Risk Of Subsidence Research Articles

Does Bone Preservation at the Anterior Edge of the Vertebral Body Affect the Subsidence of Zero-Profile Cages After Anterior Cervical Discectomy and Fusion?

ObjectiveThe purpose of this study was to investigate whether the preservation of the anterior edge of the vertebral body affects the cage subsidence and clinical outcomes after anterior cervical discectomy and fusion(ACDF)using zero-profile cages. MethodsWe retrospectively analyzed 86 patients who underwent 1-3 levels of ACDF using zero-profile cages between December 2017 and June 2023. According to whether the anterior edge was protected, the patients were divided into an intact group and a defect group. Cage subsidence was defined as a ≥2 mm decrease in vertebral height at follow-up compared with measurement on postoperative day 2. The patients' radiological parameters and clinical outcomes were also analyzed. ResultsThe subsidence rate was 17.02% (8/47) in the intact group and 41.03% (16/39) in the defect group(P=0.014). At the last follow-up, all patients in both groups achieved complete intervertebral fusion. The cervical lordosis of the two groups was effectively restored after surgery, and the VAS and NDI scores of the two groups were significantly improved. Multivariate logistic regression analysis showed that the protective factor for zero-profile cage subsidence was bone protection at the anterior edge of the vertebral body (OR=0.270,95%CI=0.091-0.804), and the risk factor was related to the height of the preoperative surgical segment (OR=2.285, 95%CI =1.395-3.743). ConclusionFor patients who undergo ACDF with zero-profile cages, especially those with a higher surgical segment, bone protection at the anterior edge of the vertebral body can effectively reduce the risk of zero-profile cage subsidence, but there is no difference in the final clinical effect.

Prediction of Ground Subsidence Risk in Urban Centers Using Underground Characteristics Information

Ground subsidence primarily occurs due to complex factors, such as damage to underground facilities and excavation work, and its occurrence can result in loss of life and damage to property. Therefore, factors that induce ground subsidence must be investigated to prevent accidents. This study aims to evaluate and predict the ground subsidence risk in urban centers in South Korea. To this end, a machine learning-based ground subsidence risk prediction model was constructed by utilizing data on the underground facility attribute information, permeability coefficient, stratigraphic thickness, and height. The random forest, XGBoost, and LightGBM machine learning algorithms were used to develop the prediction model, and the SMOTE sampling technique was employed to address data imbalance. The reliability of the developed model was verified using the evaluation metrics of F1-score and accuracy. The best-performing model was selected to create a risk map and visualize the areas with ground subsidence risk. The results indicate that the incorporation of additional data improves model performance and reliability. Thus, the machine learning model with various factors developed in this study offers foundational insights for the prevention and risk management of ground subsidence.

Bone Density Correlates With Depth of Subsidence After Expandable Interbody Cage Placement: A Biomechanical Analysis.

Biomechanical analysis. To evaluate the depth of subsidence resulting from an expandable interbody cage at varying bone foam densities. Expandable interbody cages have been shown to be associated with increased rates of subsidence. It is critical to evaluate all variables which may influence a patient's risk of subsidence following the placement of an expandable interbody cage. In the first stage of the study, subsidence depth was measured with 1Nm of input expansion torque. In the second stage, the depth of subsidence was measured following 150 N output force exerted by an expandable interbody cage. Within each stage, different bone foam densities were analyzed, including 5, 10, 15, and 20 pounds per cubic foot (PCF). Five experimental trials were performed for each PCF material, and the mean subsidence depths were calculated. Trials which failed to reach 150 N output force were considered outliers and were excluded from the analysis. There was an overall decrease in subsidence depth with increasing bone foam density. The mean subsidence depths at 150 N output force were 2.0±0.3mm for 5 PCF, 1.8±0.2mm for 10 PCF, 1.1±0.2mm for 15 PCF, and 1.1±0.2mm for 20 PCF bone foam. The mean subsidence depths at 1Nm of input torque were 2.3±0.5mm for 5 PCF, 2.3±0.5mm for 10 PCF, 1.2±0.2mm for 15 PCF, and 1.1±0.1mm for 20 PCF bone foam. Depth of subsidence was negatively correlated with bone foam density at both constant input torque and constant endplate force. Because tactile feedback of cage expansion into the subsiding bone cannot be reliably distinguished from true expansion of disc space height, surgeons should take bone quality into account when deploying expandable cages.

Precise design, preparation, and biomechanical evaluation of customized additively manufactured Ti6Al4V porous fusion cage

The stress shielding phenomenon and subsidence risk caused by the excessive stiffness of dense Ti6Al4V (Ti64) cages affects their application in lumbar fusion surgeries. Advances in additive manufacturing techniques have facilitated the production of porous Ti64 cages with decreased stiffness for the better biomechanical performance. Precise design and preparation of porous cage were crucial for achieving the optimal performance in the fusion surgery. This study introduced a workflow for precise design, preparation, and biomechanical assessment of porous Ti64 cage with designated mechanical properties. Hierarchical optimization was used to obtain the porous cage with designated mechanical properties, including microscale optimization based on the compression load condition to obtain the basic cellular structure and macroscale optimization to determine the framework layout within the cage to achieve the desired stiffness under simulated physiological loading conditions. Numerical simulations of fusion surgery confirmed that the optimized porous cage reduced the stress shielding phenomenon and the subsidence risk of the cage. Further, the cage was prepared via laser powder bed fusion and post-treated via flowing acid etching method to achieve the designed mechanical properties and topological morphology. The compression experiments confirmed that the porous cage contributed to enhancing subsidence resistance. The proposed workflow can be expanded to the precise design, preparation, and biomechanical assessment of various porous implants.

Risk Factors for Early Subsidence of 3D-Printed Artificial Vertebral After Anterior Cervical Corpectomy and Fusion

ObjectiveThe subsidence of vertebral body replacement may occur after anterior cervical corpectomy and fusion (ACCF) , which may lead to cervical kyphosis, spinal cord compression and neurological dysfunction. The authors aim to investigate the risk factors for early subsidence of 3D printed artificial vertebral (3D-PAVB) after ACCF surgery and to provide guidance for clinical practice. MethodsA retrospective analysis was conducted on the data of consecutive patients with cervical spondylosis who underwent ACCF surgery at Bethune Hospital of Shanxi from 2017 to 2020. The statistical data included age, gender, disease type, body mass index (BMI), surgical segment, vertebral height, Cobb Angle, and Hounsfeld Units (HU) values of the vertebral body and endplate. The clinical efficacy of the surgery was evaluated using Visual Analog Scale (VAS), Japanese Orthopedic Association (JOA), and Neck Disability Index (NDI). Follow-up data, such as VAS, JOA, NDI, and Cobb Angle, were obtained using a repeated-measures ANOVA analysis. Univariate analysis was conducted to identify the factors contributing to the early subsidence of the3D-PAVB, and independent risk factors were determined using logistic regression. The HU value was analyzed using the Receiver Operating Characteristic (ROC) curve and the area under the Area Under Curve (AUC) to predict the subsidence of the 3D-PAVB. ResultsA total of 66 patients were included in the study, out of which 19 patients experienced subsidence of 3D-PAVB,resulting in an incidence rate of 28.8%. The postoperative JOA, VAS, and NDI scores showed significant improvement in both the subsidence and non-subsidence groups. Upon conducting univariate analysis, significant differences were observed between the two groups in terms of age, diabetes, smoking, and lower vertebral Computed Tomography (CT) values. The average HU value of the subsidence group (251.39±52.615, n=19) was significantly lower than that of the non-subsidence group (317.06±73.587, n=47, p＜0.01). Multivariate analysis revealed that smoking and HU of the lower vertebra were independent risk factors for 3D-PAVB subsidence, with an AUC of 0.772 and an optimal threshold of 272 for HU (sensitivity 78.9%, specificity 74.5%). ConclusionThe occurrence of early subsidence of 3D-PAVB post ACCF surgery is influenced by two independent risk factors - smoking and low HU. To predict the likelihood of this outcome, it is advisable to consider smoking history and measure CT HU value prior to surgery. A lower CT HU value is indicative of a greater risk of subsidence.

Relationship of the Iliac Crest Height with Subsidence After Oblique Lateral Interbody Fusion at L4-5: A Quantitative and Categorical Analysis.

Background: This study aimed to evaluate the impact of iliac crest height on clinical and radiological outcomes following oblique lateral interbody fusion (OLIF) at the L4-5 level. Methods: Data of patients who underwent single-level OLIF at the L4-5 level for degenerative spinal stenosis were retrospectively analyzed. The patients were categorized into three groups based on their iliac crest height measured relative to the L4 and L5 pedicles. Categorical and quantitative analyses, including univariate and multivariate logistic regressions, were performed to identify subsidence predictors. Clinical outcomes, including visual analog scale scores for back and leg pain, were assessed over a minimum 2-year follow-up. Results: No significant differences in cage obliquity were observed across the iliac crest height groups (axial angles, p = 0.39; coronal angles, p = 0.79). However, subsidence was significantly more common in patients with higher iliac crest heights, particularly at crest level III, where the subsidence rate reached 43% (p = 0.01). Subsidence was predominantly associated with damage to the L5 endplate, which occurred in 83% of subsidence cases at crest level III. A cutoff value of 12 mm for iliac crest height, above which the risk of subsidence significantly increased, was identified (AUC = 0.688, p = 0.042). Conclusions: Iliac crest height is a critical factor for predicting subsidence following OLIF at the L4-5 level. Surgeons should consider alternative strategies and meticulous preoperative planning in patients with an iliac crest height ≥ 12 mm to reduce the risk of adverse outcomes. Further studies are needed to validate these findings and to explore their long-term implications.

Radiological evaluation of fusion patterns after Lateral Lumbar Interbody fusion with 3D-printed porous titanium cages vs. conventional titanium cages.

The assessment of segmental fusion after Lateral Lumbar Interbody fusion (LLIF) using 3D-printed porous titanium cage is still not well studied. Various criteria, such as the presence of bone bridges (BB) between adjacent vertebrae, serve as indicators for anterior fusion. However, limited radiological studies have investigated zygapophyseal joints (ZJ) status following LLIF with porous titanium cages vs. conventional titanium threaded cages. The porous design of the latest titanium intervertebral cages is thought to enhance the bone-to-implant fusion rate. This radiological study aimed to compare the fusion patterns post-LLIF using 3D-printed porous titanium cages against those using threaded titanium cages. This radiological study aimed to compare the fusion patterns after LLIF using 3D-printed porous titanium cages against those using threaded titanium cages. This retrospective, single-center radiological study involved 135 patients who underwent LLIF and posterior percutaneous screw fixation for degenerative spondylolisthesis. The study included 51 patients (Group A) with the novel porous titanium cages and 84 patients (Group B) with conventional threaded titanium cages. Inclusion criteria mandated complete radiological data and a minimum follow-up period of 24 months. The study evaluated intervertebral bone bridges (BB) for anterior fusion and zygapophyseal joints (ZJ) ankylotic degeneration, based on Pathria et al., as evidence of posterior fusion and segmental immobilization. Two years after surgery, intervertebral BB were identified in 83 segments (94.31%) in Group A and in 87 segments (88.77%) in Group B. ZJ Pathria grade I was observed in 2 segments (2.27%) of Group A and in 4 segments (4.08%) of Group B. Grade II was seen in 5 segments (5.68%) of Group A and in 6 segments (6.12%) of Group B. Posterior fusion, classified as grade III, was found in 81 segments (92.04%) of Group A and 88 segments (89.79%) of Group B. Subsidence incidence was 5.88% (3 segments) for the novel cage and 9.88% (8 segments) for the conventional cage. The architecture of porous titanium cages offers a promising solution for increasing bone ingrowth and bridging space, supporting successful spinal fusion while minimizing the risk of subsidence.

Finite element analysis of biomechanical investigation on diverse internal fixation techniques in oblique lumbar interbody fusion

BackgroundTo establish a three-dimensional finite element model of the lumbar spine and investigate the impact of different fixation techniques on the biomechanical characteristics of oblique lumbar interbody fusion (OLIF).MethodsThe study aimed to establish and validate a comprehensive three-dimensional model of the lower lumbar spine (L3-S1) using the finite element method. L4-L5 was selected as the surgical segment, and four distinct OLIF surgical models were constructed: Stand-alone (SA), unilateral cortical bone trajectory screw (UCBT), bilateral cortical bone trajectory screw (BCBT), and bilateral pedicle screw (BPS). The models were underwent a pure moment of 10N·m to simulate lumbar extension, flexion, left bending, right bending, left and right rotation movements. Subsequently, the range of motion (ROM), cage stress, and fixation stress were calculated.ResultsIn the L3-L5 segment, the BCBT group showed the most limited range of motion (ROM) under exercise load, indicating superior stability within this group. The ROM and cage stress values were found to be highest in the SA group. In contrast, the cage and internal fixation stress in the BPS group were observed to be lowest (9.91 ~ 53.83MPa, 44.93 ~ 84.85 MPa). With the exception of right bending and right rotation, the UCBT group demonstrated higher levels of internal fixation stress (102.20 ~ 164.62 MPa).ConclusionsThe study found that OLIF-assisted internal fixation improved segmental stability and reduced cage stress. The BPS group had advantages over the CBT group in preventing endplate damage and reducing the risk of cage subsidence. However, BCBT group has distinct merits in maintaining surgical segment stability, distributing stress load on the spinal motor unit, and reducing the likelihood of adjacent segment degeneration (ASD).

The Role of Cage Placement Angle in Optimizing Short-Term Clinical Outcomes in Lateral Lumbar Interbody Fusion

OBJECTIVEThe purpose is to investigate the impact of cage angle on clinical outcomes and indirect decompression efficacy in patients undergoing lateral lumbar interbody fusion (LLIF). METHODSA retrospective review was conducted on 87 patients with single-level lumbar degenerative disease (LDD) who underwent LLIF. Patients were grouped based on the angle of cage placement: minimal (0°-5°), mild (>5° ≤ 15°), and severe (>15°). Clinical outcomes assessed included pain intensity, functional improvement, and complication rates. Magnetic resonance imaging (MRI) evaluations included measurements of canal diameter (CD) and central canal area (CCA) pre- and postoperatively. Patient-reported outcomes were also analyzed using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ). RESULTSClinical and radiographic outcomes were significantly improved across all cage angle groups. Reductions in low back pain, leg pain, and numbness were significant in all groups, with no significant differences. MRI evaluations revealed significant increases in CD and CCA postoperatively, confirming effective indirect decompression. JOABPEQ scores showed significant improvements in all domains, including low back pain, lumbar function, walking ability, social life function, and mental health. However, the severe angle group had higher rates of delayed cage subsidence (DCS). Complications such as transient motor weakness, thigh pain, numbness, and the need for revision surgery were consistent across groups, with no significant differences. CONCLUSIONSLLIF effectively treats LDD patients, providing significant short-term clinical and radiographic improvements regardless of cage angle. However, oblique cage placement increases the risk of cage subsidence, requiring careful surgical planning and postoperative following.

Multisource geoscience data-driven framework for subsidence risk assessment in urban area

Land subsidence, especially in developed cities, poses significant risks to human life, social property, and urban sustainability. Taking Liwan District in southern China as an example, this study proposed an acceptable framework for regional land subsidence risk assessment while complying with current national assessment system. With integrating the multi-source geospatial data from remote sensing and various geology surveys into ArcGIS, the subsidence risk assessment was carried out based on the subsidence susceptibility mapping, hazard and vulnerability surveying by using a series of data-driven methods. The results showed that, (i) although not all surface deformations detected by InSAR technology were caused by subsidence, they were instrumental in updating subsidence records; (ii) with the help of spatial correlation analysis using weight evidence as well as multi-source data fusion in high spatial resolution, the Random Forest-based classification models effectively identified the land use types and accurately mapped the land subsidence susceptibility; (iii) the hazard and vulnerability surveying based on a series of newly developed combined weight methods, improved the reliability of risk assessment; (iv) the extremely high- and high-risk areas from the zoning of the land subsidence, provided target areas for further management and prevention of land subsidence. This comprehensive and quantitative assessment framework highlights the need for continued monitoring in subsidence-prone regions, helping to propose strategies for risk mitigation and adaptive planning in urban areas.

Magnetic Resonance Imaging-Based Vertebral Bone Quality Score for Prediction of Cage Subsidence and Screw Loosening in Patients Undergoing Degenerative Lumbar Surgery: A Meta-analysis.

Poor bone quality is a risk factor for postoperative complications after degenerative lumbar fusion surgery. The magnetic resonance imaging-based vertebral bone quality (VBQ) score is a good tool for assessing bone quality, and this is the first meta-analysis performed to summarize the predictive value of the VBQ score for cage subsidence and screw loosening in patients undergoing degenerative lumbar surgery. Studies were comprehensively searched in electronic databases. The quality of the studies was assessed. The pooled sensitivity, specificity and summary receiver operating characteristic curve were calculated. Publication bias was assessed and meta-regression was conducted. We ultimately included 9 studies with a total of 1,404 patients with a mean age of 60.4 years and a percentage of females of 57.0%. According to the QUADAS-2 (Quality Assessment of Diagnostic Accuracy Studies 2) tool to assess methodological quality, the quality of the included studies was relatively low and risks of bias might exist. Results showed that a high VBQ was significantly associated with cage subsidence and screw loosening, and risk factor analysis revealed that the merged odds ratio was 5.37 for cage subsidence and 3.87 for screw loosening. With a VBQ cutoff value of 3.34±0.45, the pooled sensitivity and specificity for the diagnosis of postoperative complications were 0.75 and 0.75, respectively, and the area under the curve was 0.82 (95% confidence interval, 0.78-0.85). A high VBQ was associated with a high risk of cage subsidence and screw loosening in patients who underwent degenerative lumbar surgery. The VBQ score could be considered for identifying high-risk patients for further evaluation.

Minimally-invasive trans-facet lumbar interbody fusion using a dual-dimension expandable cage: preliminary results of a multi-institutional retrospective study.

Minimally-invasive trans-facet lumbar interbody fusion (LIF) is an emerging technique that offers the advantages of being safe, enabling decompression, and facilitating patient recovery. An innovative cage that expands in two dimensions has been introduced to restore segmental lordosis and disc height while minimizing the risk of cage subsidence. This study aimed to report our surgical technique of trans-facet LIF utilizing the innovative cag and to report the early clinical outcomes. We retrospectively reviewed the medical records and radiographs of patients who underwent trans-facet LIF with dual-dimension expandable cages from two institutions: Duke University Hospital and Vail-Summit Orthopaedics and Neurosurgery. The analysis covered patient demographics, Oswestry Disability Index (ODI), visual analogue scale (VAS) for back pain, surgical data, complications, and radiographic parameters. Clinical outcomes were compared between pre- and one year post-operation, while radiographic outcomes were compared between pre- and three months post-operation. Twenty patients with a mean age of 61.2 years were included. Seventeen patients (85.0%) had spondylolisthesis, and L4/5 (68.2%) was the most common pathology level. Twelve patients (60.0%) underwent awake surgery, and the mean operative time was 164.5±36.1 minutes, with an estimated blood loss of 64.0±39.5 mL and a hospital stay of 1.75±1.2 days. Four patients (20.0%) experienced cage subsidence; however, none required additional surgery. The VAS score significantly improved from a preoperative average of 7.3±2.7 to 2.6±1.6 one year post-operation (P=0.02). The ODI score also showed a significant decrease, from 48.7±22.9 preoperatively to 16.4±11.1 one year postoperatively (P=0.03). Notably, 80% and 83.3% of patients achieved the minimum clinically important difference in VAS and ODI scores, respectively. The degree of spondylolisthesis was significantly reduced from a median of 5.9 mm preoperatively to 0 mm postoperatively (P<0.001). Additionally, both anterior and posterior disc heights significantly increased after surgery, from 9.8±4.7 to 15.1±2.6 mm (anterior) and from 4.9±3.3 to 10.5±2.2 mm (posterior) (P<0.001 for both). The mean segmental lordosis increased by 2.9 degrees and was associated with cage height (P=0.03), while spinopelvic parameters remained unchanged. Minimally-invasive trans-facet LIF with dual-dimension expandable cages demonstrates a substantial capacity for spondylolisthesis reduction and disc height restoration, and provides good short-term clinical outcomes. It may be the most appropriate method for deploying this large cage as it allows for a large, unobstructed pathway to the disc. However, future studies are needed to determine the long-term outcomes, including the arthrodesis rate.

Positive Cutibacterium acnes Intervertebral Discs Are Not Associated with Subsidence Following Anterior Cervical Discectomy and Fusion at 3 or 6 Months.

Background/Objectives:Cutibacterium acnes (C. acnes), formerly known as Propionibacterium acnes (P. acnes), is an anaerobic, low-virulent bacterium that has been associated with postoperative infections of the shoulder, knee, and cervical spine. Recent studies have highlighted an association between C. acnes and the development of degenerative disc disease (DDD). The aim of this study is to ascertain whether C. acnes increases the risk of subsidence following anterior cervical discectomy and fusion (ACDF). Methods: After IRB approval, consecutive patients undergoing elective ACDF for DDD from 2017 to 2018 were enrolled in this prospective cohort study. Intervertebral disc samples were taken at each affected level and cultured. A total of 66 patients with radiographic follow-ups were included in the final analysis. The extent of subsidence and cervical lordosis was determined immediately postoperatively and at the 3- and 6-month follow-ups. Results: No significant difference in subsidence was observed at 3 months (p = 0.07) or 6 months (p = 0.11) between culture-positive and -negative cohorts. Additionally, there was no significant difference detected in the change in cervical lordosis observed at 3 months (p = 0.16) or 6 months (p = 0.27) between culture-positive and -negative cohorts. For the most inferiorly fused segment, there was a significant difference in subsidence observed at 3 months (1.5 mm, 95% CI: 0.2-2.7 mm, p = 0.02) but not at 6 months (p = 0.17). Conclusions: Intervertebral discs with a positive C. acnes culture were not associated with greater levels of subsidence at 3 or 6 months following ACDF for DDD. Further research is necessary to endorse these results and to gauge the clinical significance of C. acnes infection.

The Utility of Magnetic Resonance Imaging-based Vertebral Bone Quality Scores as a Predictor of Cage Subsidence Following Transforaminal and Posterior Lumbar Interbody Fusion.

Retrospective study. The objectives were to determine whether vertebral bone quality (VBQ) scores are associated with interbody cage subsidence following transforaminal (TLIF) and posterior (PLIF) lumbar interbody fusions and whether there is a clinically sensitive threshold for subsidence. Interbody cage subsidence following lumbar fusion is a complication that can generate poor surgical outcomes. Prior research has correlated cage subsidence with bone mineral density. VBQ scores derived from magnetic resonance imaging (MRI) have been proposed as a tool for measuring bone mineral density, offering a potential new and convenient preoperative risk assessment tool for subsidence. The study involved patients undergoing single-level PLIF or TLIF between 2007 and 2022. Exclusions were for nondegenerative diagnoses, multilevel/revision surgeries, inadequate radiographs, missing immediate postoperative radiographs, and preoperative MRI studies older than 1 year. VBQ was calculated at L1-L4 from preoperative T1-weighted MRI images. Subsidence was assessed by changes in disc height (DH; >2mm difference) and segmental lordosis (SL; >5 degrees difference) between immediate weight-bearing postoperative and latest postoperative lateral radiographs. Statistical analysis included descriptive and inferential statistics. Subsidence was observed in 27% (SL parameter) and 47% (DH parameter) of 51 total patients. VBQ scores were significantly associated with cage subsidence based on both SL (odds ratio = 7.750, P = 0.012; correlation coefficient = 0.382, P = 0.006) and DH (odds ratio = 4.074, P = 0.026; correlation coefficient = 0.258, P = 0.057) in the combined TLIF/PLIF cohorts. In the cohort of 36 patients undergoing TLIF, a VBQ of 2.70 yielded 100.0% sensitivity and 46.2% specificity in detecting subsidence with SL measurement (area under the curve = 0.812, P < 0.001) and 86.7% sensitivity and 47.6% specificity with the DH measurement (area under the curve = 0.692, P = 0.033). We found that MRI-based VBQ scores are effective predictors of cage subsidence following TLIF surgery. A VBQ score of 2.70 demonstrated a reliable model and high sensitivity for doing so, identifying a potential clinical threshold for preoperative subsidence risk assessment. Level III.

Economic risk of differential subsidence in Mexico City (2014–2022)

Economic risk of differential subsidence in Mexico City (2014–2022)

In silico medical device testing of anatomically and mechanically conforming patient-specific spinal fusion cages designed by full-scale topology optimisation.

A full-scale topology optimisation formulation has been developed to automate the design of cages used in instrumented transforaminal lumbar interbody fusion. The method incorporates the mechanical response of the adjacent bone structures in the optimisation process, yielding patient-specific spinal fusion cages that both anatomically and mechanically conform to the patient, effectively mitigating subsidence risk compared to generic, off-the-shelf cages and patient-specific devices. In this study, in silico medical device testing on a cohort of seven patients was performed to investigate the effectiveness of the anatomically and mechanically conforming devices using titanium and PEEK implant materials. A median reduction in the subsidence risk by 89% for titanium and 94% for PEEK implant materials was demonstrated compared to an off-the-shelf implant. A median reduction of 75% was achieved for a PEEK implant material compared to an anatomically conforming implant. A credibility assessment of the computational model used to predict the subsidence risk was provided according to the ASME V&V40-2018 standard.

Geo-sustainability Challenges and Remediation Strategies: A GIS-based Assessment of Sripur Coalmine Areas, West Bengal, India

This study examines the health, risk, and safety aspects of coal mining in the Sripur area, focusing on the Bhanora West Block, Asansol, West Bengal, India as one of the 14 operational mines of Eastern Coalfields Limited in Asansol. The study addresses the increasing risks of accidents, fires, and subsidence in active, ageing, and closed mines and storage yards. The study’s incorporation of field surveys, satellite imagery, and environmental data ensures that the findings are based on a well-rounded and multi-faceted dataset. The satellite imagery data (GIS and Remote Sensing) are perceived along with available literature and environmental impact compliance reports from time to time, with particular interest in the Bhanora West coal mine, both open cast and underground. The aspect, Hill shade, LULC and stream order maps of the Damodar are generated using Q-GIS, 3.28.7. The environmental clearance data, accident data, subsidence area, and landslide data are analysed. A vast area in Sripur is observed to be under subsidence, with cracks appearing even near residential areas. The flow of the Nunia nallah is nearby, and old closed mines are not adequately backfilled, so the chance of seepage cannot be neglected though regularly attended. Pneumoconiosis (CWP), a lung disease (black lung), chronic obstructive pulmonary disease (COPD), and silicosis are common in Sripur due to dust and substandard water. Effective and riskless mining extractions using proper technologies can avoid mining hazards, such as subsidence, the influx of water in underground mines, health hazards, air/water pollution, mine fire, and intact physical landscape and observing criteria of sustainable Development Goal SDG-1 SDG-3, SDG-6, SDG 12, SDG-13, and SDG 16.

Exploring the rate and potential risk of land subsidence induced by groundwater overexploitation in a multilayer aquifer

Exploring the rate and potential risk of land subsidence induced by groundwater overexploitation in a multilayer aquifer

Anatomically and mechanically conforming patient-specific spinal fusion cages designed by full-scale topology optimization

Cage subsidence after instrumented lumbar spinal fusion surgery remains a significant cause of treatment failure, specifically for posterior or transforaminal lumbar interbody fusion. Recent advancements in computational techniques and additive manufacturing, have enabled the development of patient-specific implants and implant optimization to specific functional targets. This study aimed to introduce a novel full-scale topology optimization formulation that takes the structural response of the adjacent bone structures into account in the optimization process. The formulation includes maximum and minimum principal strain constraints that lower strain concentrations in the adjacent vertebrae. This optimization approach resulted in anatomically and mechanically conforming spinal fusion cages. Subsidence risk was quantified in a commercial finite element solver for off-the-shelf, anatomically conforming and the optimized cages, in two representative patients. We demonstrated that the anatomically and mechanically conforming cages reduced subsidence risk by 91% compared to an off-the-shelf implant with the same footprint for a patient with normal bone quality and 54% for a patient with osteopenia. Prototypes of the optimized cage were additively manufactured and mechanically tested to evaluate the manufacturability and integrity of the design and to validate the finite element model.

Semi-analytical solutions for land subsidence due to groundwater withdrawal

This paper introduces novel semi-analytical models tailored for estimating land subsidence resulting from groundwater extraction in confined aquifers. These models offer high scalability, allowing them to be applied to various well configurations and pumping schedules. Their development involves the numerical integration of two key analytical solutions: the “nucleus of strain” (NoS) (Mindlin and Chen, 1950), which represents a localised zone within the aquifer where a unit change in pore pressure leads to deformation and subsequent surface displacement, and the classic Theis equation (Theis, 1935) for the pore pressure changes induced by a constant-rate well pumping from a laterally unbounded aquifer. These integrations yield surface displacement components, both horizontal and vertical, expressed as functions of two dimensionless spatial–temporal variables, which encompass aquifer depth, thickness, well placement, pumping schedules, and critical hydro-geomechanical parameters like hydraulic conductivity, porosity, vertical compressibility, and water compressibility. Proposed are two distinct modelling approaches: one employing a lookup table (LT) derived from numerical integration results, and the other providing direct closed-form surface displacement solutions by fitting LT data with “hinge models”, which use piecewise-linear functions linked by sigmoidal curves for computational efficiency. In both cases, surface displacement components are estimated by plugging in the dimensionless variables. Conditions of variable pumping from multiple wells can be addressed by applying superposition of solutions. In essence, these semi-analytical models offer swift computational capabilities for understanding and forecasting land subsidence dynamics. Their scalability makes them adaptable to a wide array of well configurations and scheduling scenarios, rendering them valuable for numerous applications. They are particularly significant for providing preliminary estimates of the impacts of groundwater development, conducting “what-if” tests, and performing sensitivity analyses to identify key factors affecting land subsidence risk. This underscores the importance of these models in sustainable groundwater resource management and in mitigating land subsidence and its associated consequences.