Study Design. In vitro biomechanical investigation.
Objective. To assess differences in kyphosis after balloon kyphoplasty (BKP) or vertebral body stenting (VBS).
Summary of Background Data. Cement augmentation techniques allow early mobilization in patients with osteoporotic thoracolumbar fractures. Biomechanically, the grade of reduction and preservation are as important as in nonosteoporotic fractures. With BKP, negative effects of balloon deflation on the reduction and whether specific combinations of materials may preserve the reduction are as yet unclear.
Methods. Twelve bisegmental human thoracolumbar specimens (6 × T12–L2, 6 × L3–L5; age at death, 76.3 yr; range, 63–89 yr; female:male ratio, 3:3; bone mineral density, 68.1 g/cm3; mean, 12.9 g/cm3) were tested in a spine simulator with pure moments of 7.5 Nm to assess primary and secondary stability. After flexibility testing of the intact specimens, an eccentric compression force induced standardized fractures, which were reduced using either BKP or VBS against a flexional moment of 2.5 Nm. Primary and secondary stability were assessed using range of motion in a spine tester. The specimens were tested after each of 3 periods of cyclic flexion loading. The kyphotic angle of the index vertebra was measured radiographically.
Results. The 2 techniques achieved comparable reduction against a relatively high bending moment in this model. Neither technique restored the stability of the intact state; with increasing loads, the range of motion continuously increased to the level of fractured specimen to the level of the fractured specimen. Although the deflation effect on the kyphotic angle was lower with VBS (P ≤ 0.05), there were no significant differences between the techniques relative to angle restoration.
Conclusion. Both augmentation techniques are able to restore vertebral body height after thoracolumbar fractures. The deflation effect on the kyphotic angle was less with VBS than with BKP. High flexion moments during implantation limit the effectiveness of reduction using cement augmentation methods.
Level of Evidence: N/A
In a biomechanical in vitro fracture model, balloon kyphoplasty, and vertebral body stenting (VBS) achieved comparable reduction against a relatively high bending moment. Despite a reduced deflation effect on the kyphosis angle with VBS (P ≤ 0.05), the differences in angle restoration between the techniques were not significant after treatment.
*Center for Musculoskeletal Surgery, Spine Unit, CHARITÉ University Hospital, Berlin, Germany; and
†Department of Trauma Surgery, Laboratory for Biomechanics, Medical University Innsbruck, Austria.
Address correspondence and reprint requests to Alexander C. Disch, MD, Center for Musculoskeletal Surgery, Spine Unit, CHARITÉ University Hospital Berlin, Augustenburger Platz 1, 13353 Berlin, Germany; E-mail: firstname.lastname@example.org
Acknowledgment date: February 22, 2014. First revision date: May 26, 2014. Acceptance date: May 28, 2014.
The legal regulatory status of the device(s)/drug(s) that is/are the subject of this manuscript is not applicable in my country.
Synthes Ltd., Zuchwil, Switzerland, funds were received in support of this work.
Relevant financial activities outside the submitted work: consultancy, expert testimony; payment for lecture.