KYPHOPLASTY RESTORES VERTEBRAL HEIGHT AND SHAPE BETTER THAN VERTEBROPLASTY FOLLOWING SEVERE WEDGE FRACTURES

Introduction

Osteoporotic vertebral fractures can cause severe vertebral wedging and kyphotic deformity. This study tested the hypothesis that kyphoplasty restores vertebral height, shape and mechanical function to a greater extent than vertebroplasty following severe wedge fractures.

Methods

Pairs of thoracolumbar “motion segments” from seventeen cadavers (70–97 yrs) were compressed to failure in moderate flexion and then cyclically loaded to create severe wedge deformity. One of each pair underwent vertebroplasty and the other kyphoplasty. Specimens were then creep loaded at 1.0kN for 1 hour. At each stage of the experiment the following parameters were measured: vertebral height and wedge angle from radiographs, motion segment compressive stiffness, and stress distributions within the intervertebral discs. The latter indicated intra-discal pressure (IDP) and neural arch load-bearing (F_N).

Results

Fracture and cyclic loading reduced anterior vertebral height by 34%, increased wedge angle from 5.0° to 11.4°, increased F_N by 58% and reduced IDP and compressive stiffness by 96% and 44% respectively. Kyphoplasty restored anterior height to a greater extent than vertebroplasty (p<0.001), by 96% versus 59% immediately after augmentation, and by 79% versus 47% after subsequent creep loading. Wedge angle was also reduced to a greater extent following kyphoplasty than vertebroplasty (p<0.02) by 7.2° vs 4.2° after augmentation and 6.6° vs 4.0° after creep loading. IDP, F_N and compressive stiffness were restored to a similar extent by both procedures.

Conclusion

Kyphoplasty and vertebroplasty were equally effective in restoring mechanical function following severe wedge fractures, but kyphoplasty was better able to correct deformity by restoring vertebral height and reducing wedging.

No conflicts of interest

Sources of funding: Funding was provided by a Royal College of Surgeons of England Research Fellowship and the Gloucestershire Arthritis Trust. Materials were provided by Medtronic and Depuy.

This abstract has not been previously published in whole or substantial part nor has been presented previously at a national meeting.