Development of calcium phosphate cement for the augmentation of traumatically fractured porcine specimens using vertebroplasty

Sami M Tarsuslugil,Rochelle M O’Hara,Nicholas J Dunne,Fraser J Buchanan,John F Orr,David C Barton,Ruth K Wilcox

doi:10.1016/j.jbiomech.2012.11.036

Sami M Tarsuslugil, Rochelle M O’Hara + Show 5 more

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https://doi.org/10.1016/j.jbiomech.2012.11.036

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Abstract

The study aim was to develop and apply an experimental technique to determine the biomechanical effect of polymethylmethacrylate (PMMA) and calcium phosphate (CaP) cement on the stiffness and strength of augmented vertebrae following traumatic fracture. Twelve burst type fractures were generated in porcine three-vertebra segments. The specimens were randomly split into two groups (n=6), imaged using microCT and tested under axial loading. The two groups of fractured specimens underwent a vertebroplasty procedure, one group was augmented with CaP cement designed and developed at Queen's University Belfast. The other group was augmented with PMMA cement (WHW Plastics, Hull, UK). The specimens were imaged and re-tested . An intact single vertebra specimen group (n=12) was also imaged and tested under axial loading. A significant decrease (p<0.01) was found between the stiffness of the fractured and intact groups, demonstrating that the fractures generated were sufficiently severe, to adversely affect mechanical behaviour. Significant increase (p<0.01) in failure load was found for the specimen group augmented with the PMMA cement compared to the pre-augmentation group, conversely, no significant increase (p<0.01) was found in the failure load of the specimens augmented with CaP cement, this is attributed to the significantly (p<0.05) lower volume of CaP cement that was successfully injected into the fracture, compared to the PMMA cement. The effect of the percentage of cement fracture fill, cement modulus on the specimen stiffness and ultimate failure load could be investigated further by using the methods developed within this study to test a more injectable CaP cement.

Highlights

Every year, there are over 150,000 high-energy spinal fractures in the United States alone (Jones et al, 2011)
Calcium phosphate (CaP) cement has been considered as a potential alternative to PMMA because it allows the potential for bone in-growth, remodelling and the setting reaction occurs at body temperature
As the number of clinical case studies increases, there is a need to increase the understanding of the biomechanical effects of vertebroplasty on the traumatically injured spine and to develop pre-clinical models to enable such treatments to be evaluated in the laboratory

Summary

Introduction

There are over 150,000 high-energy spinal fractures in the United States alone (Jones et al, 2011). Burst fractures are reported to account for about 15% of all spinal fractures (Denis, 1983) and usually result from a high rate of axial compression impact on the vertebrae within the thoracolumbar region. These studies suggest that the treatment could reduce reliance on painkillers and increase mobility (Knavel et al, 2009). Vertebroplasty has the advantage of being a less invasive procedure, but PMMA cement may not be the optimal material for the augmentation of traumatic burst fractures It is not bioactive, so it is never incorporated into the bone.

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