I’ve recently been preparing some teaching material for a one day course on observational gait analysis which we are running this Friday. I got to the part where I normally introduce the concept of primary, secondary and tertiary abnormalities of gait. As outlined by Jim Gage (The Identification and Treatment of Gait Problems in Cerebral Palsy, 2009),   primary effects are those regarded as a the direct effects of the original brain injury. He gives loss of selective motor control, balance impairments and abnormal muscle tone as example. Secondary effects are those that are not part of the original brain injury but develop as a consequence of it. Bony torsional malalignment and muscular contractures might be seen as examples. Finally tertiary effects are those resulting from an individual’s efforts to compensate for the consequences of the injury. Vaulting, circumduction and hyperflexion of the hip are all cited as examples of compensations for a foot drop which may be a consequence of weakness of the dorsiflexors or tightness in the plantarflexors.

Although the term effects is used when first introducing these concepts the subsequent sections are headed primary gait abnormalities and secondary gait abnormalities. The terms effects and abnormalities appear to be used interchangeably in this context.

I was struggling to incorporate this into the approach that I’ve called impairment focussed interpretation. This assumes that the aim of clinical gait analysis is to identify the impairments that are most likely to be affecting the patient’s ability to walk by linking them to observed features in the gait data. This follows the WHO definition of an impairment as “a problem in body structures or functions such as significant deviation or loss” (WHO, International classification of functioning, disability and health. 2001) and my own definition of a feature as something of clinical relevance that you can see on a gait graph (or on a video).

How I wondered do my impairments and features relate to Gage’s primary, secondary and tertiary effects or abnormalities?

I’ve come to the conclusion that Gage’s primary and secondary effects are generally impairments (as the WHO has defined them). They are things that are wrong with the underlying body structures and functions and are not necessarily related to gait. His tertiary effects, by contrast, are generally features.  They are changes to the way a person walks.

It also occurs to me that the primary, secondary, tertiary terminology implies a progression from one to the next in sequence. It doesn’t take too long, however, to realise that some tertiary compensations are a direct result of a primary impairment without the requirement for a secondary intermediary.  Thus vaulting might be a direct consequence of plantarflexor spasticity, a primary impairment.

To tidy things up therefore it makes sense to me to preserve the terms primary and secondary but restrict these to impairments, and to drop the term tertiary in favour of compensation whilst restricting its use to the description gait features. The question that is now puzzling me though is, what is the best name for a feature that is the opposite of a compensation? If a compensation is an alteration to of the gait pattern in response to an impairment which makes walking easier, what do you call the an alteration to the gait pattern which is a consequence of an impairment that makes walking more difficult?

Do feel free to leave your answers as comments to this post.