Does zero-profile anchored cage accompanied by a higher postoperative subsidence compared with cage-plate construct? A meta-analysis

BACKGROUND: The zero-profile anchored cage (ZP) has been widely used for its lower occurrence of dysphagia. However, it is still controversial whether it has the same stability as the cage-plate construct (CP) and increases the incidence of postoperative subsidence. We compared the rate of subsidence after anterior cervical discectomy and fusion (ACDF) with ZP and CP to determine whether the zero-profile device had a higher subsidence rate. METHODS: We performed a meta-analysis of studies that compared the subsidence rates of ZP and CP. An extensive and systematic search covered the PubMed and Embase databases according to the PRISMA guidelines and identified ten articles that satisfied our inclusion criteria. Relevant clinical and radiological data were extracted and analyzed by the RevMan 5.3 software. RESULTS: Ten trials involving 626 patients were included in this meta-analysis. The incidence of postoperative subsidence in the ZP group was significantly higher than that in the CP group [15.1% (89/588) versus 8.8% (51/581), OR = 1.97 (1.34, 2.89), P = 0.0005]. In the subgroup analysis, we found that the definition of subsidence did not affect the higher subsidence rate in the ZP group. Considering the quantity of operative segments, there was no significant difference in the incidence of subsidence between the two groups after single-level fusion (OR 1.43, 95% CI 0.61–3.37, P = 0.41). However, the subsidence rate of the ZP group was significantly higher than that of the CP group (OR 2.61, 95% CI 1.55–4.40, P = 0.0003) after multilevel (≥ 2-level) procedures. There were no significant differences in intraoperative blood loss, JOA score, NDI score, fusion rate, or cervical alignment in the final follow-up between the two groups. In addition, the CP group had a longer operation time and a higher incidence of dysphagia than the ZP group at each follow-up time. CONCLUSION: Based on the limited evidence, we suggest that ZP has a higher risk of postoperative subsidence than CP, although with elevated swallowing discomfort. A high-quality, multicenter randomized controlled trial is required to validate our results in the future.