Subsidence after Anterior Cervical Interbody Fusion Using a Zero-Profile Device

Abstract

Zero-profile device (Zero-P) has generally been used as a stand-alone cage in anterior cervical discectomy and fusion (ACDF). However, using Zero-P has been reported to be associated with a high subsidence rate. The present study evaluates the factors that influence the subsidence of ACDF. Methods: Records of a total of 29 patients with degenerative spondylosis resulting in radiculopathy or myelopathy between C2 and C7 who underwent ACDF with Zero-P were retrospectively reviewed. The participants received 1 or 2 level ACDF with Zero-P in our clinic from December, 2011 to December, 2017. A total of 35 treatment levels were included in the analysis. Subsidence was defined when anterior segmental heights decreased by more than 2 mm during the follow-up period. The patients were divided into the subsidence and non-subsidence groups. The following factors were investigated in relation to the occurrence of subsidence: age, gender, body mass index, diabetes mellitus, cage height, perioperative distraction, segmental lordosis, pain score, fusion grade, anterior/posterior segmental height ratio, and cage distance. Results: Cage subsidence was observed in 15 cases (15/35, 42%). Cage distance at immediate postoperation was significantly different between the 2 groups; specifically, while the group with subsidence had 2.66±1.62 mm distance, the group without subsidence had 1.24±1.13 mm distance (p=0.008). Conclusion: This study confirms that the more deeply titanium part is inserted at the anterior edge, the more subsidence occurs. In order to decrease the occurrence of cage subsidence, Zero-P cages should be located the closest possible to the anterior rim of vertebral body at operation.

Biomechanical evaluation of the novel assembled internal fixed system in C2–C3 anterior cervical discectomy and fusion: a finite element analysis

“…This modification facilitates plate implantation, avoids blockage by the mandible during the insertion process, and mitigates swallowing difficulties caused by the plate's volume. Additionally, Kang et al conducted a retrospective analysis of patients treated with Zero-p ACDF and concluded that deeper insertion of the titanium part at the anterior edge leads to more subsidence [ 19 ]. Consequently, this study utilized the Zero-p design, integrating the anterior cervical plate and the interbody fusion cage into a single unit, to minimize sinking of the interbody fusion cage and excessive penetration of the titanium plate into the intervertebral disc.…”