A solution of torsional problem by energy method in case of anisotropic cross-section

We proposed an original method to investigate the problem of torsion of anisotropic cross-section. We implemented an energy method to calculate the stress function represented by infinite series of trigonometric functions adapted to rectangular cross-section. After validation, we implemented a parametric sensitivity study to investigate the influence of the cross-section aspect ratio and the anisotropy level on the stress function, the strain energy density and the torsion stiffness. The process showed a fast convergence with a very good accuracy. The model showed a potential interest for the experimental identification of anisotropic material properties

Disc volume properties from MRI in adolescent idiopathic scoliosis: correlation to surgical outcome

In young scoliotic patients, the post-operative consequence of spine fusion upon the free lower lumbar spine is one of the major concerns of the surgical treatment. The remodeling of free-motion segment and the role of discs below thoraco-lumbar fusions remains unknown. However, disc hydration and mass exchange flow between disc and vertebral body should play a significant role in the mechano-biology of the vertebral segment. Magnetic resonance imaging is relevant to study intervertebral discs in young scoliotic patients since related to hydration and non-radiant

Sagittal spino-pelvic organization influences the biomechanical behavior of the intervertebral disc after idiopathic scoliosis surgery: a prospective study with minimum 2 years follow up

Purpose: To analyse the biomechanical properties of the intervertebral disc after scoliosis surgery according to the underlying spino-pelvic organization

Spino-pelvic alignment influences disc hydration properties after AIS surgery: a prospective MRI-based study

To analyze the disc hydration and volumetric changes of the intervertebral disc after scoliosis surgery depending on the sagittal spino-pelvic organization

Hydration properties of the lumbar intervertebral discs in AIS after surgical correction:five years follow-up and comparison with an age-matched control group

We compared disc hydration properties of adolescent idiopathic scoliosis before and 5 years after spinal fusion with an age-matched control group. We conducted a prospective MRI follow-up of 23 patients. Disc and nucleus volumes were reconstructed on T2 weighted sequence. In the scoliotic group, vd and vn were lower than control group, hydration ratio (Vn/Vd) was lower. After surgery, subjacent discs rehydrated. AIS induces a loss of IVD hydration. Surgical correction can reverse homeostasis disturbances related to spinal deformity

Risk factors for adjacent segment degeneration after adolescent idiopathic scoliosis surgery: the intervertebral disc stability concept

Ideal surgical management of adolescent idiopathic scoliosis (AIS) aims for an optimal correction of the deformity while preserving mobility. An unbalanced rigid spine puts the mobile segment at higher risk of disk degeneration. The goal of our study is to clarify the long term outcome of AIS after spinal fusion

MRI evaluation of the hydration status of non-pathological lumbar intervertebral discs in a pediatric population

Introduction The intervertebral disc (IVD) is made up of the annulus fibrosus (AF) and the nucleus pulposus (NP) – an inert hydrated complex. The ability of the IVD to deform is correlated to that of the NP and depends on its hydration. As the IVD ages, its hydration decreases along with its ability to deform. In adolescent idiopathic scoliosis, one of the etiological hypotheses pertains to the IVD, thus making its condition relevant for the diagnosis and monitoring of this pathology. Hypothesis IVD hydration depends on sex, age and spine level in an asymptomatic pediatric population. The corollary is data on a control group of healthy subjects. Material and methods A cohort of 98 subjects with normal spine MRI was enrolled; their mean age was 13.3 years. The disc volume and hydration of each IVD was evaluated on T2-weighted MRI sequences, using previously validated image processing software. This evaluation focused on the lumbar spine, from the thoracolumbar junction to the lumbosacral junction. It was assumed that IVD hydration was related to the ratio of NP and AF volumes. A mixed multivariate linear analysis was used to explore the impact of age, sex and spinal level on disc hydration. Results Disc hydration was higher overall in boys than in girls, but this difference was not significant. Hydration increased with age by +0.005 for each additional year (p = 0.0213). Disc hydration appears to be higher at the thoracolumbar junction than the lumbar spine, although this difference was not significant. Conclusion Through this MRI study, we established a database of non-pathological lumbar disc hydration as a function of age, sex and spinal segment along with 95% confidence intervals

Risk factors for adjacent segment degeneration after adolescent idiopathic scoliosis surgery (AIS): the intervertebral disc stability concept

International audienceIdeal surgical management of adolescent idiopathic scoliosis (AIS) aims for an optimal correction of the deformity while preserving mobility. An unbalanced rigid spine puts the mobile segment at higher risk of disk degeneration. The goal of our study is to clarify the long term outcome of AIS after spinal fusion

Mechanical properties of fused sagittal sutures in scaphocephaly

Background: Craniosynostosis in newborns is caused by the premature closure of the cranial sutures leading to cranial vault deformity. It results in aesthetic imbalance and developmental disabilities and surgery is frequent during the first months of growth. Our study focused on scaphocephaly defined as the premature closure of the sagittal suture. We hypothesised that the effective mechanical properties of sutures were altered as compared to those of the parietal adjacent tissue considered as control. Methods: The population consisted of seven males and four females (mean age 4.9 months). Sixteen suture samples and thirty-four parietal tissue samples were harvested during corrective surgery and investigated by using three-point bending tests to obtain the structure-stiffness of specimens. An energy model was used to derive the effective Young’s modulus. A histological study complemented the experimental protocol. Findings: Fused sutures were thicker than adjacent bone and the natural curvature of sutures did not influence the static mechanical response. The stiffness of stenotic sutures was significantly higher than that of the parietal bone. The effective Young’s modulus of stenotic sutures was significantly lower than that of the parietal adjacent tissue. The parietal tissue showed a parallel bone architecture whereas the central stenotic tissue was disorganised with more vascularisation. Interpretation: The stenotic suture differed in structural and mechanical terms from the adjacent bone during calvarial growth in the first year of life. Our study emphasised the alteration of effective tissue properties in craniosynostosis. Keywords: scaphocephaly, craniosynostosis, biomechanics, mechanobiology, paediatrics, morphogenesis

Mechanical coupling effects into a L3-L5 vertebral segment

In the surgery of the adolescent idiopathic scoliosis (AIS), it has been shown that arthrodesis was increasing the intervertebral disc volume of discs below spine fusion post-operatively. Another consequence was the variation of hydration of disc remained free. The surgery induced a redistribution of strain energy but it is challenging to identify the mechanical loadings in-vivo. We hypothesized that the direct simulation of a vertebral segment under compression, bending and shear supported the analysis of mechanical transfers in-vivo