Integration of Advanced Borehole Sonic and Resistivity Image Analysis for Fracture and Stress Characterisation - Implications to Carbon Sequestration Feasibility

Borehole resistivity images and dipole sonic data analysis helps a great deal to identify fractured zones and obtain reasonable estimates of the in-situ stress conditions of geologic formations. Especially when assessing geologic formations for carbon sequestration feasibility, borehole resistivity image and borehole sonic assisted analysis provides answers on presence of fractured zones and stress-state of these fractures. While in deeper formations open fractures would favour carbon storage, in shallower formations, on the other hand, storage integrity would be potentially compromised if these fractures get reactivated, thereby causing induced seismicity due to fluid injection. This paper discusses a methodology adopted to assess the carbon dioxide sequestration feasibility of a formation in the Newark Basin in the United States, using borehole resistivity image(FMI™ Schlumberger) and borehole sonic data (SonicScaner™ Schlumberger). The borehole image was interpreted for the presence of natural and drilling-induced fractures, and also to find the direction of the horizontal stress azimuth from the identified induced fractures. Cross-dipole sonic anisotropy analysis was done to evaluate the presence of intrinsic or stress-based anisotropy in the formation and also to obtain the horizontal stress azimuth. The open or closed nature of natural fractures was deduced from both FMI fracture filling electrical character and the Stoneley reflection wave attenuation from SonicScanner monopole low frequency waveform. The magnitudes of the maximum and minimum horizontal stresses obtained from a 1-Dimensional Mechanical Earth Model were calibrated with stress magnitudes derived from the ‘Integrated Stress Analysis’ approach which takes into account the shear wave radial variation profiles in zones with visible crossover indications of dipole flexural waves. This was followed by a fracture stability analysis in order to identify critically stressed fractures. The borehole resistivity image analysis revealed the presence of abundant natural fractures and microfaults throughout the interval which was also supported by the considerable sonic slowness anisotropy present in those intervals. Stoneley reflected wave attenuation confirmed the openness of some natural fractures identified in the resistivity image. The strike of the natural fractures and microfaults showed an almost NE-SW trend, albeit with considerable variability. The azimuth of maximum horizontal stress obtained in intervals with crossover of dipole flexural waves was also found to be NE-SW in the middle part of the interval, thus coinciding with the overall trend of natural fractures. This might indicate that the stresses in those intervals are also driven by the natural fracture network. However, towards the bottom of the interval, especially from 1255ft-1380ft, where there were indications of drilling induced fractures but no stress-based sonic anisotropy, it was found that that maximum horizontal stress azimuth rotated almost about 30 degrees in orientation to an ESE-WNW trend. The stress magnitudes obtained from the 1D-Mechanical Earth Model and Integrated Stress Analysis approach point to a normal fault stress regime in that interval. The fracture stability analysis indicated some critically stressed open fractures and microfaults, mostly towards the lower intervals of the well section. These critically stressed open fractures and microfaults present at these comparatively shallower depths of the basin point to risks associated with carbon dioxide(CO2) leakage and also to induced seismicity that might result from the injection of CO2 anywhere in or immediately below this interval.

The Effect of Vertical and Oblique Inclinations on Fracture Stability and Reoperation Risks in Femoral-Neck Fractures of Nongeriatric Patient

Background: For nongeriatric patients with femoral neck fractures (FNFs), preoperative evaluation of fracture three-dimensional inclination is essential to identify fracture stability, select appropriate fixation strategies, and improved clinical prognoses. However, there is lack of evaluation system which takes into account both vertical and oblique inclinations. The purpose of this study was to comprehensively investigate the effect of vertical and oblique inclinations on fracture stability and reoperation risks.Methods: We retrospectively reviewed the medical records of 755 FNFs patients with over 2 years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.Results and Conclusion: The overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included vertical (α > 70°) and oblique (50°<α < 70° and β > 20°/β < −20°) types. Biomechanical validation showed these fractures had significantly greater (p < 0.05) interfragmentary motion (1.374–2.387 mm vs. 0.330–0.681 mm). The reoperation rate in 3-D unstable group (32.7%) is significantly (p < 0.001) higher than that in 3-D stable group (7.9%). Multivariate analysis demonstrated that 3-D inclination angle was significantly (OR = 4.699, p < 0.001) associated with reoperation. FNFs with α > 70°; 50°<α < 70° and β > 20°/β < −20° are real unstable types with significantly worse interfragmentary stability and higher reoperation risks. Fracture inclination in vertical and oblique planes is closely related to reoperation outcomes and may be a useful complement to the way FNFs are currently evaluated.

The effect of Fracture Inclination in Multiple Planes on Fracture Stability and Reoperation Risks in Femoral-Neck Fractures of Nongeriatric Patients

BackgroundFor nongeriatric patients with femoral neck fractures (FNFs), internal fixation treatment is still the primary choice. Preoperative evaluation of fracture inclination and underlying stability is essential for selecting appropriate fixation strategies, thus improving clinical prognoses. The purpose of this study was to comprehensively investigate the 3-D inclination angle in both vertical and oblique planes from CT images, and its association with fracture stability and reoperation risks.MethodsWe retrospectively reviewed the medical records of 755 FNFs patients with over two years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.ResultsThe overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included α>70°; 50°<α<70° and β>20°/ β<-20°. Biomechanical validation showed these fractures had significantly greater (p<0.05) interfragmentary motion (1.374-2.387mm vs. 0.330-0.681 mm). The reoperation rate in 3-D unstable group (32.7%) is significantly (p<0.001) higher than that in 3-D stable group (7.9%). Multivariate analysis demonstrated that 3-D inclination angle was significantly (OR=4.699, p<0.001) associated with reoperation. ConclusionsFNFs with α>70°; 50°<α<70° and β>20°/ β<-20° are real unstable types with significantly worse interfragmentary stability and higher reoperation risks. Fracture inclination in multiple planes is closely related to reoperation outcomes and may enhance the way FNFs are currently evaluated.

Laboratory Study on the Effect of Fluid Pressurization Rate on Fracture Instability

Fluid injection-induced earthquakes have been a scientific and social issue of wide concern, and fluid pressurization rate may be an important inducement. Therefore, a series of stepwise and conventional injection-induced shear tests were carried out under different fluid pressurization rates and effective normal stresses. The results show that the magnitude of fluid pressure is the main factor controlling the initiation of fracture slipping. The contribution of fluid pressure heterogeneity and permeability evolution on the initiation of fracture slipping is different with the increase of fluid pressurization rate. When the fluid pressurization rate is small, permeability evolution plays a dominant role. On the contrary, the fluid pressure heterogeneity plays a dominant role. The increase of fluid pressurization rate may lead to the transition from creep slip mode to slow stick-slip mode. Under the laboratory scale, the fluid pressure heterogeneity causes the coulomb failure stress to increase by about one times than the predicted value at the initiation of fracture slipping, and the coulomb stress increment threshold of 1.65 MPa is disadvantageous to the fracture stability.

Leg-length discrepancy and associated risk factors after paediatric femur shaft fracture: a multicentre study

Purpose This study was performed to investigate leg-length discrepancy (LLD) and associated risk factors after paediatric femur shaft fractures. Methods A total of 72 consecutive patients under 13 years old (mean age 6.7 years; 48 boys, 24 girls) with unilateral femur shaft fracture, and a minimum follow-up of 18 months, were included. The amount of LLD was calculated by subtracting the length of the uninjured from that of the injured limb. Risk factors for an LLD ≥ 1 cm and ≥ 2 cm were analyzed using multivariable logistic regression analysis. Results Hip spica casting, titanium elastic nailing and plating were performed on 22, 40 and ten patients, respectively. The mean LLD was 7.8 mm (sd 8.8) and 29 (40.3%) had a LLD of ≥ 1 cm, while nine (12.5%) had a LLD of ≥ 2 cm. There were significant differences in fracture stability (p = 0.005) and treatment methods (p = 0.011) between patients with LLD < 1 cm and ≥ 1 cm. There were significant differences in fracture site shortening (p < 0.001) and LLD (p < 0.001) between patients with length-stable and length-unstable fractures. Fracture stability was the only factor associated with LLD ≥ 1 cm (odds ratio of 4.0; p = 0.020) in the multivariable analysis. Conclusion This study demonstrated that fracture stability was significantly associated with LLD after paediatric femur shaft fractures. Therefore, the surgeon should consider the possibility of LLD after length-stable femur shaft fracture in children. Level of Evidence Prognostic level III

Determination and optimization of ideal patient candidacy for anterior odontoid screw fixation

Background: Odontoid process fractures are one of the most common spine fractures, especially in patients over age 70. There is still much controversy over the ideal candidate for anterior odontoid screw fixation (AOSF), with outcomes affected by characteristics such as fracture morphology, nonideal body habitus, and osteoporosis. Therefore, this systematic review seeks to discuss the optimal criteria, indications, and adverse postoperative considerations when deciding to pursue AOSF. Methods: This investigation was conducted from experiential recall and article selection performed using the PubMed electronic bibliographic databases. The search yielded 124 articles that were assessed and filtered for relevance. Following the screening of titles and abstracts, 48 articles were deemed significant for final selection. Results: AOSF is often utilized to treat Type IIB odontoid fractures, which has been shown to preserve atlantoaxial motion, limit soft-tissue injuries/blood loss/vertebral artery injury/reduce operative time, provide adequate osteosynthesis, incur immediate spinal stabilization, and allow motion preservation of C1 and C2. However, this technique is limited by patient characteristics such as fracture morphology, transverse ligament rupture, remote injuries, short neck or inability to extend neck, barrel chested, and severe spinal kyphosis, in addition to adverse postoperative outcomes such as dysphagia and vocal cord paralysis. Conclusion: Due to the fact that odontoid fractures have a significant morbidity in elderly population, treatment with AOSF is generally recommended for this population with higher risk for nonoperative fusion. Considerations should be made to achieve fracture stability and fusion, while lowering the risk for operative and postoperative complications.

Medial Calcar Comminution and Intramedullary Nail Failure in Unstable Geriatric Trochanteric Hip Fractures

Background and Objectives: An increasing global burden of geriatric hip fractures is anticipated. The appropriate treatment for fractures is of ongoing interest and becoming more relevant with an aging population and finite health resources. Trochanteric fractures constitute approximately half of all hip fractures with the medial calcar critical to fracture stability. In the management of unstable trochanteric fractures, it is assumed that intramedullary nails and longer implants will lead to less failure. However, the lack of power, inclusion of older generation femoral nails, and a variable definition of stability complicate interpretation of the literature. Materials and Methods: Between January 2012 and December 2017, a retrospective analysis of operatively treated geriatric trochanteric hip fracture patients were examined at a Level 1 Trauma Centre. The treatment was with a long and short version of one type of trochanteric nail. Unstable trochanteric fractures with medial calcar comminution were examined (AO31A2.3, 2.3 & 3.3). The length of the medial calcar loss, nail length, demographics, fracture morphology, and relevant technical factors were examined in univariate and multivariate analysis using competing risk regression analysis. The primary outcome was failure of fixation with post-operative death the competing event and powered to previously reported failure rates. Results: Unstable patterns with medial calcar comminution loss constituted 617 (56%) of operatively treated trochanteric fractures. Failure occurred in 16 (2.6%) at a median post-operative time of 111 days (40–413). In univariate and multivariate analysis, only younger age was a significant predictor of failure (years; SHR: 0.91, CI 95%: 0.86–0.96, p < 0.001). Nail length, medial calcar loss, varus reduction, and other technical factors did not influence nail failure. Conclusions: In a cohort of unstable geriatric trochanteric hip fractures with medial calcar insufficiency, only younger patient age was predictive of nail failure. Neither the length of the medial calcar fragment or nail was predictive of failure.

Overview of the contemporary management of supracondylar humeral fractures in children

Purpose Supracondylar fractures are common injuries accounting for approximately 15% of all fractures in children with a large body of literature on this subject. Methods This article critically appraises the available evidence to provide an overview of the treatment options including the role and timing of surgery, the geometry of wire fixation and the management of nerve and arterial injury. Conclusion Management decisions are based on a number of considerations particularly fracture stability. Closed reduction and percutaneous K-wire stabilisation are commonly recommended for an unstable displaced fracture. These techniques are however associated with the potential for iatrogenic neurological injury. Vascular injury is also rare but must be recognised and treated promptly to avoid significant permanent morbidity.

Outcomes of 173 metacarpal and phalangeal fractures treated by intramedullary headless screw fixation with a 4-year follow-up

Surgical treatment of extra-articular metacarpal and phalangeal fractures should be considered when there is instability or in patients with high demand. To overcome the issues related to the use of Kirschner wires, external fixators, and open reduction and internal fixation procedures, intramedullary headless screw fixation (IHSF) is an alternative technique to achieve primary fracture stability and early return to daily activities. We report the data of the Italian Multicentric Intra-Medullary Experience, which includes 173 cases of extra-articular unstable fractures (38 phalanges and 135 metacarpals) treated with the IHSF. After surgery, patients underwent early mobilization without splinting. The results confirm the reliability of IHSF in cases with non-articular involvement, showing a good recovery rate in terms of bone healing and range of motion. Level of evidence: IV

Implants for trochanteric fractures in Norway: the role of the trochanteric stabilizing plate—a study on 20,902 fractures from the Norwegian hip fracture register 2011–2017

Background The trochanteric stabilizing plate (TSP) is used as an adjunct to the sliding hip screw (SHS) in unstable trochanteric and subtrochanteric fractures. We wanted to describe the choice of implant for trochanteric fractures with a focus on the TSP in Norway. Methods A total of 20,902 fractures from the Norwegian Hip Fracture Register treated surgically in 43 hospitals from 2011 to 2017 were included. Logistic regression analyses were performed to detect factors potentially influencing implant choice. Results The mean age was 83 years, and 15,137 (72%) were women. An SHS was used in 13,273 (63%) fractures, of them 4407 (33%) with a TSP. Fracture classification was the most important determinant of TSP. In cases where an SHS was used, the odds ratio (OR) for using a TSP was 14 for AO/OTA 31A2 fractures and 71 for AO/OTA 31A3 and subtrochanteric fractures, compared to AO/OTA 31A1 fractures. The probability of receiving a TSP was higher in urban, academic, and high-volume hospitals (OR 1.2 to 1.3) and lower in Central and Northern Norway (OR 0.3 to 0.7). The use of an intramedullary nail (IMN) (n = 7629 (36%)) was also to a degree decided by fracture classification (OR 1.8 to 5.3). However, hospital factors, with OR 0.1 to 0.4 for IMN in academic, urban, and high-volume hospitals and OR 1.5 to 2.6 outside South-Eastern Norway (all p < 0.001), were also important. Conclusions Fracture classification was the main determinant for TSP use. Any additional benefit from a TSP on postoperative fracture stability or clinical outcome needs to be clarified.