Overloaded Vertebral Body Following Consecutive Three-Level Hybrid Surgery Comparing with Anterior Cervical Discectomy and Fusion.

Objective: Based on the varying number and relative positions of cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF) procedures, three-segment hybrid surgery (HS) presents a diverse structural approach. Currently, the potential differential effects of HS with different segment combinations and surgical procedures on overloaded vertebral body (OVB) occurrence remain unexplored. The purpose of this retrospective study is to compare the clinical and radiological outcomes of HS and ACDF in treating cervical degenerative disc disease (CDDD), aiming to provide further insights into OVB.

Methods: This study included patients with three-level CDDD who underwent ACDF or HS at our institution. Eligible patients were divided into three groups: Type I (one-level CDR and two-level ACDF), Type II (two-level CDR and one-level ACDF), and ACDF (three-level ACDF). For radiographic analysis, patients were further divided into the Replacement Segment Group and the Nonreplacement Segment Group based on the presence of replacement segments above and below the OVB. Clinical outcomes were evaluated using visual analog scale (VAS) scores for neck and arm pain, Japanese Orthopedic Association (JOA) scores, and neck disability index (NDI) scores. The cervical radiological parameters assessed included (1) vertebral cross-sectional area (CSA), (2) wedge angle (WA), (3) anterior vertebral height (AH), (4) posterior vertebral height (PH), and (5) Hounsfield unit (HU) values. Statistical methods included paired t-test, ANOVA test, and chi-square test. Independent samples t-test, Mann-Whitney U test, and Wilcoxon signed-rank test were used to compare the differences between two groups according to the results of normal distribution test.

Results: A total of 123 patients, evenly distributed among three groups, were included and were well matched in terms of demographic characteristics. The likelihood of vertebral body collapse (VBC) was notably higher in the ACDF group (41.5%) compared with the Type I (17.9%) and Type II (8.9%) groups (p < 0.01). Following surgery, both at 3 and 6 months, the ACDF group demonstrated higher VAS neck scores and NDI scores compared with the Type I and Type II groups (p < 0.01). Additionally, the WA and AH values of the upper and lower adjacent OVB were consistently lower in the ACDF group than in the Type I and Type II groups at 6 and 12 months and at the final follow-up (p < 0.01). Notably, in the Nonreplacement Segment Group, WA significantly decreased at 12 months postoperatively and at the final follow-up compared with the Replacement Segment Group (p < 0.01).

Conclusions: Three levels of HS appear to reduce stress concentrations and alleviate morphological changes in OVB. The occurrence of more VBC patients with OVB was associated with the use of Zero-P or Zero-P VA implants.