BACKGROUND: Occipitocervical fusion is a major method for malformation of craniocervical junction. In patients without osteoporosis, the degeneration of cervical vertebra mainly presents in the intervertebral disk. The height of the vertebral body is constant basically. Thus, the ratio (S value) of the height of cervical disc and the height of cervical vertebra can be used to measure the degeneration of cervical vertebra. The small S value indicates severe degeneration of cervical vertebra.
OBJECTIVE: To measure the lateral radiograph of cervical vertebra in patients with craniocervical malformation undergoing occipitocervical fusion, to analyze the relationship between occipitocervical fixed angle during fusion and lower cervical spine degeneration after fusion, and to identify an optimal angle of occipitocervical fusion.
METHODS: A total of 21 patients with craniocervical malformation undergoing occipitocervical fusion were included. According to the occipitocervical angle (0c-C2 angle) immediately after fusion, the patients with craniocervical malformation undergoing occipitocervical fusion were assigned to three groups: occipitocervical
angle 9°-22° group, occipitocervical angle <9° group, and occipitocervical angle >22° group. Immediate postoperative 0c-C2 angle in 9°-22° belonged to the normal angle range. S value and JOA score in each group were measured before and after fusion, during final follow-up. The statistics were compared.
RESULTS AND CONCLUSION: JOA scores in the occipitocervical angle 9°-22° group, occipitocervical angle <9° group, and occipitocervical angle >22° group, were respectively, (7.3±1.7) points, (7.2±1.6) points, and (7.3±1.5) points, before fusion, and (14.2±1.5) points, (13.5±1.6) points and (13.3±1.5) points after fusion. JOA scores were improved significantly in the three groups. JOA improvement was significantly better in the occipitocervical angle 9°-22° group than that in the occipitocervical angle <9° and >22° groups. Preoperative S values were respectively 0.440±0.017, 0.441±0.016, and 0.440±0.018 in the occipitocervical angle 9°-22° group, occipitocervical angle <9° group, and occipitocervical angle >22° group, and no significant difference was detected among the three groups. No significant difference in S value was detectable in the occipitocervical angle 9°-22° group between postoperative final follow-up and pre-operation. The S value was significantly smaller at postoperative final follow-up than pre-operation in the occipitocervical angle <9° and >22° groups. These results indicated that during occipitocervical fusion, occipitocervical angle should try to be normal, more than or less than normal range will accelerate the degeneration of lower cervical spine.