| BackgroundCervical degenerative disc disease (cDDD) is a common age-related neurologic disorder, substantially impairing quality of life. The incidence of cDDD increases annually with the acceleration of aging process in human society. The pathological process of cDDD is very complex, including degeneration of the disc, luschka’s joint and vertebrae, all of which can compress the neural structures and result in symptoms. The main treatment method of cDDD include non-surgical treatment and surgical treatment. Non-surgical treatment is effective for early stage of cDDD and for those symptoms are not serious. But for cervical spondylotic myelopathy(CSM) and serious radiculopathy, surgical interventions remain the only way. Direct decompression procedures create the space for rehabilitation of the neural structures. The main surgical procedures include anterior, posterior and anterior-posterior approach. When the topic is limited to anterior approaches, anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF) are the most comonly used techniques.However, biomechanical changes after long-segment fusion including concentrated stress, increased compensatory motion, and stability loss at the adjacent segments, may result in symptomatic adjacent-segment degeneration (ASD).As surgical technology progresses, cervical artificial disk replacement (cADR) has gained popularity, which maintains motion of operative level and alleviates stress distribution at adjacent-segments for preventing ASD. However, the long-term results of multi-level cADR are not well established, and hypermobility of operative segments, high risk of prosthesis-related complications and high medical expense may be potential problems. Moreover,the indications of cADR are more strictly. Thoes with serious osteophyte at the posterior edge of vertebral body, significant spinal stenosis or posterior compression, tumor, deformity, osteoporosis and infection would not be applicable.Compared to single-level cDDD, the surgical treatment of multi-level cDDD is more complex. The posterior approach represented by laminoplasty is a safe and effective technique with a wide range of decompression. But the drawbacks of laminoplasty characterized by post-operative axial symptoms, C5 plasy, progress of cervical kyphosis should not be neglected. Fusion techniques via anterior approaches including ACDF, ACCF and anterior cervical hybrid decompression and fusion (ACHDF) are benefit for cervical lordosis rescontruction.However, as describe above, long-segment fusion will induce concentrated stress, increased compensatory motion, and stability loss at the adjacent segments, all of which may result in symptomatic adjacent-segment degeneration (ASD). As mentioned above, multi-level cADR are lacking of high evidence for clinnical practice, and hypermobility of operative segments, high risk of prosthesis-related complications and high medical expense may be potential problems. Recently, a hybrid surgery consisting of ACDF and cADR has been reported withgood outcomes. The rationality behind this technique is that not all the diseased levels show the same type and extent of degeneration, and it is better to tailor the most suitable procedure according to the status of affected levels. Nonetheless, little information is documented regarding to the efficacy of Hybrid surgery for multi-level cDDD.In this context, this study is aimed (1) to investigate the safety and efficacy of hybrid surgery for multi-level cDDD and (2) to compare clinical outcomes, radiological findings, and complications between the hybrid surgery and anterior cervical decompression and fusion for multi-level cDDD. Moreover, (3) we evaluate all the biomechanical and clinical evidence available for hybrid surgery and provide a systematic review of current understanding of hybrid surgery.Objective1 To investigate the safety and efficacy of hybrid surgery for multi-level cDDD and to discuss the indications and contraindications.2 To compare clinical outcomes, radiological findings, and complications between the hybrid surgery and anterior cervical decompression and fusion for multi-level cDDD3 To evaluate all the biomechanical and clinical evidence available for hybrid surgery and provide a systematic review of current understanding of hybrid surgery.MethodSection 1:Evaluaton of the clinical efficacy of hybrid surgery for multi-level cDDDFrom January 2009 to January 2012, thirteen patients with multi-level cDDD were respectively reviewed. All patients were followed clinically andradiologically for a minimum of 24 months. Perioperative parameters(operation time, blood loss, drainage volume, hospital-stay and follow-up duration) were collected. Neck Disability Index (NDI) was used to evaluate daily activities of the patients. Neurological status was evaluated according to the Japanese Orthopedic Association (JOA) disability scale. The visual analog scale (VAS) was used to assess the neck pain intensity. All evaluations were completed preoperative-1y and at 3,6,12, and 24 months postoperatively. JOA recovery rate was calculated using the Hirabayashi method 18:(postoperative score - preoperative score)/(17-preoperative score)× 100%. Recovery rates were graded as follows:>75%, excellent; 50-74%, good; 25-49%, fair; and<25%, poor. General clinical outcomes were graded according to Odom criteria. Radiological Analysis was conducted via lateral radiographs in flexion, extension and in neutral position. The angular range of motion (ROM) of C2-C7 and adjacent-segments, and cervical lordosis were measured using the Cobb method.The radiological evidence of adjacent-level changes including new disc herniation, new osteophyte formation, new narrowing of disc space and new anterior longitudinal ligament (ALL) calcification were assessed and graded according to the Kellgren grade system. Heterotopic ossification was observed and graded following the McAfee grade system. The incidence of complications was also recorded.Section 2:Comparison of clinical outcomes, radiological findings, and complications between the hybrid surgery and anterior cervical decompression and fusion for multi-level cDDDCollecting the data of 15 patients underwent multi-level ACDF or ACCF or ACHDF(Fusion surgery, FS) at the same period in the hospital database. As mentioned in the section 1, review the clinical and radiological outcomes, perioperative parameters, as well as complications. Then making a comparison between the hybrid surgery group and fusion group statistically.Section 3:A systematic review of biomechanical and clinical evidence of hybrid surgery for multi-level cDDDPerforming a literature search to identify all available published articles from January 1960 to February 2014 by searching electronic databases, including Pubmed, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Database of Systematic Reviews. The unpublished trials were also searched for using clinical trials repositories, including the National Institute of Health, the National Research Register and Current Controlled Trials. The reference lists of the included studies were reviewed for further studies that met the eligibility criteria.The search firstly used Mesh terms, including "arthro-plasty", "arthrodesis" and "cervical vertebrae", and then a secondary free search was performed using multiple key-words, comprising "cervical disc", "cervical spine", "hybrid", "arthroplasty", "prosthesis", "replacement", "arthrodesis", "fusion", "cage" and "plate", to ensure inclusion all possible studies. The search was conducted by two dependent reviewers, with the limitation of English language. The abstract of any study potentially relevant to the topic was reviewed. The full texts were obtained if inadequate information was acquired from the abstracts. Disagreements were resolved by discussion, and a third reviewer was consulted for the final decision when necessary. For the included studies, two reviewers carefully read the full text of each study and independently extracted data. All extracted information was imported into a standardized spreadsheet. Disagreements between reviewers were resolved by discussion. A third reviewer was consulted if necessary. Information extracted included year of publi-cation, country, study type, population demographics, trial duration, indications/contraindications, selection criteria of ACDF or CDR in HS, surgical information, perioperative outcomes, biomechanical and functional outcomes, and complications. A meta-analysis and comparison were conducted if two or more included studies involved clinical and statistical homogeneous results. When not possible, due to small amount of studies or heterogeneity, a qualitative descrip-tive analysis was performed.Statistical AnalysisAll the measurements were performed 3 times independently and the mean values were used for statistical analysis. A Pearson’s x2 test or Fisher’s exact test was applied for qualitative data. A Wilcoxon test was used to assess changes between postoperative and preoperative parameters. Statistical comparisons betweengroups were performed usingMann-Whitney test. All the statistical tests were completed by the Statistical Package for Social Sciences software for Windows (Ver.19.0; SPSS Inc, Chicago, IL) and the difference was considered to be statistically significant at p<0.05.ResultsSection 1:Evaluaton of the clinical efficacy of hybrid surgery for multi-level cDDD1 Demographic summaryOf the 13 patients, the male to female ratio was 8:5. The average age (mean SD range) was 50.6±8.1 (34-69) years old. Involved levels included C3-C6 and C4-C7. The ratio was 9:4. The preoperative symptoms were radiculopathy, myelopathy and combination of radiculopathy and myelopathy. The ratio was 7:5:1.2 Perioperative parametersThe average operation time (mean SD), blood loss and postoperative drainage volume were 153.1 ±37.5min,168.5 ±25. lml,98.5 ± 24.4ml. Meanwhile, the hospital stay (Mean SD days) was 10.3±1.8 and the duration of follow-up (Mean SD months) was 33.7 ±8.1.3 Clinical outcomes evaluationNDI scores (Total:50; Mean SD) for the HC group were 32.7 ± 6.3, preoperatively; 18.7 ± 5.3,3 months postoperatively; 15.9 ± 4.1,6 months postoperatively; 14.2 ±3.7,12 months postoperatively; 12.7 ±3.5,24 months postoperatively. Compared to preoperative status, hybrid surgery showed significant recovery of NDI scores at each follow-up time postoperatively (P<0.01). JOA scores (Total:17; Mean SD) were 8.5 ± 2.1 preoperatively; 13.6 ± 2.4,3 month postoperatively; 13.5 ±2.1,6 months postoperatively; 14.1 ±2.6,12 months postoperatively; 14.5 ± 1.9,24 months postoperatively. Hybrid surgery showed significant improvements of JOA scores at each follow-up time postoperatively (P<0.05). JOA recovery were excellent in 4 (4/13) patients, good in 5 (5/13), fair in 3(3/13), and poor in 1(1/13). The neurological recovery rates (Mean SD%) at 24 months follow-up were 71.56%± 15.78%. VAS neck scores (Total:10; Mean SD) were 6.8 ±1.5, preoperatively; 4.6 ±1.7,3 month postoperatively; 3.9 ±1.6,6 months postoperatively; 2.9 ±1.7,12 months postoperatively; 2.4 ±1.5,2 years postoperatively. Significant improvements of VAS scores were found at each follow-up time postoperatively (P<0.05). VAS limb scores (Total:10; Mean SD) were 5.4 ±2.2, preoperatively; 4.2 ±1.5,3 month postoperatively; 2.1 ±1.3,6 months postoperatively; 1.7 ±0.9,12 months postoperatively; 1.2 ±0.8,2 years postoperatively. Significant improvements of VAS scores were found at each follow-up time postoperatively (P<0.05). General clinical outcomes according to Odom criteria were excellent in 3(3/13) patients, good in 9(9/13), fair in 1(1/13), and poor in 0(0/13). The rate for excellent and good was as high as 92.31%.4 Radiographic evaluationC2-C7 ROM (Mean SD, °) was 48.3±11.5 preoperatively and 37.2±9.3 at 24 months follow-up. Paired t test showed statistical difference (P<0.001). The mean ROM of superior adjacent segment (Mean SD, °) was 13.8±5.2 preoperatively and 18.1±4.5 at 24 months follow-up. Paired t test showed statistical difference (P<0.001). Hybrid surgery also showed a hyper-mobility at 24 months after surgery. (Post-op vs Pre-op:15.1±3.6 vs 11.5±4.5, P<0.001).Cervical lordosis was measured using the Cobb method. The C2-C7 Cobb angles (Mean SD, °) were 15.7±5.4 postoperatively and 10.5±6.7 preoperatively. Hybrid surgery showed significant lordosis recovery compared to the preoperative status (P<0.001). The ROM of cADR level (Mean SD, °) was 12.2 ±1.4 at 24 month postoperatively, which was similar to preoperative status.(12.2±1.4 vs 12.7±3.8, p=0.115)5 Adjacent segment degeneration and heterotopic ossificationAt adjacent levels, new osteophyte formations were found 2 after surgery, which graded as Kellgren â… and â…¡. Other degenerative changes like new narrowing of the disc space and new anterior longitudinal ligament calcification were not observed. Heterotopic ossification was found 1 graded as McAfee I.6 ComplicationsOne patient with dysphagia and one with hoarseness were found postoperatively, but were recovered at 6 week and 3 week postoperatively, respectively.l patient with cerebral fluid leakage were diagnosed. No infection, C5 plasy, hematoma developed. All the complications were cured by symptomatic treatment and did not need a further surgical intervention.Section 2:Comparison of clinical outcomes, radiological findings, and complications between the hybrid surgery and anterior cervical decompression and fusion for multi-level cDDD 1 Demographic summaryThe male to female ratio was 8:5 in HS(Hybrid Surgery) and 10:5 in FS (Fusion Surgery). The average age (mean SD range) was 50.6±8.1 (34-69) years old in the HS group and 52.3±7.6 (35-71) years old in the FS. Involved levels included C3-C6 and C4-C7. The ratio was 9:4 in the HS,9:6 in the FS group. The preoperative symptoms were radiculopathy, myelopathy and combination of radiculopathy and myelopathy. The ratio was 7:5:1 in HS group,9:4:2 in the FS group. There were no statistical significant differences between the 2 groups. (P>0.05)2 Perioperative parametersThe average operation time (mean SD), blood loss and postoperative drainage volume were 153.1±37.5min,168.5±25.lml,98.5±24.4ml in the HS group and 139.3±31.7min,178.7 ± 22.9ml,107.3±19.8ml in the FS group, respectively. There were no significant differences between the 2 groups (P>0.05). Meanwhile, the hospital stay (10.3±1.8 vs 10.7±2.1 d, P=0.606) and the duration of follow-up (33.7±8.1 vs 35.3±9.4 m, P=0.474) was comparable between the 2 groups.3 Clinical outcomes evaluationThe NDI scores (Total:50; Mean SD) for the HS group were 32.7±6.3, preoperatively; 18.7±5.3,3 months postoperatively; 15.9±4.1,6 months postoperatively; 14.2±3.7,12 months postoperatively; 12.7±3.5,24 months postoperatively. For the FS group, the corresponding NDI scores (Mean SD) were 33.9±6.1,22.1±6.5,18.4±3.5,17.5±3.9, and 15.9±3.7, respectively. Compared to preoperative status, all the 2 groups showed significant recovery of NDI scores at each follow-up time postoperatively (P<0.01), but no significant differences existed between the 2 groups at 3 and 6 months postoperatively (P>0.05). At 12 and 24 months after surgery, the HS group showed significantly better recovery of NDI scores than that of FS group (P<0.05). The JOA scores (Total:17; Mean SD) for the HS group were 8.5±2.1 preoperatively; 13.6±2.4,3 month postoperatively; 13.5± 2.1,6 months postoperatively; 14.1±2.6,12 months postoperatively; 14.5±1.9,24 months postoperatively. For the FS group, the corresponding JOA scores (Mean SD) were 8.7±1.9,12.4±2.1,12.2±2.3,13.3±2.0, and 13.5±1.1, respectively. All the 2 groups showed significant improvements of JOA scores at each follow-up time postoperatively (P<0.05), but no significant differences existed between the 2 groups at 6 and 12 months postoperatively (P>0.05). At 3 and 24 months postoperatively, the HS group showed better JOA scores than that of FS group (P<0.05). JOA Recovery Rate The JOA recovery were excellent in 4 (4/13, HS),1(1/15, ACHDF) patients, good in 5 (5/13, HS),4(4/15, FS), fair in 3(3/13, HS),9(9/15, FS), and poor in 1(1/13, HS),1 (1/15, FS), respectively. The neurological recovery rates (Mean SD%) at 24 months follow-up were 57.8±23.6 in the HS group and 38.2±18.3 in the FS group. Mann-Whitney test showed significant differences between the 2 groups for JOA recovery rate (P<0.046). Neck VAS scores (Total:10; Mean SD) for the HS group were 6.8±1.5, preoperatively; 4.6±1.7,3 month postoperatively; 3.9 ±1.6,6 months postoperatively; 2.9±1.7,12 months postoperatively; 2.4±1.5,2 years postoperatively. For the FS group, the corresponding VAS scores (Mean SD) were 6.4±1.4,5.7±1.5,4.8±1.7,4.1±1.9, and 3.7±1.6, respectively. All the 2 groups showed significant improvement of VAS scores at each follow-up time postoperatively (P<0.05), but no significant difference between the 2 groups at 3,6 and 12 months postoperatively (P>0.05). The HS group showed significantly VAS scores improvement than that of FS group at 24 months postoperatively (P<0.041). Limbs VAS scores were comparable between the 2 groups (p>0.05). General clinical outcomes according to Odom criteria were excellent in 3(3/13, HS),3(3/15, FS) patients, good in 9(9/13, HS),8(8/15, FS), fair in 1(1/13, HS),3(3/15, FS), and poor in 0(0/13, HS),1(1/15, FS), respectively. The HS group showed slightly better outcome compared with that of the FS group according to Odom Criteria, but not significantly (P=0.333).4 Radiographic evaluationBoth HS and FS group exhibited decreased ROM when compared to preoperative level (p=0.001). However, HS group showed lesscompromised ROM compared withthat of FS group (p=0.034). Significant increased ROM was found at superior and inferior adjacent-segment in both groups compared to preoperative values. However, the compensatory ROM was less in HS group (p<0.05). Cervical lordosis Reconstruction of cervical sagittal alignment was achieved both in 2 groups. The C2-C7 Cobb angles (Mean SD, °) were 15.7±5.4 postoperatively and 10.5±6.7 preoperatively in the HS group. For the FS group, the corresponding Cobb angles were 16.1±5.9 and 3.9±12.5. Both the 2 groups showed significant lordosis recovery compared to the preoperative status (P<0.001). But no statistical difference was found between the 2 groups (p=0.945).5 Adjacent segment degeneration and heterotopic ossificationAt adjacent levels, new osteophyte formations were found 2 in HS, which graded as Kellgren â… and â…¡. For FS group, Kellgren I was found 4 and Kellgren â…¡ was found 1.Other degenerative changes like new narrowing of the disc space and new anterior longitudinal ligament calcification were not observed. Heterotopic ossification was found 1 graded as McAfee I in HS group. For FS group 5 was found graded McAfee I. There were no statistical difference between 2 groups (p>0.05).6 ComplicationsOne patient with dysphagia and one with hoarseness were found in each group but no C5 palsy occurred. In the FS group,1 patient with cerebral fluid leakage and 1 with epidural hematoma were diagnosed. No infection developed in both groups. One case with subsidence of titanium mesh was found in the FS group. No other complications such as lossening of the plate and screw, dislodgment of the titanium mesh and cage, breakage of the prostheses were observed among the 2 groups. All the complications were cured by symptomatic treatment and did not need a further surgical intervention. There was no significant difference between the 2 groups (P=1.000).Section 3:A systematic review of biomechanical and clinical evidence of hybrid surgery for multi-level cDDD.1 Literature searchA total of 15 studies met our inclusion criteria, including 8 biomechanical studies [23-30] and 7 clinical studies. In the biomechanical studies, there were six cadaveric studies, one finite element analysis (FEA) and one combined study of cadaver and FEA. In the clinical studies, one RCT, three comparative studies and three non-comparative studies were identified.2 Biomechanical studiesThe ROM was decreased by 18.9% after HS while decreased by 39.7% after FS. The location of the arthroplasty, whether above or below the arthrodesis, did not significantly affect the motion response of the arthroplasty in the 2-level hybrid constructs. However, the study for 3-level hybrid constructs showed that the location and number of arthroplasty would affect the buckling. Arthroplasty at the caudal-most level resulted in significantly greater buckling than arthroplasty at cranial-most or middle level, and buckling was least for single-level arthroplasty while greatest for 3-level arthro-plasty. There remains controversy in terms of the ROM at adjacent levels. Generally, the increased ROM of inferior segment was more than that of superior segment The increase of IDP at superior adjacent level for HS was lower than that for 2-level fusion. The spine with a hybrid construct required significantly less exten-sion moment than the spine with a 2-level fusion to reach the same extension end point.3 Clinical studiesIn total, seven clinical studies with 217 patients (139 male and 78 female) were included in this review. These studies were from America, China, Italy, Korea, and Singapore. The mean age of included patients ranged from 45.7 to 55.3 years. The duration of follow-up was from 8 to 84 months. A total of 171 patients received HS, including 125 two-level,44 three-level and 2 four- level surgery. The artificial discs including ProDisc-C, Bryan, Prestige ST, Mobi-C and Prestige LP were used to perform CDR of HS, while cage with or without plate and Zero-P were for ACDF of HS. Among the included studies, there was only one RCT and six non-RCTs including three comparative studies and three non-comparative studies. For the RCT, randomization was conducted using the odd or even hospital number. It was denoted as high risk of selection bias, including random sequence generation and allocation concealment. The non-RCTs also had a high risk of bias resulting from study design limitations. The perioperative parameters such as operation time and blood loss were evaluated and the outcomes were compareable for HS and FS. All the studies reported the good results both in HS and FS postoperatively, however, one study revealed that NDI scores at 12 month and 24 month and VAS scores at 1 month and 12 month of HS postoperatively were better than that of the FS.4 Radiological outcomesThe ROM of the cervical spine was reported in five studies and shown significantly limited after surgery and then gradually recovered. However, significantly rapid recovery of ROM was shown in HS group compared to FS in the other studies.The adjacent level ROM was less comprised in HS than that of FS.5 ComplicationsAll include clinical studies evaluated the complications of HS. Among them, two studies reported no complication found in HS group. In all, there are 15 reported complications in HS group, including 8 dysphasias,5 heterotopic ossifications,1 vocal cord paralysis and 1 residual limb symptoms.Conclusion1 Hybrid surgery is a safe and effective procedure for multi-level cDDD with good clinical result. Based on the thorough decompression, the disc height and cervical lordosis were restored, and the motion of operative level was mantained. Hybrid surgery may provide an alternative for multi-level cDDD.2 Compared with the FS, HS shows equivalent results regrading operation time, blood loss, postoperative drainage and hopital stay. Besides, HS showed superiority to FS in terms of equivalent or superior early clinical outcomes, less compromised C2-C7 ROM, and less impact at adjacent-levels. However, further large, randomized controlled trials are desired to draw a firm conclusion.3 This systematic review provides an overview of the current knowledge on HS for multilevel cervical DDD. HS may be a safe and efficacious of HS to benefit certain patients with multilevel cervical DDD. However, there is insufficient evidence to draw a firm conclusion due to only low to very low quality evidence. As a new combination procedure, appropriate attention must be given to strict surgical indications, proper patient selection, improved surgical technique and associated complications. In this way, HS could have potential beneficial effects in select group of patients with cervical DDD. We believe that this systematic review will help spine surgeons to understand biomechanical and clinical characteristics of HS. However, further prospective, randomized controlled studies are needed to reach a more reliable conclusion... |
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