AFO Mechanics

Composite material advances over the past 10 years have improved the design creativity and possibility for clinical orthotists worldwide. In the past, an ankle orthosis required a completely solid and fully encompassing design in order to attain the mechanical control, durability and ultimately the function needed for corrective ankle varus bracing. These devices were essentially plastic shells that created a solid/static environment which was safer than not using a brace at all, but they were also highly problematic with patients complaining of pressure points and a clunky gait. Today we can simulate more natural gait patterns while completely avoiding pressure points.

Controlling the Tri-Planar Deformities

Custom ValgaNoodle AFO with Pre-Tibial Shell – Model: NPV

Kinetic Research offers a variety of ankle braces, each with its own character and effect to meet the needs of the user, from the most basic needs to the most complex. For folks that have foot/ankle weakness but have good alignment of their ankle, we offer the Noodle line of AFOs. These are the most dynamic and least restrictive designs for controlling drop foot. When the user has a tight heel cord with mild supination or ankle varus, they become a candidate for a PLS design. When the user has more significant ankle varus he/she becomes a candidate for the ValgaNoodle AFO. The ValgaNoodle offers the highest degree of lateral control that we can provide. It’s important to have a team approach when choosing the type of AFO that will work best for your individual needs, and there is always a trade off between control and mobility. The team is made up of the patient, the orthotist and the physician/therapist, and all have to be involved for the best results. The objective is to “put on as little as possible, but get the job done”.

Improving Stability During Gait

The ValgaNoodle is made specifically for varus control. It’s a highly custom AFO, meaning. That it is not assembled using pre-made components. The creation of a ValgaNoodle begins with a highly skilled orthotist who will evaluate and cast for the device. That attending orthotist will manipulate and control the patient’s foot while he is casting, keeping the ankle in the best position possible to maximize the effect of the finished ValgaNoodle. Evaluations and observations made by the clinical orthotist are then incorporated into a design formulation that will work best for the individual patient. The design details are then determined based on the level of control vs free movement that is needed to maximize the performance of the user. One of the objectives is to keep the ValgaNoodle lightweight and as simple to use as possible. The orthotist will select the device based on the severity of the case, as well as the users lifestyle, activities and footwear.

Fitting the Device

The one common mechanical concept for the ValgaNoodle variations of AFOs is, that they will all have a single medial strut with a floating lateral “reverse T” cuff.

Design options for the footplate:

1. Flat, in which we match the bottom of the shoe. When we make it in this format, it will usually have a custom foam removable arch support. It offers the least control but because it’s flat, we can make it flexible.
2. Contoured. This is similar to a UCBL footplate. Our technicians will adjust the cast taken by your orthotist to increase lateral control in a compact way for easy shoe selection.
3. Contoured with high control. This system goes higher than the UCBL, encompassing the dorsum of the foot, and has a special 3-point strapping system to provide maximum control.

Design options for the strut:

1. Solid ankle, the highest level of control, removing the user’s ability to dorsi/plantar flex.
2. Dynamic, which allows dorsi/plantar flexion, but with reduced lateral control.

Design options for the cuff:

1. Posterior, for a normal or hyperextended knee.
2. Anterior, generally used for knee extension weakness. Easier to don, but limited to low top shoes.

Case Study:

David B. Misener, BSc, CPO, MBA
Clinician: Clinical Prosthetics & Orthotics

Introduction

ValgaNoodle AFO

Many times I meet individuals with CMT who have had a long history of bracing in the past. They typically come with many positives and negative reviews of each and every device, and spending time reviewing these devices will help establish a successful plan for the new device. Completing a thorough evaluation will also include assessment of muscle strength, range of motion, balance and coordination, walking speeds, calluses, footwear, activities of daily living, goals, wants/needs, assistive devices used, etc. Typically gathering any kind of subjective and objective information may help in your decision-making process. The following is a case study describing the outcome of a Kinetic Research ankle foot orthosis.

Patient Profile

Patient is a 59-year-old male with the diagnosis of Charcot Marie Tooth 1a. He comes from a family with a long history of extremely prevalent CMT. He is aware of his parent, siblings, children, nieces and nephews with CMT. He began wearing bilateral simple plastic posterior leaf spring AFOs in his mid 40s and then moved to off-the-shelf Allard AFOs in his early 50s. He’s aware of the strengths and weaknesses of his body and doesn’t let the CMT interfere with his activities of daily living. He has had multiple Allard Toe-off AFOs which seemed to break after 4 to 6 months of his activities. He then progressed to the stronger Blue Rocker AFOs because of early breakage of the Toe-off AFOs and because he maintained a fairly high activity level. He was able to extend the life of the Blue Rocker AFOs but these also fractured in the 12-16 month time frame. His range of motion is within normal limits at all joints. He is able to dorsiflex to neutral but cannot dorsiflex beyond neutral at a strength of grade 2.   His plantar flexors are a grade 3. He does not use any other assistive device for ambulation. As previously stated he is busy doing activities of daily living and often walks miles at a time along with hiking on the weekends.

He requests a smaller lower profile design along with some of the biomechanical advantages of the Allard systems.   He is also hopeful that he can have a device that may be more durable and continue to facilitate his activities of daily living.

AFO design

Custom ValgaNoodle AFO with Rigid Anterior Tibial Section

Given his overall successful history with off-the-shelf carbon AFOs it was decided that custom carbon AFOs that would maintain dynamic motion and energy return would be an excellent approach to offer him support while not restricting any portion of his activities of daily living. Together we selected the custom Kinetic Research Noodle anterior panel design. Kinetic Research also has many designs to choose from. In this case the approach was to maintain the anterior panel that he was proprioceptively used to and also to custom build a stronger material layup to reduce the likelihood of early failure. Once again there would be a soft removable foot orthosis to neutralize the pathomechanics of his foot. There would only be one strap across the posterior aspect of his calf to secure the device to his limb. He would rely on good footwear to stabilize the device around his foot and ankle.

Results and Discussion

When he first observed the devices he was pleased to see a smaller, lower profile design as compared to his traditional systems. Often this aspect of bracing design isn’t emphasized as much as it could be but for the end user it is often very significant. He was pleased to see the smaller anterior panel and was also quite hopeful it would have the dynamic and energy storing properties to which he had

The Andry Tree Illustration

become accustomed. While standing he was able to flex the systems significantly yet maintain control, balance and stability. With most CMT individuals I have observed it takes many steps and, for some, weeks before they can truly give accurate feedback on a new device. While ambulating he could feel the energy return in the devices and felt that these devices offered as much as he was used to. The custom removable foot orthoses were adjusted with mild lateral posting to fully stabilize his foot from heel strike to toe-off.

One of the main goals was to extend the life of a device, something that could only be assessed with the passage of time. At his initial fitting the devices seemed to be successful and he will return for multiple follow-up sessions within the next few months. At our first follow up session he reported that he transitioned into the new Kinetic Research AFOs without problems. He felt that energy return is on par with his previous systems and the smaller anterior panel felt more open and comfortable. He continued with his high functioning level of activities of daily living. At his one year follow-up there were only simple adjustments that were completed to return the device to its original design. This device still has held strong after three years of use and has allowed the recipient to continue with his goals and activities of daily living.