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In Vitro Stabilizing Effect of a Transforaminal Compared With Two Posterior Lumbar Interbody Fusion Cages

Kettler, Annette, MD; Schmoelz, Werner, PhD; Kast, Erich, MD; Gottwald, Maria, MD; Claes, Lutz, PhD; Wilke, Hans-Joachim, MD

doi: 10.1097/01.brs.0000186466.01542.8c
Biomechanics
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Study Design. An in vitro biomechanical flexibility test on different lumbar interbody fusion cages using monosegmental lumbar spine specimens.

Objective. To investigate the stabilizing effect of a transforaminal lumbar interbody fusion (TLIF) cage compared with two established posterior lumbar interbody fusion (PLIF) cages.

Summary of Background Data. TLIF using interbody fusion cages is gaining more and more popularity in the treatment of degenerative disc disease. However, only little is known on its biomechanical behavior.

Methods. Eighteen intact human lumbar spine segments were tested for flexibility in a specially designed spine tester. Pure moments were applied in the three main planes, and range of motion and neutral zone were determined. Then, TLIF using the sickle-shaped MOON cage (AMT AG), PLIF using the cubic Stryker cages (Stryker Orthopaedics), or PLIF using the threaded BAK cages (Zimmer Spinetech) was carried out and the specimens tested again.

Results. The stability after implantation of the MOON TLIF cage did not significantly differ from that after implantation of the cubic Stryker PLIF cages (P > 0.05). In contrast, the threaded BAK PLIF cages had a significantly higher primary stability than both the MOON TLIF and the Stryker PLIF cages in lateral bending, flexion, and extension (P < 0.05) but not in axial rotation (P > 0.05).

Conclusions. In terms of its stabilizing effect, TLIF using the MOON cage can be recommended as an alternative to PLIF using the cubic Stryker cages. Compared with the threaded BAK PLIF cages, however, the MOON TLIF cage provides a lower primary stability in lateral bending, flexion, and extension.

In this in vitro study, the stabilizing effect of a transforaminal lumbar interbody fusion (TLIF) cage compared with two established posterior lumbar interbody fusion (PLIF) cages was investigated. The results indicated that, in terms of its stabilizing effect, TLIF using the sickle-shaped MOON cage can be recommended as an alternative to PLIF using the cubic Stryker cages. Compared with the threaded BAK PLIF cages, however, the MOON TLIF cage provides a lower primary stability in lateral bending and flexion and extension.

From the Department Unfallchirurgische Forschung und Biomechanik, Universitat Ulm, Ulm Germany.

Acknowledgment date: March 29, 2005. First revision date: May 12, 2005. Acceptance date: May 26, 2005.

The device(s)/drug(s) that is/are the subject of this manuscript is/are not FDA-approved for this indication and is/are not commercially available in the United States.

Corporate/Industry and Institutional funds were received in support of this work. Although one or more of the author(s) has/have received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript, benefits will be directed solely to a research fund, foundation, educational institution, or other nonprofit organization which the author(s) has/have been associated.

Address correspondence and reprint requests to Hans-Joachim Wilke, PhD, Institute for Orthopaedic Research and Biomechanics, Universitat Ulm, Helmholtzstrasse 14, Ulm 89081, Germany; E-mail: annette.kettler@medizin.uni-ulm.ed

© 2005 Lippincott Williams & Wilkins, Inc.