Improvement in vertebral endplate engagement following anterior column reconstruction using a novel expandable cage with self-adjusting, multiaxial end cap

Background: Destabilization of the vertebral column – as seen in trauma and metastatic spine disease – often requires corpectomy and anterior column reconstruction. Stresses applied to the implant can lead to subsidence, ultimately requiring in surgical revision. Here we report a cadaveric investigation of a novel expandable corpectomy cage with a self-adjusting, multiaxial end cap. Methods: Four cadaveric T11-sacrum spines (mean 67.3 yr; 75% female) were treated with L2 corpectomy and T12-L4 pedicle screw fusion. Pressure sensors were applied to the L1 and L3 endplates and anterior column reconstruction was performed with either a standard expandable corpectomy cage (T2A), an expandable corpectomy cage with a self-adjusting, multiaxial end cap (T2S), or the latter cage with oblong, extended end caps (T2S + EE). Total contact area was compared pre- and post-reduction using ANOVA general linear model. Results: Pre-reduction, the T2S constructs had a trend of higher surface contact than the conventional T2A constructs, though the results were not significant (p = 0.068); however, T2S + EE constructs did produce significantly larger contact with vertebral endplates (p = 0.04). The difference was also significant for both conditions following compression (p < 0.01 for both constructs). Conclusions: The use of an expandable corpectomy cage with a self-adjusting, multiaxial end cap produces significant increases in vertebral endplate contact area. These in vitro data suggest that the self-adjusting, multiaxial end cap may serve to decrease the risk of subsidence in patients undergoing anterior column resection and reconstruction. Clinical data would be required to confirm the relationship between endplate contact area and risk of subsidence.