Cage subsidence after anterior cervical discectomy and fusion using a cage alone or combined with anterior plate fixation.

PURPOSE: To compare the extent of cage subsidence after anterior cervical discectomy and fusion (ACDF) using a cage alone or combined with anterior plate fixation, and to assess the effect of end plate removal on cage subsidence.

METHODS: Records of 23 men and 13 women aged 32 to 82 (mean, 54) years who underwent ACDF for 61 levels using the Solis cage alone (n=46) or combined with anterior plate fixation (n=15) were reviewed. The extent of cage subsidence was determined by comparing immediately postoperative (within one week) with final follow-up radiographs. Cage subsidence was defined as the sum subsidence of the superior and inferior part of the cage into the vertebral body. Mild and major cage subsidence was defined as ≤2 mm and >2 mm, respectively.

RESULTS: Patients who underwent ACDF using a cage alone or combined with anterior plate fixation were comparable in terms of age, gender, follow-up duration, and number of levels decompressed. Cage subsidence occurred in 33 (54%) of the 61 levels decompressed. In the cage alone group, the extent of cage subsidence was greater (1.68 vs. 0.57 mm, p=0.039) and the rate of major cage subsidence was higher (28% vs. 7%, p=0.08). The inferior part of the cage was more vulnerable to subsidence compared with the superior part (median subsidence: 3.0 vs. 1.4 mm, p<0.0001). Cage subsidence occurred more often when the end plate was removed rather than preserved (58% vs. 18%, p<0.002).

CONCLUSION: The extent of cage subsidence was greater after ACDF with cage alone. Cage subsidence occurred more often when the end plate was removed. Additional anterior plate fixation is recommended when the end plate is removed.