Effect of subtalar arthroereisis on the tibiotalar contact characteristics in a cadaveric flatfoot model

Previous studies reported the effect of flatfoot deformity on tibiotalar joint contact characteristics. The lateral shift of the load which occurred in flatfeet may be responsible for degenerative changes in the ankle joint. The purpose was to assess the pattern of joint contact stress of the tibiotalar joint in intact, flat, and corrected specimens with subtalar arthroereisis. Seven fresh-frozen cadaver specimens were studied in the intact and flat-footed condition after transection of ligaments which support the medial arch. Ankle joint contact stress and plantar pressure patterns were determined from a capacitive pressure sensor inserted in the tibiotalar joint and a pressure distribution platform when the specimens were axially loaded in simulated mid-stance. Contact pressure was also assessed after subtalar arthroereisis with a 12 mm Kalix implant for correction of the flatfoot deformity. A maximum contact pressure of 1414.2±319.2 kPa was recorded in the middle-medial region in intact specimens. Flatfoot caused a lateral shift in the pressure distribution (p<0.05). In the flat specimens, the maximum contact pressure of 1394.7 8±470.5 kPa was in the anterior-central region. After subtalar arthroereisis with the Kalix implant for correction of the flatfoot deformity a maximum contact pressure of 1323.3±497.5 kPa was observed in the middle-lateral region. In a cadaver model, subtalar arthroereisis with Kalix implant failed to restore a normal intraarticular ankle joint pressure pattern. Further interventions should be considered to restore a normal pressure pattern.