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Advances in KAFOs 

Greg Bauer


A KAFO is an orthosis, or brace, that encompasses both the knee and ankle joints.  The term KAFO is an acronym for Knee-Ankle-Foot Orthosis.  Many polio survivors or anyone who experiences unilateral leg paralysis or quad weakness/absence may use a weight bearing KAFO for walking and standing.  In recent years there have been drastic advances in the design and function of this type of brace, enabling users to achieve a more natural gait pattern without sacrificing safety.

 

Until fairly recently, KAFOs presumably included manual locking knee joints, each joint located at the side of the user’s knee.  When the knee joint was in ‘locked’ mode, the user could stand securely or walk stiff-legged.  For sitting, the user could manually ‘unlock’ the joint and bend the knee. 

 

The prosthetic industry is ripe with ‘automatic’ technology.  Most prosthetic knee joints automatically switch from locked to unlocked positions.  Finally, the orthotic industry has followed the lead and there are now a number of KAFO knee designs that lock and unlock automatically. 

 

One type of lock that provides higher function is a swing phase lock, which can be obtained through Fillauer, Inc.    

 

This lock joint uses friction to regulate knee flexion during swing phase, when the knee is unlocked.  The knee joint automatically locks at heel strike and releases to swing at toe-off.  How does this translate to a more natural gait?  During the gait cycle, whenever the foot is not planted securely on the ground, the knee joints bend.   

 

Without this knee bending action, the user must either swing the stiff leg out and around (circumduction) or the user must vault on the sound limb to make enough clearance for the stiff leg.  This type of joint mimics a normal gait pattern while also providing increased security at crucial times during the gait cycle.    

 

Indications:

 

·          Isolated quadricep weakness/absence

·          Unilateral leg paralysis

 

Contraindications:

 

·          Overweight individuals

·          People with impaired cognition, severe balance issues, or lack of motivation

·          Presentation of a knee flexion contracture of more than 10 degrees

·          Uncorrectable genu varum / valgum of more than 10 degrees

·          Biological knee joint of more than 5 degrees off line of progression in swing phase

 

Another impressive development is the incorporation of microprocessor technology for the KAFO design.  Otto Bock and the Mayo Clinic teamed up to create an electronic stance control KAFO, called the Sensor Walk.  Sensors in the footplate know when the user is in late stance phase and the knee automatically unlocks into a controlled swing.  Full extension of the knee at toe-off is not required for the knee to unlock.  The knee begins to bend in late stance phase and provides an extremely natural movement.  This device also includes a ‘stumble’ recovery feature, where the microprocessor can sense when the user is unstable and the knee will block flexion. 

 

Indications:

 

·          Isolated quadriceps weakness/absence

·          Step length over level ground should exceed the length of the opposing foot. 

 

Contraindications

 

·          Body weight over 300 lbs. 

·          Extremely weak strength of torso/pelvis & inability to move device forward during ambulation

·          Hip flexor strength lower than Grade 3

 

Again, because the knee is allowed to bend during swing phase and late stance phase, this allows for a more fluid gait and reduces deviations, such as circumduction and vaulting. 



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