Abstract
BackgroundBiomechanical characteristics of noncontinuous ACDF and noncontinuous CDA in the treatment of noncontinuous cervical degenerative disc disease were still unclear. The aim of this research is to compare the differences between these two kinds of treatment methods and to verify the effectiveness of Prodisc-C in noncontinuous CDA.MethodsEight FEMs of the cervical spine (C2–C7) were built based on CT images of 8 mild CDDD volunteers. In the arthroplasty group, we inserted Prodisc-C at C3/4 and C5/6. In the fusion group, CoRoent® Contour and NuVasive® Helix ACP were implanted at C3/4 and C5/6. Initial loads of 75 N were used to simulate the head weight and muscle forces. The application of 1.0 N m moment on the top on the C2 vertebra was used to create motion in all directions. Statistical analyses were performed using STATA version 14.0 (Stata Corp LP, College Station, Texas, USA). Statistical significance was set at P < 0.05.ResultsThe IDPs in C2/3 (P < 0.001, P = 0.005, P < 0.001, P < 0.001), C4/5 (P < 0.001), and C6/7 (P < 0.001) of the intact group were significantly less than that in the fusion group in flexion, extension, lateral bending, and axial rotation, respectively. In addition, the IDPs in C2/3 (P < 0.001, P = 0.001, P < 0.001, P < 0.001), C4/5 (P < 0.001), and C6/7 (P < 0.001) of the arthroplasty group were significantly less than that in the fusion group in flexion, extension, lateral bending, and axial rotation, respectively. Contact forces of facet joints in C2/3 (P = 0.010) in the arthroplasty group was significantly less than that in the intact group. Contact forces of facet joints in C2/3 (P < 0.001), C4/5 (P < 0.001), and C6/7 (P < 0.001) in the arthroplasty group was significantly less than that in the fusion group. Contact forces of facet joints in C2/3 (P < 0.001), C4/5 (P < 0.001), and C6/7 (P < 0.001) in the intact group were significantly less than that in the fusion group.ConclusionsNoncontinuous CDA could preserve IDP and facet joint forces at the adjacent and intermediate levels to maintain the kinematics of cervical spine near preoperative values. However, noncontinuous ACDF would increase degenerative risks at adjacent and intermediate levels. In addition, the application of Prodisc-C in noncontinuous CAD may have more advantages than that of Prestige LP.
Highlights
Noncontiguous cervical degenerative disc disease (CDDD) is defined as cervical myelopathy or radiculopathy caused by two noncontiguous degenerative intervertebral discs with one normal intermediate segment (IS) [1]
Noncontinuous cervical disc arthroplasty (CDA) could preserve Intervertebral disc pressure (IDP) and facet joint forces at the adjacent and intermediate levels to maintain the kinematics of cervical spine near preoperative values
Validation of the intact finite element models (FEMs) range of motion (ROM) of our FEMs in flexion-extension, lateral bending, and axial rotation were compared with the data from
Summary
Noncontiguous cervical degenerative disc disease (CDDD) is defined as cervical myelopathy or radiculopathy caused by two noncontiguous degenerative intervertebral discs with one normal intermediate segment (IS) [1]. Anterior cervical discectomy and fusion (ACDF) has been an accepted treatment method for degenerative cervical disc disease to alleviate cervical myelopathy or radiculopathy [2]. Long segmental anterior fusion, which included the normal intermediate segments (IS), was always used to treat noncontiguous CDDD in order to decrease the stress from fusion structures on IS and avoid the adjacent segment degeneration (ASD) in IS [4,5,6]. Most of the studies preserved the IS with noncontinuous ACDF, which would bring more additive stress from the fused levels and cause hypermobility on IS; all of these would cause the acceleration of ASD [8].
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