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Finite element analysis of pectus carinatum surgical correction via a minimally invasive approach
Computer Methods In Biomechanics & Bio Engineering
Abstract and Figures
Pectus carinatum (PC) is a chest deformity caused by a disproportionate growth of the costal cartilages compared to the bony thoracic skeleton, pulling the sternum towards, which leads to its protrusion. There has been a growing interest on using the 'reversed Nuss' technique as a minimally invasive procedure for PC surgical correction. A corrective bar is introduced between the skin and the thoracic cage and positioned on top of the sternum highest protrusion area for continuous pressure. Then, it is fixed to the ribs and kept implanted for about 2-3 years. The purpose of this work was to (a) assess the stresses distribution on the thoracic cage that arise from the procedure, and (b) investigate the impact of different positioning of the corrective bar along the sternum. The higher stresses were generated on the 4th, 5th and 6th ribs backend, supporting the hypothesis of pectus deformities correction-induced scoliosis. The different bar positioning originated different stresses on the ribs' backend. The bar position that led to lower stresses generated on the ribs backend was the one that also led to the smallest sternum displacement. However, this may be preferred, as the risk of induced scoliosis is lowered.
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... Pectus carinatum (PC) is a chest deformity caused by disproportionate growth of the costal cartilages compared with the bony thoracic skeleton, which pulls the sternum forwards, leading to its protrusion, thus resulting in a deformity commonly known as "pigeon chest" [1]. The incidence rate of pectus carinatum is 1:1000 births [2], and is more common in males than females with a ratio of about 4:1 [3]. ...
Pectus carinatum (PC) is a chest deformity caused by disproportionate growth of the costal cartilages compared with the bony thoracic skeleton, pulling the sternum forwards and leading to its protrusion. Currently, the most common non-invasive treatment is external compressive bracing, by means of an orthosis. While this treatment is widely adopted, the correct magnitude of applied compressive forces remains unknown, leading to suboptimal results. Moreover, the current orthoses are not suitable to monitor the treatment. The purpose of this study is to design a force measuring system that could be directly embedded into an existing PC orthosis without relevant modifications in its construction. For that, inspired by the currently commercially available products where a solid silicone pad is used, three concepts for silicone-based sensors, two capacitive and one magnetic type, are presented and compared. Additionally, a concept of a full pipeline to capture and store the sensor data was researched. Compression tests were conducted on a calibration machine, with forces ranging from 0 N to 300 N. Local evaluation of sensors’ response in different regions was also performed. The three sensors were tested and then compared with the results of a solid silicon pad. One of the capacitive sensors presented an identical response to the solid silicon while the other two either presented poor repeatability or were too stiff, raising concerns for patient comfort. Overall, the proposed system demonstrated its potential to measure and monitor orthosis’s applied forces, corroborating its potential for clinical practice.
... One study was identified by backward citation. Eventually, 48 studies were included: 19 in category I [ 5 , 9 , 16-32 ], 21 in category II , and 8 in category III [54][55][56][57][58][59][60][61] ( Figure 1 ). ...
Background: The ceramic coated implant (CCI) Evolution was a third-generation implant design used in approximately 2000 total ankle replacements (TARs) between 2003 and 2016. Because this implant was abandoned, long-term follow-up studies are lacking.
Methods: All patients undergoing TAR using a CCI prosthesis between 2004 and 2012 were included for analysis. Preoperatively the tibiotalar alignment was measured, and postoperatively the patients were followed up clinically, with radiographs and by questionnaire. The primary outcome was implant survival at 10 years of follow-up. Implant survival was also compared for (1) inflammatory joint disease vs noninflammatory joint disease and (2) preoperative tibiotalar neutral vs varus or valgus alignment. The secondary outcomes were complications, reoperations, and function (assessed by patient-reported outcome measures).
Results: Two hundred fifty-four TARs were performed in 237 patients. Two hundred twelve additional procedures were performed to achieve stable ankles. At 10-year follow-up, the survival was 67.5%, with an average time to revision of 4.5 years. The 10-year survival of the inflammatory joint disease group was 76.8% and of the noninflammatory joint group 63.1% (P = .44). In 248 TARs, the preoperative tibiotalar alignment was measured; (62% neutral, 25% varus, and 13% valgus), these showed 10-year survival rates of 74.7%, 48.2%, and 68.9% respectively (P = .07). The complication rate was 54%; 37% of patients underwent reoperation. At a mean of 8.5 years, postoperative satisfaction scored an average of 7.0 (SD 2.26) on a 0- to 10-point numeric rating scale. The mean Foot and Ankle Ability Measure sports subscore was 24.7, the mean Foot and Ankle Outcome Score (FAOS) sports subscore was 42.8, and the mean 36-Item Short Form Health Survey score was 40.0. Regarding daily activities, the mean FAOS was 81.0.
Conclusion: This is currently the sole study reporting the long-term results of the CCI prosthesis. The survival and functional outcomes were inferior to other third-generation mobile-bearing ankle implants.
... The stiffness was calculated as the relation between the force applied to the sternum and its displacement in the same direction at the point where the HI was measured. The large displacement non-linear solution was used to ensure the accuracy of the simulation results [16,23]. ...
OBJECTIVES
To study the influence of sternal transection and costal chondrotomies on the stiffness and stresses in the rib cage of adult patients undergoing Nuss pectus excavatum procedure.
METHODS
Four pectus excavatum models with different Haller indexes were created by parameterizing a 3D model of a rib cage obtained based on a computed tomography scan of a patient with no pectus deformity. Using the finite element method, insertion of intrathoracic bars into all models was simulated in 3 conditions, namely, non-intervened, transverse sternal section and costal chondrotomies. Stiffness, stress distribution and maximum stresses for each case were obtained and compared.
RESULTS
Transverse sternotomy provided a reduction of 44% to 54% in the stiffness of the rib cage, depending on the Haller index analysed, while chondrotomies promoted a stiffness reduction of 70%. Stress distribution in the rib cage followed similar pattern for all the tested Haller index, but the maximum stress decreased by 36% when performing a transverse sternotomy, whereas when performing costal chondrotomies, it decreased by 47%.
CONCLUSIONS
Computational results report that transverse sternotomy reduces appreciably the stiffness of the rib cage, while costal chondrotomies promote even a higher stiffness reduction. Thus, these surgical procedures could improve the clinical outcomes of adult patients undergoing a pectus excavatum repair.
... The authors declare the absence of obvious and potential conflicts of interest related to the publication of this article. ковом возрасте [4,5,6,7]. Использование известных современных малоинвазивных технологий лечения деформаций грудной клетки при данном пороке значимого клинического эффекта не дает [8][9][10][11]. Попытки резекции хрящей деформированных ребер являются весьма травматичным вмешательством [12,13,14,15]. ...
Цель : Демонстрация случаев эффективного лечения редкой рукояточно-хрящевой формы деформации грудной клетки у детей. Методы : Оперативная коррекция рукояточно-хрящевой формы килевидной деформации грудной клетки проведена трем подросткам в возрасте 13–14 лет, что составило 2,2% от всех больных с КДГК. При лечении данной редкой формы деформации использована оригинальная методика, предусматривающая клиновидную резекцию грудины в месте ее деформации (на границе рукоятки и тела), видеоассистированную продольную неполную стернотомию, элевацию тела грудины с применением Nuss-процедуры, используемой для исправления воронкообразной деформации грудной клетки. Удаление металлоконструкции, обеспечивающей стабильное взаимоотношение грудинно-реберного комплекса в корригированном положении, проводилось через год. Результаты : При КДГК отсутствовали функциональные нарушения со стороны грудной клетки. Операция выполнялась по косметическим показаниям. У двоих подростков лечение закончено 4 года назад. Форма грудной клетки близка к правильной. Третий пациент находится на этапе лечения с установленной металлоконструкцией. Во всех трех случаях подростки и их родители удовлетворены результатами операции, эстетическим состоянием передней поверхности грудной клетки. Таким образом, использование вышеописанной лечебной тактики при данной форме деформации грудной клетки позволило получить хороший косметический результат.
In this study, we propose a new phenomenological approach to human chest modeling. We model the chest as an elastic truss consisting of stiff beams connected by spherical joints that hinder the relative rotation of the beams. We used this model to simulate the rib flaring effect, which is a side effect for bracing treatment of patients with pectus carinatum. We used the Ansys software that allowed us to apply finite element method (FEM) to build the model of a chest of a real patient using geometry from the CT scan. We applied a compressive force to a keel of the model and observed the effect of rib flaring. We also examined the applicability of Ansys Mechanical for modeling trusses with beams and spiral springs. For this purpose, we built two simplified models of a system of two beams under compression and then compared the theoretical solution of its equilibrium problem with the solution obtained in Ansys.
Introduction:
Modeling rib fracture stability is challenging. Computer generated finite element analysis(FEA) is an option for assessment of chest wall stability(CWS). The objective is to explore FEA as a means to assess CWS, hypothesizing it is a reliable approach to better understand rib fracture pathophysiology.
Methods:
Thoracic anatomy was generated from standardized skeletal models with internal/external organs, soft tissue and muscles using DICOM data. Material properties were assigned to bone, cartilage, skin and viscera. Simulation was performed using ANSYS Workbench. Meshing the model was completed identifying 1.3 and 2.1 million elements and nodes. An implicit solver was used for a linear/static finite element analysis with all bony contacts identified and applied. All material behavior was modeled as isotropic/linear elastic.6 load cases were evaluated from a musculoskeletal AnyBody model; forward flexion, right/left lateral bending, right/left axial rotation and 5 kg weight arm lifting. Standard application points, directions of muscle forces, and joint positions were applied.10 fracture cases (unilateral and bilateral) were defined and 66 model variations were simulated. 43 points were applied to each rib in the mid-/anterior axillary lines to assess thoracic stability. Three assessment criteria were used to quantify thoracic motion: normalized mean absolute error(NMAE), normalized root mean square error(NRMSE), and normalized interfragmentary motion(NIFM).
Results:
All three analyses demonstrated similar findings that rib fracture deformation and loss of CWS was highest for left/right axial rotation. Increased number of ribs fracture demonstrated more fracture deformation and more loss of CWS compared to a flail chest segment involving less ribs. A single rib fracture is associated with ~3% loss of CWS. NIFM deformation can increases by 230%. CWS can decrease by over 50% depending on fracture patterns.
Conclusion:
FEA is a promising technology for analyzing CWS. Future studies need to focus on clinical relevance and application of this technology.
Level of evidence:
IV.
Pectus carinatum (PC) is a chest deformity caused by disproportionate growth of the costal cartilages compared to the bony thoracic skeleton, pulling the sternum towards, which leads to its protrusion. Currently, the most common non-invasive treatment is external compressive bracing, by means of an orthosis. However, the current orthoses are not suitable to continuously monitor the forces applied to the PC, and consequently to monitor the treatment. In this work, we propose a new design of a capacitive pressure sensor to be embedded into current commercially available orthosis. Finite element analysis methods are used to study the electromechanical behavior of the projected sensors. Compression tests were conducted on both simulation and experimental sensor and similar capacitance result was achieved on both cases for forces between 0N and 300N, validating the construction process.
Introduction:
Pectus excavatum and scoliosis are associated conditions with a high rate of coincidence. However, there are no reports to guide surgeons on the management of adolescents with moderate scoliosis and pectus excavatum, because there are conflicting conclusions in the literature regarding how the Nuss procedure with substernal bar affects scoliosis.
Cases:
In 2017, we encountered two patients with moderate scoliosis treated with a spinal orthosis. After undergoing the Nuss procedure for pectus excavatum, their scoliosis acutely progressed into surgical magnitude requiring posterior instrumented spinal fusion. The first patient progressed 26° despite the pre-Nuss radiographs showing him to be Risser 4/5, while the second patient also progressed 26° from the Nuss procedure. Both patients acknowledged noncompliance with brace wear because of discomfort after the Nuss procedure. However, their progression rate still doubles the rate of reported rapid accelerators, indicating that a significant component of curve progression is directly attributed to forces on the spine from the corrective maneuver with substernal bar.
Conclusion:
The purpose of this case report is to describe the features of these two patients to help with clinical decision-making in patients with moderate scoliosis (curves >25°) who are contemplating the Nuss procedure for correction of pectus excavatum. We caution patients and providers that spinal deformity could worsen with surgical intervention of the pectus excavatum via the Nuss procedure and necessitate scoliosis surgery.
Simulation technology in mechanical engineering during product development is used routinely to reduce development time, prototypes and development cost. Nevertheless modelling and simulation technology of the human body has been mainly applied to component analysis or crash/accident simulation. The objective of this research is to explore the possibility of reducing human and animal trials for the development and optimisation of surgical methods and materials. To achieve these objectives, an in vivo and person specific simulation model is required. Leaning upon the research involving human being in the mechanical engineering, it was decided to experiment in vivo using a 50th percentile Adult Male. After obtaining ethics approval, a volunteer was selected. Three MRI scans of this volunteer were performed, each covering from the C4 vertebral level to the pubic symphysis; in two composed 3D volumes and each performed under different chest loading conditions. The 3 D MRI dataset was segmented and a Catia CAD-model created. One can manipulate and use this CAD-model derived from a human volunteer like any CAD-model in mechanical engineering. A simulation model is created from the CAD-model and non-linear analysis is carried out. The comparison of simulation results with that of test is good.
Nuss Orthopedic of Pectus Excavatum(PE) is a novel minimal invasive surgical technique for the treatment of PE, however, the surgery will fail as the Nuss bar is slipped or rotated. In this paper, the preoperative and postoperative helical CT scans were carried out for one child patient of PE, and the preoperative and postoperative D model for thorax is built according to the CT. To preoperative thorax model of PE, the Nuss orthopedic process is simulated with finite element method, and a compare made between the simulated results and the postoperative model. The results show as the depressed sternum was jacking to normal position gradually by Nuss bar, the sternum, the ribs and the rib cartilages will all move upward which make the Nuss bar support the sternum at the location lower about 1~6 mm than the end of depressed sternum end. However, original plan is that the bar should be supported just at the end of depressed sternum. After the bar is fixed, there is a torque on the bar for the pressure imposed by sternum and the force produced by the fixed place of bar forms a pair of torque. This torque may be the reason for the failure of surgery. The improvement is that the fix place of bar should be move upward 1~6mm or a distance of one rib.
In this study, a three-dimensional finite element (FE) model based on the specific anatomy of a patient presenting a femoroacetabular impingement of the 'cam'-type is developed. The FE meshes of the structures of interest are obtained from arthrographic magnetic resonance images. All soft tissues are considered linear elastic and isotropic, and the bones were assumed rigid. A compression of the femur on the acetabular cavity as well as flexural movements and internal rotations are applied. Stresses and contact pressures are evaluated in this patient-specific model in order to better interpret the mechanism of aggression of the femoral and acetabular cartilages. The corresponding results are presented and discussed. The values obtained for the contact pressures are similar to those reported by other models based on idealised geometries. An FE analysis of a non-cam hip is also performed for comparison with the pathological case.
The minimally invasive pectus excavatum repair as described by Nuss et al. is rapidly gaining acceptance as an effective method of repair of severe pectus excavatum deformities in the pediatric population. It potentially offers several advantages over previous techniques. The incidence of major complications of the procedure has been reduced by recent modifications including utilization of video-assisted thoracoscopy during placement of the Lorenz pectus bar as wen as utilizing the pectus bar stabilizer that provides more rigid fixation of the strut. We report two cases of acquired thoracic scoliosis following minimally invasive repair of severe pectus excavatum deformity. This particular complication has not been reported in previous literature and warrants concern. In both cases the thoracic scoliosis slowly improved with physical therapy and range-of-motion exercises.
The three deformities of the anterior chest wall commonly referred to as funnel chest, pigeon breast, and Harrison's groove I believe1,6-8 to be congenital and produced during infancy by abnormal, unbalanced contractions of an abnormally developed diaphragm. This etiology of pigeon breast, when first proposed in 1949,1 was justifiably questioned because of the paucity of the evidence then submitted. I shall present further evidence to support this theory. Until recently rickets was generally accepted as the etiologic factor in this deformity, and little has been written concerning it beyond Lester's2 proposal that it is primarily due to the abnormal overgrowth of the involved ribs. Recently, Chin,3 in the 1956 Hunterian Lecture delivered before the Royal College of Surgeons, came to the support of my diaphragmatic theory with biopsy and autopsy studies of diaphragms, as well as the description of a very effective operative procedure based on
We report a general purpose mesh generator for creating finite-element surface or volumetric mesh from 3D binary or gray-scale medical images. This toolbox incorporates a number of existing free mesh processing utilities and enables researchers to perform a range of mesh processing tasks for image-based mesh generation, including raw image processing, surface mesh extraction, surface re-sampling, and multi-scale/adaptive tetrahedral mesh generation. We also implemented robust algorithms for meshing open-surfaces and sub-region labeling. Atomic meshing utilities for each processing step can be accessed with simple interfaces, which can be streamlined or executed independently. The toolbox is compatible with Matlab or GNU Octave. We demonstrate the applications of this toolbox for meshing a range of challenging geometries including complex vessel network, human brain and breast.
In this paper, polyurethane matrix composites reinforced with aluminum oxide (Al2O3) particles were fabricated to improve the wear resistance of polyurethane (PUR) elastomer working in erosion conditions, the effects of Al2O3 content (0–64 wt%) and different silane coupling agents (i.e. A-1100 and A-187) on the mechanical properties and erosion wear resistances of the composites were investigated. Both the tensile strengths and the elongations at rupture of the composites were found to decrease with the content of Al2O3 particles; however, the hardness increased gradually. The composites treated with silane coupling agent A-1100 had higher tensile properties (tensile strength and elongation at rupture) than those treated with silane coupling agent A-187.Erosion tests were carried out on a self-made jet erosion machine. According to the results, the wear resistances of the two composites first increased until reaching a maximum, then decreased, with the increasing content of Al2O3 particles. The composites treated with silane coupling agent A-1100 had higher wear resistances than those treated with silane coupling agent A-187 due to the higher reaction activity of A-1100 with the matrix than A-187.The fracture surfaces and erosion area of the composites were analyzed with scanning electron microscope (SEM) and the erosion wear mechanism for the composites was discussed.
Under the lubrication by the imitated human physiological solution, the fretting behaviors of flat cortical bone were investigated against titanium (TA2) and its alloy (TC4) ball counterpart. The friction logs and coefficients were recorded automatically. The worn surfaces of cortical bone were analyzed by means of laser confocal scanning microscopy. The results show that friction logs transform from partial slip directly to gross slip without mixed regime. The wear depths of bone generally increase with the friction coefficient. The worn scar area on bone is a little bit larger than that on ball surface. The wear depths on Ti ball were only several micrometers, which were much less than those on bone. The comparison of fretting behaviors between the bone-TA2 pair and bone-TC4 pair were of particular interest. The friction coefficient of bone-TC4 pair is higher than that of bone-TA2 pairs. The maximum wear depth on bone against TA2 is about 40% the value of that on bone against TC4. The wear adaptability of bone-TA2 pair is better than that of bone-TC4 pair. The abrasive wear and delamination related to the microstructure of bone are observed on the wear scar of cortical bone.