Search Results (83)

Objective: Lumbar interbody fusion (LIF) is widely used to treat degenerative spinal disorders; however, both fixation strategies and interbody Cage designs still present biomechanical limitations. This study aimed to develop a posterior lumbar interbody fusion Cage using topology optimization and to compare the biomechanical performance of oblique pedicle screw fixation with conventional fixation. Methods: A validated three-dimensional nonlinear finite element model of the L1–L5 lumbar spine was established based on CT data. A two-step weighted topology optimization was applied to the L3–L4 interbody Cage to determine both the external contour and the internal bone graft window. Finite element models with oblique pedicle screw fixation and conventional pedicle screw–rod fixation were constructed and evaluated under static physiological loads and whole-body vibration conditions. Results: Compared with the conventional Cage, the topology-optimized Cage combined with oblique fixation significantly reduced the maximum von Mises stress on adjacent endplates and decreased Cage displacement under both static and dynamic loading. Although stresses in the Cage and screws increased relative to traditional fixation, all values remained well below material yield limits. Conclusions: The combination of a topology-optimized Cage and oblique pedicle screw fixation improves load transfer and structural stability while reducing the risk of endplate damage and Cage subsidence. This approach provides a promising alternative design strategy for posterior lumbar interbody fusion. Full article

Background: Quantifying intraoperative nociceptive responses under general anesthesia remains challenging, particularly during complex procedures such as spinal surgery. The Nociception Level (NoL) index is a multiparametric tool designed to reflect the dynamic balance between nociception and analgesia in anesthetized patients. This study aimed to evaluate NoL fluctuations during predefined phases of spinal surgery and assess their relationship to anesthetic administration. Methods: This prospective observational study enrolled 44 adult patients undergoing lumbar discectomy, laminectomy, or spinal fusion under remifentanil–propofol anesthesia. Continuous NoL monitoring was performed using the PMD100™ system. Sixteen anatomically and procedurally defined surgical phases were analyzed. The primary outcome was the mean NoL value in each phase. The secondary outcome was the association between NoL values and intraoperative infusion rates of remifentanil and propofol. Repeated-measures ANOVA with Bonferroni correction was used for phase comparisons. Results: Mean NoL values remained within the target range (10–25) in most phases. However, significant elevations were observed during pedicle screw insertion (mean 27.9, SD ± 17.7), cage insertion (27.6, SD ± 10.5), and flavectomy (28.0, SD ± 27.0), indicating increased nociceptive burden. The lowest NoL values occurred during skin closure (16.6, SD ± 11.2) and discectomy (18.0, SD ± 2.8). Propofol and remifentanil infusion rates remained within standard clinical ranges but were slightly elevated during high-NoL phases. Conclusions: Despite standardized anesthesia, distinct nociceptive peaks were observed during specific stages of spinal surgery. These findings suggest that NoL monitoring may help identify high-nociception phases and guide tailored analgesic strategies. Future randomized trials are warranted to assess whether protocolized NoL-guided anesthesia improves intraoperative management and postoperative outcomes. Full article

Background/Objective: Oblique lumbar interbody fusion (OLIF) achieves indirect decompression through restoration of disc height. Because maintenance of the restored disc space is essential for sustained neural decompression, solid fusion without cage subsidence is a key determinant of successful surgical outcomes. This study aimed to evaluate preoperative and intraoperative predictors of cage subsidence and radiographic fusion after OLIF. Methods: Seventy patients (119 levels) who underwent OLIF using a polyether–ether–ketone cage and posterior screw fixation between 2015 and 2023 were retrospectively reviewed. Preoperative bone quality was assessed using the computed tomography-based Hounsfield unit (HU) and magnetic resonance imaging-based vertebral bone quality (VBQ) score on T1-weighted images. Radiographic parameters of anterior and posterior disc height (ADH, PDH), segmental and lumbar lordotic angle (SLA, LLA), foraminal height (FH), and cage position were measured preoperatively at one-year follow-up. Results: Cage subsidence occurred in 21.0% of spinal levels (25/119 levels). Multivariate analysis identified these measures as independent predictors: HU (OR 1.017; p = 0.012), VBQ score (OR 2.716; p = 0.016), and PDH distraction (OR 1.418; p = 0.019). ROC analysis identified cutoff values of HU < 145.86 (AUC = 0.654), VBQ score > 3.30 (AUC = 0.723), and PDH distraction > 4.79 mm (AUC = 0.672). None of the evaluated factors were significantly associated with one-year radiographic fusion. Conclusions: Lower HU, higher VBQ score, and excessive PDH distraction are independent risk factors for cage subsidence after OLIF, although these factors do not appear to affect short-term fusion outcomes. Full article

Background: Biportal endoscopic transforaminal lumbar interbody fusion (BESS-TLIF) is an emerging minimally invasive technique. This study aimed to evaluate the two-year radiological fusion outcomes of single-level BESS-TLIF using a specific banana-shaped, porous titanium interbody cage. Methods: This retrospective study reviewed 51 patients who underwent the specified procedure. The primary endpoint was the radiological fusion rate, assessed by computed tomography (CT) over 24 months using a three-grade system. Factors influencing fusion, particularly bone graft composition (demineralized bone matrix [DBM] only vs. DBM with I-factor), were also analyzed. Results: The final complete fusion rate at two years was 96.1% (49/51; 95% Confidence Interval (CI), 86.5–99.5%). Bony fusion occurred predominantly in the posterior and intracage regions. The only significant factor influencing fusion was the bone graft material. The ‘DBM with I-factor’ group achieved complete fusion significantly faster than the ‘DBM only’ group (log-rank test, p < 0.001), with a higher final fusion rate (100% vs. 83.3%, p = 0.045). Conclusions: Single-level BESS-TLIF using a banana-shaped, porous titanium cage provides favourable two-year radiological fusion rates. The selective addition of I-factor as an osteoinductive supplement can significantly accelerate the time to achieve solid arthrodesis. Full article

Background: In spinal fusion surgery, intersomatic compression force is currently applied subjectively by the operating surgeon, despite its critical role on implant stability and risk of subsidence. No standardized measurement or guideline exists to control or quantify the amount of force applied. Methods: In a two-phase exploratory study, we evaluated whether proprioceptive muscle memory allows reliable reproduction of applied manual compression forces. In Phase 1, 30 participants applied force to a compression clamp equipped with a strain gauge, simulating spinal interbody compression on a 3D-printed vertebral model. They were then asked to reproduce this force using a hand dynamometer at defined time intervals. In Phase 2, intraoperative compression forces applied during spinal fusion procedures were retrospectively assessed by having the operating surgeon reproduce the force on a dynamometer. Results: Participants were able to reproduce their initial manual compression force within a 15% deviation, even 15 min after the initial application. In 116 clinical cases, an average compression force of 146.3 ± 18.5 N was recorded. No significant differences were observed across different spinal segments. Conclusions: These findings provide initial data toward defining a reproducible reference range for indirect intraoperative compression assessment. Standardization of applied force may help improve biomechanical outcomes and reduce complications such as implant migration, pseudarthrosis, or cage subsidence. Full article

Background/Objectives: Utilization of polyetheretherketone (PEEK) cages for spinal fusion has surged in the U.S., yet comprehensive comparisons evaluating its postoperative effectiveness with alternative materials remain limited. This systematic review investigates the efficacy of PEEK cages against traditional fusion materials across various surgery types, elucidating PEEK’s impact on fusion rates, postoperative outcomes, and long-term success. Methods: A systematic search of PubMed, CINAHL, Scopus, Embase, and Web of Science was conducted through 14 October 2024. Included studies were randomized controlled trials (RCTs) comparing PEEK cages with titanium, silicon nitride, and metal-coated PEEK cages for anterior cervical discectomy and fusion (ACDF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF). Article quality was assessed using GRADE criteria. Results: From 288 initially screened articles, 25 RCTs involving 2046 patients (mean follow-up 23.1 ± 18.2 months) met inclusion criteria and were determined as moderate (n = 21) or high (n = 4) quality. Fusion rates by cage material for PEEK (n = 1041), Ti-PEEK (n = 291), and titanium (n = 53) were 85.63 ± 18.00%, 80.05 ± 19.9%, and 92.75 ± 11.31%, respectively. In ACDF, titanium cages achieved higher fusion rates than PEEK (100% vs. 94%). In PLIF and TLIF, coated PEEK outperformed uncoated PEEK (75% vs. 71% and 94% vs. 84%, respectively). Uncoated PEEK achieved fusion rates of 94.04 ± 5.04% for ACDF, 71.21 ± 21.93% for PLIF, and 83.50 ± 24.66% for TLIF, with titanium outperforming PEEK in early fusion outcomes. Coated PEEK demonstrated potential improvements in fusion rates over uncoated PEEK in PLIFs and TLIFs. Conclusions: Selection of cage material for spinal fusions should be tailored to surgical requirements and patient needs. While titanium and PEEK are effective, their performance varies across contexts. New materials and surface modifications may enhance these outcomes further, warranting future research in long-term studies and development of novel materials. These findings can help surgeons choose cage materials according to procedure type, patient characteristics, and imaging needs. Full article

Introduction: Currently, static interbody cages are the gold standard for achieving solid arthrodesis in the spine, enhancing segmental stability, obtaining neuroforaminal decompression, and improving as well as maintaining segmental lordosis. It is well known that restoring sagittal balance and segmental lordosis is crucial for long-term outcomes in lumbar spine fusion. For some cases, expandable interbody cages are emerging as an alternative to static cages. This study aims to evaluate the radiographic outcomes and complications of standard open transforaminal lumbar interbody fusion (TLIF). Methods: A standard open TLIF procedure using expandable cages was performed at 1 to 3 levels in 71 patients (129 levels in total), with a follow-up of two years. All patients underwent radiological assessments preoperatively, immediately postoperatively, and at one and two years postoperatively. Radiological evaluation was conducted using standing lateral X-rays. Results: Segmental lordosis (SL) increased significantly from the preoperative value (9.0° ± 3.6°) to 24 months postoperatively (15.4° ± 3.0°), with improvements maintained throughout the 24-month follow-up period (p < 0.001). Similarly, anterior disc height (ADH), posterior disc height (PDH), and foraminal height (FH) each increased significantly from preoperative to immediate postoperative measurements, and these gains were maintained over the two-year follow-up (p < 0.001 each). Lumbar lordosis increased significantly from the preoperative value (41.9° ± 10.5°) to the immediate postoperative period (45.7° ± 10.8°); however, this improvement decreased slightly at the one- and two-year follow-ups. No revisions were required for cage-related complications. One patient experienced a surgical site infection, and two patients had mechanical complications (screw loosening and proximal junctional kyphosis). Conclusions: Expandable interbody cages enable excellent restoration and maintenance of disc height and segmental lordosis in a standard open TLIF procedures at two-year. Achieving these outcomes depends on several factors, including proper preparation of the vertebral endplates, accurate cage placement and expansion, posterior facet osteotomy, and the application of posterior compression prior to final fixation. These steps are essential to fully maximize the potential of expandable cage technology. Full article

Background: The occurrence of ALL rupture during posterior correction of adult spinal deformity (ASD) was rare before the introduction of lateral lumbar interbody fusion (LLIF) but has become more frequent recently. It remains unclear whether this phenomenon is unique to LLIF-combined procedures or primarily related to enhanced corrective ability. Methods: The research method used in this study is finite element analysis (FEA). Using preoperative computed tomography images, LLIF cage (L group) or posterior lumbar interbody fusion (PLIF) cage (P group) were placed in the disc space with identical lordotic angles and distances from the anterior vertebral body edge for the same patients’ samples. Finite element simulations of corrective procedures were conducted. A spring simulating the ALL was introduced into the FEA, and the load on the ALL was evaluated with either LLIF or PLIF cage placement. Spring elongation directly measured the load on the ALL, while the location of the rotation center served as an indirect evaluation. Two different types of corrective procedures were created, one of which is mimicking ASD correction. For both procedures, the load to ALL was measured using abovementioned parameters when either LLIF cage (L group) or PLIF cage (P group) was used. The load to ALL was compared between L group and P group. Results: The degree of spring elongation during the simulation of a corrective procedure significantly decreased in the L group compared to the P group only in the model which is mimicking ASD correction (p = 0.006, Cohen’s d = 2.33, Power (1−β) = 0.956). The rotation center was significantly more posteriorly located in the P group than that in the L group in both models. These differences were more obvious in the model mimicking ASD correction (p = 0.0013, Cohen’s d = 2.00, Power (1−β) = 0.891). Conclusions: Our findings suggest that the use of a PLIF cage, which has a longer anterior–posterior cage length, caused the posterior edge of the cage to act as a pivot point. This configuration places greater leverage on the ALL, potentially leading to rupture during posterior correction procedures. This phenomenon, ALL rupture during posterior correction for ASD, is thought to be associated with increased corrective capabilities rather than being specific to the geometry of the LLIF cage. Full article

Patient-specific technologies within the field of adult spinal deformity (ASD) aid surgeons in pre-surgical planning, accurately help identify anatomical landmarks, and can project optimal post-surgical sagittal alignment. This narrative review aims to discuss the current uses of patient-specific technologies in ASD and identify new innovations that may very soon be integrated into patient care. Pre-operatively, machine learning or artificial intelligence helps surgeons to simulate post-operative alignment and provide information for the 3D-printing of pre-contoured rods and patient-specific cages. Intraoperatively, robotic surgery and intraoperative guides allow for more accurate positioning of implants. Implant materials are being developed to allow for better osseointegration and patient outcome monitoring. Despite the significant promise of these technologies, work still needs to be performed to ensure their accuracy, safety, and cost efficacy. Full article

Background: Lumbar Interbody Fusion (LIF) is a surgical procedure aimed at addressing a range of pathological conditions affecting the structure and function of the spine. Patient-Specific Interbody Cages (PSICs) are an emerging technology that are used in LIF; however, there is a lack of clinical outcome data, making it difficult to assess the potential risks, benefits, and value of PSICs. The purpose of this present study is to contribute data to the field on this new emerging technology. The aims were to investigate Quality of Life (QoL), pain, and the complications of PSICs in LIF. To provide a comparative cohort, we performed a systematic review of patient-reported outcomes of conventional fusion techniques. Methods: This study reports on a multi-surgeon, multi-centre clinical trial of patients with lumbar degenerative disc disease, necessitating discectomy and fusion. All patients underwent LIF procedures with 3D-printed PSICs. Pain Visual Analogue Scale (VAS) and QoL (EQ-5D) scores were collected pre-operatively and at 6m, 12m, and 24m post-operatively. For comparative purposes, we performed a systematic review of the VAS scores from traditional LIF cages and analysed the Australian Spine Registry QoL data. Results: The literature search yielded 4272 publications. The studies were subdivided into four groups based on the interbody device type. All the groups demonstrated improvements in the VAS (for back pain) scores post-operatively. In total, 78 patients (109 instrumented levels) underwent LIF procedures with 3DP PSICs. There were three reoperations (3.8%) and no revisions of any PSIC. The mean VAS scores improved significantly (p < 0.01) from 7.85 (1.50 SD) pre-operatively to 2.03 (2.13 SD) at 24 months post-operatively. The mean QoL index scores improved significantly (p < 0.01) from a pre-operative 0.257 (0.332 SD) to 0.815 (0.208 SD) at 24 months. Conclusions: The systematic review indicated that device fixation to the interbody space was associated with lower VAS scores. The results from the investigational cohort suggest that PSICs may represent a new progression in implant design for spinal fusion, with an associated clinical benefit for LIF. Full article

Background/Objectives: Stand-alone lateral lumbar interbody fusion (LLIF) remains a debated approach in spinal surgery, with limited published evidence supporting its efficacy without supplemental fixation. This prospective study presents the institutional case series on single-level L3-L4 stand-alone LLIF, using next-generation 3D-printed titanium cages, as treatment for degenerative disc disease (DDD). Methods: A cohort of 49 patients with symptomatic DDD, unresponsive to conservative therapy, underwent stand-alone LLIF at L3-L4 (neither posterior pedicle screws nor lateral plating). Clinical outcomes (VAS and ODI) and radiological parameters (disc height, segmental/lumbar lordosis) were collected preoperatively and at 1, 6, and 12 months. Repeated-measures ANOVA with Bonferroni correction was adopted for statistical analysis. Results: Significant improvements were observed in pain and disability scores at all time points, with the mean VAS score decreasing from 6.53 to 0.29, and ODI from 27.6% to 3.84% at one year (p < 0.001). Radiographic analysis confirmed durable increases in disc height and segmental lordosis. Solid fusion was achieved in 97.9% of cases. No patient required posterior revision; transient neurological symptoms were mild and self-limiting. Conclusions: This study demonstrates that stand-alone LLIF at L3-L4 is safe and effective in achieving stable fusion and clinical–radiological improvement. These results challenge the necessity of supplemental fixation and support the broader adoption of a less invasive fusion paradigm. Full article

This study proposes a novel expandable spinal cage to maximize the effectiveness of spinal fusion surgery in the treatment of lumbar disk disorders and aims to verify its mechanical stability through finite element method (FEM) analysis and mechanical testing. To address the limitations of existing cages, which do not provide sufficient height and angle expansion and have constraints in independently adjusting height and angle with continuous fine-tuning, this study introduces a new linkage mechanism. This design enables precise spinal alignment restoration tailored to the individual anatomical characteristics of patients, even in minimally invasive surgical environments, distinguishing itself from traditional rack-and-pinion or wedge-based designs. The results of FEM analysis and static load testing demonstrated a high correlation between the predicted yield locations in FEM analysis and actual test results. Furthermore, the compression and compression–shear load tests confirmed that the proposed cage achieved an ultimate load exceeding the lowest fifth percentile of FDA-approved products, meeting clinical requirements. The proposed expandable spinal cage offers significant improvements over existing products and has the potential to evolve into a safer and more effective spinal fusion device through further dynamic fatigue testing and clinical studies to assess long-term durability and practical applicability. Full article

Purpose: The purpose of this scoping review was to systematically identify and summarize the existing literature on non-spinal clinical applications of EOS imaging and identify related evidence gaps. Method: The study followed the PRISMA-ScR guidelines. A systematic literature search was conducted in Embase, MEDLINE, CINAHL, Scopus, Cochrane, Academic Search Premier, and OpenGrey databases in November 2022 and updated in December 2023. Original research from 2003 to 2023 was eligible if in English, Danish, French, German, Norwegian, or Swedish. Two authors screened articles by title and abstract, while data extraction from full texts was performed by seven authors using a structured template. Results: A total of 8176 articles were identified, with 1350 selected for full-text review and 268 included in data extraction. Among adults, 187 articles were included, with 88 focused on surgical applications like hip arthroplasty or osteotomy. In pediatrics, 68 general and 13 surgery-related articles were included. Lower extremity analysis was the most frequent topic, with other uses identified, such as rib cage geometry, patellar dislocation, and X-linked hypophosphatemia. Conclusions: Key clinical applications of EOS imaging include lower extremity analysis, e.g., leg length assessment and knee/hip arthroplasty planning), pelvic and spinal alignment studies, and emerging uses in rib cage geometry. Evidence gaps include limited research on the diagnostic accuracy of EOS for cerebral shunt placement, reliability in bone age estimation, and an unclear role in foot and ankle morphology. Full article

Cervical pyogenic spondylitis (CPS) is a rare but serious spinal infection with a high risk of neurological compromise due to the cervical spine’s narrow canal and proximity to critical neurovascular structures. Early diagnosis relies on a high index of suspicion supported by MRI, inflammatory markers, blood cultures, and tissue biopsy. Empirical intravenous antibiotics remain the cornerstone of initial treatment, followed by pathogen-specific therapy. Surgical intervention is indicated in cases of neurological deterioration, spinal instability, or failure of conservative management. Anterior approaches, including anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF), are widely used, with anterior plating providing biomechanical advantages in select cases. Posterior or combined anterior–posterior approaches are recommended in multilevel disease, deformity, or posterior element involvement. Graft selection—typically autograft or titanium/PEEK cages—must consider infection severity and biomechanical demands. Challenges in CPS management include optimal debridement extent, graft choice in infected environments, the standardization of antibiotic protocols, and the prevention of recurrence. This narrative review synthesizes the cervical-spine-specific literature on diagnosis, treatment strategies, surgical techniques, and postoperative care and proposes the following practical clinical guidance: (1) early MRI for timely diagnosis, (2) prompt surgical intervention in patients with neurological deficits or mechanical instability, and (3) individualized graft selection based on infection severity and bone quality. Full article

Lumbar interbody fusion (LIF) is a standard treatment for spinal instability, yet postoperative subsidence and adjacent segment degeneration (ASD) remain critical challenges. This study evaluates the biomechanical efficacy of personalized porous fusion cages—featuring Gyroid (G-Cage) and Voronoi (V-Cage) architectures—against classic (C-Cage) and personalized (P-Cage) designs, aiming to enhance stability and mitigate subsidence risks. A finite element model of the L3–L4 segment, derived from CT scans of a healthy male volunteer, was developed to simulate six motion modes (compression, rotation, flexion, extension, and left/right bending). Biomechanical parameters, including range of motion (ROM), cage stress, endplate stress, and displacement, were analyzed. The results demonstrated that the V-Cage exhibited superior performance, reducing ROM by 51% in extension, cage stress by 41.7% in compression, and endplate stress by 63.7% in right bending compared to the C-Cage. The porous designs (G-Cage, V-Cage) exhibited biomimetic stress distribution and minimized micromotion, which was attributed to their trabecular-like architectures. These findings highlight the Voronoi-based porous cage as a biomechanically optimized solution, offering enhanced stability and reduced subsidence risk when compared to classic implants. The study underscores the potential of patient-specific porous designs in advancing LIF outcomes, warranting further clinical validation to translate computational insights into practical applications. Full article