Comparative Analysis of Flexible Stabilization Devices Based on Polymeric and Composite Materials for Degenerative Disorders: Finite Element Analysis

Abstract

The radiographic apparent assumed that the asymptomatic adjacent segment disease ASD is common after lumbar fusion, but this does not correlate with the functional outcomes while compensatory increased motion and stresses at the adjacent level of fusion is well-known to be associated to ASD [4,5,8]. Newly developed, hybrid and flexible stabilizations are allocated to substitute for mostly the superior level of the fusion in an attempt to reduce the number of fusion levels and likelihood of degeneration process at the adjacent levels during the fusion with pedicle screws. Nevertheless, its biomechanical efficiencies still remain unknown and the complications associated with failure of constructs such screw loosening and toggling should be elucidated [4]. In the current study, a finite element (FE) study was performed using a validated L2/S1 model subjected to a moment of 10 Nm and follower load of 100 N to assess the biomedical behavior of hybrid constructs based on dynamic topping off, semi-rigid fusion using polymeric and composite materials.

Biomechanical investigation of the effect of pedicle-based hybrid stabilization constructs: A finite element study

“…The degenerated NP was defined as a compressible fluid with a hydrostatic pressure of 0.1 MPa relative to surrounding atmospheric pressure. 19,43,44 The annulus fibrosus (AF) ground substance was modeled using isotropic elastic material, represented by seven concentric layers with embedded nonlinear fibers using rebar elements. 45 The seven major ligaments such as posterior longitudinal ligament (PLL), anterior longitudinal ligament (ALL), interspinous ligament (ISL), ligamentum flavum (LF), supraspinous ligament (SSL), capsular ligament (CL), and intertransverse ligament (ITL) were represented by unidirectional nonlinear hypoelastic truss elements T3D2 (Figure 1).…”

“…15–17 In general, rigid fusion is still considered the gold standard treatment of low back pain and instability. 18–20 A fusion system bond multiple vertebrae to function as a single unit that does not allow the movement at the operated level. 21,18,22 However, loss of mobility and flexibility at the operated level often lead to a hypermotion in the adjacent levels.…”

“…23–25 The posterior dynamic stabilization (PDS) aims to reduce the loss of motion associated with the rigid fusion. 19,23,26–29 Few studies reported satisfactory stability after PDS surgery. 30–33 Recently, different kinds of hybrid pedicle systems have been developed to maintain normal segmental kinematics by creating a smoother region from the instrumented to the adjacent untreated levels.…”