Influence of cage material, plating and vertebral bone quality on subsidence and long-term outcomes following anterior cervical discectomy and fusion-a retrospective analysis.

Background: Anterior cervical discectomy and fusion (ACDF) is a surgical procedure used to treat degenerative conditions of the cervical spine. Cage subsidence is a known post-operative complication, resulting in loss of indirect decompression, deformity, and radicular symptoms. The objectives of this study are to: (I) investigate associations between cage-plate constructs and postoperative subsidence after single-level ACDF; (II) determine relationships between cervical vertebral bone quality (C-VBQ) scores, subsidence, and fusion construct; and (III) identify potential risk factors that may help guide patient outcomes. Methods: Radiographic subsidence was defined as a collapse of one-third or greater of cage height. C-VBQ scores were measured from C2-C7 on preoperative T1-weighted magnetic resonance imaging (MRI) images. Comparative analysis was performed between cage material groups. Pre- and post-operative patient reported outcome measures (PROMs) were analyzed. Results: Subsidence was present in 22 of 117 patients. Subsidence was not associated with plate usage (P=0.78) or cage type (0.520). C-VBQ score was associated with a significantly increased odds of cage subsidence [odds ratio (OR) 15.264, P<0.001]. In the total population, plates were associated with decreased odds of returning to the operating room (OR 0.196, P=0.049) and lower rate of adjacent segment disease (P=0.046), despite no difference in post-operative PROM scores. In the polyetheretherketone (PEEK) plate sub-group, while there was no difference in subsidence rate (P=0.40), there were higher mean C-VBQ scores (P=0.041) and a lower rate of patient-reported outcomes measurement information system (PROMIS) minimal clinically important difference (MCID) achievement (P=0.041). Conclusions: Single-level standalone and cage-plate ACDF constructs demonstrated similar rates of post-operative subsidence. Subsidence rates were also similar between PEEK, titanium, and structural allograft cages. For PEEK constructs, plate use may have a potential protective mechanism against subsidence with worsening bone mineral density. Plate use may also demonstrate lower odds risk of returning to the operating room. These findings can better inform decision-making and post-surgical planning for ACDF surgery.