| Objective:Cervical spondylosis is a common degenerative disease of the motor system. Since the 1950s, anterior cervical discectomy and fusion (ACDF) has become a major option for surgical treatment of cervical spondylosis through several decades of development. But studies have found that the compensatory increased range of motion (ROM) of adgacent segment after ACDF, maybe the results of increased stress load, too easy to cause adjacent segment degeneration (ASD). Recently, ASD as one of long-term complications of ACDF is widely noted. And some scholars thought that the complication rates of multiple segment fusion are higher than single segment fusion. Through biomechanical studies on cadaver, artificial cervical disc replacement (ACDR) can maintain index segment motion and mechanical within physiological range, and decrease adjacent stress. Clinical studies also indicated that ACDR can maintain index motion. But the influence on adjacent segment motion and degeneration after ACDR, and ACDR applied in the surgical treatment of multiple levels cervical spondylosis, the literature reported less.This study was designed to compare the clinical efficiency and cervical spine motor function after ACDR with ProDisc-C and after ACDF. And to compare the early clinical efficiency of ACDR combined with ACDF and multiple segmental ACDR in patients with multi-level cervical spondylosis and to analyze the influence on cervical motor function. And to discuss the factors which can cause heterotopic ossification (HO), and possible measures to prevent HO.Methods:20 patients with ACDR with ProDisc-C (ProDisc-C group) and 20 patients with ACDF (ACDF group) from August 2009 to March 2012 were enrolled in this retrospective study. ProDisc-C group:10 male and 10 female with average age 49 years old range from 37 to 68 years,7 patients were diagnosed as radiculopathy,10 myelopathy and 3 with both symptoms. ACDF group:10 male and 10 female with average age 48 years old range from 35 to 63 years,5 patients were diagnosed as radiculopathy,13 myelopathy and 2 with both symptoms.15 patients with ACDR combined with ACDF (hybrid surgery group, HS group),12 patients with multi-level ACDR (M-ACDR group) and 16 patients with multi-level ACDF (M-ACDF group) from November 2009 to February 2012 were also enrolled in this retrospective study. HS group:8 male and 7 female with average age 49.2 years old range from 39 to 69 years,4 patients were diagnosed as radiculopathy,8 myelopathy and 3 with both symptoms. M-ACDR group:8 male and 4 female with average age 45.8 years old range from 35 to 55 years,5 patients were diagnosed as radiculopathy,5 myelopathy and 2 with both symptoms. M-ACDF group:11 male and 5 female with average age 50 years old range from 36 to 67 years,2 patients were diagnosed as radiculopathy,11 myelopathy and 3 with both symptoms.Visual analogue scale (VAS) for neck and arm pain intensity and neck disability index (NDI) were used to evaluate clinical efficiency. And intervertebral disc height, cervical curvature, total cervical range of motion (ROM), and segmental ROM, segmental contribution to total cervical ROM were used to evaluate the cervical spine motor function. Heterotopic ossification (HO) and device related complications also be observed.Results:The average follow-up was 23.7 months of ProDisc-C group and 27.4 months of ACDF group. No serious complications occurred intraoperative of both two groups. No prosthesis loosening and migration in ProDisc-C group. No device loosening, fragment, drop, and subsidence in ACDF group. And the operative segment of ACDF achieved bony fusion at 6 months after operation. (1) VAS scores and NDI were significantly lower at all follow-up time points compared with preoperative levels (P<0.01) but no difference were found between treatments. ProDisc-C group was lower than ACDF group. (2) The disc height of operative segment was higher postopreatively than peroperative with significant difference. The upper and lower intervertebral disc height in ProDisc group maintained in preoperative levels (P>0.05), but intervertebral disc height of ACDF group decreased without significant difference in upper adjacent segment ant all follow-up and with significant difference in lower adjacent segment at 12month and final follow-up compared with preoperative levels (P<0.05). (3) The cervical curvature was about 30 degree in ProDisc-C group and 15 degree in ACDF group. The rate of cervical curvature recovery was higher in ProDisc-C group than that of ACDF group (P<0.05). (4) The total cervical ROM of ProDisc-C group increased with significant difference compared with preoperative levels (P<0.05), but that of ACDF group decreased with no significant difference compared with preoperative levels (P>0.05). (5) The operative, upper and lower segmental ROM contribution to total cervical ROM in ProDisc-C group maintained in preoperative levels, but that in ACDF group increased with significant difference compared with preoperative levels (P<0.01). (6) Six HO,5 of ? degree and 1 of ? degree, occurred in replacement segment of ProDisc-C group and 3 in adjacent segment of ACDF group. In ACDF group, one HO occurred in upper adjacent segment and 2 in lower.The average follow-up was 21.8 months of HS group,22 months of M-ACDR group, and 27.7 months of M-ACDF group. (1) VAS score and NDI in 3 groups were significantly lower at all follow-up time points compared with preoperative levels (P<0.01). There were significant defference of NDI results between the HS group and M-ACDF group (P<0.01) at 6M,12M and last follow-up point, so were the results between the M-ACDR group and M-ACDF group (P<0.01). (2) The intervertebral height of three groups is greater than that of preoperative. Intervertebral height of HS group was 3.2% lower postoperatively, and intervertebral height of M-ACDF group decresed 1.5%, there was no statistically significant difference between the two groups (P>0.05). No significant difference was found in Upper and lower adjacent segment intervertebral height between HS group and M-ACDR group (P>0.05), and there was an obviouse decline in that of M-ACDF (P<0.05). (3) The cervical vertebrae curvature of 3 groups' was significantly increased compared with preoperative (P<0.05). (4) At the time of the last follow-up, cervical total mobility of HS group decreased compared with preoperative level, but no statistical difference (P>0.05); cervical total mobility of M-ACDR group increased postoperatively, no statistical difference was found (P>0.05); Obviouse decrease of cercical total mobility in M-ACDF group was found (P<0.05). (5) At the time of the last follow-up, the contribution of surgical segment ROM to the total cervical ROM of HS and M-ACDR groups were increased slightly (P>0.05). The ROM of upper adjacent segment of M-ACDF group was significantly enlarged (P<0.05), and so it was the contribution to total cervical ROM (P<0.01). The upper adjacent segment contribution value differences of three groups were statistically significant (P<0.05). The lower adjacent segment contribution value of M-ACDF group increased significantly compared with preoperative (P<0.01). (6) During the follow-up,5 segments of HS group were found with heterotopic ossification,3 segments in M-ACDR, and 6 in M-ACDF group. No significant difference was found in the incident rate of adjacent segmental degeneration among the three groups. No plant loose and migration were found.Conclusions:1. Compared with single segmental ACDF, ACDR can also achieve the purpose of decompressing completely and recovering the operative segment disc height. And ACDR can restore and maintain cervical physiological curvature. Post-operative recovery is better than ACDF.2. Single segmental ACDR could not only restore and maintain operative segment motion function, but also can avoid increased mobility and stress at adjacent segment caused by ACDF. It indicated that ACDR do not accelerate the natural progression of degenerative disc disease.3. The influence on adjacent segmental disc height and motion is small after ACDR combined with ACDF, and multi-level ACDR. And the restore of cervical motor function is better than multi-level ACDF.4. Compared with the multi-level ACDF, multi-level ACDR and hybrid surgery has a certain degree of protection for adjacent segment, which can decrease the incidence of adjacent segment degeneration. The upper adjacent segment mobility and degenerative changes were significantly increased after multi-level ACDF, which indicated that more stress increased at upper adjacent segment.5. The appropriate select of operation indications and peri operative management, with the chosen of appropriate models of artificial cervical intervertebral disc prosthesis which can cover the anterior and posterior edge of vertebral end-plate, especially the posterior edge, can avoid heterotopic ossification occurred in a certain extent. |
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