Abstract
Hindfoot disorders are complex 3D deformities. Current literature has assessed their influence on the full leg alignment, but the superposition of the hindfoot on plain radiographs resulted in different measurement errors. Therefore, the aim of this study is to assess the hindfoot alignment on Weight-Bearing CT (WBCT) and its influence on the radiographic Hip-Knee-Ankle (HKA) angle. A retrospective analysis was performed on a study population of 109 patients (mean age of 53 years ± 14,49) with a varus or valgus hindfoot deformity. The hindfoot angle (HA) was measured on the WBCT while the HKA angle, and the anatomical tibia axis angle towards the vertical (TAX) were analysed on the Full Leg radiographs. The mean HA in the valgus hindfoot group was 9,19°±7.94, in the varus hindfoot group −7,29°±6.09. The mean TAX was 3,32°±2.17 in the group with a valgus hindfoot and 1,89°±2.63 in the group with a varus hindfoot, which showed to be statistically different (p<0.05). The mean HKA Angle was −1,35°±2.73 in the valgus hindfoot group and 0,4°±2.89 in the varus hindfoot group, which showed to be statistically different (p<0.05). This study demonstrates a higher varus in both the HKA and TAX in valgus hindfoot and a higher tibia valgus in varus hindfoot. This contradicts the previous assumption that a varus hindfoot is associated with a varus knee or vice versa. In clinical practice, these findings contribute to a better understanding of deformity corrections of both the hindfoot and the knee.
