Three-dimensional measurements of the lower extremity in children and adolescents using a low-dose biplanar X-ray device

Objective To evaluate three-dimensional (3D) measurements of the lower extremity using a biplanar low-dose X-ray device in children and adolescents. Methods Firstly, 3D measurements of eight dried bones were analysed by a biplanar low-dose X-ray device (LDX) using stereoscopic software and compared with 3D computed tomography (CT). Secondly, 47 lower limbs of children and adolescents were studied using LDX two-dimensional (2D) and 3D measurements. Both parts were evaluated for femoral and tibial lengths and mechanical angles, frontal and lateral knee angulations, and the femoral neck-shaft angle. Results The 3D specimen comparison between LDX and CT measurements showed no significant differences: femoral length ( P = 0.069), tibial length ( P = 0.059), femoral mechanical angle ( P = 0.475), tibial mechanical angle ( P = 0.067), frontal knee angulation ( P = 0.198), lateral knee angulation ( P = 0.646) and femoral neck-shaft angle ( P = 0.068). The comparison between LDX 2D and 3D measurements showed significant differences in tibial length ( P = 0.003), femoral mechanical angle ( P