Biomechanical Evaluation of the Vertebral Jack Tool and the Inflatable Bone Tamp for Reduction of Osteoporotic Spine Fractures

Study Design. Controlled in vitro study.Objective. To compare two kyphoplasty techniques in cadaveric fractured vertebrae: an experimental vertebral jack tool (VJT) and an inflatable bone tamp (IBT).Summary of Background Data. A previous biomechanical study showed restored strength and stiffness after height restoration in cadaveric-fractured osteoporotic vertebrae using a new device for reduction of osteoporotic vertebral fractures.Methods. Anterior wedge fractures (AO type A1.2) were created in 8 ( 4 lumbar, 4 thoracic) vertebrae by displacement eccentric external forces. In all vertebrae the amount of height reduction was 35%. After compression, 4 vertebrae were restored in height using the VJT procedure. Four vertebrae were restored in height using the IBT procedure. Posttreatment strength and stiffness of the vertebrae were determined by a compression test identical to the pretreatment compression protocol.Results. In the VJT group the postrestoration strength was 81% +/- 13% of the original strength and in the IBT group it was 96% +/- 32%. The postrestoration stiffness in the VJT group was 61% +/- 42% of the original stiffness and in the IBT group 76% +/- 62% of the original stiffness. The vertebrae in the VJT group were restored to 101% +/- 2% of their original height whereas this was 104% +/- 14% in the IBT group. In this study, no cases of cement leakage were found. No cases of damaging of the end plates, new fractures or perforations were seen in both groups. The mean amount of cement inserted for the VJT group was 3.6 +/- 0.9 cm(3) and for the IBT group 5.9 +/- 0.8 cm(3).Conclusion. Both kyphoplasty procedures were able to restore height in this in vitro study, while strength and stiffness were partially restored, with no significant differences. In this study on average significant less cement was used in the VJT procedure. No complications were noted in both groups. This new end plate-to-end plate laminar augmentation technique may be of clinical advantage.