Validity of the anteroposterior talocalcaneal angle to assess congenital clubfoot correction.

Abstract

The anteroposterior talocalcaneal angle (Kite's angle) is still considered a common parameter for assessing clubfoot correction, although some dissenting opinions about its accuracy have been expressed. The purpose of this study was to evaluate the validity of the anteroposterior talocalcaneal angle for assessing correction of congenital clubfoot in adults who received the treatment as children. SUBJECTS AND METHODS. The anteroposterior talocalcaneal angle was measured in 48 treated idiopathic congenital clubfeet and 28 normal feet of 38 patients at the end of skeletal growth using both standing anteroposterior radiographs and 3D CT scan reconstructions. All the patients had been treated by manipulation, above-the-knee casting, and a complementary posteromedial release operation. The radiographic measurement of the anteroposterior talocalcaneal angle corresponded to the measurement of the same angle on the 3D CT scan reconstructions in only the normal feet and 12 clubfeet. In the other 36 clubfeet, a statistically significant difference of a mean of 15 degrees between the two measurements was noted, and the 3D CT scan reconstructions showed a superimposition of the talus and calcaneus, which had lost their normal anatomic divergence. In these cases, the marked medial angulation of the talar neck allowed a positive measurement of the anteroposterior talocalcaneal angle in the anteroposterior radiographic projection. According to our findings, the measurement of the anteroposterior talocalcaneal angle on radiography was misleading for assessing the degree of hindfoot correction in 75% of the treated congenital clubfeet. We believe that other imaging parameters should be considered instead of this angle to evaluate clubfoot correction.