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What do we know about sagittal plane stiffness of AFOs?

Following the recent publication of the paper “Comparison of Sagittal Plane Stiffness of Nonarticulated Pediatric Ankle-Foot Orthoses Designed to be Rigid” by Fatone et al I wanted to share a summary of what the article tells us.

As clinicians prescribing orthoses, the stiffness is vitally important for our prescriptions to achieve their goals. Understanding what we are trying to control allows us to choose materials that will exert an external force onto a person and influence a particular movement pattern.

Link to paper

When prescribing orthoses what do we take into consideration before we can think about material stiffness?

Diagnosis, age, weight, range of motion, muscle tone and what we want the orthosis to do. The materials available to us have evolved over time from traditional leather or metal orthoses to homo and copolymers, silicone, dynamic elastomeric fabrics, carbon composites and now nylons because we can 3D print.

The take home points from the paper are;

  • All AFOs will deform to some extent under sufficient load

  • Rigid AFOs are designed to resist peak plantarflexion and dorsiflexion loads