Towards determining soft tissue properties for modelling spine surgery: current progress and challenges

Abstract

Current complication rates for adolescent scoliosis surgery necessitate the development of better surgical planning tools to improve outcomes. Here we present our approach to developing finite element models of the thoracolumbar spine for deformity surgery simulation, with patient-specific model anatomy based on low-dose pre-operative computed tomography scans. In a first step towards defining patient-specific tissue properties, an initial 'benchmark' set of properties were used to simulate a clinically performed pre-operative spinal flexibility assessment, the fulcrum bending radiograph. Clinical data for 10 patients were compared with the simulated results for this assessment and in cases where these data differed by more than 10%, soft tissue properties for the costo-vertebral joint were altered to achieve better agreement. Results from these analyses showed that changing the costo-vertebral joint stiffness resulted in acceptable agreement between clinical and simulated flexibility in two of the six cases. In light of these results and those of our previous studies in this area, it is suggested that spinal flexibility in the fulcrum bending test is not governed by any single soft tissue structure acting in isolation. More detailed biomechanical characterisation of the fulcrum bending test is required to provide better data for determination of patient-specific soft tissue properties.

Effect of screw position on load transfer in lumbar pedicle screws: a non-idealized finite element analysis

“…However, as suggested many years ago by Halvorson (Halvorson, Kelley, Thomas, Whitecloud and Cook 1994), and more recently by Dreischarf et al,(Dreischarf et al 2014) Goel et al (Goel et al 2012), Meijer et al (Meijer et al 2011), Chevalier et al (Chevalier and Zysset 2012), and Little et al (Little and Adam 2012), FEA based on a non-idealized series of models, or patient-specific models, could be of greater value.…”

Lumbar annulus fibrosus biomechanical characterization in healthy children by ultrasound shear wave elastography

“…This is in part due to the difficulties of measuring IVD properties in vivo. Spinal flexibility and intervertebral stiffnesses have been assessed by traction, bending or fulcrum tests [10][11][12] tests; these techniques, however, do not allow direct measurement of IVD biomechanical properties and require invasive radiographic techniques. Non-invasive techniques based magnetic resonance elastography are being developed to investigate disc mechanical properties [13][14][15].…”

An FE investigation simulating intra-operative corrective forces applied to correct scoliosis deformity

“…However, the results of this study are preliminary with data for only two patients and using this technique, the resulting joint stiffness does not provide sufficient resolution to determine individual tissue behaviour. In our previous studies we have attempted to derive patient-specific soft tissue parameters for the spinal ligaments using clinical data from pre-operative flexibility assessments [17,18]. In these studies, due to the lack of literature for the adolescent tissues, an initial set of ‘benchmark’ tissue parameters were based on the mechanical properties derived from adult subjects (Table 2) [19-30].…”