#348 Sagittal Balance and Adjacent Segment Disease in the Cervical Spine
General Session: Cervical Motion Preservation
Presented by: J. Belding
J. Belding (1)
A. Bowlka (1)
A. Youseff (1)
H. Bohlman (1)
J. Eubanks (1)
(1) University Hospitals of Cleveland, Orthopedics, Cleveland, OH, USA
Introduction: Symptomatic adjacent segment disease after anterior cervical arthrodesis can be seen in up to 25% of patients at ten year follow-up. Some debate exists as to whether this degeneration represents the natural history of the adjacent disc or whether the increased biomechanical stresses placed by the fusion accelerate this degenerative cascade.
Sagittal spinal balance, and its restoration, has been implicated as an important factor in outcomes affecting patients after a spinal fusion. Preoperative loss of lordosis has been shown to lead to deleterious effects following cervical laminoplasty, and postoperative restoration of lordosis has been shown to lead to improved outcomes in disc arthroplasty.
The current study hypothesized that patients with a loss of the normal lordosis of the cervical spine would have an increased prevalence of symptomatic adjacent segment disease after anterior arthrodesis.
Methods: A retrospective review was performed on 154 patients undergoing a one to four level anterior cervical decompression and fusion by a single surgeon. Radiographs were evaluated for sagittal alignment by measuring the Cobb angle of the cervical spine (C2-7) as well as the recently defined Cervical Curvature Index. Radiographic adjacent segment degeneration was measured according to the criteria established by Hilibrand et al. and correlated with clinically symptomatic adjacent segment disease evaluated through chart review. Clinical outcome scores were graded on the Robinson and Odom criteria. Statistical analysis was performed using t tests comparing adjacent segment disease prevalence to the sagittal alignment of the spine.
Results: There were 66 men and 88 women in the study cohort. The average length of follow-up was 41.5 months. There were 44 single level fusions, 67 two level fusions, 30 three level fusions, and 13 four level fusions. Symptomatic adjacent segment disease was seen in 11.7% (18 patients) of the study population. The mean Cobb angle was 9.26 and the mean CCI was 6.00 in this patient population. The mean Cobb angle of pts with ASD was 9.1 and without was 9.3, showing no statistical association (p-.938). The mean CCI was 5.6 of pts with ASD and 6.1 of those without, showing no statistical association (p-.868). There was a small collection of patients with significantly kyphotic spines, (-20 degrees to -15 degrees) who had an increased percentage of ASD in comparison to other groups, but this trend was not statistically significant. Overall, clinical results demonstrated excellent or good Robinson scores in 82.5% of patients, whereas excellent or good Odom scores were reported in 84.4% of patients.
Conclusions: This study found no statistically significant association between preoperative sagittal alignment and progression to adjacent segment disease following ACDF. Symptomatic adjacent segment disease may represent more the natural history of the degenerating disc rather than the end product of underlying biomechanics of the spine or the change in forces created by surgical arthrodesis.