The retrospective study was conducted in a single institution. Thirty adult patients (thirty six segments) with degenerative cervical radiculopathy were selected, who have undergone anterior cervical fusion using allobone graft and dynamic rotational plate, from March 2005 to February 2009. All thirty six segments had disc herniations, and amongst them, 10 were combined with foraminal spurs. Those patients undergoing surgery for non-degenerative disease (trauma, infection, tumor, deformity, inflammation) were excluded. Zephir plate (Medtronic Sofamor Danek, Memphis, TN, USA), which is a dynamic rotational plate to enable the longitudinal rotation of a variable screw at the plate-screw interface was used. The average age of patients was 51.0, ratio of men to women was 19:11 and the average follow-up period was 15 months (range, 12 to 57 months). This study was approved by our university's institutional review board.

All patients underwent microscopic anterior cervical discectomy by anterolateral approach with a single surgeon. Total cervical discectomy, spur removal and removal of the posterior longitudinal ligament were done with the cervical alignment neutral. Partial uncinectomy were done in patients with foraminal spurs. Allobone graft was used as the graft substance. The proper size of the bone graft was measured with a surgical caliper, and bone graft was reformed by a rongeur. The end-plate of the recipient was partially removed before bone grafting. Then, bone graft was inserted while the interval of the intervertebral discs was slightly on traction. Bone graft size was 6 mm in all cases. The traction force was released, and the dynamic plate was inserted after the removal of a Caspar pin retractor. The size of the dynamic rotational plate used was 22.5 mm. The surgical wound was sutured with an absorbable suture. The Philadelphia brace was worn for six to eight weeks for postoperative external fixation.

Clinical symptom was observed each after 1, 3, 6, 12, and 24 months postoperatively. Visual analogue scale (VAS) score was used to assess the arm pain radiating to the upper extremities for cervical radiculopathy. Odom's criteria were assessed for patients with cervical radiculopathy.

The images were obtained with patients standing and looking straight ahead. Lateral radiographs were performed using standard radiographic techniques, wherein the tube was centered on the C3-C4 intervertebral disc. The radiographic film cassette was 72 inches from the tube and radiographs were taken without magnification. All oblique radiographs were taken on 45° oblique standing position with the fourth cervical vertebral body at the center with the beam angles of 15° cranially. Lateral and oblique views were taken after 1 day, 1, 3, 6, 12, and 15 months postoperatively. The height of the intervertebral foramen was measured at surgical segments on the oblique X-ray view. The height of the intervertebral disc was measured by averaging the length of three regions (anterior, middle, and posterior). The digital X-ray images were obtained on the PACS system (Π view, Infinitt, Seoul, Korea), which was used to obtain the measurements. Bone union was defined when there was a bony bridge across the graft site and no visible movements on the flexion and extension views.

A paired sample t test was used for statistical analysis. The data were marked with the average±standard deviation. Statistical significance was set positive if the value was less than 0.05. SPSS ver. 10.0 (SPSS Inc., Chicago, IL, USA) was used for analysis.

The average preoperative VAS score was 8.4±1.0 and it showed a decrement to 0.3±0.2, immediately following the operation (Table 1). Clinical outcome review of thirty patients with cervical radiculopathy confirmed that sixteen had excellent results, ten had good results and four had satisfactory results, based on the Odom's criteria. Three patients developed neck pain in the early postoperative period, and it was relieved with a pain-killer. There was no complication with surgical procedures and dynamic plates.

There was a bony bridge that crossed the graft site for all 30 patients who underwent the surgery. The bony union was achieved at 9.3 months after the operation (range, 6-12 months). Average preoperative intervertebral foraminal height was 11.6±1.7 mm on the right, and 11.4±1.7 mm on the left. Postoperative measures were increased to 13.4±1.7 mm and 12.8±1.8 mm, respectively, which showed statistically significant difference (p<0.05) (Table 2). However, follow-up results showed gradual tendency to decrease in the intervertebral foraminal height, which showed increments immediately after the operation. At 12 months after the surgery, it showed little difference compared with the preoperative data, as to be 11.7±1.7 mm for the right side and 11.4±1.7 mm for the left side (p>0.05) (Table 2). However, clinically, patients showed no increase in the radiating pain at the follow-up period. Preoperative average intervertebral disc height was 5.0±1.0 mm, and postoperatively, 7.3±1.0 mm, which indicates an increment of intervertebral disc height (p<0.05) (Table 3). Continuous decrease in the intervertebral discal height is observed during the follow-up period; however, the final height at the 15 months-follow-up showed little difference with preoperative measures (p>0.05) (Table 3). The height of the intervertebral disc was measured by averaging the length of three regions (anterior, middle, and posterior). There was no difference among the three regions at the radiographs taken after 1, 3, 6, 12, and 15 months postoperatively. It is estimated that the continuous decrement in the intervertebral disc height is attributed to reformation and resorption at the intervertebral graft.