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Neurospine > Volume 16(3); 2019 > Article
DOI:    Published online September 30, 2019.
Comparison of Adjacent Segment Degeneration, Cervical Alignment, and Clinical Outcomes After One- and Multilevel Anterior Cervical Discectomy and Fusion
Jun Jae Shin 
Department of Neurosurgery, Inje University Sanggye Paik Hospital, Inje University College of Medicine, Seoul, Korea
Corresponding Author:  Jun Jae Shin
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Received: May 17, 2019   Revised: July 12, 2019   Accepted: August 10, 2019
This study aimed to assess the influence of a fused segment on cervical range of motion (ROM) and adjacent segmental kinematics and determine whether increasing number of fusion levels causes accelerated adjacent segment degeneration (ASD) after anterior cervical discectomy and fusion (ACDF).
A total of 165 patients treated with ACDF were recruited for assessment, and they were divided into 3 groups based on the number of fusion levels. Radiological measurements and clinical outcomes included visual analogue scale (VAS) and Neck Disability Index (NDI) assessed preoperatively and at ≥2 years of follow-up.
ASD occurred in 41 of 165 patients who underwent ACDF (1-level, 12 of 78 [15.38%]; 2-level, 14 of 49 [28.57%]; 3-level, 15 of 38 [39.47%]; p=0.015) at final follow-up (mean, 31.9 months). Significant differences were found in reduction of global ROM based on the number of fusion levels (p<0.001). The upper adjacent segment ROM increased over time (p=0.004); however, lower segment ROM did not. Three-level ACDF did not obtain greater amounts of lordosis than did 1- or 2-level ACDF (p=0.003). Postoperative neck VAS scores and NDI were significantly higher for 3-level ACDF than for 1- or 2-level ACDF (p=0.033 and p=0.001).
ASD occurred predominantly in multilevel cervical fusion, more frequently in the upper segment of the prior fusion and as the number of fusion levels increased. Patients who underwent multilevel fusion had greater reduction of global ROM and increased compensatory motion at the upper adjacent segment. Three-level ACDF did not appear to restore cervical lordosis significantly compared with 1- or 2-level arthrodesis.
Keywords: Adjacent-segment degeneration, Anterior spinal fusion, Cervical degenerative disc disease, Multilevel spondylosis, Range of motion, Alignment

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