Biomechanical Effect of C₅/C₆ Intervertebral Reconstructive Height on Adjacent Segments in Anterior Cervical Discectomy and Fusion ‐ A Finite Element Analysis

Abstract

Objective: To investigate the biomechanical effect of different intervertebral reconstructive heights on adjacent segments following C 5 /C 6 anterior cervical discectomy and fusion (ACDF) through finite element analysis.Methods: A finite element model of intact C 4 -C 7 segments was developed and validated for the present study. Five additional C 4 -C 7 postoperative models were constructed with 100%, 125%, 150%, 175%, and 200% of the benchmark height of C 5 /C 6 on the basis of the intact model. The changes in intradiscal pressure (IDP) and range of motion (ROM) of adjacent segments before and after reconstruction of C 5 /C 6 were analyzed.Results: For the upper adjacent segment (C 4 /C 5 ), the IDPs under the different loading conditions all increased after reconstruction. The maximum IDPs were 0.387, 0.489, 0.491, and 0.472 MPa under flexion, extension, axial rotation, and lateral bending, respectively, observed at the reconstructive height of 200%. The minimum IDPs were observed at 150% reconstructive height under all loading conditions except extension, and were 57, 86 and 81% of the maximum IDPs under flexion, axial rotation, and lateral bending, respectively. The minimum IDP under extension occurred when the reconstructive height is 125% of the benchmark height. For the lower adjacent segment (C 6 /C 7 ), the IDPs of postoperative models under all loading conditions also increased compared to the preoperative model. The maximum IDPs after reconstruction under flexion, extension, axial rotation, and lateral bending were 0.402, 0.411, 0.461, and 0.497 MPa, respectively, when the height of the reconstruction was 200% of the benchmark. The minimum IDPs were observed after a reconstruction at 150% of the benchmark, and were 59%, 85%, 82%, and 81% of the maximum IDPs under flexion, extension, axial rotation, and lateral bending loading conditions. Conclusions:The reconstructive height is an important factor affecting the IDP and the ROM of adjacent segments after ACDF. To delay the adjacent segment disease, an intervertebral reconstructive height of 150% is an appropriate height in C 5 /C 6 ACDF.

Biomechanical Evaluation of Intervertebral Fusion Process After Anterior Cervical Discectomy and Fusion: A Finite Element Study

“…The present segmental ROMs were within the range of the results from previous experiments studies. The maximal intradiscal pressure of adjacent levels was consistent with in vitro experiments and previous finite element results ( Welke et al, 2016 ; Zhou et al, 2021 ), and the facet contact force (FCF) of the model was also well in agreement with the literature ( Lee et al, 2011 ; Wu et al, 2019 ).…”

“… Guo et al (2021 ) found that the different plate-to-disc distance had no effect on adjacent intradiscal pressure following single-level ACDF, while it may affect the stress of bone graft and titanium plate. The intervertebral reconstructive height may also influence the intradiscal pressure of adjacent segments ( Zhou et al, 2021 ). Thus, further study is needed to analyze the biomechanical effect of interbody fusion device with different structures during fusion.…”

“…Third, the position and size of the implants are likely to have variations caused by multiple factors such as the patient’s anatomical variation, surgical carpentry, and surgeon’s preference, possibly resulting in different stress distribution and changes during healing. The present study analyzed the biomechanics of only one type of interbody fusion device while the biomechanical changes after ACDF using cage plus plate or the interbody cage with different structures after ACDF may be different ( Hua et al, 2020a ; Zhou et al, 2021 ). Besides, other cervical fusion procedures, such as anterior cervical corpectomy and fusion and the posterior cervical fusion surgery, may have similar biomechanical trends to this study and deserve further analysis.…”

“… Li et al (2021 ) investigated the effect of pre-existing degeneration of adjacent segment on its biomechanics after single-level ACDF. The influences of implant selection on the adjacent-level biomechanics after ACDF were also evaluated in several FE studies ( Li et al, 2020 ; Purushothaman et al, 2020 ; Guo et al, 2021 ; Zhou et al, 2021 ). Hua et al ( 2020a ) and Hua et al (2020b ) compared the biomechanical changes of adjacent segments after one- or two-level anterior cervical surgery with different implants.…”

Comparative biomechanical analyses of lower cervical spine post anterior fusion versus intervertebral disc arthroplasty: A geometrically patient-specific poroelastic finite element investigation

“…The evaluation of the biomechanical long-term performance of different arthroplasty devices, for example, can reveal respective variations in the ROM, intradiscal pressure (IDP) and facet joint forces (FJFs), largely informing prognosis and treatment options. On the other hand, most existing relevant FE studies in literature for the biomechanical assessment of healthy, diseased and treated cervical spines are constrained to only one standard geometry, and, therefore, the effect of anatomical parameters on biomechanical responses for different patients is typically neglected [ 19 , 22 , 23 ]. Geometrically patient-specific FE models have the capability to overcome this limitation and provide more reliable results through considering personalized anatomical features.…”