The biomechanical effects of osteoporosis vertebral augmentation with cancellous bone granules or bone cement on treated and adjacent non-treated vertebral bodies: A finite element evaluation

Abstract 

Background

In order to reduce the complications of bone cement, many efforts are underway to replace bone cement augmentation with cancellous bone granule augmentation for treating compression fractures of osteoporotic vertebral bodies. The goal of this study was to investigate the biomechanical effects of cancellous bone granule augmentation of Optimesh and polymethylmethacrylate augmentation of kyphoplasty on treated and adjacent non-treated vertebral bodies.

Methods

Three-dimensional, anatomically detailed finite element models of the L1–L2 functional spinal unit were developed on the basis of cadaver computed tomography scans. The material properties and plug forms of the L2 centrum were adapted to simulate osteoporosis, cancellous bone granule and polymethylmethacrylate augmentation. The models assumed a three-column loading configuration as the following types: compression, flexion and extension.

Findings

Compared with the osteoporotic model, changes in stress and strain at adjacent levels both of cancellous bone granule and polymethylmethacrylate augmentation models were minimal, but stresses/strains within the two reinforcement material plugs were modified distinctly and differently. In addition, osteoporosis and augmentation had little effect on either the axial compressive displacement of the three columns or the average disc internal pressure in all models.

Interpretation

Both cancellous bone granule and polymethylmethacrylate augmentation restore the total strength and stiffness level of treated vertebral bodies and benefit the reconstruction of vertebral function. Regarding the material mechanical compatibility and the biocompatibility of the treated vertebral body and reinforcement material, however, the morcelized cancellous bone is better than polymethylmethacrylate augmentation.

Keywords: Functional spinal unit, Osteoporosis, Augmentation, Kyphoplasty, Finite element analysis, Material mechanical compatibility, Biocompatibility