The influence of different magnitudes and methods of applying preload on fusion and disc replacement constructs in the lumbar spine: a finite element analysis.
In a finite element (FE) analysis of the lumbar spine, different preload application methods that are used in biomechanical studies may yield diverging results. To investigate how the biomechanical behaviour of a spinal implant is affected by the method of applying the preload, hybrid-controlled FE analysis was used to evaluate the biomechanical behaviour of the lumbar spine under different preload application methods. The FE models of anterior lumbar interbody fusion (ALIF) and artificial disc replacement (ADR) were tested under three different loading conditions: a 150 N pressure preload (PP) and 150 and 400 N follower loads (FLs). This study analysed the resulting range of motion (ROM), facet contact force (FCF), inlay contact pressure (ICP) and stress distribution of adjacent discs. The FE results indicated that the ROM of both surgical constructs was related to the preload application method and magnitude; differences in the ROM were within 7% for the ALIF model and 32% for the ADR model. Following the application of the FL and after increasing the FL magnitude, the FCF of the ADR model gradually increased, reaching 45% at the implanted level in torsion. The maximum ICP gradually decreased by 34.1% in torsion and 28.4% in lateral bending. This study concluded that the preload magnitude and application method affect the biomechanical behaviour of the lumbar spine. For the ADR, remarkable alteration was observed while increasing the FL magnitude, particularly in the ROM, FCF and ICP. However, for the ALIF, PP and FL methods had no remarkable alteration in terms of ROM and adjacent disc stress.
a Department of Physical Therapy and Assistive Technology , National Yang-Ming University , 155, Section 2, Li-Nung Street, Taipei , Taiwan.
Zheng-Cheng
ZC
Zhong
Chinghua
C
Hung
Hung-Ming
HM
Lin
Ying-Hui
YH
Wang
Chang-Hung
CH
Huang
Chen-Sheng
CS
Chen
D001696:Biomechanical Phenomena; D020342:Finite Element Analysis; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D019736:Prostheses and Implants; D016059:Range of Motion, Articular; D013123:Spinal Fusion; D059145:Total Disc Replacement; D016474:Weight-Bearing