• Jinshui Chen, Fengjin Zhou, Bin Ni, Qunfeng Guo, Huapeng Guan, Tianming Xu, and Qi Liu.
• ‡Department of Orthopedics, Fuzhou General Hospital, Nanjing Military Command, Fuzhou, P.R. China;§Department of Orthopedics, Changzheng Hospital, The Second Military Medical University, Shanghai, P.R. China;¶Department of Orthopedics, No. 451 Hospital of PLA, Xi'an, P.R. China.
• Neurosurgery. 2016 May 1; 78 (5): 735-41.

BackgroundLoss of axial rotation and lateral bending after atlantoaxial fusion reduces a patient's quality of life. Therefore, effective, nonfusion fixation alternatives are needed for atlantoaxial instability.ObjectiveTo evaluate the initial stability and function of posterior atlantoaxial restricted nonfusion fixation (PAARNF), a new protocol, using cadaveric cervical spines compared with the intact state, destabilization, and posterior C1-C2 rod fixation.MethodsCervical areas C0 through C3 were used from 6 cadaveric spines to test flexion-extension, lateral bending, and axial rotation range of motion (ROM). With the use of a machine, 1.5-Nm torque at a rate of 0.1 Nm/s was used and held for 10 seconds. The specimens were loaded 3 times, and data were collected in the third cycle and tested in the following sequence: (1) intact, (2) destabilization (using a type II odontoid fracture model), (3) destabilization with PAARNF (PAARNF group), and (4) rod implantation (rod group). The order of tests for the PAARNF and rod groups was randomly assigned.ResultsThe average flexion-extension ROM in the PAARNF group was 7.44 ± 2.05°, which was significantly less than in the intact (P = .00) and destabilization (P = .00) groups but not significantly different from that of the rod group (P = .07). The average lateral bending ROM (10.59 ± 2.33°; P = .00) and axial rotation ROM (38.79 ± 13.41°; P = .00) of the PAARNF group were significantly greater than in the rod group. However, the values of the PAARNF group showed no significant differences compared with those of the intact group.ConclusionPAARNF restricted atlantoaxial flexion-extension but preserved axial rotation and lateral bending at the atlantoaxial joint in a type II odontoid fracture model. However, it should not be used clinically until further studies have been performed to test the long-term effects of this procedure.

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