Background: Adolescent idiopathic scoliosis (AIS), the most common spinal deformity, possibly develops due to imbalanced spinal loading following asymmetric development. Since altered loading patterns may affect standing balance and gait, we investigated whether a correlation exists between balance ability, gait pattern, and the three-dimensional radiographic spinopelvic parameters in AIS patients. Methods: A cross-sectional observational study was conducted with 34 AIS patients (aged 10-18 years) and an equal number of healthy age and sex-matched teenagers (normal group). We obtained the spinopelvic three-dimensional parameters and balance parameters simultaneously through the EOS imaging system and gait and center of pressure (CoP) characteristics using a plantar pressure measurement mat. Besides determining the intergroup differences in balance and gait parameters, multiple linear regression analyses were performed to identify any correlation between the static plantar pressure and radiographic parameters. Results: Compared to the normal group, the CoPx is lower, the CoP path length and 90% confidence ellipse area were significantly higher in AIS patients (AIS: -13.7 ± 5.7 mm, 147.4 ± 58.1 mm, 150.5 ± 62.8 mm2; normal: -7.0 ± 5.4 mm, 78.8 ± 32.0 mm, 92.1 ± 41.7 mm2, respectively), correlated with apical vertebra translation, sagittal pelvic tilt, and pelvis axial rotation, respectively. Moreover, AIS patients had a shorter stance phase (61.35 ± 0.97 s vs. 62.39 ± 1.09 s), a longer swing phase (38.66 ± 0.97 s vs. 37.62 ± 1.08 s), and smaller maximum pressure peaks in the gait cycle, especially on the left foot, as compared to healthy subjects. Moreover, the CoP trajectory in AIS patients was different from the latter, and changes in the bipedal trend were not consistent. Conclusion: The standing balance and gait characteristics of AIS patients are different from those of healthy subjects, as reflected in their three-dimensional spinopelvic radiographic parameters. Trial registration: The study protocol was registered with the Chinese Clinical Trial Registry (Number ChCTR1800018310) and the Human Subject Committee of Guangzhou Sport University (Number: 2018LCLL003).

Hip arthroplasty is a frequently used procedure with high success rates. Its main indications are primary or secondary advanced osteoarthritis, due to acute fracture, osteonecrosis of the femoral head, and hip dysplasia. The goals of HA are to reduce pain and restore normal hip biomechanics, allowing a return to the patient\'s normal activities. To reach those goals, the size of implants must suit, and their positioning must meet, quality criteria, which can be determined by preoperative imaging. Moreover, mechanical complications can be influenced by implant size and position, and could be avoided by precise preoperative templating. Templating used to rely on standard radiographs, but recently the use of EOS® imaging and CT has been growing, given the 3D approach provided by these methods. However, there is no consensus on the optimal imaging work-up, which may have an impact on the outcomes of the procedure. This article reviews the current principles of templating, the various imaging techniques used for it, as well as their advantages and drawbacks, and their expected results.

BACKGROUND: Bracing is the most common conservative treatment for preventing the progression of adolescent idiopathic scoliosis (AIS) in patients with a curve of 25°-40°. X-ray examinations are traditionally performed in the standing position. However, school-age teenagers may take more time to sit. Thus far, little is known about three-dimensional (3D) correction in the sitting position. Hence, this study aimed to determine the effects of standing and sitting positions on 3D parameters during brace correction.
METHODS: We evaluated a single-center cohort of patients receiving conservative treatment for thoracic curvature (32 patients with AIS with a Lenke I curve). The 3D parameters of their standing and sitting positions were analyzed using the EOS imaging system during their first visit and after bracing.
RESULTS: At the patients\' first visit, sagittal plane parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), and sacral slope decreased when transitioning from the standing position to the sitting position (standing 29° ± 6°, 42° ± 8°, and 42° ± 8° vs. sitting 22° ± 5°, 27° ± 6°, and 24° ± 4°; p < 0.001), whereas pelvic tilt (PT) increased and sagittal vertical axis shifted forward (standing 9° ± 6° and 1.6 ± 2.7 cm vs. sitting 24° ± 4° and 3.8 ± 2.3 cm; p < 0.001). After bracing, TK and LL decreased slightly (from 29° ± 6° and 42° ± 8° to 23° ± 3° and 38° ± 6°; p < 0.001), whereas the thoracolumbar junction (TLJ) value increased (from 3° ± 3° to 11° ± 3°; p < 0.001). When transitioning to the sitting position, similar characteristics were observed during the first visit, except for a subtle increase in the TLJ and PT values (standing 11° ± 3° and 9° ± 4° vs. sitting 14° ± 3° and 28° ± 4°; p < 0.001). Moreover, the coronal and axial parameters at different positions measured at the same time showed no significant change.
CONCLUSIONS: In brace-wearing patients with thoracic scoliosis, compensatory sagittal plane straightening may be observed with a slight increase in thoracolumbar kyphosis, particularly when transitioning from the standing position to the sitting position, due to posterior rotation of the pelvis. Our results highlight that sagittal alignment in AIS with brace treatment is not completely analyzed with only standing X-Ray.
BACKGROUND: The study protocol was registered with the Chinese Clinical Trial Registry (ChiCTR1800018310).

Spinal deformities in adolescent idiopathic scoliosis (AIS) are measured on 2D radiographs. Due to the 3D nature of the curve in AIS, such 2D measurements fail to differentiate between the true curve patterns, which in turn may adversly impact the clinical care and surgical planning. The use of 3D models of the spinal radiographs largely remains limited to the 3D measurements of the 2D parameters. The use of the true 3D variables of the spinal curves in describing the differences between the AIS patients is not fully explored.
A cohort of 141 Lenke 1 AIS with two-view spinal stereoradiographs and 3D models of the spines were included. The 3D model of the spine was used to determine the spinal centerlines. The writhe and torsion of the 3D centerlines, which, respectively, quantify the coiling and twist of the curve, were calculated using differential geometry. Patients were clustered based on the writhe and torsion values to determine the patient groups with significantly different 3D curve characteristics. The relationship between the writhe and torsion was statistically determined. The distribution of the writhe and torsion groups between the lumbar modifier types was determined.
Two writhe and two torsion clusters were determined. Lumbar orientation of plane of maximum curvature (PMC) was significantly different between the torsion clusters and thoracic and lumbar PMC and thoracic Cobb angles were significantly different between the writhe groups, p < 0.05. More than 50% of the patients had high writhe and low torsion except for Lumbar modifier C that mainly belonged to the low writhe group.
Two geometrical parameters of the spinal centerline determine true 3D characteristics of the scoliotic curves. The parameters were complimentary and weakly correlated, quantifying different characteristics of the scoliotic spines.