Introduction
Methods
Data searches and study selection
Category | Search string |
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Discectomy (1) | “ACDF”[tiab] OR “discectomy”[tiab] OR “diskectomy”[tiab] OR “Diskectomy”[Mesh] OR diskectom*[tiab] OR discectom*[tiab] OR “Anterior Cervical Discectomy and Fusion”[all fields] OR “Anterior Cervical Diskectomy and Fusion”[all fields] |
Cervical spine (2) | “Cervical Vertebrae”[Mesh] OR “cervical vertebrae”[all fields] OR “cervical vertebra”[all fields] OR “cervical spine”[all fields] OR “cervical”[tiab] |
Fusion (3) | “Spinal Fusion”[mesh] OR “spinal fusion”[all fields] OR “fusion”[tiab] OR “spondylodesis”[all fields] OR “non-union”[all fields] |
Intervertebral device (4) | “Prostheses and Implants”[mesh] OR “implant”[all fields] OR “implants”[all fields] OR “total disc replacement”[mesh] OR “total disc replacement”[all fields] OR “total disk replacement”[all fields] OR “cage”[all fields] OR “cages”[all fields] OR “spacer”[all fields] OR “implantation”[all fields] OR “intervertebral device”[all fields] OR “bone transplantation”[mesh] OR “bone graft”[all fields] |
Combined search string | (1) AND (2) AND (3) AND (4) |
Results | 14/01/2016 |
PubMed | 1018 results |
Embase (search string adjusted accordingly) | 1099 results, 403 unique |
Total | 1421 unique results |
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The article was published in English or Dutch;
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The article was an original report presenting primary data;
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The article was published on or after 1 January 2000;
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The study had a minimum of 10 patients;
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The study focused on the cervical spine (C2-Th1);
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The study presented patients undergoing a 1- or 2-level anterior cervical discectomy and fusion with an intervertebral device (exempting prostheses) or a bone graft;
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The included patients did not undergo revision surgery or surgery as treatment for trauma;
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The method of assessing fusion was described;
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The study assessed fusion with CT scan or X-ray;
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The article was published in a peer-reviewed journal.
Quality assessment
Award 1 point if | |
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Selection bias (3 pts.)
| |
Goal and inclusion | Goal of the study is stated and study explicitly states the inclusion criteria |
Selection of patients | Selective recruitment of patients can be ruled out |
Patient characteristics | Study reports the age range and mean age and states the distribution of gender |
Outcome bias (3 pts.)
| |
Definition of fusion | Definition classification and radiological tools to measure fusion were stated |
Clinical outcome | Clinical outcome was systematically evaluated in correlation with fusion |
Radiographic method | Fusion was measured through CT scan |
Follow-up bias (3 pts.)
| |
Follow-up time frame | Follow-up range, period and mean were given and loss to follow-up < 20% |
Prospective study | Data in the study were collected prospectively |
Multiple moments | Follow-up was divided into multiple moments in time |
Total (9 pts.) |
Data extraction
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Number of participating patients;
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Mean time and range of follow-up;
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Percentage of fusion at 3, 6, 12 and 24 months and at final follow-up;
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Method of measuring bony fusion;
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Use of bone growth stimulation;
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Distribution of patients over different implant types;
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Use of plate and/or screws;
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Clinical outcome and correlation to bony fusion;
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Contact area and height of the implant.
Statistical analysis
Results
Characteristics of included studies
Risk of bias
Bony fusion
Time point (months) | Studies (n) | Mean risk of bias score | Patients (n) | Fusion (%) |
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3 | 18 | 6.4 | 1420 | 51.1 |
6 | 44 | 6.1 | 3129 | 78.3 |
12 | 53 | 5.9 | 4202 | 87.6 |
24 | 29 | 6.1 | 2174 | 92.6 |
Methods of measuring bony fusion
Method | Mean risk of bias score | Patients (n) | Median time to final FU (months) | Fusion (%) |
---|---|---|---|---|
CT | 6.5 | 1528 | 15.3 | 90.1 |
X-plain | 5.4 | 3963 | 23.2 | 88.3 |
X-flex/ex | 5.3 | 4571 | 15.9 | 91.7 |
Cut-off levels | Studies (n) | Mean risk of bias score | Patients (n) | Median time to final follow-up (months) | Fusion (%) |
---|---|---|---|---|---|
0 mm | 1 | 3.0 | 21 | 12.0 | 91.3 |
≤ 2 mm | 9 | 5.7 | 790 | 18.0 | 80.0 |
≤ 3 mm | 1 | 7 | 66 | 16.0 | 85.0 |
≤ 2° | 15 | 5.2 | 1149 | 23.7 | 93.9 |
≤ 4° | 2 | 6.5 | 248 | 24.0 | 94.9 |
Unspecified | 27 | 5.1 | 2297 | 14.0 | 94.4 |
Correlation fusion and type of implant
Material | Mean risk of bias score | Patients (n) | Median time to final FU (months) | Fusion (%) |
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Bone graft | 5.5 | 3200 | 22.0 | 91.4 |
PEEK | 5.5 | 4671 | 15.5 | 89.1 |
PMMA | 5.4 | 348 | 12.0 | 83.4 |
Carbon fibre | 6.0 | 239 | 13.0 | 92.9 |
Titanium | 5.6 | 1750 | 24.0 | 91.3 |
Correlation bony fusion and use of plates and/or screws
Method | Mean risk of bias score | Patients (n) | Median time final follow-up (months) | Fusion (%) |
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Plate/screws | 5.4 | 3971 | 21.0 | 91.4 |
Screws | 5.6 | 499 | 15.3 | 96.6 |
Stand-alone | 5.6 | 5738 | 20.7 | 88.6 |
Using bone growth stimulation
Type | Mean risk of bias score | Patients (n) | Median time to final FU (months) | Fusion (%) |
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Autologous | 5.5 | 3985 | 23.2 | 90.3 |
No filling | 5.6 | 1724 | 16 | 87.4 |
Cadaveric | 4.9 | 1188 | 23 | 91.2 |
Allogenic | 5.3 | 690 | 17.5 | 93.3 |
β-TCP | 5.5 | 474 | 12 | 96.8 |
Plasmapore | 6 | 424 | 24 | 96.1 |
HA | 5.8 | 311 | 16.1 | 74.8 |
Correlation of bony fusion and height and surface of implant
Correlation between bony fusion and clinical outcome
Reference | Bias | Patients (n) | Fusion (%) | Method of fusion measure | Outcome measure | Correlation |
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Cabraja et al. [112] | 6 | 86 | 90.7 | Flexion/extension X-ray | VAS neck + arm, NDI and Odom’s criteria | No correlation |
Choi et al. [117] | 5 | 109 | 91.6 | Flexion/extension X-ray | VAS neck + arm and Robinson’s criteria | No correlation |
Kim et al. [25] | 5 | 96 | 100 | Flexion/extension X-ray | VAS (NS) and Odom’s criteria | No correlation |
Klingler et al. [109] | 7 | 107 | 52.3 | CT: trabeculae | VAS (NS), NDI, SF-36 and PSI | In the PMMA group, fused patients showed a statistically significant better physical component summary of the SF-36 than non-fused patients (p = 0.024). There was no correlation in the other outcome measures or in the PEEK group |
Moon et al. [105] | 4 | 27 | 77.8 | Flexion/extension X-ray | VAS neck + arm and NDI | No correlation |
Nunley et al. [118] | 7 | 66 | 85.0 | Flexion/extension X-ray | VAS (NS) and NDI | No correlation |
Park et al. [119] | 8 | 31 | 90.3 | CT: trabeculae | VAS (NS), NDI and Odom’s criteria | No correlation |
Ragab et al. [37] | 6 | 35 | 97.1 | Plain X-ray: trabeculae | Not specified | No correlation |
Ramzi et al. [107] | 6 | 40 | 45.0 | Flexion/extension X-ray | VAS neck + arm | No correlation |
Samartzis et al. [40] | 5 | 69 | 95.7 | Plain X-ray: trabeculae | Odom’s criteria | No correlation |
Scholz et al. [84] | 7 | 53 | 97.0 | CT: trabeculae | VAS neck + arm and NPDI-G | No correlation |
Schroder et al. [120] | 7 | 100 | 74.0 | Plain X-ray: trabeculae | Odom’s criteria | Evidence of fusion was correlated with excellent/good results, and the absence of fusion was correlated with satisfactory/poor results (p = 0.0364) |
Shiban et al. [121] | 6 | 265 | 92.0 | Flexion/extension X-ray | VAS neck + arm and EQ-5D | No correlation |
Wang et al. [95] | 7 | 16 | 93.8 | CT: trabeculae | Odom’s criteria and JOA-score | No correlation |
Wright et al. [122] | 7 | 97 | 82.9 | Flexion/extension X-ray | VAS neck + arm | The absence of fusion was correlated with higher VAS scores for neck pain |
Yan et al. [63] | 6 | 32 | 100 | Plain X-ray: trabeculae | Odom’s criteria | No correlation |
Yoo et al. [116] | 7 | 58 | 74.1 | Flexion/extension X-ray | VAS neck + arm, Odom’s criteria and NDI | No correlation |
Zhou et al. [123] | 6 | 15 | 93.3 | CT: trabeculae | JOA-score and Odom’s criteria | No correlation |