Dominique Folinais

Evaluation of a new low-dose biplanar system to assess lower-limb alignment in 3D: a phantom study

ObjectiveKnee coronal alignment is routinely assessed on a full-length radiograph of the lower limbs. However, poor positioning of the knee during the procedure affects the accuracy of this kind of measurement, particularly in cases combining knee rotation and flexion. The purpose of this study was to assess the value of a three-dimensional assessment of the hip-knee-ankle (HKA) angle based on a biplanar radiographic system.Materials and methodsA biplanar slot scanning system was used to take radiographs of three lower-limb synthetic models with similar frontal deviation (5°valgus) but different flexion angulations (0°, 9°, and 18°). Biplane acquisitions were done with lower-limb axial rotations ranging from 20° of internal rotation to 20° of external rotation on each of the lower limb models. Three independent observers performed standard 2D measurements of the HKA angle from each anteroposterior (AP) image and also modeled the lower limb in 3D for each biplane acquisition with dedicated software. The HKA angle was automatically calculated from the 3D models. The results of the 2D and 3D techniques were compared.ResultsAxial rotation provoked 2D HKA measurement errors up to, respectively, 1.4°, 4.7°, and 6.8° for the lower extremities with 0°, 9°, and 18° flexion, while it never affected the 3D HKA measurement for more than 1.5°. Interobserver errors were 0.7° (SD = 0.5°) for the 2D measurements and 0.6° (SD = 0.4°) for the 3D measurements.ConclusionsThe 3D modeling allows for a more accurate evaluation of coronal alignment compared to 2D, eliminating bias due to wrong knee positioning.

Total Hip Prostheses in Standing, Sitting and Squatting Positions: An Overview of Our 8 Years Practice Using the EOS Imaging Technology

More total hip arthroplasty (THA) is performed worldwide and especially in younger and more active patients compared to earlier decades. One of the focuses of THA research in the future will be on optimizing the radiological follow-up of these patients using 2D and 3D measurements of implants position while reducing the radiation dose delivered. Low-dose EOS® imaging is an innovative slot-scanning radiograph system providing valuable information in patient functional positions (standing, sitting and even squatting positions). EOS has been proven accurate and reliable without significant inconvenience caused by the metallic artifacts of implants. The ability to obtain precise data on implant orientation according to the patient posture opens new perspectives for a comprehensive analysis of the pelvic frontal and sagittal balance and its potential impact on implants function and failures. We report our 8 years experience on our first 300 THA patients using this technology routinely for pre and post op evaluation. Our results will be compared and confronted with the actual literature about this innovative technology. We shall especially emphasize our experience about patients with abnormal posture and the evolution of the subject over time, because the phenomenon of an aging spine is frequently associated with the process of aging hips.

Measuring extension of the lumbar-pelvic-femoral complex with the EOS® system.

IntroductionSagittal balance of the coxofemoral joint in standing position and its extension capacity determine hip/spine adaptation, especially in relation to pelvic retroversion, which may be age-associated or follow either spinal arthrodesis or vertebral osteotomies. The concept of extension reserve is essential for assessing posterior hip impingement. The global visualization of the lumbar–pelvic–femoral complex obtained by EOS® imaging enables this sagittal analysis of both the subpelvic region and lumbar spine by combining the reference standing position and the possibility of dynamic tests.Materials and methodsWe studied 46 patients and their 92 hips. The EOS® radiography was performed in neutral standing position and with one foot on a step, alternately the right and left feet. Pelvic incidence, sacral slope, pelvic version, and femoral version were measured twice by two operators. The global extension reserve (GER) was defined by the sum of the intrinsic extension reserve (allowed by the hips, IER) and the extrinsic extension reserve (allowed by the spine, EER). The IER for each hip corresponds to the difference in the sacrofemoral angle (SFA) for each of the two positions. The EER was measured by the difference in the sacral slope. A descriptive study was performed, together with studies of inter- and intra-observer reproducibility, right/left symmetry, and an analysis according to age, sex, and BMI.ResultsThe mean femoral version in the reference position was 11.7° (SD 14.3°). The reproducibility of the SFA measurement was statistically verified. The IER (mean 8.8°), EER (mean −0.7°), and GER (mean 8.2°) all differed significantly between the two sides for each patient and were not associated with age, sex, or BMI.DiscussionThe femoral axis is not perpendicular to the ground in neutral position, contrary to the conventional view of this position. The measurements proposed for dynamic sagittal analysis of the hip are reproducible and make it possible to identify the IER within the GER of the spinal–pelvic–femoral complex.ConclusionThe assessment of the lumbar–pelvic–femoral complex by EOS imaging makes it possible to define the intrinsic and extrinsec extension reserves to describe the reciprocal adaptive capacities of the hips and spine.Level of evidenceIV.

What is the impact of a spinal fusion on acetabular implant orientation in functional standing and sitting positions

BACKGROUND This study used EOS imaging of primary total hip arthroplasty (THA) patients, with and without predating spinal fusion, to investigate (1) the impact of spinal fusion on acetabular implant anteversion and inclination, and (2) whether more extensive spinal fusion (fusion starting above the thoracolumbar junction or extension of fusion to the sacrum) affects acetabular implant orientation differently than lumbar only spinal fusion. METHODS Ninety-three patients had spinal fusion (case group), and 150 patients were without spinal fusion (controls). None of the patients experienced dislocation. The change in sacral slope (SS) and cup orientation from standing to sitting was measured. RESULTS Mean SS change from the standing to sitting positions was -7.9°in the fusion group vs -18.4°in controls (P = .0001). Mean change in cup inclination from the standing to sitting positions was 4.9°in the fusion group vs 10.2°in controls (P = .0001). Mean change in cup anteversion from standing to sitting positions was 7.1°in the fusion group vs 12.1°in controls (P = .0001). For each additional level of spinal fusion, the change in SS from standing to sitting positions decreased by 1.6(95% confidence interval [CI], 2.2073-1.0741), the change in cup inclination decreased by 0.8(95% CI, 0.380-1.203), and the change in cup anteversion decreased by 0.9(95% CI, 0.518-1.352; P < .001 in all cases). CONCLUSION Patients with spinal fusion demonstrated less adaptability of the lumbosacral junction. Longer spinal fusion or inclusion of the pelvis in the fusion critically impacts hip-spine biomechanics and significantly affects the ability to compensate in the standing-to-sitting transition.