Figure - available from: Journal of Orthopaedic Surgery and Research
This content is subject to copyright. Terms and conditions apply.
A view of the cage a and b lateral plate, c bilateral pedicle screws, and d translaminar facet joint + unilateral pedicle screws fixation instruments
Source publication
Background
To explore the biomechanical differences in oblique lumbar interbody fusion (OLIF) augmented by different types of instrumentation.
Methods
A three-dimensional nonlinear finite element (FE) model of an intact L3-S1 lumbar spine was built and validated. The intact model was modified to develop five OLIF surgery models (Stand-alone OLIF;...
Similar publications
Background
A novel interspinous distraction fusion (ISDF) device has been used to treat lumbar degenerative diseases. As a minimally invasive technique, ISDF differs from the traditional interspinous process distraction devices. Currently, biomechanical studies on ISDF are rare.
Objective
To investigate the biomechanical properties of the ISDF dev...
Citations
... Parisien A's systematic review of 245 OLIF patients revealed an average subsidence rate of 17.6%, reaching 36.9% in some cases [26]. Bilateral pedicle screw fixation is considered optimal for preventing subsidence, as supported by biomechanical studies [27]. Hiyama A's randomized controlled study revealed significantly lower subsidence rates with bilateral fixation [28]. ...
Background
The objective of this study was to evaluate the potential of zoledronic acid for reducing the incidence of cage subsidence and enhancing interbody fusion rates following oblique lumbar interbody fusion (OLIF) surgery, particularly as the first reported evidence of the role of zoledronic acid combined with OLIF.
Methods
A retrospective analysis was conducted on data from 108 elderly patients treated for degenerative lumbar diseases using OLIF combined with bilateral pedicle screw fixation from January 2018 to December 2021. Patients were divided into the zoledronic acid (ZOL) group (43 patients, 67 surgical segments) and the control group (65 patients, 86 surgical segments). A comparative analysis of the radiographic and clinical outcomes between the groups was performed, employing univariate and multivariate regression analyses to explore the relationships between cage subsidence and the independent variables.
Results
Radiographic outcomes, including anterior height, posterior height, disc height, coronal disc angle, foraminal height, and lumbar lordosis, were not significantly different between the two groups. Similarly, no statistically significant differences were noted in the back visual analog scale (VAS) scores and Oswestry Disability Index (ODI) scores between the groups. However, at the 1-year follow-up, the leg VAS score was lower in the ZOL group than in the control group (P = 0.028). The ZOL group demonstrated a notably lower cage subsidence rate (20.9%) than did the control group (43.0%) (P < 0.001). There was no significant difference in the interbody fusion rate between the ZOL group (93.0%) and the control group (90.8%). Non-use of zoledronic acid emerged as an independent risk factor for cage subsidence (OR = 6.047, P = 0.003), along with lower bone mineral density, lower postoperative anterior height, and concave endplate morphology. The model exhibited robust discriminative performance, with an area under the curve (AUC) of 0.872.
Conclusion
The administration of zoledronic acid mitigates the risk of cage subsidence following OLIF combined with bilateral pedicle screw fixation in elderly patients; however, it does not improve the interbody fusion rate.
... A relatively novel type of lateral plate is the self anchoring standalone (SSA) system where the plate is also attached to the intervertebral cage in addition to the vertebrae. Based on the literature [7,8,9], and the most recent data published by Bereczki et al. [10], posteriorly placed pedicle screws provide greater primary stability compared to the lateral stabilization approaches with normal bone quality, although they require longer operative times and impose greater surgical loads on the patient. This difference appears to be exacerbated by the presence of osteoporosis [10]. ...
... The geometries and positions of the BPS and SSA implants relative to the vertebral bodies remained unchanged compared to the previous FE publication [10]. Tie constrains were defined in all bone-implant, PMMAtitanium, and titanium-titanium contact surfaces [7,10]. ...
... Based on the results, the BPS system provides greater primary stability compared to the SSA construct, and this difference is further increased by osteoporosis. These findings align with existing literature, which has investigated similar, albeit slightly different boundary and loading conditions [7,8,10,40]. In normal bony conditions, BPS exhibited smaller ROM values, except for left bending. ...
BACKGROUND CONTEXT
Oblique lumbar interbody fusion (OLIF) can provide an ideal minimally invasive solution for achieving spinal fusion in an older, more frail population where decreased bone quality can be a limiting factor. Stabilization can be achieved with bilateral pedicle screws (BPS), which require additional incisions and longer operative time. Alternatively, a novel self-anchoring stand-alone lateral plate system (SSA) can be used, where no additional incisions are required. Based on the relevant literature, BPS constructs provide greater primary biomechanical stability compared to lateral plate constructs, including SSA. This difference is further increased by osteoporosis. Screw augmentation in spinal fusion surgeries is commonly used; however, in the case of OLIF, it is a fairly new concept, lacking a consensus-based guideline.
PURPOSE
This comparative finite element (FE) study aimed to investigate the effect of PMMA screw augmentation on the primary stability of a stand-alone implant construct versus posterior stabilization in OLIF with osteoporotic bone quality.
STUDY DESIGN
The biomechanical effect of screw augmentation was studied inside an in-silico environment using computer-aided FE analysis.
METHODS
A previously validated and published L2-L4 FE model with normal and osteoporotic bone material properties was used. Geometries based on the OLIF implants (BPS, SSA) were created and placed inside the L3-L4 motion segment with increasing volumes (1–6 cm3) of PMMA augmentation. A follower load of 400 N and 10 Nm bending moment (in the three anatomical planes) were applied to the surgical FE models with different bone material properties. The operated L3-L4 segmental range of motion (ROM), the inserted cage's maximal caudal displacements, and L4 cranial bony endplate principal stress values were measured.
RESULTS
The non-augmented values for the BPS construct were generally lower compared to SSA, and the difference was increased by osteoporosis. In osteoporotic bone, PMMA augmentation gradually decreased the investigated parameters and the difference between the two constructs as well. Between 3 cm3 and 4 cm3 of injected PMMA volume per screw, the difference between augmented SSA and standard BPS became comparable.
CONCLUSIONS
Based on this study, augmentation can enhance the primary stability of the constructs and decrease the difference between them. Considering leakage as a possible complication, between 3 cm3 and 4 cm3 of injected PMMA per screw can be an adequate amount for SSA augmentation. However, further in silico, and possibly in vitro and clinical testing is required to thoroughly understand the investigated biomechanical aspects.
CLINICAL SIGNIFICANCE
This study sheds light on the possible biomechanical advantage offered by augmented OLIF implants and provides a theoretical augmentation amount for the SSA construct. Based on the findings, the concept of an SSA device with PMMA augmentation capability is desirable.
... The nucleus pulposus was treated as a linearly elastic fluid element, and the fibrous annulus was represented by a mixture of matrix and collagen fibers buried in the matrix, which travel in a scissor-like fashion in the annulus and at an average ± 30° angle to the disc plane [20,25]. Fibrillar collagen fibers and ligaments were defined as spring elements with nonlinear properties [23,26]. The nucleus pulposus accounts for 40% of the disc volume and the annulus fibrosus for 60% [22]. ...
Background
Finite element analysis (FEA) was performed to investigate the biomechanical differences between different adjunct fixation methods for oblique lumbar interbody fusion (OLIF) and to further analyze its effect on adjacent segmental degeneration.
Methods
We built a single-segment (Si-segment) finite element model (FEM) for L4-5 and a double-segment (Do-segment) FEM for L3-5. Each complete FEM was supplemented and modified, and both developed two surgical models of OLIF with assisted internal fixation. They were OLIF with posterior bilateral percutaneous pedicle screw (TINA system) fixation (OLIF + BPS) and OLIF with lateral plate system (OLIF + LPS). The range of motion (ROM) and displacement of the vertebral body, cage stress, adjacent segment disc stress, and spinal ligament tension were recorded for the four models during flexion/extension, right/left bending, and right/left rotation by applying follower load.
Results
For the BPS and LPS systems in the six postures of flexion, extension, right/left bending, and right/left rotation, the ROM of L4 in the Si-segment FEM were 0.32°/1.83°, 0.33°/1.34°, 0.23°/0.47°, 0.24°/0.45°, 0.33°/0.79°, and 0.34°/0.62°; the ROM of L4 in the Do-segment FEM were 0.39°/2.00°, 0.37°/1.38°, 0.23°/0.47°, 0.21°/0.44°, 0.33°/0.57°, and 0.31°/0.62°, and the ROM of L3 in the Do-segment FEM were 6.03°/7.31°, 2.52°/3.50°, 4.21°/4.38°, 4.21°/4.42°, 2.09°/2.32°, and 2.07°/2.43°. BPS system had less vertebral displacement, less cage maximum stress, and less spinal ligament tension in Si/Do-segment FEM relative to the LPS system. BPS system had a smaller upper adjacent vertebral ROM, greater intervertebral disc stress in terms of left and right bending as well as left and right rotation compared to the LPS system in the L3-4 of the Do-segment FEM. There was little biomechanical difference between the same fixation system in the Si/Do-segment FEM.
Conclusions
Our finite element analysis showed that compared to OLIF + LPS, OLIF + BPS (TINA) is more effective in reducing interbody stress and spinal ligament tension, and it better maintains the stability of the target segment and provides a better fusion environment to resist cage subsidence. However, OLIF + BPS (TINA) may be more likely to cause adjacent segment degeneration than OLIF + LPS.
... As far as we know, there have been many studies on cage subsidence after OLIF operation in recent years. Current biomechanical concerns have focused on the combination of OLIF with different posterior assisted fixation systems, while cage itself does not seem to have received much attention [11][12][13][14]. In addition, some previous biomechanical experiments on OLIF used traditional straight interbody fusion cage, and few people studied the biomechanical differences of cage with different shapes after OLIF surgery. ...
... There are many reasons for endplate injury and cage subsidence after OLIF, such as obesity, osteoporosis, intraoperative iatrogenic endplate injury, intraoperative cage placement, and too small cage [35,36]. Many scholars have found that OLIF + BPSF is an ideal internal fixation method and has the best biomechanical properties through the study of OLIF combined with different internal fixation systems [11,37]. However, excessive rigid fixation with additional posterior pedicle screw fixation system also increases the risk of adjacent segment degeneration and vertebral instrument-related osteoporosis [38,39]. ...
... Therefore, in this study, we designed two kinds of OLIF cage combined with stand-alone and BPSF, respectively, a total of four models, four evaluation The greater the postoperative segment rigidity, the smaller the ROM, and the stronger the ability to limit displacement and deformation. Postoperative segmental instability can increase the incidence of complications, such as subsidence and non-fusion [11,13]. Cai et al. [11] developed five OLIF surgical models, and the ROM of all surgical segments decreased by more than 80%. ...
Background
Oblique lateral lumbar fusion (OLIF) is widely used in spinal degeneration, deformity and other diseases. The purpose of this study was to investigate the biomechanical differences between two different shapes of OLIF cages on whether to add posterior internal fixation system, using finite element analysis.
Methods
A complete three-dimensional finite element model is established and verified for L3–L5. Surgical simulation was performed on the verified model, and the L4–L5 was the surgical segment. A total of the stand-alone group (Model A1, Model B1) and the BPSF group (Model A2, Model B2) were constructed. The four OLIF surgical models were: A1. Stand-alone OLIF with a kidney-shaped Cage; B1. Stand-alone OLIF with a straight cage; A2. OLIF with a kidney-shaped cage + BPSF; B2. Stand-alone OLIF with a straight cage + BPSF, respectively. The differences in the range of motion of the surgical segment (ROM), equivalent stress peak of the cage (ESPC), the maximum equivalent stress of the endplate (MESE) and the maximum stress of the internal fixation (MSIF) were compared between different models.
Results
All OLIF surgical models showed that ROM declines between 74.87 and 96.77% at L4–L5 operative levels. The decreasing order of ROM was Model A2 > Model B2 > Model A1 > Model A2. In addition, the ESPC and MESE of Model A2 are smaller than those of other OLIF models. Except for the left-bending position, the MSIF of Model B2 increased by 1.51–16.69% compared with Model A2 in each position. The maximum value of MESE was 124.4 Mpa for Model B1 in the backward extension position, and the minimum value was 7.91 Mpa for Model A2 in the right rotation. Stand-alone group showed significantly higher ROMs and ESPCs than the BPSF group, with maximum values of 66.66% and 70.59%. For MESE, the BPSF group model can be reduced by 89.88% compared to the stand-alone group model.
Conclusions
Compared with the traditional straight OLIF cage, the kidney-shaped OLIF cage can further improve the stability of the surgical segment, reduce ESPC, MESE and MSIF, and help to reduce the risk of cage subsidence.
... Zhang et al. [27] investigated the efficiency of stand-alone OLIF for the treatment of ADS and showed 16.7% cage subsidence. Cai et al. [47] explored the biomechanical differences among stand-alone OLIF, OLIF with lateral plate fixation, OLIF with unilateral pedicle screws fixation, OLIF with bilateral pedicle screws fixation and OLIF with translaminar facet joint fixation combined unilateral pedicle screws fixation in a three-dimensional nonlinear finite element model, finding that OLIF with bilateral pedicle screws fixation had the best ability in restoring lumbar stability and resisting cage subsidence. Previous studies also had similar reports. ...
Background
Oblique lumbar interbody fusion (OLIF) has been a popular technique for treating lumbar degenerative diseases. Previous studies have shown its efficiency in lumbar spinal stenosis; yet, only a few studies have investigated its application to severe lumbar spinal stenosis. Herein, we investigated the clinical and radiographic outcome of OLIF with percutaneous pedicle screws in the treatment of severe lumbar spinal stenosis.
Methods
A total of 15 patients who underwent OLIF with percutaneous pedicle screws were retrospectively analysed. All patients were diagnosed with severe lumbar stenosis (Schizas grade C or D) through preoperative magnetic resonance image (MRI) and received OLIF combined with percutaneous pedicle screw surgery. Clinical outcomes, including visual analogue scale (VAS)-back and VAS-leg scores, and Oswestry Disability Index (ODI), as well as mean disc height (DH), mean foraminal height (FH), segmental lumbar lordosis (SLL) and cross-sectional area (CSA) of the spinal canal, were analysed before and after surgery and at the last follow-up. Intraoperative data, complications and fusion rate were also investigated.
Results
OLIF combined with percutaneous pedicle screws was performed on 18 segments in 15 patients. Mean follow-up was 23.1 ± 4.6 months (range 15–29 months). VAS-back, VAS-leg, and ODI scores were significantly improved at the last follow-up. DH increased from 8.86 ± 3.06 mm before surgery to 13.31 ± 2.14 mm after; at the last follow-up, DH was 11.69 ± 1.87 mm. FH increased from 17.85 ± 2.26 mm before surgery to 22.09 ± 1.36 mm after; at the last follow-up, FH was 20.41 ± 0.99 mm. CSA of the spinal canal increased from 30.83 ± 21.15 mm ² before surgery to 74.99 ± 33.65 mm ² after the operation and 81.22 ± 35.53 mm ² at the last follow-up. The segmental LL before surgery, after surgery and at last follow-up was 20.27 ± 6.25 degrees, 20.83 ± 6.52 degrees and 19.75 ± 5.87 degrees, respectively. All patients have gained fusion at the last follow-up.
Conclusion
OLIF with percutaneous pedicle screws could achieve satisfactory clinical and radiographic effects through indirect compression by increasing DH, FH and CSA of the spinal canal in severe lumbar stenosis patients.
... As for the lumbar pathologies, despite the paucity of direct research on instrument-related subsidence, biomechanical comparison of different instrumentation in OLIF had been well conducted, in which lateral instrument was shown to provide stronger rigidity than standalone technique, but weaker than bilateral pedicle screw-rod system. 21 Furthermore, Zindrick et al. had described a "windshield wiper" effect due to the rotation center shifting to the distal screw tip secondary to asymmetrical purchase between the cortical end and cancellous end, which would expose the distal end of the screw to excessive mechanical loading, leading to risk of cage subsidence, 22 indicating screws' structural susceptibility to cage subsidence. Therefore, we thought the inferior rigidity of the vertebral screw due to shorter trajectory combined with uneven purchase between two ends had been an important factor associated with cage subsidence in lateral fixation and it was reasonable to modify the current lateral fixation technique for stronger rigidity, to effectively decease the incidence of postoperative cage subsidence. ...
Objective
Cage subsidence is a common morbidity after oblique lumbar interbody fusion (OLIF), with risk of compromising clinical and radiographic outcomes. The study aims to describe an innovative reverse lumbar pedicle screw (RLPS) technique in OLIF and compare its effect on restricting cage subsidence with classical lateral fixation (LF) in radiological and clinical evaluation.
Method
Consecutive patients having undergone single‐level OLIF‐LF/RLPS from 2018 to 2020 were retrospectively reviewed. In OLIF‐RLPS, the upper entry point was determined at the intersection between one horizontal line (1 cm above inferior endplate) and one vertical line (dissecting anterior and middle thirds of the vertebra) while the inferior entry point between one horizontal line (5 mm below superior endplate) and the same vertical line. Trajectories were from vertebrae reverse into contralateral pedicle. Radiological evaluation included disc height (DH) and segmental lordosis (SL); cage subsidence was evaluated by DH loss. Clinical assessment included visual analogue scale (VAS) and Oswestry disability index (ODI). Student t or Mann–Whitney U test was used for continuous variation according to normality analysis while Chi‐square test for category variation.
Results
A total of 29 patients had been enrolled in the study including 14 cases in the RLPS group and 15 cases in the LF group. The DH in the OLIF‐RLPS group had increased from the preoperative 9.07 ± 1.73 mm to 13.73 ± 1.83 mm postoperatively, without significant difference compared with the OLIF‐LF group during the perioperative, but decreased to 12.53 ± 1.74 mm in 3 months and maintained at 12.00 ± 1.45 mm in 12 months, significantly higher than the OLIF‐LF group ( p < 0.05). At the last follow‐up, 7.1% (1/14) cases in the OLIF‐RLPS group had shown subsidence of grade I, significantly less than 46.7% (7/15) cases in the OLIF‐LF group. Pain and disability had improved similarly in two groups, without significant difference detected between two groups at the last follow‐up.
Conclusion
RLPS technique with modified entry points and prolonged trajectory could effectively restrict cage subsidence in OLIF postoperatively compared with traditional lateral fixation.
... Therefore, the condition of the bone after implantation could not be known [17]. Cai et al. showed that BPSF is a better fixation method in OLIF surgeries [18]. Although this study observed endplate values, only L4 or L5 peak stress values were observed, and whether peak stress occurs on the L4 or L5 endplate is unknown. ...
... Furthermore, observation of the stress on the implanted cage showed that under the same movements, the UPSF implantation method resulted in greater stress on the cage, which is primarily because two pedicle screws were used for fixation in BPSF, and this produces external protective effects on the case, thereby decreasing cage deformation and resulting in low cage stress. The trend in this study's results is consistent with other previous studies [17,18]. Moreover, the direction of lateral pedicle screw implantation under LPSF is almost parallel to the cage. ...
Oblique lumbar interbody fusion (OLIF) can be combined with different screw instrumentations. The standard screw instrumentation is bilateral pedicle screw fixation (BPSF). However, the operation is time consuming because a lateral recumbent position must be adopted for OLIF during surgery before a prone position is adopted for BPSF. This study aimed to employ a finite element analysis to investigate the biomechanical effects of OLIF combined with BPSF, unilateral pedicle screw fixation (UPSF), or lateral pedicle screw fixation (LPSF). In this study, three lumbar vertebra finite element models for OLIF surgery with three different fixation methods were developed. The finite element models were assigned six loading conditions (flexion, extension, right lateral bending, left lateral bending, right axial rotation, and left axial rotation), and the total deformation and von Mises stress distribution of the finite element models were observed. The study results showed unremarkable differences in total deformation among different groups (the maximum difference range is approximately 0.6248% to 1.3227%), and that flexion has larger total deformation (5.3604 mm to 5.4011 mm). The groups exhibited different endplate stress because of different movements, but these differences were not large (the maximum difference range between each group is approximately 0.455% to 5.0102%). Using UPSF fixation may lead to higher cage stress (411.08 MPa); however, the stress produced on the endplate was comparable to that in the other two groups. Therefore, the length of surgery can be shortened when unilateral back screws are used for UPSF. In addition, the total deformation and endplate stress of UPSF did not differ much from that of BPSF. Hence, combining OLIF with UPSF can save time and enhance stability, which is comparable to a standard BPSF surgery; thus, this method can be considered by spine surgeons.
... Therefore, more and more spine surgeons are performing OLIF with internal fixation to avoid CAGE subsidence and improve the stability of the operated segment 55 . OLIF with internal fixation also reduces fusion loosening and improves intervertebral fusion [56][57][58][59] . Pedicle screw is the gold standard for internal fixation in spine surgery as it maintains the stability of the three columns of the vertebral body 60 . ...
Multi-segmental lumbar degenerative disease, including intersegmental disc degeneration, is found in clinical practice. Controversy still exists regarding the treatment for cross-segment degeneration. Oblique Lateral Interbody Fusion (OLIF) with several internal fixations was used to treat cross-segment lumbar degenerative disease. A whole lumbar spine model was extracted from CT images of the whole lumbar spine of patients with lumbar degeneration. The L2-3 and L4-5 intervertebral spaces were fused with OLIF using modeling software, the Pedicle screws were performed on L2-3 and L4-5, and different internal fixations were performed on L3-4 in Finite Element (FE) software. Among the six 10 Nm moments of different directions, the L3-4 no surgery (NS) group had the relatively largest Range of Motion (ROM) in the whole lumbar spine, while the L2-5 Long segmental fixation (LSF)group had the smallest ROM and the other groups had similar ROM. The ROM in the L1-2 and L5-S1 was relatively close in the six group models, and the articular cartilage stress and disc stress on the L1-2 and L5-S1 were relatively close. In contrast, the L3-4 ROM differed relatively greatly, with the LSF ROM the smallest and the NS ROM the largest, and the L3-4 Coflex (Coflex) group more active than the L3-4 Bacfuse (Bacfuse) group and the L3-4 translaminar facet screw fixation (TFSF) group. The stress on the articular cartilage and disc at L3-4 was relatively greater in the NS disc and articular cartilage, and greater in the Coflex group than in the Bacfuse and TFSF groups, with the greatest stress on the internal fixation in the TFSF group, followed by the Coflex group, and relatively similar stress in the Bacfuse, LSF, and NS groups. In the TFSF group, the stress on the internal fixation was greater than the yield strength among different directional moments of 10 Nm, which means it is unsuitable to be an internal fixation. The LSF group had the greatest overall ROM, which may lead to postoperative low back discomfort. The NS group has the greatest overall ROM, but its increased stress on the L3-4 disc and articular cartilage may lead to accelerated degeneration of the L3-4 disc and articular cartilage. The Coflex and Bacfuse groups had a reduced L3-4 ROM but a greater stress on disc compared to the LSF group, which may lead to disc degeneration in the long term. However, their stress on the articular cartilage was relatively low. Coflex and Bacfuse can still be considered better surgical options.
... Linear elastic material models were used for the bony tissues. Facet cartilage and intervertebral discs were modeled using Neo-Hookean and Mooney-Rivlin hyperelastic materials (Du et al., 2014;Cai et al., 2020;Cai et al., 2022;Liu et al., 2022). The nucleus pulposus constituted 50% of the disc and the cortical bone thickness was 0.5 mm Zhang et al., 2022). ...
Objective: Using finite element analysis to identify the optimal internal fixation method for oblique lateral lumbar interbody fusion (OLIF), providing guidance for clinical practice.
Methods: A finite element model of the L4 – L5 segment was created. Five types of internal fixations were simulated in the generated L4-L5 finite element (FE) model. Then, six loading scenarios, i.e., flexion, extension, left-leaning, right-leaning, rotate left, and rotate right, were simulated in the FE models with different types of fixations. The biomechanical stability of the spinal segment after different fixations was investigated.
Results: Regarding the range of motion (ROM) of the fused segment, OLIF + Bilateral Pedicle Screws (BPS) has a maximum ROM of 1.82° during backward bending and the smallest ROM in all directions of motion compared with other models. In terms of the von Mises stress distribution on the cage, the average stress on every motion direction of OLIF + BPS is about 17.08MPa, and of OLIF + Unilateral Vertebral Screw - Pedicle Screw (UVS-PS) is about 19.29 MPa. As for the von Mises stress distribution on the internal fixation, OLIF + BPS has the maximum internal fixator stress in left rotation (31.85 MPa) and OLIF + Unilateral Pedicle Screw (UPS) has the maximum internal fixator stress in posterior extension (76.59 MPa). The data of these two models were smaller than those of other models.
Conclusion: OLIF + BPS provides the greatest biomechanical stability, OLIF + UPS has adequate biomechanical stability, OLIF + UVS-PS is inferior to OLIF + UPS synthetically, and OLIF + Double row vertical screw (DRVS) and Individual OLIF (IO) do not present significant obvious advantages.
... Interestingly, a recent biomechanical study suggests that stand-alone anterior cages can be considered for an alternative treatment of ASD, but in case of severe instability, the circumferential approach seems to provide the most biomechanically stable construct [48]. In addition, several biomechanical studies suggest that the addition of a posterior instrumentation improves the stability and rigidity of the construction and reduces the risk of complications [49][50][51][52]. ...
Background: Radiological evidence of adjacent segment disease (ASD) has been reported to have a prevalence of more than 30% and several risk factors have been reported. The aim of this study is to evaluate the clinical and radiological outcomes of patients with symptomatic ASD treated with stand-alone OLIF and compare results with a posterior revision surgery cohort. Methods: This is a retrospective case-control study. Clinical-patient-reported outcomes were obtained at preoperative, postoperative and final follow-up visits using the Short Form (SF-36) scale, the Oswestry Disability Index (ODI) and the visual analog scale (VAS). Radiological measures include lumbar lordosis (LL), segmental lordosis (SL), pelvic incidence-lumbar lordosis (PI-LL) mismatch, segmental coronal Cobb angle and intervertebral disc height (DH). The data are compared with a retrospective series of patients that underwent a posterior revision surgery for ASD. Results: Twenty-eight patients in the OLIF group and 25 patients in the posterior group meet inclusion criteria. The mean ages at the time of the surgery are 65.1 years and 67.5, respectively. The mean follow-up time is 36.1 months (range of 14–56). The clinical outcomes significantly improve from preoperative values from the surgery in both groups. The radiological parameters are significantly improved postoperatively and were maintained at the last follow-up in both groups. A statistically significant difference is observed between the two groups for minor complication rate, length of surgery, blood loss and DH restoration. Conclusions: Stand-alone OLIF is an effective and safe technique with low morbidity and complication rates for the treatment of selected patients with symptomatic ASD following a previous lumbar fusion.
