The Changes in Neural Foramen Shown on Computed Tomography Depending on the Changes in the Height of Intervertebral Disc after Anterior Cervical Discectomy and Fusion (ACDF)

ABSTRACT

STUDY DESIGN: A prospective radiological assessment. OBJECTIVES: Changes in the height, area, and width--captured using computed tomography (CT)--of the neural foramen with respect to changes in the intervertebral disc height, after undergoing an anterior cervical disc removal and fusion procedure. SUMMARY OF LITERATURE REVIEW The multiple authors of this study, by obtaining central canal and area of neural foramen by increasing the disc spacing height and area of the neural foramen, attempted to assess the height increase of disc spacing. It is necessary to consider the synergistic effects of decompression through dissection of the posterior longitudinal ligament (PLL). MATERIALS AND METHODS: The authors studied 17 patient cases that underwent one segment anterior cervical discectomy and fusion (ACDF) for degenerative cervical disease from June 2006 to March 2007. All patient cases underwent autogenous iliac bone graft or cage insertion with plate fixation procedure. We measured the areas of the neural foramen, heights of the vertebra body above and below the removed intervertebral disc with CT before and after ACDF. Radiographic measurements were averaged. RESULTS: Among the 17 cases, the height of the cervical disc increased in 15 cases and decreased in 2 cases. The heights of the neural foramen increased in 19 cases and showed no changes in 13 cases. The areas of the neural foramen increased in 23 cases and decreased in 6 cases. The heights of vertebral body above and below the removed disc increased by 5.4% (p=0.734), and the heights of the neural foramen increased by 13.3% (p=0.002). The area of the neural foramen increased by 13.6% (p=0.192). The widths of the neural foramen increased by 2.3% (p=0.586). The intervertebral disc height, neural foramen height, and neural foramen area increased by 39.6%, 8.4%, and 17.9%, respectively, after a 2mm lengthening of bone transplant. The intervertebral disc height, neural foramen height, and neural foramen area increased by 59.8%, 22.9%, and 10.3%, respectively, after a 3mm lengthening of bone transplant. The height and area of neural foramen increased by 18.3% and 18.2%, respectively, after the PLL removal and dissection. CONCLUSIONS: The follow-up observations of the intervertebral disc height, neural foramen height, and neural foramen area showed increases after one segment ACDF in cervical disease cases, when compared to the preoperative radiographic findings. As the height of bone transplant increased, the intervertebral disc height, neural foramen height, and neural foramen area increased. The neural foramen height and neural foramen area significantly increased, when PLL was dissected.