283 - Effect of an Outer Sleeve on an Inflatable Balloon Tamp in Terms of He...

#283 Effect of an Outer Sleeve on an Inflatable Balloon Tamp in Terms of Height Restoration under Simulated Physiological Load

Basic Sciences-Research

Poster Presented by: S. Chinthakunta

Author(s):

M. Gordon (1)
W. Beutler (2)
W.C. Peppelman (2)
S.R. Chinthakunta (3)
D. O Halloran (3)

(1) Newport Orthopedic Institute, Orthopaedics, Newport, CA, USA
(2) Pennsylvania Spine Institute, Spine, Harrisburg, PA, USA
(3) Globus Medical Inc, Research, Audbon, PA, USA

Abstract

Purpose of the Study: Previous biomechanical studies have showed that kyphoplasty allows near total restoration of lost vertebral height in unloaded conditions and partial height restoration under simulated physiological loads. Loss of reduction after balloon tamp deflation, prior to cement injection, has not yet been resolved. The authors are not aware of a study that has evaluated the effect of an outer sleeve on the balloon tamp in terms of height restoration. The optional sleeve surrounds the balloon tamp (Fig 1) to help maintain height during the kyphoplasty procedure while filling the created cavity with bone cement on the contralateral side.

Methods: Eighteen osteoporotic vertebral bodies (T11-L4) were alternately assigned to one of the two treatment groups: Group A - KYPHON (Kyphon Inc., Sunnyvale, CA) and Group B - AFFIRM™ with sleeve (Globus Medical Inc.). The vertebral bodies (VB) were compressed axially on an MTS Bionix 858 machine at a rate of 5mm/min until compressed to 40% of the initial anterior height. Load to failure was recorded. The fractured VBs then underwent kyphoplasty with cement augmentation while still maintain the load. The augmented vertebral bodies were then re-compressed and anterior vertebral body height (mm) and kyphotic angle (degrees) was 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 effect of kyphoplasty on vertebral height, kyphotic angle, and inflation pressures were compared between the treatment groups using an unpaired t-test (p< 0.05). Failure load (N) data were compared between intact and repaired VBs using a paired t-test (p< 0.05). The volume of cement (6-8cc) was maintained constant for both the groups.

Results: Average height loss following compression was 29% and 30% in Group A and Group B, respectively. Height gained following inflation was 72% and 82% in Group A and Group B, respectively. Average height loss due to deflation was 32% and 12% in Group A and Group B, respectively. Average percentage of lost VB height restored in Group A was 30%, compared to 56% for Group B. The mean changes in kyphotic angle was similar to those of vertebral height measurements. No significant difference in mean inflation pressures (Group A 182 ±33 psi; Group B 160 ±36 psi) were found between the two groups. Average percentage increase in failure load was 218% and 212% in Group A and B, respectively.

Conclusions: Some height restoration was observed using the commercially available balloon tamp in fractured vertebral bodies under simulated physiological load. The use of an outer sleeve significantly enhanced height restoration compared to the inflatable balloon tamp alone. No significant difference between mean inflation pressures and failure load was demonstrated between the two groups.

Figure 1