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Total Atlanto-odontoid Joint Arthroplasty System: A Novel Motion Preservation Device for Atlantoaxial Instability After Odontoidectomy

Cai, Xuan MD; He, Xijing MD, PhD; Li, Haopeng MD; Wang, Dong MD

doi: 10.1097/BRS.0b013e318288052a

Study Design. An in vitro biomechanical study.

Objective. To determine the initial stability and function of a novel total atlanto-odontoid joint arthroplasty system (TAAS) in human cadaveric cervical spine models by comparing it with a conventional method.

Summary of Background Data. Resection of the odontoid and anterior arch of the atlas results in atlantoaxial instability, which if left uncorrected may lead to severe neurological complications. Currently, such atlantoaxial instability is corrected by anterior and/or posterior atlantoaxial fusion. However, this results in considerable motion loss of the atlantoaxial complex.

Methods. Flexibility tests were conducted on 24 human cadaveric craniocervical specimens in the following sequence: (1) intact, (2) after dissection of the atlantoaxial ligaments and odontoidectomy, (3) after the TAAS implantation, and (4) after Harms rigid fixation. Rotational angles of the C1–C2 segment were measured to study the immediate stability and function of the TAAS implantation compared with the intact and Harms rigid fixation.

Results. Comparing the TAAS implantation to the intact state, the range of motion and neutral zone changed little in flexion, extension, and lateral bending but increased significantly in axial rotation (P < 0.001). Compared with Harms rigid fixation, the TAAS implantation significantly increased range of motion and neutral zone in all directions (P < 0.001).

Conclusion. We have designed the TAAS for correcting atlantoaxial instability arising from C1–C2 anterior decompression procedures. The unique aspect of the TAAS is that it restores, to a great extent, the C1–C2 motion that is lost during current stabilization procedures.

Level of Evidence: N/A

This study evaluated the biomechanical characteristics of a novel total atlanto-odontoid joint arthroplasty system (TAAS). The results showed that the TAAS not only stabilizes the atlantoaxial complex but also preserves movement of all directions of the C1–C2 segment and can be implanted onto the defect created by the anterior decompression.

From the Department of Orthopaedic Surgery, Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China.

Address correspondence and reprint requests to Xijing He, MD, PhD, Department of Orthopaedic Surgery, Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, 157 Xiwulu, Xi'an, 710004, Shaanxi, People's Republic of China; E-mail:

Acknowledgment date: November 26, 2012. Revision date: January 6, 2013. Acceptance date: January 10, 2013.

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.

No funds were received in support of this work.

No relevant financial activities outside the submitted work.

© 2013 Lippincott Williams & Wilkins, Inc.