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 micr oscopic ACD and interbody fusion underwent thin-slice (1.5 mm) spiral compu terized tomography scanning 1 day preoperatively, 1 day postoperatively, an d 1 year postoperatively. Oblique sagittal reconstructions were made throug h both foramina; the height of each foramen and the angle between the end p lates were measured. Because 16 cages were implanted, 32 foramina were inve stigated. Preoperatively, the mean height of the foramina (+/- standard dev iation) was 8.1 +/- 1.5 mm (range 5.7-12 mm), and at 1 day postoperatively it was 9.7 +/- 1.4 mm (range 7.5-12.8 mm). This difference reached statisti cal 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 I- year measurement still reached statistical difference (p < 0.005) but not w ith the direct postoperative mean foraminal height. Preoperatively the mean value of the angle between the two adjacent endplates was 1.3 +/- 2.4 degr ees (range 0-8 degrees), and postoperatively it was 7.8 +/- 2.9 degrees (ra nge 2-12 degrees), which was statistically significant (p < 0.0005). Conclusions. The cervical carbon fiber cage effectively increased the heigh t of the foramen even after 1 year, which contributed to decompression of t he nerve root. The wedge shape of the device may contribute to restoration of lordosis.