The effects of cages implantation on surgical and adjacent segmental intervertebral foramina

OBJECTION: The overarching goal of our research was to compare the clinical and radiological outcomes with different sizes of cages implantation in anterior cervical discectomy and fusion (ACDF), and to evaluate the effects on surgical and adjacent segmental intervertebral foramina. METHODS: The clinical data of 61 patients were analyzed retrospectively. The radiological data included the surgical intervertebral disk space height before (H(0)) and after surgery (H), the preoperative mean height of adjacent segments (H(m)), the area and height of the surgical and adjacent segment foramen, the surgical segmental Cobb angle (α(1)), and C2-7Cobb angle (α(2)). The calculation of clinical data was conducted by Japanese Orthopaedic Association Scores (JOA), the recovery rate of JOA scores and visual analog scales (VAS). In accordance with the different ranges of distraction (H/H(m)), patients were classified into three groups: group A (H/H(m)<1.20, n=13), group B (1.20≤H/H(m)≤1.80, n=37), and group C (H/H(m)>1.80, n=11). RESULTS: After the operation and at the final follow-up, our data has demonstrated that the area and height of surgical segmental foramen all increased by comparing those of preoperation in three groups (all P<0.05). However, except for a decrease in group C (all P<0.05), the adjacent segmental foramina showed no significant changes (all P>0.05). The area and height of the surgical segment foramen and the distraction degree were positively correlated (0<R<1, all P<0.05), while the adjacent segments were negatively correlated with it (0<R<1, P=0.002~0.067). JOA scores improved markedly in all groups with similar recovery rates. However, during the final follow-up (P=0.034), it was observed that there were significant differences in visual simulation scores among the three groups. CONCLUSION: The oversize cage might give a rise to a negative impact on the adjacent intervertebral foramen in ACDF. The mean value of the adjacent intervertebral disk space height (H(m)) could be used as a reference standard. Moreover, the 1.20~1.80 fold of distraction (H/H(m)) with optimal cages would achieve a better long-term prognosis.