Biomechanical Evaluation of Rigid Interspinous Process Fixation Combined With Lumbar Interbody Fusion Using Hybrid Testing Protocol

Abstract

Rigid interspinous process fixation (RIPF) has been recently discussed as an alternative to pedicle screw fixation (PSF) for reducing trauma in lumbar interbody fusion (LIF) surgery. This study aimed to investigate biomechanics of the lumbar spine with RIPF, and also to compare biomechanical differences between two postoperative stages (before and after bony fusion). Based on an intact finite-element model of lumbosacral spine, the models of single-level LIF with RIPF or conventional PSF were developed and were computed for biomechanical responses to the moments of four physiological motions using hybrid testing protocol. It was found that compared with PSF, range of motion (ROM), intradiscal pressure (IDP), and facet joint forces (FJF) at adjacent segments of surgical level for RIPF were decreased by up to 8.4%,2.3%and16.8%, but ROM and endplate stress at surgical segment were increased by up to 285.3%and174.3%. The results of comparison between lumbar spine with RIPF before and after bony fusion showed that ROM and endplate stress at surgical segment were decreased by up to 62.6%and40.4%, when achieved to bony fusion. These findings suggest that lumbar spine with RIPF as compared to PSF has potential to decrease the risk of adjacent segment degeneration but might have lower stability of surgical segment and an increased risk of cage subsidence; When achieved bony fusion, it might be helpful for the lumbar spine with RIPF in increasing stability of surgical segment and reducing failure of bone contact with cage.

Determining a relative total lumbar range of motion to alleviate adjacent segment degeneration after transforaminal lumbar interbody fusion: a finite element analysis

“…The finite element study by Du et al also revealed that the ROM, IDP, and FJF of adjacent segments increased after lumbar interbody fusion because the pattern of motion and load distribution had been modified [ 9 ]. The reduced ROM of the fixed segment is compensated by other segments to restore the overall motor function of the spine, which can lead to an abnormal increase in IDP and FJF [ 10 ]. Thus, the published literature has mainly focused on reducing ROM, IDP, and FJF to alleviate ASD by improving surgical techniques, such as semirigid fixation and dynamic fixation [ 11 – 13 ].…”

A Biomechanical Comparison of 2 Different Topping-off Devices and Their Influence on the Sacroiliac Joint Following Lumbosacral Fusion Surgery

“…From a biomechanics perspective, the use of implants in fusion surgery, such as intervertebral cage and rigid fixator, can cause increased stiffness and thus result in load redistribution at neighboring levels. As a result, adjacent segments experience increased mobility and stress, which can contribute to the ASD development [ 2 - 4 ]. By considering this evidence associated with ASD, the dynamic implants made of more compliant materials were developed to establish stabilization and load-bearing capacity, while also allowing moderate motion in the instrumented segments [ 5 , 6 ].…”