BACKGROUND: Physiological thoracic kyphosis (TK) allows sagittal balance of human body. Unlike lumbar lordosis (LL), TK has been relatively neglected in the literature. EOS is an imaging technique employing high-sensitivity xenon particles, featured by low-dose exposure combined with high accuracy compared to conventional radiography. The aim of this study was to investigate predictors of TK in patients with phyiological spine morphology using EOS imaging.
METHODS: EOS images of 455 patients without spinal anomalies were retrospectively assessed for TK (T1- T12), upper thoracic kyphosis (UTK, T1-T5), lower thoracic kyphosis (LTK, T5-T12), LL (L1-S1) and pelvic incidence (PI). The latter curves were measured by two researchers separately and the average of the two measurements was used for further analysis. Spearman non-parametric correlation was estimated for age, PI, LL, LTK, UTK and TK. Multiple robust linear regression analysis was employed to estimate TK, controlling for the effect of age, sex, LL and LTK.
RESULTS: The mean age of patients was 28.3 ± 19.2 years and 302 (66.4%) of them were females. The mean TK, UTK and LTK was 45.5° ± 9.3, 16 ± 7.4° and 29.7° ± 8.9, respectively. The mean UTK in people under 40 years of age was 17.0° ± 7.2, whereas for patients 40+ years old it was 13.6° ± 7.4. At univariable analysis TK positively correlated with UTK (p<0.001), LTK (p<0.001) an LL (p<0.001). At multivariable linear regression TK increased with LTK (RC = 0.67; 95%CI: 0.59; 0.75) or LL (RC = 0.12; 95%CI: 0.06; 0.18), whereas it decreased with age (RC = -0.06; 95%CI: -0.09;-0.02).
CONCLUSIONS: If EOS technology is available, the above linear regression model could be used to estimate TK based upon information on age, sex, LL and LTK. Alternatively, TK could be estimated by adding to LTK 17.0° ± 7.4 for patients < 40 years of age, or 13.6° ± 7.4 in patients 40 + years old. The evidence from the present study may be used as reference for research purposes and clinical practice, including spine examination of particular occupational categories or athletes.

BACKGROUND: The radiological study of the sagittal alignment of the spine in static and dynamic positions has allowed a better understanding of the clinical results of total hip prostheses. According to the Roussouly classification, the sacral slope in a standing position characterizes the patient with a stiff spine (less than 35̊) or a flexible spine (greater than 35̊). The objectives of this study were to compare, in a population of patients operated on for femoroacetabular impingement (FAI), firstly, the kinematics of the lumbar-pelvic-femoral complex and secondly, the clinical presentation depending on whether the spine is stiff or flexible.
OBJECTIVE: Patients with stiff spines (SS<35̊) were \"hip users\" and had less ability to compensate for their hip pathology.
METHODS: This prospective and comparative multicenter study was conducted with patients operated on arthroscopically for FAI between 2020 and 2021. All patients included received preoperative EOS imaging of the lower limbs and spine, in standing and seated positions. The following parameters were measured: pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), and sacral slope (SS), as well as dynamic parameters (intrinsic mobility of the hip: delta standing/sitting femoral sacral angle, and of the pelvis: delta standing/sitting sacral slope). The functional result was evaluated at 1 year.
RESULTS: In the stiff spine group, 62 patients were included versus 138 in the flexible spine group. The mean follow-up was 15.1±3.3 months (9.2-24.3). Nineteen patients were lost to follow-up and there were 2 revisions for iterative arthroscopy. Intrinsic pelvic mobility and intrinsic hip mobility were 16̊±13.5 (-12; 44) and 44.5̊±28.5 (-9; 99) respectively in the stiff spine group. In the flexible spine group, these same measurements were 22̊±11.5 (-30; 45) and 29.7̊±22.7 (-33; 82) respectively. In the stiff spine group, the symptoms occurred at a significantly younger age: 28.3 years±9.5 (18-51) versus 31 years±8 (18-54) (p=0.017).
CONCLUSIONS: The sacral slope is a determining factor in the kinematics of impingement and the appearance of symptoms. The sacral slope helps define the concept of a \"hip user\" in symptomatic FAI.
METHODS: IV.

Unintended rotation of the distal tibia occurs during medial open-wedge high tibial osteotomy (MOWHTO). Computed tomography (CT) is the standard method of measuring lower limb alignment; however, the new low-dose EOS system allows three-dimensional limb modeling with automated measurements of lower limb alignment. This study investigated the differences between the changes in lower limb alignment profiles obtained using the EOS system and CT in patients who underwent MOWHTO. We investigated whether any factors contributed to the degree of deformation. Thirty patients were prospectively enrolled between October 2019 and February 2023. Changes in femoral and tibial torsion, femorotibial rotation, and posterior tibial slope were measured using pre- and post-MOWHTO CT and EOS images. We found no significant difference in pre- and postoperative tibial torsion or posterior tibial slope between CT and EOS. No variables showed a significant correlation with changes in the tibial torsion or posterior tibial slope. This study confirmed the possibility that the EOS system could replace CT in measuring changes in several parameters pre- and postoperatively. Furthermore, we confirmed that the distal tibia tended to be internally rotated after MOWHTO; however, we found no significantly related parameters related to deformation caused by MOWHTO.

UNASSIGNED: Patients with adult spinal deformity (ASD) develop compensatory mechanisms. The Cobb angle between T4 and T12 has been used as a standard to define thoracic kyphosis (TK) because radiological evaluation is difficult in upper thoracic region. The upper thoracic compensatory mechanism has not been sufficiently explored, and focal thoracic compensation remains poorly understood. This study aimed to determine upper sagittal thoracic compensation and features of thoracic compensation in ASD patients.
UNASSIGNED: The records of 218 consecutive patients who underwent full-standing EOS imaging were retrospectively examined. Spinopelvic parameters-including the T1-T12, T4-T12, T1-T4, T5-T8, and T9-T12 angles-were measured using a dedicated and validated software. The relationship between the thoracic and spinopelvic parameters was statistically evaluated. Thoracic compensation was compared among four typical types of spinal deformity.
UNASSIGNED: A total of 127 ASD patients met the inclusion criteria. TK(1-12) was negatively correlated with the sagittal vertical axis (SVA) (r=-0.35), T1 pelvic angle (TPA) (r=-0.29), and pelvic incidence minus lumbar lordosis (PI-LL) (r=-0.60). TK(1-4) showed a stronger correlation with the SVA and TPA than TK(5-8) or TK(9-12) (r=-0.39, -0.38, respectively). TK(1-4), TK(5-8), and TK(9-12) had a similar negative correlation with PI-LL; however, TK(5-8) had the strongest correlation (r=-0.38). Both age and TK(9-12) were significantly associated with decreased TK(1-4), and vertebral fracture was significantly associated with increased TK(9-12). Both patients with high SVA and those in the hyperthoracic kyphosis group had lower TK(1-4) angles.
UNASSIGNED: In ASD patients, upper thoracic spine compensation plays an important role in countering global malalignment. The middle part of the thoracic spine has a strong correlation with LL. This study findings can help clinicians better manage ASD patients.

METHODS: Single centre, cross-sectional study.
OBJECTIVE: The objective is to report the prevalence of spondylolisthesis and retrolisthesis, analyse both conditions in terms of the affected levels and severity, as well as identify their risk factors.
METHODS: A review of clinical data and radiographic images of consecutive spine patients seen in outpatient clinics over a 1-month period is performed. Images are obtained using the EOS® technology under standardised protocol, and radiographic measurements were performed by 2 independent, blinded spine surgeons. The prevalence of both conditions were shown and categorised based on the spinal level involvement and severity. Associated risk factors were identified.
RESULTS: A total of 256 subjects (46.1% males) with 2304 discs from T9/10 to L5/S1 were studied. Their mean age was 52.2(± 18.7) years. The overall prevalence of spondylolisthesis and retrolisthesis was 25.9% and 17.1% respectively. Spondylolisthesis occurs frequently at L4/5(16.3%), and retrolisthesis at L3/4(6.8%). Majority of the patients with spondylolisthesis had a Grade I slip (84.3%), while those with retrolisthesis had a Grade I slip. The presence of spondylolisthesis was found associated with increased age (P < .001), female gender (OR: 2.310; P = .005), predominantly sitting occupations (OR:2.421; P = .008), higher American Society of Anaesthesiology grades (P = .001), and lower limb radiculopathy (OR: 2.175; P = .007). Patients with spondylolisthesis had larger Pelvic Incidence (P < .001), Pelvic Tilt (P < .001) and Knee alignment angle (P = .011), but smaller Thoracolumbar junctional angle (P = .008), Spinocoxa angle (P = .007). Retrolisthesis was associated with a larger Thoracolumbar junctional angle (P =.039).
CONCLUSIONS: This is the first study that details the prevalence of spondylolisthesis and retrolisthesis simultaneously, using the EOS technology and updated sagittal radiographic parameters. It allows better understanding of both conditions, their mutual relationship, and associated clinical and radiographic risk factors.

Hybrid constructs with sublaminar bands have recently regained popularity as an alternative to all-screw construct for correction of adolescent idiopathic scoliosis (AIS). The aim of this study is to evaluate the ability of hybrid constructs with sublaminar bands to achieve a tridimensional correction of the scoliotic deformity. Our hypothesis is that hybrid construct with sublaminar bands are able to achieve a substantial derotation of the apical vertebrae, while preserving the thoracic kyphosis.
A prospective evaluation of 50 consecutive cases (41 F, 9 M, mean age 14.7 ± 2 years) of AIS correction with hybrid construct was performed. In all cases, sublaminar bands were used at the apex of the main curve on concave side. All patients underwent pre and postoperative X-rays with EOS System, with full 3D reconstruction. Spinopelvic parameters and axial rotation of the vertebrae were measured pre and postoperatively.
2.7 ± 0.9 mean sublaminar bands were used per patient. Mean correction of deformity was 50 ± 9.5%. on the coronal plane. The mean axial rotation of the apical vertebra went from 18° ± 11.5° preoperatively to 9.4° ± 7.2° postoperatively (p < 0.001) with a mean derotation of 47.7%. Thoracic kyphosis went from 32.1° ± 18° preoperatively to 37.3° ± 13.1° postoperatively (p < 0.05). No intraoperative complications due to sublaminar bands were recorded.
Hybrid construct with sublaminar band have been showed to be safe and effective in deformity correction and in maintaining or restoring thoracic kyphosis. This study showed that with sublaminar bands applied at the curve apex a substantial derotation of the apical vertebrae can be achieved.

UNASSIGNED: Reverse shoulder arthroplasty (RSA) is associated with high rates of midterm complications including scapular notching, implant wear, and mechanical impingement. Scapulo-humeral rhythm (SHR), described by Codman in the 1920\'s, is defined as the ratio of glenohumeral motion to scapulothoracic motion. SHR is used as an indicator of shoulder dysfunction, as alterations in SHR can have profound implications on shoulder biomechanics. The determination of SHR can be hindered by soft-tissue motion artifacts and high radiation burdens associated with traditional surface marker or fluoroscopic analysis. EOS low dose stereoradiographic imaging analysis utilizing 3D model construction from a 2D X-ray series may offer an alternative modality for characterizing SHR following RSA.
UNASSIGNED: Patients (n=10) underwent an EOS imaging analysis to determine SHR at six and twelve months post-RSA. Leveraging 3D models of the implants, 2D/3D image registration methods were used to calculate relative glenohumeral and scapulothoracic positioning at 60, 90 and 120° of shoulder elevation. Subject-specific SHR curves were assessed and midterm changes in post-RSA SHR associated with follow-up time and motion phase were evaluated. Pearson correlations assessed associations between patient-specific factors and post-RSA SHR.
UNASSIGNED: Mean post-RSA SHR was 0.81:1 across subjects during the entire midterm postoperative period. As a cohort, post-RSA SHR was more variable for 60-90° of shoulder motion. SHR for 90-120° of motion decreased (0.43:1) at twelve months post-RSA. Post-RSA SHR could be categorized using three relative motion curve patterns, and was not strongly associated with demographic factors such as BMI. 50% of subjects demonstrated a different SHR relative motion curve shape at twelve months post-RSA, and SHR during the 90120° of motion was found to generally decrease at twelve months.
UNASSIGNED: Midterm post-RSA SHR was successfully evaluated using EOS technology, revealing lower SHR values (i.e., greater scapulothoracic motion) compared to normal values reported in the literature. SHR continued to change for some subjects during the midterm post-RSA period, with the greatest change during 90-120° of shoulder motion. Study findings suggest that future post RSA rehabilitation efforts to address elevated scapulothoracic motion may benefit from being patient-specific in nature and targeting scapular stabilization during 90-120° of shoulder motion. Level of Evidence: IV.

UNASSIGNED: Planning of surgical procedures for spinal fusion is performed on standing radiographs, neglecting the fact that patients are mostly in the sitting position during daily life. The awareness about the differences in the standing and sitting configuration of the spine has increased during the last years. The purpose was to provide an overview of studies related to seated imaging for spinal fusion surgery, identify knowledge gaps and evaluate future research questions.
UNASSIGNED: A literature search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) extension for Scoping Reviews (PRISMASc) was performed to identify reports related to seated imaging for spinal deformity surgery. A summary of the finding is presented for healthy individuals as well as patients with a spinal disorder and/or surgery.
UNASSIGNED: The systematic search identified 30 original studies reporting on 1) the pre- and postoperative use of seated imaging of the spine (n=12), 2) seated imaging of the spine for non - surgical evaluation (n=7) and 3) seated imaging of the spine among healthy individuals (12). The summarized evidence illuminates that sitting leads to a straightening of the spine decreasing thoracic kyphosis (TK), lumbar lordosis (LL), the sacral slope (SS). Further, the postural change between standing and sitting is more significant on the lower segments of the spine. Also, the adjacent segment compensates the needed postural change of the lumbar spine while sitting with hyperkyphosis.
UNASSIGNED: The spine has a different configuration in standing and sitting. This systematic review summarizes the current knowledge about such differences and reveals that there is minimal evidence about their consideration for surgical planning of spinal fusion surgery. Further, it identifies gaps in knowledge and areas of further research.

Hip osteoarthritis may be caused by increased or abnormal intra-articular forces, which are known to be related to structural articular cartilage damage. Femoral torsional deformities have previously been correlated with hip pain and labral damage, and they may contribute to the onset of hip osteoarthritis by exacerbating the effects of existing pathoanatomies, such as cam and pincer morphologies. A comprehensive understanding of the influence of femoral morphotypes on hip joint loading requires subject-specific morphometric and biomechanical data on the movement characteristics of individuals exhibiting varying degrees of femoral torsion. The aim of this study was to evaluate hip kinematics and kinetics as well as muscle and joint loads during gait in a group of adult subjects presenting a heterogeneous range of femoral torsion by means of personalized musculoskeletal models. Thirty-seven healthy volunteers underwent a 3D gait analysis at a self-selected walking speed. Femoral torsion was evaluated with low-dosage biplanar radiography. The collected motion capture data were used as input for an inverse dynamics analysis. Personalized musculoskeletal models were created by including femoral geometries that matched each subject\'s radiographically measured femoral torsion. Correlations between femoral torsion and hip kinematics and kinetics, hip contact forces (HCFs), and muscle forces were analyzed. Within the investigated cohort, higher femoral antetorsion led to significantly higher anteromedial HCFs during gait (medial during loaded stance phase and anterior during swing phase). Most of the loads during gait are transmitted through the anterior/superolateral quadrant of the acetabulum. Correlations with hip kinematics and muscle forces were also observed. Femoral antetorsion, through altered kinematic strategies and different muscle activations and forces, may therefore lead to altered joint mechanics and pose a risk for articular damage. The method proposed in this study, which accounts for both morphological and kinematic characteristics, might help in identifying in a clinical setting patients who, as a consequence of altered femoral torsional alignment, present more severe functional impairments and altered joint mechanics and are therefore at a higher risk for cartilage damage and early onset of hip osteoarthritis.

UNASSIGNED: Accurate radiographic assessment of adolescent idiopathic scoliosis (AIS) is crucial to achieving surgical correction, yet pelvic rotation may alter measurements. In Lenke Type 1/2 AIS patients, we conducted a pilot study to assess how pelvic rotation (i.e., the patient\'s position in the X-ray scanner) affected sagittal, coronal, and rotational measurements.
UNASSIGNED: A retrospective, pilot study of Type 1/2 AIS patients was undertaken. Demographics and three-dimensional (3D) SterEOS imaging were obtained. Measurements were compared between two scenarios: (I) radio plane-patient\'s natural position in the scanner; and (II) patient plane-patient\'s position after correcting to the transverse plane. Sagittal, coronal, and rotational measurements were compared, including: thoracic kyphosis (TK), lumbar lordosis (LL), main thoracic (MT) and thoracolumbar/lumbar (TL-L) Cobb, and apical vertebral rotation (AVR) in the proximal thoracic (PT), MT, and TL/L regions.
UNASSIGNED: Of 15 patients, average age was 15.7 years and 67% were female. Average baseline pelvic obliquity was 4.0 mm and pelvis rotation was 5.1°. Significant differences were seen between the radio vs. patient plane, respectively, in the following three measurements: TK, LL, and AVR: (I) TK (T1-12: 36.5° vs. 32.8°, P=0.003; T4-12: 28.4° vs. 22.7°, P<0.001); (II) LL (L1-5: 46.6° vs. 42.8°, P=0.002; L1-S1: 58.2° vs. 55.1°, P=0.003); (III) AVR (PT-AVR: 4.0° vs. 8.2°, P=0.003; MT-AVR: -14.8° vs. -10.5°, P=0.004; TL/L-AVR: (4.5° vs. 8.7°, P=0.003). No significant differences were seen in coronal cobb angles.
UNASSIGNED: After accounting for pelvic rotation, sagittal and rotational measurements were significantly altered. These results have implications for measurement accuracy, surgical decision-making, and postoperative monitoring.