Clinical Observation Of Adjacent Segment Degeneration After ACDF And Analysis Of Its Related Factors

ObjectiveThe present study was undertaken to investigate the incidence of adjacent segment degeneration after anterior cervical discectomy and fusion and to identify the factors that are related to the development of it.MethodsFrom Jan 2003 to Sep 2004, 125 patients who had undergone anterior cervical discectomy and fusion were followed up for an average time of 50.6 months (40-62months). 36 (28.8%) patients underwent a single-level fusion; 63 (50.4%) underwent two-level fusion, and 26 (20.8%) had three levels fused. Lateral radiographs of the cervical spine were taken preoperatively, one week postoperatively and at last follow-up. Lordosis of the fusion segment was both measured with Cobb's angle and lordosis of the cervical spine was measured with D numerical value. Adjacent segment degeneration was diagnosed based on the degrees of disc height narrowing and anterior osteophyte formation. The patients' neurological findings were graded by the JOA score and compared with those preoperative. The data was compared statistically with chi square test and t-test.ResultsThe mean preoperative JOA score of all patients was 8.1±2.7, the mean postoperative JOA score was 12.4±1.9,and the average JOA recovery rate was 48.3%; the mean JOA score at last follow up was 14.1±1.17,and the average recovery rate was 67.4%. The mean D numerical value was 1.78±1.53mm preoperatively, it was improved to 5.45±3.98mm postoperatively and was 5.12±4.25mm at last follow up. The mean Cobb's angle was 3.28°±5.84°preoperatively, it was improved to 9.95°±3.83° postoperatively and was 9.82°±4.52°at last follow up.Additional radiologic degeneration at the adjacent segments was found in 24 patients (19.2%), and 25 levels were involved. Among these patients, 16 were male while 8 were female, and the average age at the operation was 52.1 years old. 4 patients underwent single-level fusion; 13 underwent two-level fusion, and 7 had three levels fused. The degenerative changes were seen at the superior level in 15 patients, inferior level in 8 patients, and at both levels in 1 patient. The mean age, gender, length of follow-up, number of fused levels, preoperative JOA score, one week postoperative JOA score, last follow-up JOA score, preoperative and postoperative Cobb's angle did not differ significantly between patients with adjacent segment degeneration from those without it. Preoperative and postoperative D numerical values were both significantly smaller in the degeneration group than in the normal group. The restoration of cervical lordosis was significantly more insufficient in the degeneration group than in the normal group.ConclusionAnterior cervical discectomy and fusion has obviously curative effect. It can improve neurologic function, restore and maintain cervical lordosis.Adjacent segment degeneration maybe due to less lordosis both preoperatively and postoperatively, and insufficient recovery of the cervical lordosis after operation.