Lumbar facet joint stabilization for symptomatic spinal degenerative disease: A systematic review of the literature

Objective: Lumbar spinal degenerative disease (LSDD), unresponsive to conservative therapy, is commonly treated by surgical decompression and interbody fusion. Since facet joint incompetence has been suggested as responsible for the entire phenomenon of spinal degeneration, facet stabilization can be considered as an alternative technique to treat symptomatic spinal degenerative disease. The purpose of this study was to systematically review the literature for studies utilizing lumbar facet joint fixation techniques for LSDD to assess their safety and efficacy. Methods: A systematic literature review was performed following the preferred reporting items for systematic reviews and meta-analyses statement, with no limits in terms of date of publication. Demographic data, inclusion criteria, clinical and radiological outcome, frequency of adverse events (AEs), and follow-up time were evaluated. Results: A total of 19 studies were included with a total of 1577 patients. The techniques used for facet arthrodesis were Goel intra-articular spacers in 21 patients (5.3%), Facet Wedge in 198 patients (15.8%), facet screws fixation techniques in 1062 patients (52.6%), and facet joints arthroplasty in 296 patients (26.3%). Clinical outcomes were assessed through the evaluation of pain relief and improvement in functional outcome. Radiological outcomes were assessed by the evaluation of proper positioning of instrumentation, solid bony fusion rate, and preservation of disk height. AE's mainly observed were pseudoarthrosis, reoperation, instrumentation displacement/malpositioning/migration, neurological impairment, deep vein thrombosis, and infections. The mean follow-up time ranged from 6 months to 11.7 years. Conclusion: Our data demonstrate that facet joint arthrodesis appears to be effective in managing LSDD. These findings, however, are limited by the small sample size of patients. Accordingly, larger series are needed before formal recommendations can be made

Biomechanical comparison of a new stand-alone anterior lumbar interbody fusion cage with established fixation techniques – a three-dimensional finite element analysis

<p>Abstract</p> <p>Background</p> <p>Initial promise of a stand-alone interbody fusion cage to treat chronic back pain and restore disc height has not been realized. In some instances, a posterior spinal fixation has been used to enhance stability and increase fusion rate. In this manuscript, a new stand-alone cage is compared with conventional fixation methods based on the finite element analysis, with a focus on investigating cage-bone interface mechanics and stress distribution on the adjacent tissues.</p> <p>Methods</p> <p>Three trapezoid 8° interbody fusion cage models (dual paralleled cages, a single large cage, or a two-part cage consisting of a trapezoid box and threaded cylinder) were created with or without pedicle screws fixation to investigate the relative importance of the screws on the spinal segmental response. The contact stress on the facet joint, slip displacement of the cage on the endplate, and rotational angle of the upper vertebra were measured under different loading conditions.</p> <p>Results</p> <p>Simulation results demonstrated less facet stress and slip displacement with the maximal contact on the cage-bone interface. A stand-alone two-part cage had good slip behavior under compression, flexion, extension, lateral bending and torsion, as compared with the other two interbody cages, even with the additional posterior fixation. However, the two-part cage had the lowest rotational angles under flexion and torsion, but had no differences under extension and lateral bending.</p> <p>Conclusion</p> <p>The biomechanical benefit of a stand-alone two-part fusion cage can be justified. This device provided the stability required for interbody fusion, which supports clinical trials of the cage as an alternative to circumferential fixations.</p

In vitro comparison of a new stand-alone anterior lumbar interbody cage device with established fixation techniques

Around 70% of the population in the United States experience low back pain at some point of their lives, of these 4% underwent surgical intervention on the lumbar spine to relieve the pain. Spinal arthrodesis, i.e. joint fusion, is beneficial in many cases as the final option for patients suffering from certain types of low back pain (LBP). In order to promote solid fusion across a decompressed spinal segment, interbody spacers/cages are used with and without posterior instrumentation to provide an initial rigid fixation of the segment. In this study three fresh/frozen human cadaveric lumbar spines were used. Each lumbar spine was dissected into two Functional Spinal Units (FSUs, L3-L4 and L5-S1) making a total of 6 motion segments. The objective of this study was to evaluate the biomechanical behavior of a new stand-alone anterior lumbar interbody device, by assessing its performance in terms of FSU motion in comparison with the intact FSU and FSUs additional posterior fixation (i.e., facet bolts and pedicle screws). Descriptive statistics and analysis of variance (ANOVA) was used to determine if the differences between the different treatment groups are significant or not. Statistical analysis was also used to determine the contribution of the supplemental fixation for the anterior interbody fusion device (AFD) system

Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

OBJECTIVE: To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. METHODS: A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. RESULTS: The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. CONCLUSION: The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study.ope

Biomechanical evaluation of three surgical scenarios of posterior lumbar interbody fusion by finite element analysis

BACKGROUND: For the treatment of low back pain, the following three scenarios of posterior lumbar interbody fusion (PLIF) were usually used, i.e., PLIF procedure with autogenous iliac bone (PAIB model), PLIF with cages made of PEEK (PCP model) or titanium (Ti) (PCT model) materiel. But the benefits or adverse effects among the three surgical scenarios were still not fully understood. METHOD: Finite element analysis (FEA), as an efficient tool for the analysis of lumbar diseases, was used to establish a three-dimensional nonlinear L1-S1 FE model (intact model) with the ligaments of solid elements. Then it was modified to simulate the three scenarios of PLIF. 10 Nm moments with 400 N preload were applied to the upper L1 vertebral body under the loading conditions of extension, flexion, lateral bending and torsion, respectively. RESULTS: Different mechanical parameters were calculated to evaluate the differences among the three surgical models. The lowest stresses on the bone grafts and the greatest stresses on endplate were found in the PCT model. The PCP model obtained considerable stresses on the bone grafts and less stresses on ligaments. But the changes of stresses on the adjacent discs and endplate were minimal in the PAIB model. CONCLUSIONS: The PCT model was inferior to the other two models. Both the PCP and PAIB models had their own relative merits. The findings provide theoretical basis for the choice of a suitable surgical scenario for different patients

Comparing Mid Lumbar Interbody Fusion (MIDLF) with Traditional Posterior Lumbar Interbody Fusion (PLIF)

Mid-lumbar interbody fusion (MIDLF) uses a novel cortical bone trajectory (CBT) screw that provides robust fixation that is less dependent on cancellous bone quality than a traditional pedicle screw. MIDLF also allows for decompression and instrumentation through a smaller central surgical window. The aim of this study is to compare MIDLF with posterior lumbar interbody fusion (PLIF) with regards to perioperative complications, operative time, blood loss, length in hospital, radiographic outcomes and post-operative patient functional scores. A retrospective review of our institutional database was performed of patients undergoing MIDLF. Matched PLIF controls were then selected from the same database for comparison. 20 MIDLF patients were identified as were 20 matched PLIF controls. Primary outcomes included perioperative clinical and radiographic measures as well as postoperative patient self-reported function. Results demonstrated no significant difference between the two groups with respect to all clinical, radiographic and patient self-reported measures

Comparison of short-segment monoaxial and polyaxial pedicle screw fixation combined with intermediate screws in traumatic thoracolumbar fractures: a finite element study and clinical radiographic review

OBJECTIVES: No studies have compared monoaxial and polyaxial pedicle screws with regard to the von Mises stress of the instrumentation, intradiscal pressures of the adjacent segment and adjacent segment degeneration. METHODS: Short-segment monoaxial/polyaxial pedicle screw fixation techniques were compared using finite element methods, and the redistributed T11-L1 segment range of motion, largest maximal von Mises stress of the instrumentation, and intradiscal pressures of the adjacent segment under displacement loading were evaluated. Radiographic results of 230 patients with traumatic thoracolumbar fractures treated with these fixations were reviewed, and the sagittal Cobb’s angle, vertebral body angle, anterior vertebral body height of the fractured vertebrae and adjacent segment degeneration were calculated and evaluated. RESULTS: The largest maximal values of the von Mises stress were 376.8 MPa for the pedicle screws in the short-segment monoaxial pedicle screw fixation model and 439.9 MPa for the rods in the intermediate monoaxial pedicle screw fixation model. The maximal intradiscal pressures of the upper adjacent segments were all greater than those of the lower adjacent segments. The maximal intradiscal pressures of the monoaxial pedicle screw fixation model were larger than those in the corresponding segments of the normal model. The radiographic results at the final follow-up evaluation showed that the mean loss of correction of the sagittal Cobb’s angle, vertebral body angle and anterior vertebral body height were smallest in the intermediate monoaxial pedicle screw fixation group. Adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group but more likely to be observed in the intermediate monoaxial pedicle screw fixation group. CONCLUSION: Smaller von Mises stress in the pedicle screws and lower intradiscal pressure in the adjacent segment were observed in the polyaxial screw model than in the monoaxial pedicle screw fixation spine models. Fracture-level fixation could significantly correct kyphosis and reduce correction loss, and adjacent segment degeneration was less likely to be observed in the intermediate polyaxial pedicle screw fixation group

ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design

[EN] Study design Biomechanical study in cadaveric specimens. Background The commercially available lumbar disc prostheses do not reproduce the intact disc's Instantaneous centre of Rotation (ICR), thus inducing an overload on adjacent anatomical structures, promoting secondary degeneration. Aim To examine biomechanical testing of cadaveric lumbar spine specimens in order to evaluate and define the ICR of intact lumbar discs. Material and Methods Twelve cold preserved fresh human cadaveric lumbosacral spine specimens were subjected to computerized tomography (CT), magnetic resonance imaging (MRI) and biomechanical testing. Kinematic studies were performed to analyse range of movements in order to determine ICR. Results Flexoextension and lateral bending tests showed a positive linear correlation between the angle rotated and the displacement of the ICR in different axes. Discussion ICR has not been taken into account in any of the available literature regarding lumbar disc prosthesis. Considering our results, neither the actual ball-and-socket nor the withdrawn elastomeric nucleus models fit the biomechanics of the lumbar spine, which could at least in part explain the failure rates of the implants in terms of postoperative failed back syndrome (low back pain). It is reasonable to consider then that an implant should also adapt the equations of the movement of the intact ICR of the joint to the post-surgical ICR. Conclusions This is the first cadaveric study on the ICR of the human lumbar spine. We have shown that it is feasible to calculate and consider this parameter in order to design future prosthesis with improved clinical and biomechanical characteristics.Vanaclocha-Saiz, A.; Atienza Vicente, CM.; Vanaclocha, V.; Belloch, V.; Santabarbara, JM.; Jordá-Gómez, P.; Vanaclocha, L. (2020). ICR in human cadaveric specimens: An essential parameter to consider in a new lumbar disc prosthesis design. North American Spine Society Journal. 2:1-8. https://doi.org/10.1016/j.xnsj.2020.100016S18