Is Pedicle-Based Hybrid Stabilization (PBHS) protecting posterior lumbar fixation from adjacent-segment failure? Finite element analysis and comparison of different systems - 19/08/21

Doi : 10.1016/j.otsr.2021.103038

Moustafa Mesbah ^a, Abdelwahed Barkaoui ^b,^c,⁎
^a Laboratory of Numerical and Experimental Modeling of Mechanical Phenomena, Department of Mechanical Engineering, Université Abdelhamid-Ibn-Badis, BP 227, 27000 Mostaganem, Algeria
^b Laboratoire des énergies renouvelables et matériaux avancés, université internationale de Rabat, parc Technopolis Rabat–Shore, Rocade Rabat-Salé, 11100 Sala-El-Jadida, Morocco
^c Laboratoire de mécanique appliquée et ingénierie (LRMAI), école nationale d’ingénieurs de Tunis, université de Tunis-El-Manar, rue Béchir-Salem-Belkhiria campus universitaire, BP 37, 1002, Le Bélvédère, 1002 Tunis, Tunisia

^⁎Corresponding author.

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Abstract

Introduction

Interbody fusion is a very common surgical treatment for degenerative disc diseases. It is necessary to explain the effect of Pedicle Based Hybrid Stabilization systems (PBHS) on the lumbar spine, as there is no consensus in the literature about their performance.

Hypothesis

Topping off a fusion with a PBHS may provide some protection against adjacent segment failure.

Material and methods

The biomechanical effect PBHS on fused and adjacent to fusion levels were investigated, including range of motion, bending stiffness, Von Mises stress A 3D Finite Element model of the L2-S1 spine was used and modified to simulate pre and postoperative changes during combined loading. Five models instrumented with different systems [Titanium and PEEK fusion; Dynesys hybrid system; NFlex hybrid stabilization and PEEK topping off fusion] were compared to those of healthy model.

Results

After hybrid instrumentation, the L4–L5 level did not lose its motion completely, NFlex hybrid stabilization system maintained 82% of flexion at the adjacent to fusion level, reduced bending stiffness by 40% in axial rotation. Dynesys hybrid system represented more restricted motion than NFlex. PEEK topping off fusion system was the most rigid one among all three systems. It increased bending stiffness at the adjacent level and increased the axial motion by 25%. High risk of rod breakage was computed for PEEK topping off system as 48.8MPa in lateral bending.

Conclusion

Hybrid stabilization can delay adjacent segment failure and compensate lumbar spine mobility. However, it is clear that PBHS need to be further tested before being considered for clinical use.