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

This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.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

Offset and anteversion reconstruction after cemented and uncemented total hip arthroplasty: an evaluation with the low-dose EOS system comparing two- and three-dimensional imaging

Purpose Accurate evaluation of femoral offset is difficult with conventional anteroposterior (AP) X-rays. The EOS imaging system is a system that makes the acquisition of simultaneous and orthogonal AP and lateral images of the patient in the standing position possible. These twodimensional (2D) images are equivalent to standard plane Xrays. Three-dimensional (3D) reconstructions are obtained from these paired images according to a validated protocol. This prospective study explores the value of the EOS imaging system for comparing measurements of femoral offset from these 2D images and the 3D reconstructions. Methods We included 110 patients with unilateral total hip arthroplasty (THA). The 2D offset was measured on the AP view with the same protocol as for standard X-rays. The 3D offset was calculated from the reconstructions based on the orthogonal AP and lateral views. Reproducibility and repeatability studies were conducted for each measurement. We compared the 2D and 3D offset for both hips (with and without THA). Results For the global series (110 hips with and 110 without THA), 2D offset was 40 mm (SD 7.3; 7–57 mm). The standard deviation was 6.5 mm for repeatability and 7.5 mm for reproducibility. Three-dimensional offset was 43mm(SD 6.6; 22–62 mm), with a standard deviation of 4.6 for repeatability and 5.5 for reproducibility. Two-dimensional offset for the hips without THA was 40 mm (SD 7.0; 26–56 mm), and 3D offset 43 mm (SD 6.6; 28–62 mm). For THA side, 2D offset was 41mm(SD 8.2; 7–57mm) and 3D offset 45mm(SD 4.8; 22–61 mm). Comparison of the two protocols shows a significant difference between the 2D and 3D measurements, with the 3D offset having higher values. Comparison of the side with and without surgery for each case showed a 5-mm deficit for the offset in 35 % of the patients according to the 2D measurement but in only 26 % according to the 3D calculation. Conclusions This study points out the limitations of 2D measurements of femoral offset on standard plane Xrays.The reliability of the EOS 3D models has been previously demonstrated with CT scan reconstructions as a reference. The EOS imaging system could be an option for obtaining accurate and reliable offset measurements while significantly limiting the patient’s exposure to radiation

The global alignment in patients with lumbar spinal stenosis: our experience using the EOS full-body images

Lumbar stenosis is frequently observed and treated by spine surgeons. The extent of neurological decompression and the potential spinal fixation are the basic concerns when surgery is planned. But this segmented approach to the problem is sometimes insufficient due to the complex functional situations induced by a sagittal imbalance of the patient and the combination of pathologies known as hip-spine or knee-spine syndromes. A total of 373 consecutive patients included from our EOS and clinical data base. Patients were divided in two groups. Group A included patients presenting exclusive spinal issues (172 cases) out of whom 117 (68 %) had sagittal imbalance. Among 201 patients with associated lower limbs issues (group B), 122 (61 %) had sagittal imbalance. The perception of imbalance was noticed in 54 % (93 cases) in group A and 57 % (115 cases) in group B. In the global series of 239 imbalanced cases, the key point was a spine issue for 165 patients (the 117 patients with only spine problems and 48/122 cases with combined spine and lower limbs problems). But in the patients with combined spine and lower limbs problems, we individualized hipspine syndromes (24/122 patients) and knee-spine syndromes (13/122 patients). In some cases, (37/122 patients) the anatomical and functional situations were more complex to characterize a spine-hip or a hip-spine problem. The EOS full-body images provide new information regarding the global spinal and lower limbs alignment to improve the understanding of the patient functional posture. This study highlights the importance of the lower limb evaluation not only as compensatory mechanism of the spinal problems but also as an individualized parameter with its own influence on the global balance analysis. Level of evidence IV diagnostic case series

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

Introduction Sagittal 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 methods We 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. Results The 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. Discussion The 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. Conclusion The 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 evidence IV