Virtual prototyping of a brace design for the correction of scoliotic deformities

The distribution of stresses in the scoliotic spine is still not well known despite its biomechanical importance in the pathomechanisms and treatment of scoliosis. Gravitational forces are one of the sources of these stresses. Existing finite element models (FEMs), when considering gravity, applied these forces on a geometry acquired from radiographs while the patient was already subjected to gravity, which resulted in a deformed spine different from the actual one. A new method to include gravitational forces on a scoliotic trunk FEM and compute the stresses in the spine was consequently developed. The 3D geometry of three scoliotic patients was acquired using a multi-view X-ray 3D reconstruction technique and surface topography. The FEM of the patients' trunk was created using this geometry. A simulation process was developed to apply the gravitational forces at the centers of gravity of each vertebra level. First the "zero-gravity" geometry was determined by applying adequate upwards forces on the initial geometry. The stresses were reset to zero and then the gravity forces were applied to compute the geometry of the spine subjected to gravity. An optimization process was necessary to find the appropriate zero-gravity and gravity geometries. The design variables were the forces applied on the model to find the zero-gravity geometry. After optimization the difference between the vertebral positions acquired from radiographs and the vertebral positions simulated with the model was inferior to 3 mm. The forces and compressive stresses in the scoliotic spine were then computed. There was an asymmetrical load in the coronal plane, particularly, at the apices of the scoliotic curves. Difference of mean compressive stresses between concavity and convexity of the scoliotic curves ranged between 0.1 and 0.2 MPa. In conclusion, a realistic way of integrating gravity in a scoliotic trunk FEM was developed and stresses due to gravity were explicitly computed. This is a valuable improvement for further biomechanical modeling studies of scoliosis.

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“…Main components of the model of the spine, rib cage, and pelvis have been described elsewhere [3] and are here summarized (Fig. 1d).…”

Section: Trunk Modelmentioning

confidence: 99%

“…Mechanical properties of all the components of the model were taken from experimental and published data [3]. They are summarized in Table 1.…”

Section: Trunk Modelmentioning

confidence: 99%

A new method to include the gravitational forces in a finite element model of the scoliotic spine

Clin

Aubin

Lalonde

et al. 2011

Med Biol Eng Comput

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“…Computational and finite element models have been developed in previous studies, to simulate varying levels of complexity in the spinal geometry-from individual intervertebral discs [8] and spinal motion segments [9,10,14,21] to whole spine osseous/osseoligamentous models [2,6,11,15]. Increasingly, it is becoming desirable to base these models on patient specific rather than average or idealized data, in order to simulate the specific response of a patient's spinal anatomy to surgical procedures [3,5,6,11,12,15]. Thus, in this study of cadaveric specimens, subject specific geometry for the intervertebral disc was obtained.…”

Section: Discussionmentioning

confidence: 99%

Parametric equations to represent the profile of the human intervertebral disc in the transverse plane

2007

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Computational and finite element models of the spine are used to investigate spine and disc mechanics. Subject specific data for the transverse profile of the disc could improve the geometric accuracy of these models. The current study aimed to develop a mathematical algorithm to describe the profile of the disc components, using subject-specific data points. Using data points measured from pictures of human intervertebral discs sectioned in the transverse plane, parametric formulae were derived that mapped the outer profile of the anulus and nucleus. The computed anulus and nucleus profile were a similar shape to the discs from which they were derived. The computed total disc area was similar to the experimental data. The nucleus:disc area ratios were sensitive to the data points defined for each disc. The developed formulae can be easily implemented to provide patient specific data for the disc profile in computational models of the spine.

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“…Bracing simulation with those personalized biomechanical models showed similar results to real in-brace geometry and revealed the potential to optimize bracing treatment of AIS through personalized evaluation and design improvement. A recently developed patient-specific brace simulator was developed based on refinements of the finite element models [43], and allowed to test and assess the efficiency of hundreds of different virtual braces for a given patient, thus optimizing the design of each brace [44]. Labelle et al [38] undertook a randomized control trial comparing brace design using computer-assisted tool combining surface topography, surface pressure measurement with 3D reconstruction of the trunk (test group) with the conventional manner (control group).…”

Section: Methods Developed To Assist Bracing Treatmentmentioning

confidence: 99%

Computer algorithms and applications used to assist the evaluation and treatment of adolescent idiopathic scoliosis: a review of published articles 2000–2009

et al. 2011

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Adolescent idiopathic scoliosis (AIS) is a complex spinal deformity whose assessment and treatment present many challenges. Computer applications have been developed to assist clinicians. A literature review on computer applications used in AIS evaluation and treatment has been undertaken. The algorithms used, their accuracy and clinical usability were analyzed. Computer applications have been used to create new classifications for AIS based on 2D and 3D features, assess scoliosis severity or risk of progression and assist bracing and surgical treatment. It was found that classification accuracy could be improved using computer algorithms that AIS patient follow-up and screening could be done using surface topography thereby limiting radiation and that bracing and surgical treatment could be optimized using simulations. Yet few computer applications are routinely used in clinics. With the development of 3D imaging and databases, huge amounts of clinical and geometrical data need to be taken into consideration when researching and managing AIS. Computer applications based on advanced algorithms will be able to handle tasks that could otherwise not be done which can possibly improve AIS patients' management. Clinically oriented applications and evidence that they can improve current care will be required for their integration in the clinical setting.

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Virtual prototyping of a brace design for the correction of scoliotic deformities

Cited by 44 publications

References 28 publications

A new method to include the gravitational forces in a finite element model of the scoliotic spine

A new method to include the gravitational forces in a finite element model of the scoliotic spine

Parametric equations to represent the profile of the human intervertebral disc in the transverse plane

Computer algorithms and applications used to assist the evaluation and treatment of adolescent idiopathic scoliosis: a review of published articles 2000–2009

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