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

OBJECT: 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.
METHODS: 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).
CONCLUSIONS: 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.