Biomechanical simulations of scoliotic spine correction due to prone position and anaesthesia prior to surgical instrumentation

Duke, Kajsa; Aubin, Carl‐Éric; Dansereau, J.

doi:10.1016/j.clinbiomech.2005.05.006

Cited by 39 publications

(37 citation statements)

References 24 publications

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“…It should be noted that the spine stiffness of the scoliotic patient is probably quite different than the mechanical properties chosen here from experimental studies using cadaveric specimen. A method allowing personalizing the mechanical properties to individual patient, as the one developed by Petit [25] or Duke [9] should be implemented to improve this issue. Moreover, only the ''passive'' action of the brace was considered as no muscles were modeled.…”

Section: Discussionmentioning

confidence: 99%

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

2007

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Based on a three-dimensional patient-specific finite element model of the spine, rib cage, pelvis and abdomen, a parametric model of a thoraco-lumbo-sacral orthosis (TLSO) was built. Its geometry is custom-fit to the patient. The rigid shell, pads and openings are all represented. The interaction between the trunk and the brace is modeled by a point-to-surface contact interface. During the nonlinear simulation process, the brace is opened, positioned on the patient and strap tension is applied. A TLSO similar to Boston brace system was built for a right-thoracic scoliotic patient. The influences of the trochanter pad and strap tension on the 3-D geometrical corrections and on the forces generated by the brace were evaluated. The role of the trochanter pad as a lever arm is confirmed by the model. The brace induces a reduction of the lordosis and pelvic tilt. The reduction of the frontal curvature is about 20% for a strap tension of 60 N. Axial rotation does not significantly change and rib hump is worsened. By using an explicit brace model and a contact interface, a more realistic simulation of orthotic treatment of scoliosis can be achieved. The stabilization of the brace on the patient can be represented and less restrictive boundary conditions can be applied. This model could be used to study the effect of design parameters on the brace efficiency.

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Section: Discussionmentioning

confidence: 99%

“…The Ansys 9.0 FE Package is used (Ansys Inc., Canonsburg, PA, USA). The main components of the model have been described elsewhere [2,8,9,12,[22][23][24] and are summarized here. It contains 3,163 nodes and 3,209 elements representing the osseo-ligamentous structures of the spine, rib cage, pelvis and abdominal tissues.…”

Section: Methodsmentioning

confidence: 99%

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

2007

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“…Thus far, the primary focus has been on the modulation of lumbar lordosis due to positioning of the lower limbs [3][4][5] and as a consequence many surgical frames now allow flexion or extension of patients' hips. While some studies have attempted to quantify the impact of prone positioning on thoracic kyphosis [6][7][8], no devices have been introduced which allow modulation of thoracic kyphosis intra-operatively.…”

Section: Introductionmentioning

confidence: 99%

The impact of intra-operative sternum vertical displacement on the sagittal curves of the spine

et al. 2009

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Patient positioning is an important step in spinal surgeries. Many surgical frames allow for lumbar lordosis modulation due to lower limb displacement, however, they do not include a feature which can modulate thoracic kyphosis. A sternum vertical displacer (SVD) prototype has been developed which can increase a subject's thoracic kyphosis relative to the neutral prone position on a surgical frame. The kyphosis increase is obtained by lifting the subject's torso off the thoracic cushions with a dedicated sternum cushion that can be displaced vertically. The objective of this study was to evaluate the impact of SVD utilization on the sagittal curves of the spine. Experimental testing was performed on six healthy volunteers. Lateral radiographs were taken in the neutral and sternum raised positions and then analyzed in order to compare the values of sagittal curves. The displacement of volunteers and surgical frame components between positions was recorded using an optoelectronic device. Finally, interface pressures between the volunteers and surgical frame cushions were recorded using a force sensing array. Average results show that passing from the neutral to sternum raised positions caused an increase of 53% in thoracic kyphosis and 24% in lumbar lordosis; both statistically significant. Sensors showed that the sternum was raised a total of 8 cm and that interface pressures were considerably higher in the raised position. The SVD provides a novel way of increasing a patient's thoracic kyphosis intra-operatively which can be used to improve access to posterior vertebral elements and improve sagittal balance. It is recommended that its use should be limited in time due to the increase in interface pressures observed.

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“…[1,2], however in more recent models the disc and ligaments are still modelled as a 'lumped' stiffness using single elastic beams, but the zygapophyseal joints and costovertebral joints are modelled as separate structures, e.g. [12]. A 2006 study by Rohlmann et al [14] used a 3D continuum model for the intervertebral discs (defined using isotropic linear elastic material properties), but the ligaments, facet joints, and ribcage were idealized using spring elements between adjacent vertebrae.…”

Section: Discussionmentioning

confidence: 99%

Patient‐specific computational biomechanics for simulating adolescent scoliosis surgery: Predicted vs clinical correction for a preliminary series of six patients

Little

Adam

2010

Numer Methods Biomed Eng

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SUMMARYScoliosis is a spinal deformity that requires surgical correction in progressive cases. In order to optimize surgery outcomes, patient-specific finite element models are being developed by our group. In this paper, a single rod anterior correction procedure is simulated for a group of six scoliosis patients. For each patient, personalized model geometry was derived from low-dose CT scans, and clinically measured intra-operative corrective forces were applied. However, tissue material properties were not patient-specific, being derived from existing literature. Clinically, the patient group had a mean initial Cobb angle of 47.3 • , which was corrected to 17.5 • after surgery. The mean simulated post-operative Cobb angle for the group was 18.1 • . Although this represents good agreement between clinical and simulated corrections, the discrepancy between clinical and simulated Cobb angle for individual patients varied between −10.3 and +8.6 • , with only three of the six patients matching the clinical result to within accepted Cobb measurement error of ±5 • . The results of this study suggest that spinal tissue material properties play an important role in governing the correction obtained during surgery, and that patient-specific modelling approaches must address the question of how to prescribe patient-specific soft tissue properties for spine surgery simulation.

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Biomechanical simulations of scoliotic spine correction due to prone position and anaesthesia prior to surgical instrumentation

Cited by 39 publications

References 24 publications

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

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

The impact of intra-operative sternum vertical displacement on the sagittal curves of the spine

Patient‐specific computational biomechanics for simulating adolescent scoliosis surgery: Predicted vs clinical correction for a preliminary series of six patients

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