Primary isolated subtalar arthrodesis: outcome after 2 to 5 years followup.

Background: Favorable to excellent clinical results have been reported for isolated subtalar joint arthrodesis. Pedobarography after subtalar bone-block distraction arthrodesis have demonstrated a more laterally shifted gait line. However pedobarographic measurements after primary in-situ isolated subtalar arthrodesis have not been reported. This is the first study considering this.

Materials And Methods: Physical examination, AOFAS Hindfoot score, full weightbearing anterior/posterior and lateral radiographs were assessed in 15 feet. Peak pressures, ground reaction force and force distribution at foot-flat and push-off were measured.

Results: Average AOFAS-Score significantly improved. Subjective satisfaction was high. Non-union was found in 1 foot (7%), screws were removed in 4 of the 15 feet (27%). One new asymptomatic arthritic talonavicular joint was found. The pressure and force distributions under the operated and contralateral foot showed a different pattern compared to a normal foot. Ground reaction force under both the operated and contralateral feet were lower than a normal foot.

Discussion: This study found good clinical, subjective and radiographic results matching that of the reported literature. However, pedobarographic assessment suggests that great functional differences still remain when compared to a normal foot. Subtalar arthrodesis may induce an abnormal gait pattern by preventing compensation of axial rotation of the tibia. This is also reflected in the unaffected side, which may indicate an effort in the general locomotor control to keep a symmetrical gait pattern. This finally alters the pressure and force distribution under both feet. Nevertheless, subtalar arthrodesis is considered a valuable treatment for various isolated subtalar disorders.