Abstract
Currently, the Spinal Instability Neoplastic Score system is used in clinics to evaluate the risk of fracture in patients with spinal metastases. This method, however, does not always provide a clear guideline due to the complexity in accounting for the effect of metastatic lesions on vertebral stability. The aim of this study was to use a validated micro Finite Element (microFE) modelling approach to analyse the effect of the size and location of lytic metastases on the mechanical properties of human vertebral bodies. Micro Computed Tomography based microFE models were generated with and without lytic lesions simulated as holes within a human vertebral body. Single and multiple lytic lesions were simulated with four different sizes and in five different locations. Bone was assumed homogenous, isotropic and linear elastic, and each vertebra was loaded in axial compression. It was observed that the size of lytic lesions was linearly related with the reduction in structural properties of the vertebral body (reduction of stiffness between 3% and 30% for lesion volume between 4% and 35%). The location of lytic lesions did not show a clear effect on predicted structural properties. Single or multiple lesions with the same volume provided similar results. Locally, there was a homogeneous distribution of axial principal strains among the models with and without lytic lesions. This study highlights the potential of microFE models to study the effect of lesions on the mechanical properties of the human vertebral body.
Highlights
Lytic lesions represent 95% of the spinal metastases developed at advanced stages of a cancer (Vialle et al, 2015)
The results showed that the size of the simulated lytic lesions was linearly related to a decrease in predicted structural properties, with limited contribution of the position of the lesion or of multiple lesions scenario
It remains to be investigated whether the same linear relationship would hold for larger simulated lytic lesions and for different specimens with different microarchitecture
Summary
Lytic lesions represent 95% of the spinal metastases developed at advanced stages of a cancer (Vialle et al, 2015) These lesions are described as focal regions of bone loss, which cause an increase in bone fragility and risk of pathological fractures (Burke et al, 2018; Hardisty et al, 2012; Ebihara et al, 2004). The SINS system does not account for the effect of the structural properties of the lesion, as its size and location, over vertebral stability. Such parameters are already used to assess the instability of long bones affected by metastatic lesions (Mirel's scoring system), even though it remains to be investigated their relevance for the assessment of spinal instability
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