Effects of a UCBL orthosis and a calcaneal osteotomy on tibiotalar contact characteristics in a cadaver flatfoot model.

BACKGROUND

A flatfoot deformity alters the contact characteristics of the ankle joint, shifting the location of articulation posterolaterally, increasing pressure, and decreasing the contact area within the ankle. These changes may explain the pattern of articular degeneration and subsequent angulation observed in a long-standing adult acquired flatfoot. Corrective orthoses and surgical reconstruction have been used to realign pes planovalgus feet, but the effects of these treatments on tibiotalar contact characteristics are unknown. We hypothesized that realignment of a flatfoot with either corrective orthosis or surgical reconstruction would restore the contact characteristics of the ankle to the intact state.

METHODS

The mean value of the contact area, contact pressure, peak contact pressure, and the relative locations of the global contact area and peak pressure within the ankle joint were determined from imprints created on pressure sensitive film for a series of cadaver lower limbs subjected to a weightbearing load in simulated midstance phase of gait. Each limb was loaded sequentially under four conditions: intact, flatfoot, flatfoot realigned with UCBL orthosis, and flatfoot realigned with a medial translational osteotomy of the calcaneus.

RESULTS

The use of the UCBL orthosis and calcaneal osteotomy altered the contact characteristics of the ankle when compared with the flatfoot condition. Both interventions significantly decreased the mean global contact pressure from the flatfoot value, with the orthosis, demonstrating a significantly greater correction than the osteotomy. The orthosis also significantly reduced the peak contact pressure from the flatfoot value. Both interventions significantly corrected the lateral shift of the center of the peak contact pressure from the flatfoot value. The shift in the center of the global contact area approached significance when the orthosis was compared with the flatfoot.

CONCLUSIONS

The changes observed in the magnitude and location of the mean and peak pressures indicate that the UCBL orthosis and calcaneal osteotomy altered hindfoot alignment to significantly influence tibiotalar contact characteristics. The results further suggest that the UCBL orthosis corrected ankle malalignment better than the calcaneal osteotomy in an adult acquired flatfoot. This study provides biomechanical data to support the clinical impression that realignment of the hindfoot corrects the pathologic tibiotalar contact characteristics associated with an adult acquired flatfoot. The results support the conclusion that the clinical management of a pes planovalgus foot with a UCBL orthosis or a medial translational osteotomy of the calcaneus may avert the onset of pantalar disease seen with late-stage posterior tibial tendon dysfunction.