Influencing factors for paravertebral ossification in patients with cervical degenerative disease after Bryan artificial disc replacement

HAN Xiao; TIAN Wei; LIU Bo; HE Da; LYU Yanwei; MA Chi; WANG Jinchao

doi:10.3969/j.issn.1002-266X.2017.04.002

Abstract：Objective To discuss the relationship of segmental range of motion ( ROM) , implant deviation and im-plant tilt with the paravertebral ossification ( PO) in patients with cervical degenerative disease after Bryan cervical artificial disc replacement ( CADR) .Methods A total of 90 Bryan discs which were implanted into 76 patients with cervical de-generative disease were retrospectively analyzed .The average follow-up time was more than 10 years.The segmental ROM was measured by X-ray at the preoperation , 3 months′follow-up and the last follow-up.We used the coronal reconstruction CT to evaluate the implant deviation and implant tilt at the last follow-up, and determined the grades of PO by McAfee at the last follow-up.We retrospectively analyzed the influence factors of grade 4 PO as well as the relationship of segmental ROM, implant deviation and implant tilt with the grade of PO .Results The segmental ROM at preoperation , 3 months′follow-up and the last follow-up was 9.2°±4.7°, 8.2°±4.8°and 8.7 ±5.1°(all P>0.05).The segmental ROM at 3 months′follow-up and the last follow-up was positively correlated (r=0.572, P<0.01).The median and interquartile range of implant deviation was 0.61 (0-7.08) mm and 0.84 (0.01-9.79)°.The implant tilt was negatively correlated with segmental ROM at the last follow-up (r=-0.379, P=0.001).At the last follow-up there were 17 segments (15 pa-tients) with grade 4 PO and 73 segments (63 patients) with grade 0-3 PO.Patients who had grade 4 PO were older than the patients with the grade 0-3 PO (P<0.05).Patients with the grade 4 PO had less segmental ROM than that of patients with the grade 0-3 PO at the 3 months′and last follow-up (all P<0.01).The segment whose implant deviation was greater than 3 mm would have a higher PO grade (P<0.01), and less ROM at the last follow-up (all P<0.01).The segment whose implant tilt was greater than 5°would have a higher PO grade (P<0.01), and less ROM at the last follow-up (P<0.05).Conclusions Maintaining the segmental ROM after the early stage of CADR can avoid the grade 4 PO.The im-plant deviation or implant tilt will cause the higher grade of PO in the long-term follow-up and will influence the long term ROM, and especially we should avoid the implant deviation more than 3 mm or implant tilt more than 5°.