adjustable length, short supra-condular cuff,
light weight(~1.25 lb.), low profile, and extension assist spring loaded
knee joint with adjustable extension stop. The cuff used the previous
designed ventilation system that used a double chamber with an external
solid shell and internal tissues containment membrane net. The new knee
mechanism is very compact, lightweight and strong. This eliminated the
bulky mechanism along both the lateral and medial sides of the knee on
the Horton system. This
year, we fabricated a brace with our actuation system and it was evaluated
on a patient during a long term test. The brace was worn daily for several
months. The actuation system was found to be robust though the patient
did not feel very stable with the stance control system. We also
preformed an analysis of the stiffness of the normal child’s knee
using gait data from children’s Hospital of Los Angeles. This analysis
revealed nonlinear spring like characteristics in the motion of the knee
during gait. We have developed some nonlinear spring that mimic this stiffness
and should allow a KAFO to better encourage normal gait. Additionally,
they should help reduce impact to the knee and hip joints, and provide
better energy return. Our latest
model is significantly improved and incorporates many lessons learned
in previous designs. This KAFO is completely posterior – it uses
a posterior nonlinear strut developed in Project 5, a posterior, low profile,
stance controlled locking knee joint unlocked via range of motion at the
ankle, knee springs, and a piston compensating thigh cuff. Several able-bodied
subjects have evaluated this brace. Improvements have been identified
in this brace and are currently being integrated.
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Publications Last modified: July 28, 2005 |
