Novel posterior artificial atlanto-odontoid joint for atlantoaxial instability: a biomechanical study.
OBJECTIVE Atlantoaxial instability is usually corrected by anterior and/or posterior C1-2 fusion. However, fusion can lead to considerable loss of movement at the C1-2 level, which can adversely impact a patient's quality of life. In this study, the authors investigated the stability and function of a novel posterior artificial atlanto-odontoid joint (NPAAJ) by using cadaveric cervical spines. METHODS The Oc-C7 regions from 10 cadaveric spines were used for anteroposterior (AP) translation and range of motion (ROM) tests while intact and after destabilization, NPAAJ implantation, and double-rod fixation. RESULTS The mean AP C1-2 translational distances in the intact, destabilization, and double-rod groups were 6.53 ± 1.07 mm, 11.54 ± 1.59 mm, and 3.24 ± 0.99 mm, respectively, and the AP translational distance in the NPAAJ group was significantly different from that in the intact group (p < 0.05). The AP translational distance in the NPAAJ group was not significantly different from that in the double-rod group (p = 0.24). The mean flexion, extension, and axial rotation ROM values of the NPAAJ group were 9.87° ± 0.91°, 8.75° ± 0.99°, and 61.93° ± 2.93°, respectively, and these were lower than the corresponding values in the intact group (p < 0.05). The mean lateral bending ROM in the NPAAJ group (9.26° ± 0.86°) was not significantly different from that in the intact group (p = 0.23), and the flexion, extension, and rotation ranges in the NPAAJ group were 79.5%, 85.2%, and 82.3%, respectively, of those in the intact group. CONCLUSIONS Use of NPAAJ for correction of atlantoaxial instability disorders caused by congenital odontoid dysplasia, odontoid fracture nonunion, and C-1 transverse ligament disruption (IA, IB, and IIB) may restore the stability and preserve most of the ROM of C1-2. Additionally, the NPAAJ may prevent soft tissue from embedding within the joint. However, additional studies should be performed before the NPAAJ is used clinically.
['Shen|Kai|K|', 'Deng|Zhongliang|Z|', 'Yang|Junsong|J|', 'Liu|Chao|C|', 'Zhang|Ranxi|R|']
D000293:Adolescent D000328:Adult D000368:Aged D001268:Atlanto-Axial Joint D001696:Biomechanical Phenomena D005260:Female D006801:Humans D021621:Imaging, Three-Dimensional D016268:Internal Fixators D007593:Joint Instability D007595:Joint Prosthesis D008297:Male D008875:Middle Aged D009809:Odontoid Process D011474:Prosthesis Design D016059:Range of Motion, Articular D013122:Spinal Diseases D014057:Tomography, X-Ray Computed D055815:Young Adult
artificial atlanto-odontoid joint atlantoaxial instability biomechanical cervical AAI = atlantoaxial instability AP = anteroposterior NPAAJ = novel posterior artificial atlanto-odontoid joint ROM = range of motion posterior approach