Several recent reports define the line from the centre of the femoral head to the lowest point of the calcaneus. The purpose of this study was to comparatively examine the usefulness of the hip–calcaneus (HC) line and hip–ankle (HA) line for the evaluation of lower-limb alignment in healthy individuals and in patients with osteoarthritis (OA).
Participants included 34 healthy individuals (mean age, 26.4 years) and 34 patients with OA (mean age, 74.2 years). Frontal radiographs of the entire lower limb were taken in single- and double-leg stances. For each group, the hip–knee–ankle (HKA) and hip–knee–calcaneus (HKC) angles were assessed and compared within and between stances. In addition, the HA line and HC line were assessed as the passing line in the knee, and were similarly compared.
Significant differences between the HKA and HKC angles, and between the HA line and HC line were observed in both groups during both stances. In addition, significant stance-related differences in the HKA and HKC angles, HA line, and HC line were found in the OA group, but not in the healthy group.
Our results suggest that the HC line of the lower limb differs from the HA line. Furthermore, single- and double-leg stances should also be considered, especially in patients with OA. These considerations may affect preoperative planning for high tibial osteotomies and TKA.