Our approach combines hands-on evaluation, prototyping, and clinical evaluation, prototyping, and clinical evaluation at all stages of development, combined with a rigorous quantitative development process.

In phase one, we developed an experimental brace that allowed the adjustment of several geometrical parameters such as length of the proximal trim-line (orthosis height) and separate controls of the stiffness in plantarflexion and dorsiflexion.

We have tested major characteristics of the experimental AFO (including non-functional ones such as confort and the capability to interface with gait lab equipment) with an adult able bodied person and a stroke patient.

The effect of eleven brace settings on eight gait parameters revealed that none of the brace settings met all the biomechanical criteria.

Positive results are:

1. Velocity as a percent of normal generally increased.
2. Knee extension moments were increased.
3. Ankle power generally increased.
4. Knee velocity generally increases.
5. Ankle power absorption improved with post spring at the 0 deg and 5 deg conditions.

1. Dorsiflexion angles were unchanged or decreased.
2. Knee moments in terminals stance were generally unchanged.
3. Knee power absorption was generally unchanged.

The negative results of applying the modified braces were:

1. Knee moments in loading were generally increased.
2. Knee moment in terminal stance was badly affected when using a posterior spring and a dorsiflexion stop of -5 deg.

To meet these criteria, we developed a prototype, dorsiflexion-stop, posterior AFO with a leaf spring actuated dorsiflexion assist.

This brace was evaluated by one myelomeningocele patient and it was detemined that the dorsifexion assist needed to be adjustable, stiffer, and more robust. A second prototype brace was designed with the leaf spring replaced by a double coil compression spring. This spring system was adjusted and stiffer,but it was determined that it still needed improvements in robustness.

During phase one, we also performed several quantitative analyses – we determined the anthropometrics of a baseline patient, the definition of normal gait, the stiffness of the normal foot at each point the gait cycle, the load applied to the brace during gait, and quantative metrics that the brace should meet when completed.

One of the most important of these was the stiffness of the normal foot at each point in the gait cycle. We determined this stiffness by analyzing the gait data from children’s Hospital of Los Angeles’s database of normal patients. From this data, we were able to derive a nonlinear expression describing the optimal brace stiffness for any child. We then developed a non-linear spring to duplicate this stiffness.

In summary, phase one achieved a rigorous, qualitative and quantitative definition of what the brace needs to do.

We currently are in phase two, the mechanical design of the AFO. In this phase, we brainstorming and evaluating many different designs options for fulfilling the requirements defined in the metrics. We have developed a spreadsheet based stress analysis system to assist in this progress. It allows quick evaluation of the geometrical sizing, material selection, and product feasibility. Many innovative ideas have been generated and rough prototypes fabricated.

One particularly promising brace using our nonlinear spring was evaluated by a patient. The patient liked the stiffness response though improvements need to be made in its manufacturability.

In the upcoming phase, we will be selecting the best brace concepts, performing detailed analyses of them, mechanically testing them, and performing a complete clinical study of their effectiveness.

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