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A New Stand-Alone Cervical Anterior Interbody Fusion Device: Biomechanical Comparison With Established Anterior Cervical Fixation Devices

Scholz, Matti, MD*; Reyes, Phillip M., BSE; Schleicher, Philipp, MD*; Sawa, Anna G. U., MS; Baek, Seungwon, MS; Kandziora, Frank, MD*; Marciano, Frederick F., MD, PhD; Crawford, Neil R., PhD

doi: 10.1097/BRS.0b013e31818ff9c4
Biomechanics
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Study Design. A new anchored spacer—a low-profile cervical interbody fusion cage with integrated anterior fixation—was compared biomechanically to established anterior cervical devices.

Objective. To evaluate the fixation properties of the new stand-alone device and compare these properties with established fixation methods. The hypothesis is that the new device will provide stability comparable to that provided by an anterior cervical cage when supplemented with an anterior plate.

Summary of Background Data. It is accepted that the use of anterior cervical plating increases the chance of achieving a solid fusion. However, its use may be associated with an increase in operation time and a higher postoperative morbidity caused by a larger anterior approach and disruption of the anterior musculature. This dilemma has led to the development of a new, low profile stand-alone cervical anterior cage device with integrated screw fixation.

Methods. Twenty-four human cadaveric C4–C7 cervical spines were loaded nondestructively with pure moments in a nonconstraining testing apparatus to induce flexion, extension, lateral bending, and axial rotation while angular motion was measured optoelectronically. The specimens were tested:

  • 1. Intact (N = 24).
  • 2. After discectomy and anterior stabilization.
  • a. Interbody cage + locking plate (N = 8).
  • b. Interbody cage + dynamic plate (N = 8).
  • c. Anchored spacer (N = 8).
  • 3. After ventral plate removal of group 2a and 2b (N = 16).

Results. All fixation techniques decreased range of motion (ROM) and lax zone (LZ) (P < 0.05) in all test modes compared with the intact motion segment and cage-only group. There were no significant differences between the anchored spacer and cage + locking plate or cage + dynamic plate.

Conclusion. The anchored spacer provided a similar biomechanical stability to that of the established anterior fusion technique using an anterior plate plus cage and has a potentially lower perioperative and postoperative morbidity. These results support progression to clinical trials using the cervical anchored spacer as a stand-alone implant.

A new anchored spacer—a low-profile cervical interbody fusion cage with integrated anterior fixation—was compared biomechanically to established anterior cervical fusion devices. The results of the study show that the anchored spacer provided a similar biomechanical stability to that of the established anterior fusion technique using an anterior plate plus cage.

From the *Center for Spinesurgery and Neurotraumatology, Trauma Clinic Frankfurt/Main, Germany; †Spinal Biomechanics Research Laboratory, and ‡Division of Neurological Surgery, Barrow Neurological Institute, Phoenix, AZ.

Acknowledgment date: May 14, 2008. First revision date: August 20, 2008. Acceptance date: 25, 2008.

The device(s)/drug(s) FDA-approved or approved by corresponding national agency for this indication.

Corporate/Industry funds were received in support of this work. One or more author(s) has/have received benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript: e.g., honoraria, gifts, consultancies.

Address correspondence and reprint requests to Matti Scholz, MD, Center for Spinesurgery and Neurotraumatology, Trauma Clinic Frankfurt/Main, Friedberger Landstraße 430, 60389 Frankfurt/Main, Germany; E-mail: matti.scholz@bgu-frankfurt.de

© 2009 Lippincott Williams & Wilkins, Inc.