Validity of the EOS-determined pelvic parameters and orientation with pelvic positional variation: a phantom study

Abstract

The EOS is a medical imaging system that incorporates simultaneous orthogonal images, producing three-dimensional (3D) reconstructions of the whole skeletal system in various functional positions. Despite growing interest in the pelvic 3D position, the validity of the EOS has not yet been well studied. We investigated the trueness and precision of EOS imaging for pelvic parameters and orientation and assessed whether the measurement using the EOS was affected by the pelvic orientation itself. The orientation of the anterior pelvic plane and pelvic parameters of a custom-made pelvic phantom were measured by three raters using the EOS, and the measurements obtained were compared with the true values. The standard deviations of the measurement errors were 3.23°, 0.26°, 0.23°, 2.98°, 0.88°, and 3.22° for flexion, obliquity, rotation, pelvic incidence, spinopelvic tilt, and sacral slope, respectively. The root-mean square averages of the standard deviation of each measurement were 4.05°, 0.41°, 0.28°, 4.80°, 0.99°, and 5.13°, respectively. The measurement errors for sacral slope correlated significantly with geometric means of flexion, obliquity, and rotation (r = 0.364, p = 2.67 × 10–11). The EOS rendered accurate and reliable measurements regarding pelvic 3D position, even with positional variation, but positional variation could affect measurements of sacral slope.

The Relationship between Frontal, Axial Leg Alignment, and Ankle Joint Line Orientation—a Radiographic Analysis of Healthy Subjects

“…A correction of leg alignment demonstrated a close relationship to the correction of AJLO and the mechanical load shift in the ankle, 8 underlining the importance of evaluating the whole kinematic chain of the lower extremities under weight‐bearing conditions. Previous studies mainly focused on the frontal leg alignment and interconnected relationship of the hip, knee, and ankle, neglecting the importance of axial alignment 7–9 . This focus solely on frontal alignment seems insufficient, as it is most likely not only frontal but also axial leg alignment and sagittal pelvic orientation, which influence the kinematic chain under weight‐bearing load and, therefore, AJLO.…”

“…Hip-knee-ankle angle (HKA), femoral antetorsion, tibial torsion, and pelvic tilt were measured using SterEOS software (EOS Imaging, Paris, France). Three-dimensional (3D) models of the femur and tibia were semi-automatically registered onto bony landmarks of the biplanar long leg radiograph as described by Buck et al 12 The software performed an automatic measurement procedure of HKA, femoral antetorsion, tibial torsion, and pelvic tilt and has previously been reported with a high accuracy 8,12 and reliability. 13,14 HKA ( ) was measured in the frontal plane between a line formed by the hip center and the center of the tibial eminences and a line connecting the tibial eminences and the center of the tibial plafond.…”

“…Therefore, the influence of leg alignment, especially varus/valgus deformities, on AJLO has gained attention following osteotomies around the knee or total knee arthroplasty (TKA) 6,7 . A correction of leg alignment demonstrated a close relationship to the correction of AJLO and the mechanical load shift in the ankle, 8 underlining the importance of evaluating the whole kinematic chain of the lower extremities under weight‐bearing conditions. Previous studies mainly focused on the frontal leg alignment and interconnected relationship of the hip, knee, and ankle, neglecting the importance of axial alignment 7–9 .…”

“…Previous studies mainly focused on the frontal leg alignment and interconnected relationship of the hip, knee, and ankle, neglecting the importance of axial alignment. 7 , 8 , 9 This focus solely on frontal alignment seems insufficient, as it is most likely not only frontal but also axial leg alignment and sagittal pelvic orientation, which influence the kinematic chain under weight‐bearing load and, therefore, AJLO. This is especially of clinical relevance, when evaluating patients with concomitant joint disorders at the lower extremities either for a TAA or an axial realignment of the lower extremity.…”