DATA SOURCES: Several classic publications were consulted because of their overwhelming influence. The work of Merton L. Root and his colleagues in the 1970s was carefully examined. Careful evaluations were performed to determine how faithfully Root's central concepts were subsequently followed. Studies attempting to validate this and other orthotic paradigms were also reviewed.
RESULTS: Epidemiologic studies provide strong support for the clinical advantages of orthoses, yet explanations of foot orthotic mechanisms remain elusive. Considerable variability has crept into the literature with respect to Root's core theoretical concepts of how and why to determine the neutral position of the subtalar joint (weight-bearing vs non-weight-bearing, palpation vs range-checking). Numerous studies document poor clinical reliability and validity; indeed, this paradigm appears to favor supination, thereby violating its "neutral" premise. Mechanisms other than those of the classic Root theory must be at work. Accordingly, successes have been achieved with alternate paradigms that use much simpler casting techniques. Although less frequently cited, successes have been gained with various viscoelastic materials that enhance shock-absorption and proprioception, as well as custom-made flexible orthotic designs that emphasize the 3 natural arches of the foot.
CONCLUSIONS: The use of foot orthoses is well documented for the treatment of many maladies, yet clinical successes have been achieved both inside and outside of the classic Root paradigm. Clearly, a more complete theoretical understanding of the mechanisms of foot orthotics awaits discovery.
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