Bone resorption phenomenon following anterior-posterior combined cervical fusion surgery: is it a pathologic finding?

Anterior vertebral bone resorption, commonly observed in cervical disc replacement (CDR) and anterior cervical discectomy and fusion (ACDF), has not been extensively studied in the context of APCF. This study aims to investigate the phenomenon of anterior vertebral bone resorption following APCF, its potential causes, and its clinical significance.

A retrospective analysis was performed on 177 patients (857 vertebral segments) who underwent multilevel APCF between April 2014 and April 2022. Radiographs and CT scans were used to measure anterior-posterior vertebral body length (APL) and its ratio to the C2 vertebra (APLR) immediate-postoperatively and at 1-year follow-up. The bone resorption ratio (BRR) quantified changes in APLR. Correlations between lordosis and BRR were evaluated using Pearson's correlation and linear regression. Intra- and inter-observer reliability were assessed using intraclass correlation coefficients (ICC).

Bone resorption was significantly greater in well-fused AP group compared to pseudoarthrosis or posterior-only fused segments (mean BRR: 11.9%, 5.1%, -1.3%, respectively; P < 0.001). Greater postoperative lordosis correlated positively with higher BRR (R = 0.263, P < 0.001), while a reduction in lordosis correlated negatively with BRR (R=-0.285, P = 0.01). Intra- and inter-observer reliability were excellent, with ICC values ranging from 0.77 to 0.85.

Anterior vertebral bone resorption in APCF is a physiological phenomenon reflecting biomechanical adaptation according to Wolff's law. It is more pronounced in well-fused segments with a greater degree of lordosis and may indicate successful fusion and good sagittal alignment restoration. Further research is needed to evaluate its long-term clinical implications.