What exactly is a dynamic AFO?

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.