Investigation of fusion and artificial disc replacement in the cervical spine A finite element modeling approach

Abstract

Degenerative disease progression in the adjacent segment spine after conventional newlineAnterior Cervical Discectomy and Fusion (ACDF) is a clinical complication. Cervical newlineDisc Arthroplasty (CDA) has been introduced with various types of designs to overcome newlinethe limitations of the ACDF protocol. CDA leads to changes in load path and newlinedegeneration of facets and discs in the adjacent segments. Hence there is a need to newlinestudy the effect of ACDF and the efficacy of CDAs using Range of Motion (ROM), newlineintervertebral disc pressure, and facet loads for different types of FDA-approved CDA newlinedevices in one-level, two-level, and hybrid construct under physiological loading conditions. newlineAn earlier finite element model was used in this study for further development newlineand validation of the intact cervical spine column (C2-T1). The intact model was modified newlineto represent postoperative Finite Element (FE) models simulating ACDF and CDAs newlineimplanted at the C5-C6 for one level and C5-C6-C7 for two levels and hybrid construct newlinewere made according to the standard surgical protocols with the support of clinicians. newlineThe hybrid loading protocol was used for the study, with an intact load of 2 Nm and an newlineaxial follower load of 75 N being applied at the top superior end. The endplate, inferior newlineto the T1 vertebra was constrained in all directions. Physiological loading flexion, extension, newlineand lateral bending were studied, and ROM, intervertebral disc pressure, and newlinefacet loads parameters were obtained at the index and adjacent levels. newlineIn all the load cases, ACDF demonstrated an increased intervertebral motion, along newlinewith disc pressures at the adjacent levels up to 27% while a decrease in the intervertebral newlinemotion was observed at the implanted level. In the case of CDA at the implanted newlinelevel, for one level study, all CDAs except for the Bryan disc predicted an increase in newlinemotion. The motions at the adjacent levels decreased in flexion, extension, and lateral newlinebending modes. Bryan disc reduced the intervertebral motion at the implanted level newlineunder flexion (29%),