Geometrical values of the normal and arthritic hip and knee detected with the EOS imaging system

EOS 2D/3D is an integrated, low-dose orthopedic digital radioimaging solution, which, due to its groundbreaking properties, has recently shown an increasing application in scoliosis surgery. Its integrated sterEOS 3D software allows creation of patient-specific three-dimensional (3D) lower limb models, and can produce geometrical parameters in 3D. Currently there are a limited number of reports on EOS for lower limb applications. Three-dimensional reconstructions of 256 hip and knee joints of 128 healthy subjects, as well as 53 hips and 46 knees of 69 patients with hip or knee arthritis, were evaluated based on orthogonal EOS two-dimensional (2D) images. Measurements for hips included femur and tibia length, total length of the extremity, femoral antetorsion and offset, femoral neck length, neck-shaft and hip-knee-shaft (HKS) angles. Lower limb alignment in both frontal and sagittal planes were determined in normal and arthritic knees. Values were compared with those obtained by standard methods published by others. Normal hip and knee geometrical parameters were found in our healthy subjects. In osteoarthritic cases, values for neck-shaft angle, femoral antetorsion, femur length and total length of the extremity were shown to decrease non-significantly. Evaluation of lower limb alignment in healthy and arthritic knees showed normal values in healthy subjects apart from three cases with an average six degrees varus. Arthritic knees were most frequently found to have a varus angulation, with the exception of 11 cases with normal or valgus alignment. EOS 2D/3D with its sterEOS 3D reconstruction is useful for a comprehensive 3D examination of the lower limb. In the near future it may be suitable for daily routine diagnostics of orthopedic lower limb deformities as a primary examination method.