Characterization of graft subsidence in anterior cervical discectomy and fusion with rigid anterior plate fixation.

This study addressed radiographically the evaluation, presence, location, and degree of subsidence with secondary focus on the various clinical parameters and outcomes in 32 patients who underwent anterior cervical discectomy and fusion (ACDF) with tricortical iliac crest bone grafts and rigid anterior plate fixation. Postoperative follow-up plain radiographs were evaluated to determine subsidence on lateral neutral images by measuring the change in height of interscrew distance (ISD) and anterior (AVD), mid (MVD), and posterior (PVD) vertebral endplate-to-endplate vertical distances. Clinical functional outcome and various risk factors were also addressed. A 100% fusion rate was achieved, no instrumentation-related complications were noted, and mild graft subsidence occurred in each patient after the initial 2 months of surgery. Mean AVD, MVD, and PVD were 1.2 mm, 0.4 mm and 0.6 mm, respectively. Mean ISD was 0.6 mm. Percent change for AVD, MVD, PVD, and ISD was 2.3%, 0.8%, 1.2%, and 1.2%, respectively. Subsidence was more pronounced at the anterior vertebral graft-endplate interface (P < .05). Satisfactory clinical results were reported in 90.9% of the patients. With such a sample size, age, sex, smoking status, plate design, graft type, and operative or number of fused levels did not demonstrate statistically significant differences to the degree of subsidence. This paper has shown that ACDF with tricortical bone grafts and rigid plating is associated with slight subsidence, graft load-sharing, high fusion rate, and excellent clinical outcome.