Biomechanical evaluation of adjacent segment degeneration after one- or two-level anterior cervical discectomy and fusion versus cervical disc arthroplasty: A finite element analysis
Introduction
Anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA) are common surgical treatments for patients with cervical myelopathy, radiculopathy, or myeloradiculopathy [1], [2], [3], [4]. Despite ACDF was considered as the “gold standard”, symptomatic adjacent segment degeneration (ASD) may develop after fusion surgery [1], [2], [3], [4]. Compared with the standard ACDF, the primary goal of CDA is to preserve the range of motion (ROM) at the surgery segment, avoiding or mitigating ASD [1], [2], [3], [5]. Many previous studies have shown that ASD is more likely to occur after cervical fusion compared with CDA during long-term follow-up [1], [2], [3]. Abnormal segmental ROM and intradiscal pressure may be the main causes of ASD [2], [3], [6], [7]. Different internal fixation devices were of different biomechanical design and kinematic properties [8], [9], [10], [11]. Even though the incidence rate of ASD has been investigated and compared in many clinical studies and biomechanical studies, the biomechanics changes of adjacent segments after one- and two-level standard ACDF and CDA were still uncertain [3], [4], [12], [13].
The finite element (FE) analysis has been widely used to investigate the spinal biomechanics, and to predict the biomechanical response after different spine surgeries [8], [9], [10], [11]. In the present study, a FE model consisting of C2-C7 vertebrae was developed. We aimed to compare the segmental ROM and intradiscal pressure after one- or two-level ACDF and CDA using FE analysis.
Section snippets
Development of intact cervical model
The three-dimensional FE model of C2-C7 vertebrae was developed according to the computed tomography (CT) images of a healthy volunteer (male, 22 years old, 175 cm, 65 kg) without history of cervical disc disease. Written informed consent was obtained from the volunteer. The CT images of the subject were obtained with an interval of 0.625 mm (Dual Source CT; Siemens, Munich, Germany). The intact model consists of six vertebrae (C2-C7), five intervertebral discs and associated ligaments. The
Validation of the intact cervical model
The present intact cervical model of C2-C7 vertebrae was compared with previous biomechanical models to assess the validity. The predicted segmental ROM of the flexion-extension, lateral bending, and axial rotation of the intact cervical model were well in agreement with previous experiments studies (Table 3, Fig. 4) [10], [15].
One-level ACDF and CDA
The segmental ROM of one-level ACDF and CDA models were listed in Table 4. The ROM at C5-C6 of the one-level ACDF model was significantly decreased, while the ROM at
Discussion
Whether ASD is caused by natural degeneration or aggravated by cervical surgery is still unknown [3], [6], [17], [18]. ASD was statistically less frequent after CDA than ACDF in most of the clinical trials [18]. The C5-C6 segment behaves as the most flexible segment [19], [20]. As a result, one-level surgery models were constructed at C5-C6, and two-level surgery models were constructed at both C4-C5 and C5-C6. Most FE studies based on one- or two-level cervical surgery have explored the
Conclusions
According the FE analysis, abnormal ROM and intradiscal pressure at the adjacent segments may contribute to the higher risk of ASD after one- or two-level ACDF. However, no significant difference of the ROM and intradiscal pressure can be observed at the adjacent segments after one- or two-level CDA.
Declaration of Competing Interest
The authors declare that they have no conflict of interest.
Acknowledgements
This work was supported by the National Key Research and Development Program of China (2018YFB1105700), the National Natural Science Foundation of China (Grant nos. 81904020 and 81772401), the Natural Science Foundation of Hubei Province (2019CFB305), and the Fundamental Research Funds for the Central Universities (2019kfyXMBZ063).
References (32)
- et al.
The 5-year cost-effectiveness of two-level anterior cervical discectomy and fusion or cervical disc replacement: a markov analysis
Spine J.
(2018) - et al.
Reduction in segmental flexibility because of disc degeneration is accompanied by higher changes in facet loads than changes in disc pressure: a poroelastic c5-c6 finite element investigation
Spine J.
(2010) - et al.
A new cervical artificial disc prosthesis based on physiological curvature of end plate: a finite element analysis
Spine J.
(2016) - et al.
Finite element analysis of influence of axial position of center of rotation of a cervical total disc replacement on biomechanical parameters: simulated 2-level replacement based on a validated model
World Neurosurg.
(2017) - et al.
Maintaining range of motion after cervical discectomy does not prevent adjacent segment degeneration
Spine J.
(2019) - et al.
Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion?
Spine J.
(2004) - et al.
Artificial disc versus fusion: a prospective, randomized study with 2-year follow-up on 99 patients
Spine (Phila Pa 1976)
(2007) - et al.
Comparison of radiographic changes after acdf versus bryan disc arthroplasty in single and bi-level cases
Eur. Spine J.
(2009) - et al.
The seven-year cost-effectiveness of anterior cervical discectomy and fusion versus cervical disc arthroplasty: a markov analysis
Spine (Phila Pa 1976)
(2018) - et al.
Randomized, controlled, multicenter, clinical trial comparing bryan cervical disc arthroplasty with anterior cervical decompression and fusion in china
Spine
(2012)
Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion
Spine (Phila Pa 1976)
Changes in adjacent-level disc pressure and facet joint force after cervical arthroplasty compared with cervical discectomy and fusion
J. Neurosurg. Spine
Finite element analysis of cervical arthroplasty combined with fusion against 2-level fusion
J. Spinal Disord. Tech.
Analysis of load sharing on uncovertebral and facet joints at the c5-6 level with implantation of the bryan, prestige lp, or prodisc-c cervical disc prosthesis: an in vivo image-based finite element study
Neurosurg. Focus
Comparison of cervical spine biomechanics after fixed- and mobile-core artificial disc replacement: a finite element analysis
Spine (Phila Pa 1976)
A biomechanical analysis of an artificial disc with a shock-absorbing core property by using whole-cervical spine finite element analysis
Spine (Phila Pa 1976)
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These authors contributed equally to this work.