Endplate preparation for anterior cervical discectomy and fusion: does the amount of endplate removed affect cage subsidence risk?

PURPOSE: Subsidence after anterior cervical discectomy and fusion (ACDF) is a common complication that may be influenced by the degree of endplate removal prior to cage insertion. The optimal degree of endplate removal remains unclear; therefore, we performed a series of ex vivo experiments to elucidate the relationship between the aggressiveness of endplate preparation and subsidence risk.

METHODS

Human cadaveric subaxial cervical endplates were partially decorticated either conservatively (n = 10) or aggressively (n = 9). The degree of endplate removal was quantified using microCT. Subsidence was modelled by measuring the strength and stiffness of each specimen when an interbody cage was axially compressed into the endplate.

RESULTS

Conservative endplate preparation resulted in less endplate removal than aggressive endplate preparation (mass: 150 vs. 301 mg, p < 0.001; volume: 47 vs. 88mm3, p = 0.01; thickness: 0.02 vs. 0.16 mm, p = 0.004). There was no significant difference between the two groups with respect to endplate strength (2.04 vs. 2.04kN, p = 0.99) or stiffness (2.38 vs. 2.41kN/mm, p = 0.89). Bone mineral density (BMD) was similar between the two groups (271.6 vs. 271.9 mg/cm3, p = 0.98) but positively correlated with endplate strength (effect size 0.68, p = 0.001).

CONCLUSIONS

When performing partial cervical endplate decortication, the degree of bony endplate removal did not significantly predict endplate integrity during ex vivo compression testing, but greater BMD was associated with increased strength. The degree of endplate removal should be based on individual patient factors and intraoperative findings to achieve the ideal cage-endplate interface.