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Aims This study addressed two questions: first, does surgical correction of an idiopathic scoliosis increase the volume of the rib cage, and second, is it possible to evaluate the change in lung function after corrective surgery for adolescent idiopathic scoliosis (AIS) using biplanar radiographs of the ribcage with 3D reconstruction? Methods A total of 45 patients with a thoracic AIS which needed surgical correction and fusion were included in a prospective study. All patients underwent pulmonary function testing (PFT) and low-dose biplanar radiographs both preoperatively and one year after surgery. The following measurements were recorded: forced vital capacity (FVC), slow vital capacity (SVC), and total lung capacity (TLC). Rib cage volume (RCV), maximum rib hump, main thoracic curve Cobb angle (MCCA), medial-lateral and anteroposterior diameter, and T4-T12 kyphosis were calculated from 3D reconstructions of the biplanar radiographs. Results All spinal and thoracic measurements improved significantly after surgery (p < 0.001). RCV increased from 4.9 l (SD 1) preoperatively to 5.3 l (SD 0.9) (p < 0.001) while TLC increased from 4.1 l (SD 0.9) preoperatively to 4.3 l (SD 0.8) (p < 0.001). RCV was correlated with all functional indexes before and after correction of the deformity. Improvement in RCV was weakly correlated with correction of the mean thoracic Cobb angle (p = 0.006). The difference in TLC was significantly correlated with changes in RCV (p = 0.041). It was possible to predict postoperative TLC from the postoperative RCV. Conclusion 3D rib cage assessment from biplanar radiographs could be a minimally invasive method of estimating pulmonary function before and after spinal fusion in patients with an AIS. The 3D RCV reflects virtual chest capacity and hence pulmonary function in this group of patients. Cite this article: Bone Joint J 2022;104-B(1):112–119.

Introduction In hip osteoarthritis, hip flexion contracture can severely alter the patient’s alignment, and, therefore, affect the patient’s quality of life (QOL). Hip contracture is not well-studied, partly because of the difficulties of its diagnosis. The aim of this study was to propose a quantitative definition of hip flexion contracture, and to analyse sagittal alignment in these patients compared to non-contracture ones, before and 12 months after total hip arthroplasty (THA). Materials and methods Consecutive patients with hip arthrosis and an indication for THA were included (N = 123). Sagittal full-body radiographs were acquired in free standing position and in extension. QOL questionnaires were administered before and after surgery. Spinopelvic parameters were measured, including the pelvic–femur angle (PFA). Patients with low pelvic incidence ( 5°, or PFA > -5° when pelvic incidence ≥ 45°. Results 29% of patients were in the hip flexion contracture group, and they showed lower pelvic tilt than the no-contracture group (p

International audience; Introduction: This study analyzes anatomical variations of the thoracic cage (TC) according to spinopelvic alignment, age and gender using stereoradiography in erect position.Methods: This retrospective multicentric study analyzed computed parameters collected from free-standing position bi-planar radiographs, among healthy subjects. Collected data were: age, gender, pelvic parameters (Pelvic Incidence, Pelvic Tilt (PT) and Sacral Slope), T1-T12 Kyphosis (TK), L1-S1 Lordosis (LL), curvilinear spinal length, global TC parameters (maximum thickness and width, rib cage volume, mean Spinal Penetration Index (SPI)), 1st–10th rib parameters (absolute and relative (to the corresponding vertebra) sagittal angles).Results: Totally, 256 subjects were included (140 females). Mean age was 34 (range: 8–83). Significant correlations were found between TK and TC thickness (0.3, p

Adolescent idiopathic scoliosis (AIS) is the most common spinal disorder in children. A severity index was recently proposed to identify the stable from the progressive scoliosis at the first standardized biplanar radiographic exam. The aim of this work was to extend the validation of the severity index and to determine if curve location influences its predictive capabilities. AIS patients with Cobb angle between 10° and 25°, Risser 0–2, and no previous treatment were included. They underwent standing biplanar radiography and 3D reconstruction of the spine and pelvis, which allowed to calculate their severity index. Patients were grouped by curve location (thoracic, thoracolumbar, lumbar). Patients were followed up until skeletal maturity (Risser ≥ 3) or brace prescription. Their outcome was compared to the prediction made by the severity index. In total, 205 AIS patients were included; 82% of them (155/189, 95% confidence interval [74–90%]) were correctly classified by the index, while 16 patients were unclassified. Positive predictive ratio was 78% and negative predictive ratio was 86%. Specificity (78%) was not significantly affected by curve location, while patients with thoracic and lumbar curves showed higher sensitivity (≥ 89%) than those with thoracolumbar curves (74%). In this multicentric cohort of 205 patients, the severity index was used to predict the risk of progression from mild to moderate scoliosis, with similar results of typical major curve types. This index represents a novel tool to aid the clinician and the patient in the modulation of the follow-up and, for progressive patients, their decision for brace treatment. • The severity index of adolescent idiopathic scoliosis has the potential to detect patients with progressive scoliosis as early as the first exam. • Out of 205 patients, 82% were correctly classified as either stable or progressive by the severity index. • The location of the main curve had small effect on the predictive capability of the index.

International audience; Spine deformity during adolescent idiopathic scoliosis can induce a rib-cage deformity. This bone deformity can have direct consequences on the chest-wall muscles, including intercostal muscles, leading to respiratory impairments in individuals with severe cases. The aim of this study was to determine whether shear-wave elastography can be used to measure intercostal-muscle shear-wave speed (SWS) in healthy children and those with adolescent idiopathic scoliosis (AIS). Nineteen healthy participants and 16 with AIS took part. SWS measurements were taken by three operators, twice each. Average SWS was 2.3 ± 0.4 m/s, and inter-operator reproducibility was 0.2 m/s. SWS was significantly higher during apnea than in normal breathing (p < 0.01) in both groups. No significant difference was observed between groups in apnea or in normal breathing. Characterization of the intercostal muscles by ultrasound elastography is therefore feasible and reliable for children and adolescents with and without scoliosis.

Purpose: To evaluate the global alignment of non-operated subjects with adolescent idiopathic scoliosis. Method: A total of 254 subjects with AIS and 64 controls underwent low dose biplanar X-rays and had their spine, pelvis, and rib cage reconstructed in 3D. Global alignment was measured in the sagittal and frontal planes by calculating the OD-HA angle (between C2 dens to hip axis with the vertical). Subjects with AIS were classified as malaligned if the OD-HA was > 95th percentile relative to controls. Results: The sagittal OD-HA in AIS remained within the normal ranges. In the frontal plane, 182 AIS were normally aligned (Group 1, OD-HA = 0.9°) but 72 were malaligned (Group 2, OD-HA = 2.9°). Group 2 had a more severe spinal deformity in the frontal and horizontal planes compared to Group 1 (Cobb: 42 ± 16° vs. 30 ± 18°; apical vertebral rotation AVR: 19 ± 10° vs. 12 ± 7°, all p < 0.05). Group 2 subjects were mainly classified as Lenke 5 or 6. 19/72 malaligned subjects had a mild deformity (Cobb < 30°) but a progressive scoliosis (severity index ≥ 0.6). The frontal OD-HA angle was found to be mainly determined (adjusted-R2 = 0.22) by the apical vertebral rotation and secondarily by the Lenke type. Conclusions: This study showed that frontal malalignment is more common in distal major structural scoliosis and its main driver is the apical vertebral rotation. This highlights the importance of monitoring the axial plane deformity in order to avoid worsening of the frontal global alignment.

Vertebral burst fractures are usually due to traumatic high-energy distraction of the vertebra. They often require pedicle screw fixation to stabilize the spine during the healing process but once the fusion of the fractured vertebra has occurred, the posterior fixation can be removed or shortened to restore part of the spinal mobility. The importance of sparing fusion levels to ensure optimal functional results has been demonstrated. In surgical planning, the rule is therefore to ensure the osteosynthesis stability while limiting the number of levels included. Immobilization or fixation of a vertebral segment may be responsible for degeneration of the intervertebral disc and in case of surgical treatment the adjacent disc. Therefore, we can ask whether removal of a vertebral fixation could decrease the stress on adjacent segments. Ultrasound shearwave elastography is a new innovative and non-invasive technique allowing evaluation of soft tissue’s elastic modulus through the measurement of shear wave speed (SWS). This non-invasive imaging method has shown its added value in breast or in liver oncology and, more recently, in musculoskeletal pathologies assessment. In particular, Langlais et al. found that SWS measured in annulus fibrosus was significantly higher in progressive adolescent idiopathic scoliosis than in asymptomatic population, which is associated with a stiffer tissue. The same authors defined a corridor of normality (2.3–3.7 m/s) for the asymptomatic population and observed that annulus SWS tended to normalize 1 year after fusion surgery in severe adolescent idiopathic scoliosis. The aim of this case was to analyze the effect of removing the posterior fixation in a case of burst fracture on the mechanical properties of the bridged and adjacent intervertebral discs.

Hip arthrosis and total hip arthroplasty (THA) can alter a patient’s balance and spinopelvic mobility. In this study, we hypothesized that lumbar, pelvic, and hip mobility and their inter-relations are affected by THA and that their study could give an insight in our understanding of postoperative balance and mobility. A total of 165 patients with hip arthrosis and with an indication for THA were included in this single-center prospective cohort. Sagittal radiographs were acquired in four positions: free-standing, standing extension, relaxed-seating and flexed-seating preoperatively and at 6 and 12 months. Spinopelvic parameters were measured (pelvic tilt and incidence, sacral slope, lumbar lordosis, pelvic-femoral angle). Standing spinopelvic parameters did not significantly change postoperatively. However, the postural changes occurring between positions were significantly altered after THA. In particular, pelvic and lumbar mobility was significantly reduced postoperatively, while hip mobility was increased. Correlations were observed between the changes in lumbar, pelvic and hip mobility before and after THA. This study confirmed that there is a relationship between lumbar, pelvic and hip mobility in osteoarthritis, and that this relationship is modified by the postoperative compensation mechanisms deployed by the patient in dynamic postures. Hence, surgeons should consider these relationships when planning surgery, in order to obtain a physiological pelvic tilt postoperatively and to account for the potential increased risk of impingement and dislocation with hip hypermobility.

Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine. Spine slenderness, which represents its potential instability to buckling under compressive loads, was shown to be higher in AIS patients than non-scoliotic subjects, but it is not clear at what stage of the progression this difference appeared, nor if slenderness could be used as an early sign of progression. In this study, we hypothesized that slenderness could be an early sign of progression. One-hundred thirty-eight patients and 93 non-scoliotic subjects were included. They underwent standing biplanar radiography and 3D reconstruction of the spine, which allowed computing vertebra and disc slenderness ratio. Then, patients were followed until progression of the deformity or skeletal maturity (stable patients). Vertebral slenderness ratio in AIS patients varied between 2.9 [2.7; 3.0] (T9) and 3.4 [3.2; 3.6] (T1), while disc slenderness ranged from 0.6 [0.6; 0.7] at T6-T7 to 1.2 [1.1; 1.3] at L4-L5. Slenderness ratio increased with age, while disc slenderness tended to decrease with age and Cobb angle. Slenderness was similar between progressive and stable patients, and also between patients and non-scoliotic subjects. In conclusion, spinal slenderness does not appear to be an early sign of progression. Further studies should analyse the development of slenderness during growth, and how it could be affected by non-operative treatment.

Background: Balanced global spinopelvic balance is important in the maintenance of the physiological alignment of all body segments above the pelvis with minimum energy expenditure. The key determinants affecting the 3D index-odontoid-hip axis (OD-HA) angle, and in particular its alterations, have not been clearly defined. The aim of this study is to identify the determinants of the 3D OD-HA angle in maintaining global spinopelvic balance in a large Chinese adult cohort of different gender and age groups. Methods: A total of 516 asymptomatic adults were enrolled in this study. Biplanar radiographies were performed to reconstruct the subject’s inter-acetabular axis and C2 odontoid process. The 3D angle formed by the vertical and the line between odontoid and mid-interacetabular axis (OD-HA angle) was computed and projected in the subject’s sagittal and coronal planes. Thoracic kyphosis (TK), lumbar lordosis (LL), T1 pelvic angle (TPA) and sagittal vertical axis (SVA) were measured. Results: The mean values of sagittal and coronal OD-HA were −0.2°±2.5° and 0.2°±1.1°, respectively. Both sagittal and coronal OD-HA had significant correlation with age (r=0.265 and r=−0.143, P

International audience; The interface between the intervertebral disc and the vertebral body is important to the discs’ biomechanics and physiology, and is widely implicated in its pathology. This study aimed to explore biochemically and structurally the bony endplate, cartilage endplate and intervertebral disc, below the nucleus and below the annulus in healthy bovine tails. Multiphoton imaging and spontaneous Raman spectroscopy were employed. Raman spectroscopy provided relative quantification of mineral and matrix components across the vertebral endplate and its adjacent areas with microscopic spatial resolution. Microscopy utilising second-harmonic generation (SHG) and two-photon fluorescence (TPF) allowed for the structural identification of distinct endplate regions. The cartilage endplate was revealed as structurally distinct from both the bone and disc, supporting its biomechanical function as a transition zone between the soft and hard tissue components. The collagen fibres were continuous across the tidemark which defines the interface between the mineralised and non-mineralised regions of the endplate. Raman spectroscopy revealed gradients in phosphate and carbonate content through the depth of the endplate and also differences beneath the nucleus and annulus consistent with a higher rate of remodelling under the annulus.

To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS). Fifty-five AIS patients were prospectively included (age 10–15, Cobb 16° ± 4°). Patients underwent low-dose biplanar X-rays, and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first examination, based on 3D parameters of the scoliotic curve, and it was compared with the patient’s final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen’s kappa and intra-class correlation coefficient). Eighty-five percentage of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first examination. The novel severity index assessment took less than 4 min of operator time. The fast and semiautomatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery. These slides can be retrieved under Electronic Supplementary Material.

Study design: Case-Control Study Objectives: To analyse global sagittal alignment including the cranial center of mass (CCOM) and proximal junctional kyphosis (PJK) in Adolescent Idiopathic Scoliosis (AIS) patients treated with posterior instrumentation. Summary of background data: PJK plays an important role in the global sagittal alignment in AIS patients. Maintaining the head above the pelvis allows for a minimization of energy expense in ambulation and upright posture. Numerous studies have been performed to understand PJK phenomena in AIS patients. However, to our knowledge, no study performed on AIS patients included the head in the analysis of global sagittal alignment and PJK. Methods: This study included 85 AIS patients and 51 asymptomatic adolescents. Low-dose bi-planar X-rays were acquired for each subject preoperatively and at two years follow up. Two global sagittal alignment parameters were calculated, i.e. the angle between the vertical and the line joining the center of the bi-coxofemoral axis (HA) and either the most superior point of the dentiform apophysis of C2 (OD) or the cranial center of mass (CCOM). Results: Among normal adolescents, the average OD-HA and CCOM-HA angles were -2.3°±2° and -1.5°±1.8°, respectively. Among AIS patients the average OD-HA and CCOM-HA angles were respectively -2.3°±1.9° and -1.3°±1.8° preoperatively and -2.8°±1.7° and -1.9°±1.7° at the last follow up. 13% of the patients developed PJK postoperatively. Case-by-case analysis showed that adjusting the thoracic kyphosis and the compensations required to maintain this constant could provide explanatory elements. Conclusions: OD-HA and CCOM-HA angles remain almost constant among normal group and patients, pre- and post-operatively, whether PJK or non-PJK. Five patients without PJK and only one patient with PJK produced abnormal values relative to the asymptomatic subjects. Therefore, PJK could be a compensation mechanism, which allows for CCOM-HA and, to a lesser extent, OD-HA to remain invariant. Level of Evidence: III BiomecAM chair on musculoskeletal modeling, with the support of Cotrel and ParisTech Foundations, Société Générale, Covea and Proteor.

International audience; Background: Biplanar X-ray system providing anteroposterior and sagittal plane with an ultra-low radiation dose and in weight-bearing position is increasingly used for spine imaging. The original three-dimensional (3D) reconstruction method from biplanar X-rays has been widely used for clinical parameters, however, the main issue is that manual adjustments of the 3D model was quite time-consuming and limited to thoracolumbar spine. A quasi-automated 3D reconstruction method of the spine from cervical vertebra to pelvis was proposed, which proved fast and accurate in 57 patients with adolescent idiopathic scoliosis. The aim of this study was to compare the newly developed technique of quasi-automatic 3D measurement with classical 2D measurements in a large cohort.Methods: A total of 494 adults with biplanar EOS X-ray scanning were included in this study and divided into health and deformity group according to the presence of spinal deformity. The proposed method of quasi-automatic 3D measurement was applied to all these subjects. The radiographic parameters included: thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sagittal vertical axis (SVA), T1 pelvic angle (TPA) in sagittal plane, and cobb angle in coronal plane. Comparison was made between quasi-automatic and manual measurement.Results: The mean age was 53.7±19.9 years old. In the whole population, the mean differences between the two methods were 3.9° for TK (30.5°±9.9° vs. 26.5°±9.3°, P30°, respectively. Correlation analysis showed r2 for all clinical parameters ranged from 0.667 to 0.923. On average, the new method takes 5 minutes to compute all the parameters for one case.Conclusions: In conclusion, this ergonomic and efficient quasi-automatic method for full spine proved fast and accurate measurement in a large population, which showed great potential in extensive clinical application

International audience; Objective: Our objective was to establish a corridor of normality for the external shape 3D parameters and then to assess these variables in adolescent idiopathic scoliosis (AIS).Methods: Adolescent with mild and severe AIS were included prospectively, as well as a control group of asymptomatic subjects. A quasi‐automatic 3D reconstruction of the spine and manual 3D reconstruction of the external envelope was performed from biplanar radiography. The center of mass position, the axial intersegmental moment resulting at the apex and junctional vertebrae, and the coronal trunk balance were automatically computed. A normality corridor of asymptomatic subjects was calculated as the range [5th-95th percentiles] for external shape parameters at each vertebral level.Results: Forty-one asymptomatic subjects (19 females; 22 males; 21 yo, SD=4) and sixty AIS (56 females; 4 males; 13 years old, SD=1.9; 30 mild and 30 severe; 34 thoracic curves and 26 thoraco-lumbar or lumbar curves) were included. All parameters based on the external shape showed differences between AIS and controls, as well as between mild and severe scoliosis. For instance, the intersegmental moment applied to the upper junctional vertebra was above the 95th percentile of controls in 70% of AIS patient. The percentage of severe patients showing parameters higher than the normality corridor was significantly higher than mild patients (p

Investigate the axial plane deformity in the scoliotic segment and its relationship to the deformity in the frontal and sagittal planes.Two hundred subjects with AIS (Cobb ≥ 20°) underwent low dose biplanar X-rays with 3D reconstruction of the spine and pelvis. All structural curves were considered and were distributed as follows: 142 thoracic (T), 70 thoracolumbar (TL), and 47 lumbar curves (L). Common 3D spino-pelvic and scoliosis parameters were collected such as: frontal Cobb; torsion index (TI); hypokyphosis/lordosis index (HI). Parameters were compared between each type of curvature and correlations were investigated between the 3 planes.Frontal Cobb was higher in all T (45 ± 19°) and TL (41 ± 15°) curves compared to L curves (35 ± 14°, p = 0.004). TI was higher in T curves when compared to TL and L curves (TI: 15 ± 8°, 9 ± 6°, 7 ± 5°, p 0.001). HI was similar between curve types. T curves showed significant correlations between the 3 planes: Cobb vs. TI (r = 0.76), Cobb vs. HI (r = - 0.54) and HI vs. TI (r = - 0.42). The axial plane deformity was related to the frontal deformity and the type of curvature (adjusted-RBeside showing the most severe deformity frontally and axially compared to TL and L curves, the T curves showed strong correlations between the 3 planes of the deformity. Moreover, this study showed that the axial plane deformity cannot be fully determined by the frontal and sagittal deformities, which highlights the importance of 3D assessment in the setting of AIS.

The study procedure was conducted in accordance to guidelines approved by the institutional clinical research ethics committee (CREC No. 2016.722) and the Declaration of Helsinki. Written informed consent was obtained from all subjects and their parents before participating in this study. AbstractThis study aimed to characterize global sagittal alignment in adolescent idiopathic scoliosis (AIS) with normal kyphosis (NTK, kyphosis > 10°) and with thoracic hypokyphosis (THK, kyphosis 21). Biplanar radiographies were acquired at baseline, immediate post-operatively, 1-year and 2-year follow-up, and 3D reconstruction of the spine and pelvis was performed. NTK and THK showed different global sagittal alignment, as well as differences compared to controls. AIS with THK at baseline had higher SVA/SFD (2.0 ± 2.9 vs − 0.4 ± 1.9; P

International audience; Growth-preserving spinal surgery suffer from high complications rate. A recent bipolar instrumentation using two anchoring points (thoracic and pelvic) showed lower rates, but its biomechanical behaviour has not been characterised yet. The aim of this work was to combine in vitro and in vivo data to improve and validate a finite element model (FEM) of the spine, and to apply it to compare bipolar and classical all-screws implants.Spinal segments were tested in vitro to measure range of motion (ROM). Thoracic segments were also tested with bipolar instrumentation to measure ROM and rod strain using a strain gage.A subject-specific FEM of the spine, pelvis and ribcage of an in vivo asymptomatic subject was built. Spinal segments were extracted from it to reproduce the in-vitro mechanical tests. Experimental and simulated ROM and rod strain were compared. Then, the full trunk FEM was used to compare bipolar and all-screws instrumentations.The FEM fell within 1° of the experimental corridors, and both in silico and in vitro instrumentation rods showed 0.01% maximal axial strain. Bipolar and all-screws constructs had similar maximal Von Mises stresses.This work represents a first step towards subject-specific simulation to evaluate spinal constructs for neuromuscular scoliosis in children.

International audience; PurposeInvestigate the axial plane deformity in the scoliotic segment and its relationship to the deformity in the frontal and sagittal planes.MethodsTwo hundred subjects with AIS (Cobb ≥ 20°) underwent low dose biplanar X-rays with 3D reconstruction of the spine and pelvis. All structural curves were considered and were distributed as follows: 142 thoracic (T), 70 thoracolumbar (TL), and 47 lumbar curves (L). Common 3D spino-pelvic and scoliosis parameters were collected such as: frontal Cobb; torsion index (TI); hypokyphosis/lordosis index (HI). Parameters were compared between each type of curvature and correlations were investigated between the 3 planes.ResultsFrontal Cobb was higher in all T (45 ± 19°) and TL (41 ± 15°) curves compared to L curves (35 ± 14°, p = 0.004). TI was higher in T curves when compared to TL and L curves (TI: 15 ± 8°, 9 ± 6°, 7 ± 5°, p

STUDY DESIGN A prospective study. OBJECTIVE The aim of this study was to report the results of an alternative technique to growing rods (GR) for neuromuscular scoliosis using a minimally invasive fusionless surgery with a minimum of 5 years' follow-up. SUMMARY OF BACKGROUND DATA Conservative treatment is not effective in progressive neuromuscular scoliosis. Early surgery using GR is increasingly advocated to control the deformity while preserving spinal and thoracic growth before arthrodesis. These techniques still provide a high rate of complications. METHODS The technique relies on a bilateral double rod sliding instrumentation anchored proximally by four hooks claws and distally to the pelvis by iliosacral screws through a minimally invasive approach. The clinical and radiological outcomes of 100 consecutive patients with neuromuscular scoliosis who underwent this fusionless surgery with a minimum follow-up of 5 years were reviewed. RESULTS 6.5 ± 0.7 years after initial surgery, six patients were lost of follow-up and 11 died of unrelated raison. Of the 83 remaining patients at latest follow-up, mean Cobb angle was stable to 35.0° which correspond to 61% correction of the initial deformation. Mean pelvic obliquity was 29.6° (0.3°-80.0°) preoperatively and 7.2 (0.2°-23.5°) at latest follow-up. Correction of the hyper kyphosis remained stable. Skeletal maturitywas reached in 42 of 83 patients (50.6%). None of these patients has required spinal fusion. The global complication rate was 31.3%. CONCLUSION The outcomes of this minimally invasive fusionless technique at 5 years follow-up showed a stable correction of spinal deformities and pelvic obliquity over time, with a reduced rate of complication. The arthrodesis was not required for all patients at skeletal maturity. This technique could be a good alternative to arthrodesis for neuromuscular scoliosis.Level of Evidence: 3.

International audience; Study Design: This was a multicentric cross-sectional descriptive study.Objective: To analyze patterns of 3D rib cage deformity in subjects with adolescent idiopathic scoliosis (AIS) and their relationship with the spinal deformity.Summary of Background Data: Subjects with AIS present with rib cage deformity that can affect respiratory functions. The 3D rib cage deformities in AIS and their relationship to the spinal deformity are still unelucidated.Methods: A total of 200 AIS and 71 controls underwent low-dose biplanar x-rays and had their spine and rib cage reconstructed in 3-dimensional (D). Classic spinopelvic parameters were calculated in 3D and: rib cage gibbosity, thickness, width, volume and volumetric spinal penetration index (VSPI). Subjects with AIS were classified as: group I with mild rib cage deformity (n=88), group II with severe rib cage deformity (n=112) subgrouped into IIa (high gibbosity, n=48), IIb (high VSPI, n=48), and IIc (both high gibbosity and VSPI, n=16).Results: Groups IIa and IIb had a higher Cobb angle (33 vs. 54 degrees and 46 degrees, respectively) and torsion index (11 vs. 14 degrees and 13 degrees, respectively) than group I. Group IIb showed more severe hypokyphosis (IIb=21 degrees; IIa=33 degrees; I=36 degrees; control=42 degrees) with a reduced rib cage volume (IIb=4731 cm3; IIa=4985 cm3; I=5257 cm3; control=5254 cm3) and thickness (IIb=135 mm; IIa=148 mm; I=144 mm; control=144 mm). Group IIa showed an increasingly large local gibbosity descending from proximal to distal levels and did not follow the axial rotation of the spine. Group IIc showed characteristics of both groups IIa and IIb.Conclusions: This new classification of 3D rib cage deformity in AIS shows that the management of cases with high VSPI (groups IIb and IIc) should focus on restoring as much kyphosis as possible to avoid respiratory repercussions. Treatment indications in groups I and IIa would follow the consensual basic principles reported in the literature regarding bracing and surgery.

Shear wave elastography (SWE) is an ultrasound technique to obtain soft tissue mechanical properties. The aim of this study was to establish the reliability of SWE in young children, define reference data on healthy ones and compare the shear modulus of healthy and spastic muscles from cerebral palsy (CP). The reproducibility is evaluated: at rest, on 7 children without any musculoskeletal pathology by 3 different operators, on 2 muscles: biceps brachii long head and medial gastrocnemius. The comparison study was made, on the same 2 muscles, at rest and under passive stretching, with a control group (29 healthy children), a spastic group (spastic muscles of 16 children from CP) and a non-spastic group (non-spastic muscles of 14 children from CP). The intra-operator reliability and inter-operator reliability, in terms of standard deviation, were 0.6 kPa (11.2% coefficient of variation (CV)) and 0.8 kPa (14.9% CV) for the biceps, respectively, and 0.4 kPa (11.5% CV) and 0.5 kPa (13.8% CV) for the gastrocnemius. At rest, no significant difference was found. Under passive stretching, the non-spastic CP biceps were significantly stiffer than the control ones (p = 0.033). Spastic gastrocnemius had a higher shear modulus than in the control muscles (p = 0.0003) or the non-spastic CP muscles (p = 0.017). CP stretched medial gastrocnemius presented an abnormally high shear moduli for 50% of patients.

International audience; The aim of this work was to determine the feasibility of combined ultrasonography and elastography measurement to characterize the mechanical properties of the intercostal space during breathing. Eighteen asymptomatic participants (ages 13 ± 2 y) and six participants with adolescent idiopathic scoliosis (AIS) were included (Cobb angle 60° ± 12°). Ultrasonographic and elastographic clips were acquired of T8–T9 ribs and the intercostal space. The two adjacent ribs were tracked to infer the breathing cycle. Shear-wave speed (SWS) was measured in the intercostal space at different stages of the breathing cycle. SWS was symmetric in the control group, during both expiration and inspiration. In AIS, the SWS during inspiration was higher in the convex side than in the concave one (p = 0.02). Furthermore, SWS was higher during inspiration than expiration in the control group and in the AIS convex side, but not in the AIS concave side (p > 0.05). This new method combining echography and shear-wave elastography allowed measurement of the mechanical characteristics of the intercostal space at different phases of the breathing cycle and highlighted differences between the AIS and control groups. This approach opens the way to further analyses of the biomechanical characteristics of breathing in severe AIS.

Purpose The aim of this work is to propose a classification algorithm to automatically detect treatment for scoliosis (brace, implant or no treatment) in postero-anterior radiographs. Such automatic labelling of radiographs could represent a step towards global automatic radiological analysis. Methods Seven hundred and ninety-six frontal radiographies of adolescents were collected (84 patients wearing a brace, 325 with a spinal implant and 387 reference images with no treatment). The dataset was augmented to a total of 2096 images. A classification model was built, composed by a forward convolutional neural network (CNN) followed by a discriminant analysis; the output was a probability for a given image to contain a brace, a spinal implant or none. The model was validated with a stratified tenfold cross-validation procedure. Performance was estimated by calculating the average accuracy. Results 98.3% of the radiographs were correctly classified as either reference, brace or implant, excluding 2.0% unclassified images. 99.7% of brace radiographs were correctly detected, while most of the errors occurred in the reference group (i.e. 2.1% of reference images were wrongly classified). Conclusion The proposed classification model, the originality of which is the coupling of a CNN with discriminant analysis, can be used to automatically label radiographs for the presence of scoliosis treatment. This information is usually missing from DICOM metadata, so such method could facilitate the use of large databases. Furthermore, the same model architecture could potentially be applied for other radiograph classifications, such as sex and presence of scoliotic deformity. Acknowledgements The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling (with the support of ParisTech and Yves Cotrel Foundations, Société Générale, Proteor and Covea).

The data collection was approved of by the ethical commit-tee (CPP 6001 Ile de France V), and patients and their parents signed an informed consent. Bracing is the most common treatment to stop the progression of adolescent idiopathic scoliosis. Finite element modeling could help improve brace design, but model validation is still a challenge. In this work, the clinical relevance of a predictive and subject-specific model for bracing was evaluated in forty-six AIS patients. The model reproduces brace action and the patient’s spinopelvic adjustments to keep balance. The model simulated 70% or more patients with geometrical parameters within a preselected tolerance level. Although the model simulation of the sagittal plane could be improved, the approach is promising for a realistic and predictive simulation of brace action. The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling (with the support of ParisTech and Yves Cotrel Foundations, Proteor, Société Génerale and Covea). We are also thankful to David Barrie Colridge for his support.

OBJECTIVEThe best predictors of height gain due to surgical correction are the number of fused vertebrae and the degrees of the corrected Cobb angle. Existing studies of predictive models measured the radiographic spinal height and did not report the clinical height gain. The aims of this study were to determine the best predictive factors of clinical height gain before surgical correction, construct a predictive model using patient population data for machine learning, and test the performance of this model on a validation population.METHODSThe authors reviewed 145 medical records of consecutive patients who underwent surgery that included placement of posterior spinal instrumentation and fusion for idiopathic scoliosis between 2012 and 2016. Standing and sitting clinical heights were measured before and after surgery in patients who had been surgically treated under similar conditions. Multivariate analysis was then performed and the results were used to develop a predictive model for height gain after surgery. The data from the included patients were randomly assigned to a learning set or a test set.RESULTSIn total, 116 patients were included in the analysis, for whom the average postoperative clinical height gain in a standing position was 4.2 ± 1.8 cm (range 0–11 cm). The best prediction model was calculated as follows: standing clinical height gain (cm) = 1 − 0.023 × sitting clinical height (cm) − 0.19 × Risser stage + 0.058 × Cobb preoperative angle (°) + 0.021 × T5–12 kyphosis (°) + 0.14 × number of levels fused. In the validation cohort, 91% of the predicted values had an error of less than one-half of the actual height gain.CONCLUSIONSThis predictive model formula for calculating the potential postoperative height gain after surgical treatment can be used preoperatively to inform idiopathic scoliosis patients of what outcomes they may expect from posterior spinal instrumentation and fusion (taking into account the model’s uncertainty).

International audience; Study design Biomechanical human cadaver study.Objective To determine the three-dimensional intervertebral ranges of motion (ROMs) of intact and hook-instrumented tho-racic spine specimens subjected to physiological loads, using an in vitro experimental protocol with EOS biplane radiography.Summary of background data Pedicle screws are commonly used in thoracic instrumentation constructs, and their biome-chanical properties have been widely studied. Promising clinical results have been reported using a T1–T5 thoracic hook–claw construct for proximal rod anchoring. Instrumentation stability is a crucial factor in minimizing mechanical complications rates but had not been assessed for this construct in a biomechanical study.Methods Six fresh-frozen human cadaver C6–T7 thoracic spines were studied. The first thoracic vertebrae were instrumented using two claws of supra-laminar and pedicle hooks, each fixed on two adjacent vertebrae, on either side of a single free vertebra. Quasi-static pure-moment loads up to 5 Nm were applied to each specimen before and after instrumentation, in flexion–extension, right and left bending, and axial rotation. Five steel beads impacted in each vertebra allowed 3D tracking of vertebral movements on EOS biplanar radiographs acquired after each loading step. The relative ranges of motion (ROMs) of each pair of vertebras were computed.Results Mean ROMs with the intact specimens were 17° in flexion–extension, 27.9° in lateral bending, and 29.5° in axial rotation. Corresponding values with the instrumented specimens were 0.9°, 2.6°, and 7.3°, respectively. Instrumentation sig-nificantly (P < 0.05) decreased flexion–extension (by 92–98%), lateral bending (by 87–96%), and axial rotation (by 68–84%).Conclusion This study establishes the biomechanical stability of a double claw–hook construct in the upper thoracic spine, which may well explain the low mechanical complication rate in previous clinical studies.Level of evidence Not applicable, experimental cadaver study.

Methods to reconstruct anatomical structures in 3D are gaining interest in medicine because they give access to quantitative information on the patient’s geometry. However, these methods are user-dependent and require a trained operator, which is time consuming and a source of error and unreliability. The aim of this work was to validate a novel method of landmark selection to perform the 3D reconstruction of the rib cage from biplanar calibrated radiographies. The method uses digital painting for digitization of anatomical landmarks (eight ribs midlines, posterior extrema, sternum) to build a first estimate of the 3D ribcage geometry. Twenty scoliotic patients were included (Cobb angle: 43° ± 11°) and their ribcage was reconstructed twice with the proposed method by four trained operators. Measurement reproducibility was similar to previously validated methods. Uncertainty (95% CI) was 2.3° for the rib hump measurement, 9.7 mm and 3.8 mm for maximal antero-posterior and lateral diameter, 395 cm3 for ribcage volume. The method was qualitatively considered more user-friendly than previous versions, although it still requires a trained operator, and it took approximately 2 minutes of manual digitization. The new method should facilitate diffusion of 3D quantitative analysis of ribcage in clinical routine.

Resume Introduction La prise en charge de la scoliose idiopathique de l’adolescent (SIA) peut necessiter des traitements chirurgicaux aux consequences lourdes. L’existence d’un desequilibre frontal, authentifie par l’examen clinique a l’aide d’un fil a plomb (DFFP) est un element important qui pousse a un traitement chirurgical. La technique de reference pour l’appreciation de l’equilibre postural du tronc reste neanmoins la materialisation de la ligne de gravite (LG) et sa projection dans un referentiel determine et connu. De recentes etudes ont montre la possibilite de materialiser la LG d’un patient a partir de stereoradiographies apres reconstruction de l’enveloppe corporelle (technique de barycentremetrie). L’hypothese que nous nous proposons de verifier est qu’il existe une concordance entre le DFFP et la LG. Materiels et methodes Dans un premier temps la determination de la LG par la methode de barycentremetrie a ete validee chez 14 SIA en la comparant aux donnees recueillies sur une plate-forme de force. Les valeurs normales de DFFP et LG ont ensuite ete determinees chez 27 adolescents asymptomatiques au moyen d’une technique stereoradiographique. Une comparaison de ces memes valeurs a ete ensuite realisee sur une population de 53 patients porteurs d’une SIA. Resultats La fiabilite des mesures de la LG dans le plan frontal avec la technique de barycentremetrie etait de 2,4 mm (intervalle de confiance a 95 %). Il existait une concordance statistiquement forte entre la distance de la LG par rapport au milieu de la ligne joignant les centres des 2 tetes femorales (LG/HA) et le DFFP calcule comme la distance entre la verticale au milieu de T1 et le centre du plateau sacre (T1 V/S) : r = 0,71 p Conclusion Cette etude valide la determination de la LG a partir de stereoradiographies dans une population de SIA. Le DFFP etait statistiquement correle a la LG, mais moins precis pour decider d’une indication chirurgicale. Niveau de preuve IV, Etude retrospective.

Inter- and intraobserver reliability study.To assess the reliability of a new radiographic classification of degenerative spondylolisthesis of the lumbar spine (DSLS).DSLS is a common cause of chronic low back and leg pain in adults. To this date, there is no consensus for a comprehensive analysis of DSLS. The reliability of a new DSLS classification system based on sagittal alignment was assessed.Ninety-nine patients admitted to our spinal surgery department for surgical treatment of DSLS between January 2012 and December 2015 were included. Three observers measured sagittal alignment parameters with validated software: segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis (SVA). Full body low-dose lateral view radiographs were analyzed and classified according to three main types: Type 1A: preserved LL and SL; Type 1B: preserved LL and reduced SL (≤5°); Type 2A: PI-LL ≥10° without pelvic compensation (PT25°); Type 2B: PI-LL ≥10° with pelvic compensation (PT ≥25°); Type 3: global sagittal malalignment (SVA ≥40 mm). The three observers classified radiographs twice with a 3-week interval for intraobserver reproducibility. Interobserver reproducibility was calculated using Fleiss κ and intra-class coefficient. Intraobserver reproducibility was calculated using Cohen κ.Mean age was 68.8 ± 9.8 years. Mean sagittal alignment parameters values were the following: PI: 60.1° ± 12.7°; PI-LL was 12.2° ± 13.9°, PT: 24.7° ± 8.5°; SVA: 44.9 mm ± 44.6 mm; SL: 16.6° ± 8.4°. Intraobserver repeatability showed an almost perfect agreement (ICC0.92 and Cohen κ0.89 for each observer). Fleiss κ value for interobserver reproducibility was 0.82, with percentage agreement among observers between 88% and 89%.This new classification showed an excellent inter- and intraobserver reliability. This simple method could be an additional sagittal balance tool helping surgeons improve their preoperative DSLS analysis.

International audience; Needle injection has been widely used in spinal therapeutic or diagnostic processes, such as discography. The use of needles has been suspected in causing mild disc degeneration which can lead to long-term back pain. However, the localised microscopic damage caused by needles has not been well studied. The local progressive damage on a microscopic level caused by needle punctures on the surface of bovine annulus fibrosus was investigated. Four different sizes of needle were used for the puncture and twenty-nine bovine intervertebral discs were studied. Polarization-resolved second harmonic generation and fluorescent microscopy were used to study the local microscopic structural changes in collagen and cell nuclei due to needle damage. Repeated 70 cyclic loadings at ±5% of axial strain were applied after the needle puncture in order to assess progressive damage caused by the needle. Puncture damage on annulus fibrosus were observed either collagen fibre bundles being pushed aside, being cut through or combination of both with part being lift or pushed in. The progressive damage was found less relevant to the needle size and more progressive damage was only observed using the larger needle. Two distinct populations of collagen, in which one was relatively more organised than the other population, were observed especially after the puncture from skewed distribution of polarization-SHG analysis. Cell shape was found rounder near the puncture site where collagen fibres were damaged.

There is no consensus for a comprehensive analysis of degenerative spondylolisthesis of the lumbar spine (DSLS). A new classification system for DSLS based on sagittal alignment was proposed. Its clinical relevance was explored. Health-related quality-of-life scales (HRQOLs) and clinical parameters were collected: SF-12, ODI, and low back and leg pain visual analog scales (BP-VAS, LP-VAS). Radiographic analysis included Meyerding grading and sagittal parameters: segmental lordosis (SL), L1–S1 lumbar lordosis (LL), T1–T12 thoracic kyphosis (TK), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis (SVA). Patients were classified according to three main types—1A: preserved LL and SL; 1B: preserved LL and reduced SL (≤5°); 2A: PI–LL ≥10° without pelvic compensation (PT

The complex structure of the annulus fibrosus is strongly related to its mechanical properties. Recent work showed that it is possible to observe the relative movement of fibre bundles in loaded cow tail annulus; the aim of this work was to describe and quantify annulus fibrosus micromechanics in degenerated human disc, and compare it with cow tail annulus, an animal model often used in the literature. Second harmonic generation was used to image the collagen matrix in twenty strips of annulus fibrosus harvested from intervertebral disc of seven patients undergoing surgery. Samples were loaded to 6% tensile strain in 1% steps. Elastic modulus was calculated from loading curves, and micromechanical strains were calculated from the images using custom software. The same protocol was applied to twenty strips of annulus harvested from cow tail discs. Significant morphological differences were found between human and cow tail samples, the most striking being the lack of collagen fibre crimp in the former. Fibres were also observed bending and running from one lamella to the other, forming a strong flexible interface. Interdigitation of fibre bundles was also present at this interface. Quantitative results show complex patterns of inter-bundle and inter-lamellar behaviour, with inter-bundle sliding being the main strain mechanism. Elastic modulus was similar between species, and it was not affected by the degree of degeneration. This work gives an insight into the complex structure and mechanical function of the annulus fibrosus, which should be accounted for in disc numerical modelling. Electronic supplementary material The online version of this article (doi:10.1007/s10237-017-0900-z) contains supplementary material, which is available to authorized users.

International audience; AbstractObjectives To determine lumbar intervertebral disc properties with shear wave elastography in adolescent idiopathic scoliotic(AIS) patients before and after surgery, and compare them with asymptomatic controls.Methods Twenty-five severe AIS patients with an indication for fusion surgery (15 ± 1.5 years old, the Cobb angle rangingbetween 40 and 93°) and fifty-nine asymptomatic adolescents (13 ± 2 years old) were included prospectively. Shear wave speed(SWS) was measured in the annulus fibrosus of L3-L4, L4-L5, and L5-S1 discs of each subject. In AIS patients, measurementstook place before surgery, and 3 months (N = 13) or 1 year after (N = 12).Results No difference was observed between disc levels in any group. When pooling disc levels, SWS was significantly higher inpreop AIS patients (4.0 ± 0.5 m/s) than in asymptomatic subjects (3.1 ± 0.5 m/s, p < 0.0001). SWS decreased 3 months postop(3.5 ± 0.3 m/s), and it decreased further towards normal values 1 year after (3.3 ± 0.4 m/s). SWS in preop AIS patients tended todecrease with the Cobb angle (Spearman’s rho = − 0.4, p = 0.05).Conclusion Shear wave elastography measurements showed that discs in AIS patients were altered relative to asymptomaticones, and this alteration tended to normalize 1 year post fusion surgery. Further studies should aim at determining if bracing ofmild scoliosis has an effect on disc properties.Key Points• Shear wave elastography shows alteration of annulus fibrosus in adolescent idiopathic scoliosis.• Disc elastography tends to normalize 1 year after surgery.