Biomechanical Evaluation of Spinal Column after Percutaneous Cement Discoplasty: A Finite Element Analysis

Abstract

Objective: To compare the biomechanical properties of percutaneous cement discoplasty (PCD) in the spinal column between different implant-endplate friction.

Methods: A validated L3-Scarumfinite element (FE) model was modified for simulation. In the PCD model, the L4/5 level was modified based on model 1 (M1) and model 2 (M2). In M1, the interaction between bone cement and endplate was defined as face-to-face contact with a friction coefficient of 0.3; in M2, the contact was defined as a Tie constraint. 7.5 N m moments of four physiological motions and axial load of 15, 100 and 400 N preload were imposed at the top of L3. The range of motion (ROM) and interface stress analysis of endplates, annulus fibrosus and bone cement of the operated level were calculated for comparisons among the three models.

Results: The ROM of M1 and M2 increased when compared with the intact model during flexion (FL) (17.5% vs 10.0%), extension (EX) (8.8% vs -8.8%), left bending (LB) (19.0% vs -17.2%) and left axial rotation (LR) (34.6% vs -3.8%). The stress of annulus fibrosus in M1 and M2 decreased in FL (-48.4% vs -57.5%), EX (-25.7% vs -14.7%), LB (-47.5% vs -52.4%), LR (-61.4% vs -68.7%) and axis loading of 100 N (-41.5% vs -15.3%), and 400 N (-27.9% vs -27.3%). The stress of upper endplate of M1 and M2 increased in FL (24.6% vs 24.7%), LB (82.2% vs 89.5%), LR (119% vs 62.4%) and axis loading of 100 N (64.6% vs 45.5%), and 400 N (58.2% vs 24.3%), but was similar in EX (2.9% vs 0.3%). The stress of lower endplate of M1 and M2 increased in FL (170.9% vs 175.0%), EX (180.8% vs 207.7%), LB (302.6% vs 274.7%), LR (332.4% vs 132.8%) and axis loading of 100 N (350.7% vs 168.6%), and 400 N (165.2% vs 106.7%).

Conclusion: Percutaneous cement discoplasty procedure could make effect on the mobility or stiffness. The fusion of bone cement and endplate might have more biomechanical advantages, including of the decreasing rate of implant subsidence and dislocation, and the increase spine stability.

Keywords: Biomechanical; Bone cement; Finite element analysis; Lumbar spinal stenosis; PMMA; Percutaneous cement discoplasty.

Fig. 1

FE models of L3‐S used in this article: (A, B) intact model, (C) model 1, the interaction between bone cement and endplate was defined as face‐to‐face contact; (D) model 2, the interaction was defined as a Tie constraint

Fig. 2

MTS Bionix® Servohydraulic Test Systems and the cadaveric vertebral column specimens of L4/5

Fig. 3

L4/5 level range of motion in flexion (A), extension (B), left bending (C) and left rotation (D) motions between FE model and the experimental data. The trend line shows a similar growth trend between the two groups of data

Fig. 4

The range of motion (A) and the change of ROM comparing with the intact model (B) on L4/5 level in the motion models of flexion, extension, left bending and left axial rotation

Fig. 5

Maximum stress (A) and changes of maximum stress comparing with the intact model (B) on annulus fibrosus in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N

Fig. 6

Cloud map of intradiscal pressure at annulus fibrosus in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N

Fig. 7

Maximum stress on bone cement in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N

Fig. 8

Cloud map of stress in the superior bone cement‐endplate interface for in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N

Fig. 9

Maximum stress (A) and changes of maximum stress comparing with the intact model (B) on superior and inferior endplate in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N

Fig. 10

Cloud map of stress in the superior and inferior endplate in the motion models of flexion, extension, left bending, left axial rotation and axial load of 100 and 400 N