Height of cervical foramina after anterior discectomy and implantation of a carbon fiber cage

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Abstract
The authors evaluate the effects of implantation of a carbon fiber cage after anterior cervical discectomy (ACD) on the height of the foramen and the angulation between endplates of the disc space. Thirteen consecutive patients who were scheduled for standard microscopic ACD and interbody fusion underwent thin-slice (1.5 mm) spiral computerized tomography scanning 1 day preoperatively, 1 day postoperatively, and 1 year postoperatively. Oblique sagittal reconstructions were made through both foramina; the height of each foramen and the angle between the endplates were measured. Because 16 cages were implanted, 32 foramina were investigated. Preoperatively, the mean height of the foramina (+/- standard deviation) was 8.1 +/- 1.5 mm (range 5.7-12 mm), and at I day postoperatively it was 9.7 +/- 1.4 mm (range 7.5-12.8 mm). This difference reached statistical significance (p < 0.0005). The mean foraminal height after 1 year was 9.4 +/- 1.4 mm (range 6.9-12.7 mm). In terms of the preoperative value, the 1-year measurement still reached statistical difference (p < 0.005) but not with the direct postoperative mean foraminal height. Preoperatively the mean value of the angle between the two adjacent endplates was 1.3 +/- 2.4 degrees (range 0-8 degrees), and postoperatively it was 7.8 +/- 2.9 degrees (rauge 2-12 degrees), which was statistically significant (p < 0.0005). The cervical carbon fiber cage effectively increased the height of the foramen even after 1 year, which contributed to decompression of the nerve root. The wedge shape of the device may contribute to restoration of lordosis.