CEMENT DISTRIBUTION AFFECTS LOAD-BEARING BY FRACTURED AND NEIGHBOURING VERTEBRAE FOLLOWING VERTEBROPLASTY

Introduction

Vertebroplasty helps to restore mechanical function to a fractured vertebra. We investigated how the distribution of injected cement benefits both fractured and neighbouring vertebrae.

Methods

Nine pairs of three-vertebra cadaver spine specimens (aged 67–90 yr) were compressed to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. Before and after vertebroplasty, compressive stiffness was determined, and stress profilometry was performed by pulling a pressure-transducer through each disc whilst under 1.0kN load. Profiles indicated intradiscal pressure (IDP) and compressive load-bearing by the neural arch (F_N) at both disc levels. Micro-CT was used to quantify cement fill in the anterior and posterior halves of each augmented vertebral body, and also in the region immediately adjacent to the fractured endplate

Results

Fracture reduced stiffness and IDP, and increased F_N. Following vertebroplasty, anterior fill was greater for Cortoss (30%) than PMMA (17%) (P<0.01). With Cortoss, increased posterior fill was associated with a greater restoration of IDP in the adjacent disc (P<0.05). Furthermore, specimen stiffness increased in proportion to cement fill adjacent to the fractured end-plate. With PMMA, increased anterior fill caused a greater reduction in F_N in the non-adjacent disc (P<0.05), whereas increased posterior fill and increased fill adjacent to the fracture caused a greater restoration of IDP in the adjacent disc (P<0.05).

Conclusion

Cement distribution varied between the two cements. However, increased filling immediately adjacent to the fractured endplate was linked most consistently to improved mechanical function.

Conflicts of Interest

None

Source of Funding

This work was funded by Action Medical Research. Vertebroplasty materials were provided by Stryker and by Orthovita.

We can confirm that this abstract has not been published previously in whole or substantial part, and the findings have not been presented previously at a national meeting.