Patient Getting Fit for an ExoSym Product

Often Orthotists receive referrals stating ‘for dynamic AFO please’, or in passing conversations with AHP’s for a more dynamic AFO. Often it can feel like little more than a buzzword in the industries marketing and often we see it being confused with a DAFO. I think though crucially we need to be more specific with our use of the term with regards to note keeping and referrals, in order to prevent confusion and also extend upon the definition to make sense of what we are prescribing. In an ever changing material science age I think it’s now more than ever that we need to define this term.  We will stay clear of the rationale and benefits of these types of AFO’s in this blog, but just concentrate first on the term.

So let’s look at the standard dictionary definition of the word:

1  – (of a process or system) characterized by constant change, activity, or progress.

2 – Physics Relating to forces producing motion. Often contrasted with static

Synonyms:

Energetic, spirited, active, lively, zestful, vital, vigorous, strong, forceful, powerful, potent, positive, effective, effectual, high-powered, aggressive, driving, pushing, bold, enterprising.

Not particularly helpful? Still no clearer? Me neither, but those words above you will see filter into our text below. Let us first tackle the most obvious confusion, the term DAFO (Dynamic Ankle Foot Orthosis). What we have here is simply a Supra Malleolar ankle foot orthosis developed in 1985 as a collaboration between Don Buethorn, CPO and Nancy M. Hylton, PT. This thin, flexible brace initially for paediatric patients with neurodevelopment challenges was created by the Cascade DAFO Company. Now at the time the definition worked, as largely all other orthosis where rigid typical AFO types and the trim line of the DAFO allowed an increased range of motion whilst providing minimal support; somewhat more ‘dynamic’ than the rigid (static) AFO’s of the time. However in 2018 the dynamic AFO is not constrained to a Supra Malleolar trim line. Therefore I would suggest we refer to this style of brace as to what it actually is, a SMO (Supra Malleolar Orthosis).

I think we can all agree that we can adopt the rationale that Dynamic AFO means non static / fixed motion at the ankle, with availability or assistance of a degree of tibial inclination or reclination, +/- energy return at terminal stance, mimicking as close to a normal gait as possible. In an attempt to be more accurate and prescriptive to prevent confusion of the above I think we need to sub divide dynamic AFO into two categories, but we have those AFO’s that I feel crossover into both categories.

1.Passive Dynamic AFO

This first category can be a simple foot up type, flexible PLS, passive single axis ankle joint, composite semi rigid single strut to footplate style AFO’s, of which we have many different designs and stiffness OTS and custom.  The ability to 3D print now also opens up huge possibilities to introduce strength and flexibility where we need it.

More recently the use of pre tensioned rods like the Dynamic Walk from Denovo, and recent explosions of posterior strut and peak rod components allows a modular manufacture. The Otto Bock ankle 7 type struts, Blatchford Momentum / Hanger ExoSym style braces, which can dial in tibial advancement ROM and a degree of energy return spring to mind; it is these braces that it seems bridge the gap between passive and active dynamic categories due to the loading and release of an active assist to dorsiflexion, or simulated terminal stance plantar flexor response.

2. Active Dynamic AFO

This second category has a more assistive quality to the brace, rather than reliability on material properties and trim lines to initiate an effect.  We have a mechanical assistance. This could be simple dorsiflexion assist ankle joints, those which allow ankle ROM like the Step-On, to more advanced systems like the Fior and Gentz Neuro Swing, and Otto Bock Nexgear Tango, with increased adjustability of exact assistance and ROM control. It is these braces in this category which are most exciting, as individual adjustments can be made to the clients brace throughout rehabilitation and this is truly dynamic in every sense of the word; in its form, fit, and function.

So firstly when we write our notes we can be more specific, for example we could write ‘free motion, active, articulating AFO’, or ‘passive composite stiff footplate’. They are both dynamic, but completely different and secondly when we have a referral for a dynamic AFO, we should question and delve further into the referrer to be more specific to the biomechanical deficit and biomechanical goal, so we can have a better understanding of the dynamic requirement. It truly is a fantastic time to be an Orthotist.

What does Dynamic AFO mean to you in your clinical practise? Let’s try and debunk the term so we all have a standard abbreviation for our industry.

“We can rebuild him. We have the technology. We can make him better than he was. Better, stronger, faster.”

If you’re old enough to remember the above quote from the 1974 six million dollar man (currently 30 million with inflation) it was pure sci-fi that we could rebuild and restore limbs with identical biomechanical function.  It seems prosthetics are leaps ahead of orthotics in terms of R & D, with progress made year on year and technology filtering down to clinicians. I would suggest watching the several TED talks from amputee and MIT professor Hugh Herr on his neuro embodied design principals – prosthetics are closing in on replicating normal spatiotemporal parameters and ankle joint kinematics / kinetics, alongside proprioceptive integration.

Depending on the patient’s pathological gait, the Orthotists goal is to align the orthosis to provide the required lever effect whilst resisting / assisting motion where required, often with a reliance of ground reaction forces to assist in correction of the phases of gait.

Where it becomes challenging for the Orthotist is that it has become difficult to produce a perfectly effective orthosis due to the lack of adjustment options, and limitations of materials; although 3D printing does open up some interesting options. Do we get close? Yes. Do we mimic perfectly normal pathological gait? No, and how could we? We rely on tuning in conjunction with further modifications to footwear in order to try and optimise as close to the pathological gait as possible.  Somewhere a compromise is made.

Since all current AFO treatment options have their pros and cons. Almost all current AFOs limit plantar flexion and make it difficult to achieve the best possible compromise of dorsiflexion assist effect if available, energy storage for push off, and heel strike loading response.

In theory if we can match the spatiotemporal parameters and ankle joint kinematics / kinetics, then the correct cerebral connections are established through motor impulses and in some cases we have the potential for single muscle groups to be strengthened resulting in gait that is much closer to a physiological one.

With an adjustable ankle joint it can constantly be adapted to the patient’s rehab. The ability to lock / unlock, control dorsiflexion and plantarflexion ROM, and regulate dorsiflexion vs plantar flexion assistance has to be the future for articulating AFO’s. Currently Fior & Gentz are leading this methodology and technology with good results from Neuro swing.

Do we have evidence favouring the adjustable articulating AFO’s over non-articulating? It certainly seems strong, but still very limited; I would suggest reading articles by Yamamoto, Singer, Kobayashi, Kerkum, and Shabbagh.

What are your thoughts on this developing technology? Has anyone had any experience of actual objective data with regard to adjustable articulating AFO’s? As Orthotists we are largely under resourced in clinic and have to rely largely on subjective data, so any comments on this topic would be welcome.