Introduction: Loss of reduction after bone tamp deflation, prior to cement injection remains a concern with kyphoplasty.
Methods: Twenty seven osteoporotic vertebral bodies (T11-L4) were sequentially assigned to one of three treatment groups: Group A, commercially available bone tamp I; Group B, commercially available bone tamp II; and Group C, bone tamp I with sleeve (Figure 1). Each vertebral body (VB) was compressed axially on an MTS Bionix 858 machine at a rate of 5mm/min until compressed by 40% of the initial anterior height. The fractured VBs then underwent kyphoplasty with cement augmentation. After the cement cured, augmented vertebral bodies were then recompressed. The anterior vertebral body height (mm) and wedge angle (degrees) were measured initially, after mechanically creating an anterior wedge fracture, and after repairing the compression fracture. Each vertebral body was subjected to 111N load to simulate in vivo physiologic loading during inflation and cement augmentation. The vertebral height, wedge angle, cement volume, and inflation pressure was compared between the treatment groups using an unpaired t-test (p<0.05). Failure loads were compared between intact and repaired VBs using a paired t-test (p<0.05).
Results: The average percentage of lost VB height restored in Group A,B,C was 29%, 30% and 56%, respectively. A similar trend was observed in the mean changes in vertebral body wedge angle. No significant difference in mean inflation pressures (Group A,B,C: 182 ±33 psi; 175 ±37 psi; 160 ±36 psi) and cement volume (Group A, B, C: 6.73 ±0.41cc;6.65 ±0.65cc;6.72 ± 0.56cc) was found among the three groups. Average percentage increase in failure load was 218%, 241%, and 212% in Group A, B, and C, respectively.
Conclusions: The fracture reduction achieved by the two inflatable bone tamps was equivalent. The use of an outer sleeve significantly enhanced height restoration compared to the two inflatable bone tamps alone.
Patient Care: Surgeon general can employ an outer sleeve to avoid loss of reduction after bone tamp deflation, prior to cement injection during kyphoplasty and enhance height restoration in patients with vertebral compression fractures.
Learning Objectives: By the conclusion of this study, participants should be able to understand that the use of an outer sleeve enhances reduction of the vertebral compression fracture, and is a viable option for vertebral augmentation.