Total atlanto-odontoid joint arthroplasty system: a novel motion preservation device for atlantoaxial instability after odontoidectomy.
METHODS
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.


BACKGROUND
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).


CONCLUSIONS
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.
Department of Orthopaedic Surgery, Second Affiliated Hospital of Medical School of Xi'an Jiaotong University, Xi'an, Shaanxi, People's Republic of China. caixuanqsc@foxmail.com
Xuan
X
Cai
Xijing
X
He
Haopeng
H
Li
Dong
D
Wang
D000328:Adult; D001178:Arthroplasty / Q000295:instrumentation / Q000379:methods*; D001268:Atlanto-Axial Joint / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009038:Motion; D009809:Odontoid Process / Q000503:physiopathology / Q000601:surgery*; D016059:Range of Motion, Articular; D055815:Young Adult