Keys To The Biomechanical Evaluation Of The Symptomatic Adult-Acquired Flatfoot

Douglas Richie, DPM, FACFAS, FAAPSM

   Most updated variations focus on subdivisions of Stage II deformity.8-10 The biggest challenge for clinical decision making is with Stage II deformity. Stage II can have various levels of deformity, depending on the extent of ligament attenuation and stability of the medial column. Although initial treatment is almost always non-operative, the choice of modalities varies significantly depending on the level of deformity. The table “A Guide To The Updated Staging System For Adult-Acquired Flatfoot” below outlines the newer classification system along with key clinical exam features and also proposes certain treatment options that are relevant to each stage.9,10

   In Stage I deformity, treatment focuses on treating the tenosynovitis. The fact that the posterior tibial tendon is still functioning in Stage I and there is no evidence of ligament attenuation means most of these patients can get successful treatment with short-term immobilization followed by long-term stabilization with custom functional foot orthotic therapy.11

   In Stage II, the loss of ligament stabilization of the hindfoot causes a disruption of coupling or a lack of movement transfer between the foot and the leg. Foot orthoses are usually ineffective in this situation. Functional bracing with ankle foot orthoses has shown impressive results in resolving the symptoms of Stage II flatfoot and avoiding the need for surgery.12-16

   In Stage III and IV flatfoot, functional bracing with more rigid devices is recommended but the results are not as positive as those for Stage II deformity.17 Surgery may be a better option for patients with Stage III or Stage IV flatfoot, but often other medical issues facing this patient population can increase complications and delay healing. In any case, the clinician must be able to evaluate the specific biomechanical findings carefully in each patient to choose the appropriate combination of surgical procedures to correct the deformity and restore mobility.

   The following steps are recommended in the biomechanical exam of the patient presenting with a symptomatic flatfoot deformity. Since most cases of symptomatic adult-acquired flatfoot begin in one foot only, comparison to the asymptomatic side can be very helpful in measuring the progression of the deformity.

What A Comprehensive Gait Analysis Can Reveal

I suggest that the examination of the patient with symptoms of adult-acquired flatfoot begin with an evaluation of barefoot gait. Very quickly, the practitioner will learn the severity of the deformity and its symptoms. If the patient walks with a noticeable limp from significant pain, one may need to postpone the remainder of the biomechanical exam. Many of the clinical tests I describe here are invalid if pain causes splinting and reduced range of motion. In this case, I recommend immobilization with a walking boot for 14 days. After this period, the clinical examination may be much more accurate.

   As with many of the clinical tests for adult-acquired flatfoot, gait analysis will allow a side-to-side comparison of deformity. The key differentiating feature comparing Stage I and II adult-acquired flatfoot is the fact that Stage I is characterized by tenosynovitis, but there is no visible collapse of the symptomatic foot in comparison to the contralateral side.18 While both feet look “flat and pronated,” one should evaluate the symptomatic side in Stage II for severity of rotation in all three body planes. As the flatfoot deformity progresses, three distinct changes occur. These changes are hindfoot eversion, forefoot abduction and lowering of the medial longitudinal arch, which will become accentuated during the late stance phase of gait.19

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