Risk factors of the occurrence of adjacent segment angular loss after anterior cervical fusion in patients with cervical injury

English Keywords:Anterior cervical fusion  Kyphosis  Disc  Facet fracture

English Abstract:

  【Abstract】 Objectives: To investigate risk factors of adjacent segment angular loss after anterior cervical fusion(ACF) in patients with cervical injury. Methods: A retrospective analysis was carried out, 396 patients undergoing ACF were included in the study. Factors such as age, gender, follow-up time, operation methods, ASIA scores(grade A-E recorded as 1-5 score respectively) in admission and at final follow-up were recorded. Radiographic parameters such as kyphosis, fusion segment angle, adjacent vertebral angle, adjacent intervertebral angle were measured, adjacent segment injury was identified by using MRI and CT. Patients were divided into two groups based on the angle loss at adjacent segment for 5°. 23 cases were in angular loss group(group A) and 373 in non angular loss group(group B). The comparative results between the two groups were analyzed by T-test, Chi-square test or Fisher exact probability. Risk factors of adjacent segment angle loss after ACF were analyzed by using multivariate logistic regression. To identify the majority of the angle loss of adjacent segment after ACF, the proportion of the adjacent intervertebral angle, the vertebral angle and the fusion segment angle in the local kyphosis, the upper region angle and the lower region angle were analyzed. Results: The occurrence of adjacent segment angular loss after ACF was 5.81%(23/396). Age was 48.26±8.61 and 31.04±6.17 years(P=0.021) in group A and B, ASIA in admission for group A and B was 3.5±0.8 and 3.7±1.0(P=0.045). Follow-up time, operation method, gender and ASIA at final follow-up showed no significant differences between group A and B (P＞0.05). Significant difference was noted with respect to adjacent segment injury including abnormal disc signals in non-operation segment on MRI, unilateral, undisplaced cervical facet joint fracture without disc-ligament complex injury appeared in group A compared with group B(P＜0.001 and P=0.003, respectively). Age, abnormal disc signals in non-operation segment on MRI, unilateral, undisplaced facet fracture without disc-ligament complex injury were independent risk factors of this complication by using multivariate logistic regression(P=0.031, 0.006, 0.002, respectively). By analyzing radiographic parameters, the angular loss of upper adjacent intervertebral space in the local kyphosis, the caudal angle and the distal angle was 78.07%, 85.00% and 90.19%, respectively. The angular lose in upper adjacent disc resulted in a progressive angular lose of adjacent segment. Conclusions: The incidence of adjacent segment angle loss after ACF is correlated to age, abnormal disc signals of non-operation segment on MRI, unilateral, undisplaced facet joint fracture without disc-ligament complex injury is considerable, mainly in the upper adjacent segment.