Shen Qiang 1, Ding Hao 1, Zhu Zong-hao 1, Zhu Liang 1, Wei Xiao-kang 1, He Xu-feng 2

20 48 20161125 Chinese Journal of Tissue Engineering Research November 25, 2016 Vol.20, No.48 Anterior cervical discectomy and fusion versus anterior cervical corpectomy and fusion for treating two-level contiguous cervical spondylotic myelopathy Shen Qiang 1, Ding Hao 1, Zhu Zong-hao 1, Zhu Liang 1, Wei Xiao-kang 1, He Xu-feng 2 1 Department of Orthopedic Surgery, Shanghai First People s Hospital, Shanghai Jiao Tong University, Shanghai 200080, China 2 Department of Traumatology, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine, Shanghai 200025, China Cite this article: Shen Q, Ding H, Zhu ZH, Zhu L, Wei XK, He XF. Anterior cervical discectomy and fusion versus anterior cervical corpectomy and fusion for treating two-level contiguous cervical spondylotic myelopathy. Zhongguo Zuzhi Gongcheng Yanjiu. 2016;20(48):7175-7184. DOI:10.3969/j.issn.2095-4344.2016.48.005 ORCID: 0000-0001-6416-247X(Shen Qiang) Abstract BACKGROUND: Anterior cervical discectomy and fusion with stand-alone cages and anterior cervical corpectomy and fusion with plate-mesh are widely used techniques in the treatment of cervical spondylotic myelopathy. There were less comparative studies about these two techniques in surgical treatment of two-level contiguous cervical spondylotic myelopathy patients based long-term follow-up. OBJECTIVE: To compare the efficacy between the anterior cervical discectomy and fusion and anterior cervical corpectomy and fusion procedures in patients with two-level contiguous cervical spondylotic myelopathy in clinical and radiological findings. METHODS: Between December 2006 and December 2009, 80 consecutive patients with two-level contiguous cervical spondylotic myelopathy were randomized into anterior cervical discectomy and fusion group and anterior cervical corpectomy and fusion group. The clinical and radiographic results were compared between the two groups. RESULTS AND CONCLUSION: The overall follow-up period of the patients ranged from 62 to 98 months (average 83.6 months). There were no significant differences between the two groups in Japanese Orthopedic Association score, Visual Analog Scale score, Odom s criteria, fusion rates and complications. There were no significant differences between the two groups in the segmental and C 27 Cobb angles at post-operation and 5-year follow-up. In anterior cervical discectomy and fusion group, both post-operative and 5-year follow-up segmental height was significantly larger than pre-operative segment height; in anterior cervical corpectomy and fusion group, only post-operative segmental height was significantly larger than pre-operative segmental height, not 5-year follow-up segmental height. More significant incensement of the segmental height was observed in anterior cervical discectomy and fusion cage group than that in anterior cervical corpectomy and fusion group at post-operative and 5-year follow-up. The instrument subsidence rates were similar between the two groups. In surgical treatment of two-level cervical spondylotic myelopathy, anterior cervical discectomy and fusion with stand-alone cage technique resulted in the same excellent clinical outcome as anterior cervical corpectomy and fusion with plate-mesh. However, anterior cervical discectomy and fusion with stand-alone cage technique exhibited better restoration of intervertebral height than that of anterior cervical corpectomy and fusion with plate-mesh technique. Subject headings: Bone Transplantation; Spinal Fusion; Tissue Engineering Funding: The Key Project for Medical Science from the Shanghai Committee of Science and Technology of China, No.12441900702 Shen Qiang, M.D., Chief physician, Professor, Department of Orthopedic Surgery, Shanghai First People s Hospital, Shanghai Jiao Tong University, Shanghai 200080, China Accepted: 2016-09-12 ISSN 2095-4344 CN 21-1581/R CODEN: ZLKHAH 7175

INTRODUCTION Cervical spondylotic myelopathy (CSM) is a degenerative disc disease that causes spinal cord compression and dysfunction. Patients with symptomatic cervical myelopathy should be considered surgical treatment if conservative treatment is ineffective [1]. Anterior cervical discectomies and interbody cage fusion with or without plate fixation has been proven to be a safe and effective procedure for 1- to 2-level CSM [2-4]. Anterior cervical corpectomy and reconstruction and fusion using plate and titanium mesh may be considered for patients with developmental stenosis and the larger posterior osteophyte or a free disc fragment that has migrated posterior to the vertebral body. When CSM does not include the above corpectomy criteria, controversy exists regarding which is the optimal anterior technique in the treatment of 2-level contiguous CSM [4-6]. To compare the differences in the surgical treatment of two-level CSM between discectomy with stand-alone cage technique and corpectomy with plate-mesh technique, we prospectively observed the clinical and radiological results of the patients with 2-level CSM who had treated with one of these techniques based on a minimum 5-year follow-up. SUBJECTS AND METHODS Design This is a prospective, randomized, contrastive clinical study. Time and setting This study was conducted at the Shanghai First People s Hospital Affiliated to Shanghai Jiao Tong University in China between December 2006 and December 2009. Subjects A total of 80 patients with a consecutive sequence of hospitalization were randomized in a 1:1 ratio to a anterior cervical discectomy and fusion group (ACDF group) and a anterior cervical corpectomy and fusion group (ACCF group) using the envelope method [7]. The inclusion criteria were (1) cervical myelopathy with no response to 6 weeks of conservative treatment and (2) cervical spine radiography, CT, and/or MRI showing two-level contiguous intervertebral disc herniation and/or posterior border osteophyte of vertebral body. The exclusion criteria were single-level or more than two-level CSM, two-level CSM without continuity, and CSM with congenital deformity, previous cervical injury and/or cervical surgery, and ossification of the posterior longitudinal ligament. All patients provided informed consent before surgery. The study was approved by the Ethics Committee of Shanghai First People s Hospital. Materials A total of 66 cages, including Bengal (19 patients), Depuy Synthes Spine, Raynham, MA, USA; Stryker Solis (7 patients), Stryker Australia Pty. Ltd., St. Leonards, NSW, Australia; AO Syncage (7 patients), Synthes Spine, West Chester, PA, USA, were used in ACDF group. A total of 36 plate-meshes, including Codman (4 patients), Codman & Shurtleff, Inc., Raynham, MA, USA; Slim-Loc (3 patients), DepuySynthes Spine; Skyline (9 patients), DepuySynthes Spine; Orion (4 patients), Medtronic, Inc., Minneapolis, MN, USA; Zephir (9 patients), Medtronic, Inc.; CSLP-VA (3 patients), Synthes GmbH, Oberdorf, Switzerland; Reflex Hybrid (4 patients), Stryker Spine, Mahwah, NJ, USA, were used in ACCF group. Methods Operation The preoperative American Society of Anesthesiologists (ASA) classification scores of all patients were less than 3. Patients received general anesthetic via tracheal intubation. The patient was supine on operating table and neck was supported with sandbag in neutral position. Anterior approach through the transverse incision along the skin crease was made to expose the anterior surface of vertebrae through the space between the carotid sheath and the trachea and esophagus. Disc level was identified using a needle mark inserted into the disc space and was confirmed by intraoperative fluoroscopy. For patients in the ACDF group, after an interbody pin distractor system was used above and below the discectomy site, a transverse incision through the anterior longitudinal ligament was made at the middle of the disc space. The disc tissue and endplate cartilage were cut and removed using 7176 P.O. Box 10002, Shenyang 110180

curette. After flushing the space with cold saline, an expanding decompression was made using the different angle smaller diameter curettes to remove the osteophytes on the posterior lips of the vertebrae, then used 1-mm laminectomy punch to cut the posterior longitudinal ligament at the disc space. The dura matter was inspected and no compression of dura matter was assured. After re-flushing the decompressed space with cold saline, small-size gelfoam was inserted into the deep part of the disc space. After appropriate-size cages were selected to fit the interbody space defect. The cages were packed with local decompression bone harvested from the decompression of the posterior border of vertebral body and were then inserted into corresponding interbody space defect under further 1-mm more traction. Proper hardware placement was confirmed by intraoperative fluoroscopy. For patients in the ACCF group, an interbody pin distractor system was used above and below the corpectomy site. After incised the anterior longitudinal ligament and disc tissue and endplate cartilage at affected disc space, the corresponding interspace vertebral body was excised using a rongeur and different angle smaller diameter curettes. The corresponding posterior longitudinal ligament was incised used 1.02.0 mm laminectomy punch. The dura matter was inspected and no compression of dura matter was assured. After flushing the space with cold saline, proper size gelfoam was carefully placed on the dura matter. An appropriate titanium mesh was selected and cut down to fit the corpectomy defect. The mesh was packed with local vertebra bone harvested from decompression and was then inserted into the corpectomy defect under further 1 mm traction. Finally, an anterior cervical titanium plate and screws were applied to achieve anterior cervical fixation. Proper hardware placement was confirmed by intraoperative fluoroscopy. After operation for both groups, the patients were placed in a soft collar for 6 weeks and encouraged to resume their normal activities. Clinical evaluation All data were collected and reviewed by an independent spine surgeon (LZ) using a standardized data-collection form. The neurological function improvement was assessed by the Japanese Orthopaedic Association (JOA) score, which was recorded before surgery and at 5-year follow-up. A full JOA score was defined as 17 points, 8 for upper and lower motor function, 6 for sensory functions, and 3 for bladder rectal function [3]. Neck and radicular pain was evaluated using the Visual Analogue Scale (VAS) before surgery and at 5-year follow-up. Clinical outcome was assessed according to the Odom criteria as shown in Table 1. Table 1 Odom criteria Grade Excellent Good Average Poor Evaluation standard All preoperative symptoms relieved, able to carry out daily occupations without impairment Minimum persistence of preoperative symptoms, able to carry out daily occupations without significant interference Relief of some preoperative symptoms, but whose physical activities were significantly limited Symptoms and signs unchanged or worse Radiological evaluation The cervical lordoses were indicated by the methods of Cobb angle of C 2-7 and operated segments. The C 2-7 Cobb angle was the angle between the inferior endplate line of C 2 and inferior endplate line of C 7 in a neutral position. The segmental Cobb angle was the angle between the superior endplate line of the cephalad vertebral body and the inferior endplate line of caudal vertebral body of the operated segments in a neutral position. Lordosis is shown as a positive value and kyphosis is shown as a negative value (Figure 1). The Segmental height was measured using the method of Oh et al. [6] and defined as the distance between the midlines of involvedcranial vertebral bodies and caudal vertebral bodies (Figure 1). Instrument subsidence was recorded when the loss of segmental height correction was over 3 mm. Fusion was considered according to the following accepted criteria: (1) absence of motion between the spinous processes at dynamic lateral radiographs, (2) presence of continuous bridging bony trabeculae at the graft-endplate interface [8]. Main outcome measures There were (1) perioperative parameters, including patients age, sex, smoking condition, body mass index, ASA classification scores, and surgery levels; (2) clinical evaluations included JOA score and VAS score before and at 5-year follow-up after surgery. The Odom score, fusion rate, and complications at 5-year follow-up after surgery. (3) Radiological ISSN 2095-4344 CN 21-1581/R CODEN: ZLKHAH 7177

Enrollment Assessed for eligibility (n=382) Randomized (n=80) Excluded (n=302) Not meeting inclusion criteria (n=212) Declined to participate (n=61) Other reasons (n=29) Allocated to ACDF group (n=40) Received allocated intervention (n=40) Did not receive allocated intervention (give reasons) (n=0) Allocation Allocated to ACCF group (n=40) Received allocated intervention (n=40) Did not receive allocated intervention (give reasons) (n=0) Lost to follow-up (n=4) Discontinued intervention (2 cervical spine injuries, 1 lumbar disc operation) (n=3) Follow-up Lost to follow-up (Relocation) (n=3) Discontinued intervention (1 lumbar disc herniation) (n=1) Analyzed (n=33) Excluded from analysis (give reasons) (n=0) Analysis Analyzed (n=36) Excluded from analysis (give reasons) (n=0) Figure 2 Flow chart of the study comparing the two groups Note: ACDF: Anterior cervical discectomy and fusion; ACCF: anterior cervical corpectomy and fusion. Figure 1 Radiologic parameters in patients of ACDF and ACCF groups Note: (A) Before operation, sagittal radiographs showing Cobb angle of C : α, Cobb angle of operated segments: β, and segmental height: c. (B) After operation in ACDF group, sagittal radiographs showing Cobb angle of C : α, Cobb angle of operated segments: β, and segmental height: c. (C) After operation in ACCF group, sagittal radiographs showing Cobb angle of C : α, Cobb angle of operated segments: β, and segmental height: c. ACDF: Anterior cervical discectomy and fusion; ACCF: anterior cervical corpectomy and fusion. evaluations included the segmental and C 2-7 Cobb angles, segmental heights, the instrument subsidence rates, and the instrument dislocations before and at 5-year follow-up after surgery. Statistical analysis Between-group comparisons of the continuous variables were performed using the two-sample F-test for variances, followed by unpaired t-tests. Between-group comparisons of the categorical variables were performed using the chi-square test or Fisher s exact test. The analysis of Cobb s angles and segmental heights between groups at each corresponding time point used t-test (two-sample assuming equal variances or unequal variances according its F-test two-sample for variances). The analysis of Cobb s angles and segmental heights within group at each corresponding time point used t-test (paired two-sample for means).the statistical tests were completed by the SPSS 17.0 software (SPSS Inc, Chicago, IL, USA). In all tests, the difference was considered to be statistically significant at the P values less than 0.05 level. RESULTS Quantitative analysis of participants The follow-up period of the patients ranged from 62 to 98 months (average 83.6). Of the original 80 patients, 11 (14%) withdrew from the study, and 7 were lost to follow-up (4 in ACDF group; 3 in ACCF group). Two of the patients in ACDF group withdrew from the study because of a cervical spine injury during follow-up, and another withdrew because of a lumbar disc disease operation during follow-up. In addition, one patient in the ACCF group withdrew because of lumbar disc herniation during follow-up. Of the remaining 69 patients (86%), 33 were in the ACDF group, and 36 were in the ACCF group. 7178 P.O. Box 10002, Shenyang 110180

ACDF group comprised 15 men and 18 women with a mean age of 52.3 years (range: 37 67 years), whereas ACCF group comprised 23 men and 13 women with a mean age of 55.8 years (range: 2571 years). The surgery levels involved were C 3 5 in 10 cases, C 4-6 in 36 cases, and C 5-7 in 23 cases. Study flow chart is shown in Figure 2. The demographic data, including age, sex, smoking status, body mass index, ASA classification scores, surgery level in each group and follow-up period were summarized in Table 2. Table 2 Demographics and perioperative parameters between groups Item ACDF group ACCF group P n 33 36 Age (x±s, year) 52.3±8.2 55.8±10.0 0.116 Female [n(%)] 18(55) 13(36) 0.195 Smokers [n(%)] 4(15) 6(17) 1.000 BMI (x±s, kg/m ) 23.91±2.85 23.83±2.55 0.937 ASA classification scores [n(%)] 0.62 1 7(22) 8(22) 2 26(78) 26(72) 3 0 2(6) Surgery level [n(%)] 0.714 C 4(12) 6(17) C 19(58) 17(47) C 10(30) 13(36) Follow-up period (month) 82.7 84.3 0.497 Note: ACDF: Anterior cervical discectomy and fusion; ACCF: anterior cervical corpectomy and fusion; BMI: body mass index; ASA: American Society of Anesthesiologists. Clinical outcome The JOA scores significantly increased in the ACDF group and ACCF group (P < 0.01). The corresponding VAS scores significantly decreased in the ACDF group and ACCF group (P < 0.01). According to Odom s criteria, the percentage of patients with excellent and good clinical outcomes was 85% in the ACDF group and 81% in the ACCF group. Although significant JOA scores and VAS scores improvement have been achieved in each group at the final follow-up, there were no significant differences between groups (P > 0.05; Table 3). Radiological analysis results The mean operated segmental Cobb angles at pre-, post-operation and 5-year follow-ups were 6.54, 16.65, and 10.48 degrees for ACDF group and 6.63, 10.83, and 9.88 degrees for ACCF group, respectively. There were significant differences in operated segmental Cobb angel between pre-operation and post-operation or 5-year follow-up in each group (P < 0.05). There was no significant difference in the operated segmental Cobb angle between these two groups at 5-year follow-up. The mean C 2-7 Cobb angles at pre-, post-operation and 5-year follow-ups were 18.67, 20, and 21.96 degrees for ACDF group and 20.67, 17.63, and 19.88 degrees for ACCF group, respectively. There were no significant differences in C 2-7 Cobb angel between pre-operation and post-operation or 5-year follow-up in each group. There was no significant difference in C 2-7 Cobb angle between these two groups (Table 4). In the ACDF group, both post-operative and 5-year follow-up segmental height was significantly larger than pre-operative segmental height (P < 0.05); in the ACCF group, only post-operative segmental height was significantly larger than pre-operative segmental height (P < 0.05), not 5-year follow-up segmental height. At both post-operation and 5-year follow-up, segmental height of the ACDF group was significantly larger than that of ACCF group (P < 0.05). The loss of correction of segmental height in the ACDF group was significantly larger than that in the ACCF group at 5-year follow-up (P < 0.05; Table 4). Table 3 Clinical results of two-level anterior cervical discectomy using stand-alone cages technique versus one-level corpectomy using plate-mesh technique in the surgical treatment of two-level contiguous cervical spondylotic myelopathy patients Item ACDF group (n = 33) ACCF group (n = 36) JOA scores (x±s) Preoperative 11.14±2.33 11.64±1.99 > 0.05 5-year follow-up 16.34±0.97 16.03±1.06 > 0.05 VAS scores (x±s) Preoperative 7.10±2.54 7.39±2.43 > 0.05 5-year follow-up 0.90±1.54 1.14±1.36 > 0.05 Odom criteria (percentage of excellent and good) 85% 81% > 0.05 Complications (n) Wound swelling 1 1 > 0.05 Dysphagia 2 1 > 0.05 Acute radicular pain 0 1 > 0.05 CSF leakage 0 1 > 0.05 Hoarseness 0 1 > 0.05 Note: ACDF: Anterior cervical discectomy and fusion; ACCF: anterior cervical corpectomy and fusion; JOA: Japanese Orthopedic Association, VAS: Visual Analog Scale; CSF: cerebrospinal fluid; P < 0.05, vs. preoperation. P ISSN 2095-4344 CN 21-1581/R CODEN: ZLKHAH 7179

Table 4 Radiological results of two-level anterior cervical discectomy using stand-alone cages technique versus one-level corpectomy using plate-mesh technique in the surgical treatment of two-level contiguous cervical spondylotic myelopathy patients (x±s) Item The subsidence rates were 31% and 13% in the ACDF group and ACCF group, respectively. There was no significant difference between them. Solid fusion and bone union in the operated segments were observed in all patients at 5-year follow-up. No patient presented with instrumentation displacement. Typical cases Case one: This patient, male, aged 62 years, was diagnosed as CSM at C 4 6 that underwent cervical discectomy and fusion at C 4 5 and C 5 6 with stand-alone cages (Figure 3). 7180 ACDF group ACCF group P (n=33) (n=36) Cobb angle of the operated segment ( ) Preoperative 6.54±7.42 6.63±7.61 > 0.05 Postoperative 16.65±6.89 10.83±7.17 < 0.05 5-year follow-up 10.48±8.54 9.88±6.85 > 0.05 Loss of Cobb angle correction 6.00±6.49 0.96±3.94 < 0.05 Cobb angle of C ( ) Preoperative 18.67±8.54 20.67±10.50 > 0.05 Postoperative 20.00±9.96 17.63±12.44 > 0.05 5-year follow-up 21.96±10.47 19.88±11.56 > 0.05 Loss of Cobb angle correction 1.61±7.28 2.25±8.20 > 0.05 Segmental height of the operated segment (mm) Preoperative 53.52±5.84 53.04±4.99 > 0.05 Postoperative 58.82±6.46 54.20±5.64 < 0.05 5-year follow-up 56.99±6.72 53.51±4.79 < 0.05 Loss of segmental height correction 1.82±1.97 0.68±1.98 < 0.05 Note: ACDF: Anterior cervical discectomy and fusion; ACCF: anterior cervical corpectomy and fusion. P < 0.05, vs. preoperation Figure 3 Representative sagittal magnetic resonance and lateral radiograph in a patient from the anterior cervical discectomy and fusion group Note: This patient, male, aged 62 years, was diagnosed as cervical spondylotic myelopathy at C that underwent cervical discectomy and fusion at C and C with stand-alone cages. (A) Sagittal magnetic resonance before operation. (B) Lateral radiographs 3 month after operation. Case two: This patient, male, aged 44 years, was diagnosed as CSM at C 5-7 that underwent cervical corpectomy and fusion at C 5-7 with titanium mesh and plate and screw fixation (Figure 4). Adverse reactions There were some complications after the surgical treatment (Table 2). These complications were completely recovered within two months of after surgery. Figure 4 Representative sagittal magnetic resonance and lateral radiograph in a patient from the anterior cervical corpectomy and fusion group Note: This patient, male, aged 44 years, was diagnosed as cervical spondylotic myelopathy at C that underwent cervical corpectomy and fusion at C with titanium mesh and plate and screws fixation. (A) Sagittal magnetic resonance before operation. (B) Lateral radiographs 5 years after operation. (C) Sagittal magnetic resonance 3-year after operation. DISCUSSION The pathophysiology of CSM determines that the relief of the anterior compression of the spinal cord or nerve root is the most direct treatment of CSM [9]. In this study, anterior cervical discectomy or corpectomy operations were performed according to the methods previously described [10-11]. For patients from both groups, we confirmed effective compression by incised the posterior longitudinal ligament and exposed corresponding dura matter used 12 mm laminectomy punch during operation. After decompression, the operated segments should be stabilized early by fixation and later by bone fusion [12-15]. The intervertebral height and cervical lordosis should be restored to maintain cervical spine biomechanical requirements [1]. In this study, all patient used autograft harvested from decompression bone cutting. For the maximum restoration of intervertebral height, after decompression and before cage or mesh insertion, we further distracted the interbody pin distractor system 1 mm more, so for ACDF group, 2 mm more distraction and ACCF group, 1 mm more. ACDF group was stabilized through tension-band P.O. Box 10002, Shenyang 110180

mechanism and ACCF group added titanium plate and screw fixation early post-operatively. The use of stand-alone cage technique in cervical spondylosis was first introduced by Bagby [16]. Stand-alone cages have been widely applied in 1- or 2-level pathologies of cervical spondylosis [17-22]. Cho et al. [18] evaluated treatment of multilevel cervical stand-alone cage fusion without plating and autogenous iliac crest graft with plating in 180 consecutive cases of multilevel cervical degenerative disease. They found that both methods were good for interbody fusion in multilevel cervical degenerative diseases, but stand-alone cage fusion was preferred, because it has the fewest complication rates and the least amount of blood loss. Chen et al. [3] compared stand-alone titanium and polyetheretherketon cage in the surgical treatment of multilevel spondylotic myelopathy with over 7-year follow-up and found both groups had good clinical outcome, but polyetheretherketon cage was superior to titanium cage in maintenance of intervertebral height and cervical lordosis. Jang et al [4] reported anterior cervical reconstruction using titanium mesh and plate in patients with cervical degenerative disease. Their result provided good clinical and radiologic outcomes, but the titanium mesh subsidence occurred frequently, especially at the posterior part of the mesh. They concluded that despite the prominent posterior subsidence of the mesh, segmental angle and cervical sagittal angle were improved on final follow-up radiographs, suggesting that posterior subsidence may contribute to cervical lordosis. In this study, we also found that both groups had good cervical lordosis. There was no instrument displacement post-operation and all patients acquired bone fusion at 5-year follow-up. Many contrastive studies have reported similarly good clinical outcomes for ACCF and ACDF [5-6, 23-24]. Recent meta-analysis combining the results of 15 non-randomized controlled clinical studies reported equivalent outcomes in terms of Odom s criteria and JOA, VAS, and neck disability index scores in the two treatment groups [25]. In the present study, we compared stand-alone cages ACDF technique and plate and mesh ACCF technique in the treatment of CSM patients. For clinical symptoms and function, both groups had significant improved as indicated by JOA scores and VAS scores and there were no significant differences between these two groups. According to Odom s criteria, the percentages of patients with excellent and good clinical outcomes were 85% in the ACDF group and 81% in the ACCF group. This study supported that for the two-level contiguous CSM patients, ACDF with stand-alone cages technique and ACCF with plate-mesh technique can provide equivalent effects of spinal cord and nerve roots decompression. Park et al. [24] reported no significant differences in sagittal alignment, cervical lordosis, graft collapse, and adjacent-level ossification between single-level ACCF and two-level ACDF with fibula strut allograft and variable-angle screw-plate fixation. Cage subsidence is considered the greatest problem with stand-alone cage technology, with titanium cage subsidence observed in 13%45 % of cases in two large series [26-27]. Oh et al. [6] reported that the ACCF group was associated with more vertebral body height loss and a reduced lordotic curvature than the ACDF group and believed that a decrease in cervical lordosis may explain the poor improvement in neck pain achieved following ACCF. Therefore, because of using different graft and fixation techniques within ACCF or ACDF, there existed differences about sagittal alignment, cervical lordosis, and graft collapse. According to author s review, no contrastive study about stand-alone cage ACDF technique and plate-mesh ACCF technique have been reported. In the present study, we found that stand-alone cages ACDF technique significantly increase total segmental height than plate and mesh ACCF technique in 5-year follow-up, although the loss of correction of segmental height in stand-alone cages group was significantly larger than that in plate and mesh group. In stand-alone cages group, both post-operation and 5-year follow-up segmental height were significant larger than pre-operative segmental height; in plate and mesh group, only post-operative segmental height was significantly larger than pre-operative segmental height, not 5-year follow-up segmental height. This made for restoration of intervertebral height, especially when patients associated with congenital spinal canal narrow to obtain indirect decompression by stretching the inward ligament flava is possible. In the present study, no significant differences in the operated segmental and C 2 7 Cobb angles were detected between these two groups. In both groups, post-operative and 5-year follow-up operated segmental Cobb angles were significantly better ISSN 2095-4344 CN 21-1581/R CODEN: ZLKHAH 7181

than pre-operative ones. Flynn [28] reported 311 neurologic complications following 82 114 anterior cervical discectomy and fusion procedures done by 704 neurosurgeons. The rate of temporary recurrent laryngeal nerve paralysis has been reported in 1.69% to 11% of patients following an anterior cervical approach [29-30]. Dysphagia incidences of 50.2%, 32.2%, 17.8%, and 12.5% were found at 1, 2, 6, and 12 months, respectively, after anterior surgery. The risk of dysphagiais higher after multilevel procedures and in patients with longstanding neck pain, and female gender, but the type of procedure (discectomy or corpectomy) and the use of an anterior plate do not influence the prevalence of postoperative dysphagia [31-32]. In this study, the complication rates were 9% and 14% in ACDF group and ACCF group, respectively. One patient in ACCF group had acute radicular pain immediately after operation and the symptom relieved within one month after operation. Three patients had dysphagia which improved 2 months after operation. One patient had temporary hoarseness after operation in the ACCF group. One patient affected cerebrospinal fluid leakage after operation, which was recovered within one week. Hilibrand et al. [33] reported 93% solid arthrodesis rate with strut grafting, as compared with 66% solid arthrodesis with multiple interbody grafting, both without fixation. Recently, with the use of internal fixation, several reports have concluded that ACDF is not inferior to ACCF in terms of fusion. Wang et al. [34] reported that fusion rates, complication rates, and clinical outcomes were not significantly different between corpectomy and 2-level discectomy with autograft fusion and plate fixation. In the present study, we found that fusion rates, complication rates, and clinical outcomes were not significantly different between corpectomy and 2-level discectomy with autograft fusion by using plate-mesh fixation or stand-alone cages fixation. In surgical treatment of two-level CSM, ACDF with stand-alone cages technique result in same clinical outcome as ACCF with plate-mash technique according to JOA score, VAS score, Odom s criteria, fusion rates, and complications, and restoration of operated segmental and cervical lordosis, but ACDF with stand-alone cages technique group exhibited better restoration of intervertebral height than that of the ACCF with plate-mesh technique group in 5-years follow-up. This made for restoration of intervertebral height, especially when patients associated with congenital spinal canal narrow to obtain indirect decompression by stretching the inward ligament flava is possible. REFERENCES [1] Rao RD, Currier BL, Albert TJ, et al. Degenerative cervical spondylosis: clinical syndromes, pathogenesis, and management. J Bone Joint Surg Am. 2007;89(6):1360-1378. [2] Topuz K, Colak A, Kaya S, et al. Two-level contiguous cervical disc disease treated with peek cages packed with demineralized bone matrix: results of 3-year follow-up. Eur Spine J. 2009;18(2):238-243. [3] Chen Y, Wang X, Lu X, et al. Comparison of titanium and polyetheretherketone (PEEK) cages in the surgical treatment of multilevel cervical spondylotic myelopathy: a prospective, randomized, control study with over 7-year follow-up. Eur Spine J. 2013;22(7): 1539-1546. [4] Jang JW, Lee JK, Lee JH, et al. Effect of posterior subsidence on cervical alignment after anterior cervical corpectomy and reconstruction using titanium mesh cages in degenerative cervical disease. J Clin Neurosci. 2014;21(10):1779-1785. [5] 5. Song KJ, Lee KB, Song JH. Efficacy of multilevel anterior cervical discectomy and fusion versus corpectomy and fusion for multilevel cervical spondylotic myelopathy: a minimum 5-year follow-up study. Eur Spine J. 2012;21(8):1551-1557. [6] Oh MC, Zhang HY, Park JY, et al. Two-level anterior cervical discectomy versus one-level corpectomy in cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2009;34(7):692-696. [7] Mason RL, Gunst RF, Hess JL. Statistical Design and Analysis of Experiments: With Applications to Engineering and Science. 2nd ed. New Jersey: John Wiley and Sons, Inc. 2003:14-19. [8] Hacker RJ, Cauthen JC, Gilbert TJ, et al. A prospective randomized multicenter clinical evaluation of an anterior cervical fusion cage. Spine (Phila Pa 1976). 2000;25(20):2646-2654; discussion 2655. [9] Fessler RG, Steck JC, Giovanini MA. Anterior cervical corpectomy for cervical spondylotic myelopathy. Neurosurgery. 1998;43(2):257-265; discussion 265-267. [10] Cloward RB. The anterior approach for removal of ruptured cervical disks. J Neurosurg. 1958;15(6): 602-617. [11] Matz PG, Pritchard PR, Hadley MN. Anterior cervical approach for the treatment of cervical myelopathy. Neurosurgery. 2007;60(1 Supp1 1):S64-70. 7182 P.O. Box 10002, Shenyang 110180

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1 1 1 1 1 2 ( 1 200080 2 200025) 80 2 (n=40) (n=40) 5 1962 1985 2 2006 12 2009 12 80 2 5 2 2 6298 83.6 5 2 Odom s 2 Cobb Cobb 1 5 1 1 5 2 5 (12441900702) CNKI 3 ( ) : R394.2 : A : 2095-4344(2016)48-07175-10. [J]. 201620(48):7175-7184. (Edited by Yu ZR, Hao J/Yu J/Qiu Y) 7184 P.O. Box 10002, Shenyang 110180