February 2013

Out on a limb: Forces of habit

Jordana-twitterJordana Bieze Foster, Editor

One of the best things about visiting Negril, Jamaica, is taking a yoga class from Fanette Johnson. And one of the first things Fanette will do in class is have you sit cross-legged on your mat, then have you re-cross your legs in the manner that feels less natural. Later in the class, she’ll have you intertwine your fingers, then re-intertwine them so the opposite thumb is on top.

It’s a theme. The position that comes naturally, Fanette says, is a “body habit.” And body habits, left unchecked for years and years in most people, can leave a body unbalanced.

That’s probably not news to lower extremity practitioners, who regularly face the challenge of reconciling the need for a certain degree of symmetry in gait with the fact that a limb is almost never an exact replica of its contralateral counterpart and, in some cases, the two are very different.

Some of the most extreme cases involve patients with hemiplegia, although they might argue that a body habit is less habit than necessity when half your muscles simply don’t function properly. Nevertheless, practitioners who treat these patients are all too familiar with the unique kinematic and kinetic patterns that develop over time when one limb is favored over another. And although most of the focus to date has been on how those body habits affect the hemiplegic limb, researchers and practitioners increasingly are also becoming aware of how the so-called uninvolved limb is actually very much involved (see “Hemiplegic CP: Effects in the uninvolved limb”).

When practitioners are aware of such imbalances, interventions can be designed to treat not just the favored limb but also the limb that has been forced to compensate. But in other cases, an intervention that by necessity affects one limb and not the other can also lead to unwanted body habits in patients whose gait was relatively symmetrical to begin with.

Researchers have found, for example, that the imbalances in limb length and weight associated with wearing an instant total contact cast can adversely affect balance even in healthy individuals (see “Off balance”). Similarly, researchers have found that wearing a walking boot on one limb significantly increases calcaneal peak pressures in the contralateral foot.

Correcting the body habits associated with these interventions requires yet another set of interventions. The iTCC study found that adding a heel lift to the contralateral foot helped improve balance statically, although further tweaks may be needed to achieve significant changes dynamically. And the walking boot study found that pairing the walking boot with either a modified boot or an athletic shoe—both of which addressed the leg-length discrepancy—significantly lowered calcaneal peak pressures in the uninvolved foot (see “Pair walking boot with athletic shoe to decrease contralateral pressures”).

Of course, it’s also possible that the second set of interventions could lead to yet another set of compensations, which could require yet another set of interventions. One could spend a lifetime unlearning body habits.

Fanette would call that time well spent.

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