Subsidence of anchored cage after anterior cervical discectomy

Cage subsidence (CS) represents a risk factor for adjacent segment degeneration (ASD) and unfavorable results of anterior cervical discectomy (ACD).

Sixty-one patients after level 1 or 2 of ACD with implantation of Zero Profile VA cage were included in the study. CS was assessed with a follow-up period of 12 months after ACD. The impacts of factors such as sex, age, number of operated segments, osteoporosis and extent of peroperative distraction were assessed in relation to the incidence of CS. The influences of CS on clinical results (VAS, NDI, Odom's criteria) and ASD incidence were evaluated.

In 74 % of cases there was the presence of CS into both adjacent vertebral bodies. CS into the ventral part of motion segment was dominant during the entire follow-up period. CS had no influence on clinical results of ACD. Parallel CS into both ventral and dorsal parts of motion segments significantly increased the incidence of proximal ASD (p = 0.0163). Osteoporosis and extent of peroperative distraction were linked to higher incidence of CS into the dorsal part of motion segment (p ˂ 0.05).

Osteoporosis and the extent of peroperative distraction are risk factors for the subsidence of anchored cage and while increasing the incidence of proximal adjacent segment degeneration it has no significant influence on clinical results of surgery (Tab. 3, Fig. 5, Ref. 32).