Balloon kyphoplasty (BKP) is a minimally invasive surgical technique used to correct kyphosis and vertebral compression fractures. BKP uses cement to fill a void created by the inflation of a balloon in a vertebra, it can be used as an alternative to vertebroplasty to reduce cement extravasation. Issues such as poor inter digitisation of the cement and the trabecular bone can arise with the BKP method. This can be due to a compacted layer created during the procedure which can cause complications post-surgery. The primary aim of this study was to investigate alternative cement application methods which could improve the mechanical strength of the bone-cement interface. Three alternative methods were investigated, and cylindrical bone-cement specimens were created for all methods (BKP and three alternatives). An important part of this study was to replicate the compacted layer created by the inflation of the balloon tamp in BKP. Synthetic trabecular bone specimens (Sawbones®, Pacific Research Laboratories, Vashon Island, Washington, USA) were pre-loaded in compression and the resultant compacted layers were found to replicate the compacted layers found in surgery. Mechanical testing was carried out with an MTS Model 858 Bionix^® Servohydraulic load frame using static tensile and torsion loads. Static tests revealed that two of the three alternative methods were an improvement on BKP, with a high statistical significance in relation to the mechanical performance of the bone-cement interface (P < 0.001). This data illustrates the potential to improve the standard BKP technique, in terms of bone-cement interface performance.

Summary Statement

Spinal flexibility in bending and axial torque has been shown to exhibit very modest changes with advancing disc degeneration. This study is the first to address the possible relationship in pure anterior shear and no clear relationship was observed.