A BIOMECHANICAL COMPARISON OF KYPHOPLASTY USING A BALLOON BONE TAMP VS EXPANDABLE POLYMER BONE TAMP USING A DEER SPINE MODEL

Abstract

Objectives: Ex vivo biomechanical study to compare the properties of isolated, fractured, vertebral bodies after treatment by kyphoplasty with one of two bone tamps: a balloon bone tamp (Kyphon®) or an expandable polymer bone tamp (SKyBone®).

Methods: Simulated compression fractures were created in 21 vertebral bodies (L3–5) harvested from red deer (sp. elaphus. elaphus), with initial strength and stiffness determined concurrently. Deer spine was selected as an alternative to human cadaveric spine due to its availability and its very similar bone density and morphological profile. Vertebral bodies were assigned to one of three groups: (1) unaugmented (control); (2) kyphoplasty using a balloon bone tamp (BBT); and (3) kyphoplasty using a polymer bone tamp (PBT). The kyphoplasty treatment consisted of deploying the bone tamp biped-icularly, then filling the created voids with standardised low viscosity cement. All vertebrae were then recom-pressed to determine their augmented strength and stiffness. Data was analysed using one-way analysis of variance test and paired samples T-Test.

Result: Following fracture and subsequent kyphoplasty augmentation, the median strength of the BBT group was 6.71kN (± 2.71) vs 7.36kN (± 3.43) in the PBT group. Median stiffness in the balloon bone tamp group was 1.885 kN/mm (± 0.340) compared with 1.882 kN/ mm (± 0.868). Augmented strength tended to be greater in the PBT group than for BBT group, but this difference was not significantly different (p> .8). Significantly greater strength was obtained after kyphoplasty using BBT or PBT, compared with control group (p=.001 and .04, respectively). BBT and PBT groups were not statistically different for augmented stiffness (p=.4). Both BBT and PBT groups have greater augmented stiffness as compared to the control group (p=.007 and .005, respectively).

Conclusions: The use of a polymer bone tamp creates similar augmented vertebral body strength and stiffness as compared with the widely used balloon bone tamp in a deer spine model. Similar results would be expected in human spine and consequently the polymer bone tamp may be used as an alternative bone tamp for kyphoplasty.