Application of an interspinous process device after minimally invasive lumbar decompression could lead to stress redistribution at the pars interarticularis: a finite element analysis

Abstract

Background An interspinous process device, the Device for Intervertebral Assisted Motion (DIAM™) designed to treat lumbar neurogenic disease secondary to the lumbar spinal stenosis, it provides dynamic stabilization after minimally invasive (MI) lumbar decompression. The current study was conducted using an experimentally validated L1-L5 spinal finite element model (FEM) to evaluate the limited decompression on range of motion (ROM) and stress distribution on a neural arch implanted with the DIAM. Methods The study simulated bilateral laminotomies with partial discectomy at L3-L4, as well as unilateral and bilateral laminotomies with partial discectomy combined with implementation of the DIAM at L3-L4. The ROM and maximum von Mises stresses in flexion, extension, lateral bending, and axial torsion were analyzed in response to the hybrid protocol in comparison with the intact model. Results The investigation revealed that decreased ROM, intradiscal stress, and facet joint force at the implant level, but considerably increased stress at the pars interarticularis were found during flexion and torsion at the L4, as well as during extension, lateral bending, and torsion at the L3, when the DIAM was implanted compared with the defect model. Conclusion The results demonstrate that the DIAM may be beneficial in reducing the symptoms of stress-induced low back pain. Nevertheless, the results also suggest that a surgeon should be cognizant of the stress redistribution at the pars interarticularis results from MI decompression plus the application of the interspinous process device.

Effect of different designs of interspinous process devices on the instrumented and adjacent levels after double-level lumbar decompression surgery: A finite element analysis

“…The ROM of each vertebra and the facet joint forces at all segments was computed. Subsequently, 1000 N axial compressive force was acting on the top of L1 vertebra and the intradiscal pressures were calculated in comparing to published literatures [15][16][17][18][19][20]. The material properties are listed in Table 1 [16][17][18].…”

Biomechanical modelling of the facet joints: a review of methods and validation processes in finite element analysis

“…Friction model Cartilage material model 2012Mooney-Rivlin 2nd order, incompressible Noailly et al (2007) Asymmetric tension/compression, with hypoeleastic cartilage in compression Hussain et al (2010) Poroelastic using: E = 10.4 MPa , = 0.4 present) or maximum overclosure values (max gap) but usually did not provide much information about the pressureoverclosure relationship. Fourteen studies (out of 49) did not provide any other information than using a "soft contact" or "non-linear contact" formulation (Aroeira et al 2018;Bermel et al 2018;Charles et al 2013;Cheung et al 2003;Deng et al 2017;Goto et al 2002;Kim et al 1991;Lo et al 2019;Pitzen et al 2002;Song et al 2014Song et al , 2018Teo and Ng 2001;Zeng et al 2017). Only six of the 50 models with cartilage behaviour modelled as soft contact reported all required information on the pressureoverclosure law, of which only four also reported friction behaviour.…”

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“…For the DIAM device, Bellini et al reported that the ROM of the instrumented level decreased in both flexion and extension after DIAM insertion, whereas the ROM of the adjacent levels was unchanged [24]. It is considered that the Coflex and DIAM devices are not capable of fully compensating for an unstable spine when loaded in different directions, with the exception of extension with a single-level insertion [5,20,25,26]. Similarly, the M-PEEK model constrained the ROM of instrumented levels in extension, but movements on…”

“…An "M" geometry rod with 5.5 mm diameter is attached to the base poles and the concave part is placed underneath the spinous process. The three FE implanted models were constructed according to the real implant dimension as well as material properties posted, and were validated in previous studies [15,19,20]. According to the surgical procedures, the Coflex and DIAM interspinous spacers were inserted between adjacent spinous processes of the lumbar spine to resist hyperextension of the lumbar spine.…”

“…Previous studies evaluating the contact forces on the facet joints reported that the highest force occurred during extension [20,29]. As such, this study focused on the facet force during extension, while loading during lateral bending or rotation were not addressed.…”