Automatic segmentation of femoral tumors by nnU-net.

Background: Metastatic femoral tumors may lead to pathological fractures during daily activities. A CT-based finite element analysis of a patient's femurs was shown to assist orthopedic surgeons in making informed decisions about the risk of fracture and the need for a prophylactic fixation. Improving the accuracy of such analyses ruqires an automatic and accurate segmentation of the tumors and their automatic inclusion in the finite element model.

The influence of femoral lytic tumors segmentation on autonomous finite element analysis.

Background: The validated CT-based autonomous finite element system Simfini (Yosibash et al., 2020) is used in clinical practice to assist orthopedic oncologists in determining the risk of pathological femoral fractures due to metastatic tumors. The finite element models are created automatically from CT-scans, assigning to lytic tumors a relatively low stiffness as if these were a low-density bone tissue because the tumors could not be automatically identified.

Hip Fracture Risk Assessment in Elderly and Diabetic Patients: Combining Autonomous Finite Element Analysis and Machine Learning.

Autonomous finite element analyses (AFE) based on CT scans predict the biomechanical response of femurs during stance and sidewise fall positions. We combine AFE with patient data via a machine learning (ML) algorithm to predict the risk of hip fracture. An opportunistic retrospective clinical study of CT scans is presented, aimed at developing a ML algorithm with AFE for hip fracture risk assessment in type 2 diabetic mellitus (T2DM) and non-T2DM patients.

On the influence of computed tomography's slice thickness on computer tomography based finite element analyses results.

Background: Patient-specific autonomous finite element analyses of femurs, based on clinical computed tomography scans may be used to monitor the progression of bone-related diseases. Some CT scan protocols provide lower resolution (slice thickness of 3 mm) that affects the accuracy. To investigate the impact of low-resolution scans on the CT-based finite element analyses results, identical CT raw data were reconstructed twice to generate a 1 mm ("gold standard") and a 3 mm slice thickness scans.

Can neck fractures in proximal humeri be predicted by CT-based FEA?

Background: Proximal humeri fractures at anatomical and surgical neck (∼5% and ∼50% incidence respectively) are frequent in elderly population. Yet, neither in-vitro experiments nor CT-based finite element analyses (CTFEA) have investigated these in depth. Herein we enhance (Dahan et al.

Assessing hip fracture risk in type-2 diabetic patients using CT-based autonomous finite element methods : a feasibility study.

Aims: Type 2 diabetes mellitus (T2DM) impairs bone strength and is a significant risk factor for hip fracture, yet currently there is no reliable tool to assess this risk. Most risk stratification methods rely on bone mineral density, which is not impaired by diabetes, rendering current tests ineffective. CT-based finite element analysis (CTFEA) calculates the mechanical response of bone to load and uses the yield strain, which is reduced in T2DM patients, to measure bone strength.

Patient-specific computed tomography-based finite element analysis: a new tool to assess fracture risk in benign bone lesions of the femur.

Background: Most benign active and latent lesions of proximal femur do not predispose a patient to a pathologic fracture. Nonetheless, there is a tendency to perform internal fixation due to the lack of accurate clinical tools that may reliably confirm low risk of pathologic fracture. As many as 30% of these surgeries may be unnecessary.

Strain shielding for cemented hip implants.

Background: Long-term survival of hip implants is of increasing relevance due to the rising life expectancy. The biomechanical effect of strain shielding as a result of implant insertion may lead to bone resorption, thus increasing risk for implant loosening and periprosthetic fractures. Patient-specific quantification of strain shielding could assist orthopedic surgeons in choosing the biomechanically most appropriate prosthesis.

New insights on the proximal femur biomechanics using Digital Image Correlation.

Finite element analyses (FEAs) of human femurs are mostly validated by ex-vivo experimental observations. Such validations were largely performed by comparing local strains at a small subset of points to the gold standard strain gauge (SG) measurements. A comprehensive full field validation of femoral FEAs including both strains and displacements using digital image correlation (DIC) full field measurements, especially at medial and lateral surfaces of the neck that experience the highest strains, provide new insights on femurs' mechanical behavior.

Finite element analyses for predicting anatomical neck fractures in the proximal humerus.

Background: Proximal humerus fractures which occur as a result of a fall on an outstretched arm are frequent among the elderly population. The necessity of stabilizing such fractures by surgical procedures is a controversial matter among surgeons. Validating a personalized FE analysis by ex-vivo experiments of humeri and mimicking such fractures by experiments is the first step along the path to determine the necessity of such surgeries.

A novel phase field method for modeling the fracture of long bones.

A proximal humerus fracture is an injury to the shoulder joint that necessitates medical attention. While it is one of the most common fracture injuries impacting the elder community and those who suffer from traumatic falls or forceful collisions, there are almost no validated computational methods that can accurately model these fractures. This could be due to the complex, inhomogeneous bone microstructure, complex geometries, and the limitations of current fracture mechanics methods.

Scanner influence on the mechanical response of QCT-based finite element analysis of long bones.

Patient-specific QCT-based finite element (QCTFE) analyses enable highly accurate quantification of bone strength. We evaluated CT scanner influence on QCTFE models of long bones. A femur, humerus, and proximal femur without the head were scanned with KHPO phantoms by seven CT scanners (four models) using typical clinical protocols.

Patient-specific finite element analysis of femurs with cemented hip implants.

Background: Over 1.6 million hip replacements are performed annually in Organisation for Economic Cooperation and Development countries, half of which involve cemented implants. Quantitative computer tomography based finite element methods may be used to assess the change in strain field in a femur following such a hip replacement, and thus determine a patient-specific optimal implant.

Pathological fracture risk assessment in patients with femoral metastases using CT-based finite element methods. A retrospective clinical study.

Physician recommendation for prophylactic surgical fixation of a femur with metastatic bone disease (MBD) is usually based on Mirels' criteria and clinical experience, both of which suffer from poor specificity. This may result in a significant number of these health compromised patients undergoing unnecessary surgery. CT-based finite element analyses (CTFEA) have been shown to accurately predict strength in femurs with metastatic tumors in an ex-vivo study.

Phase-field boundary conditions for the voxel finite cell method: Surface-free stress analysis of CT-based bone structures.

The voxel finite cell method uses unfitted finite element meshes and voxel quadrature rules to seamlessly transfer computed tomography data into patient-specific bone discretizations. The method, however, still requires the explicit parametrization of boundary surfaces to impose traction and displacement boundary conditions, which constitutes a potential roadblock to automation. We explore a phase-field-based formulation for imposing traction and displacement constraints in a diffuse sense.

Further experimental evidence of the compressibility of arteries.

Further experimental evidence on the compressibility of arteries under normal physiological pressure range is provided using the experimental apparatus introduced in Yosibash et al., JMBBM 39(2014):339-354. We enlarged the experimental database by including almost twice the number of experiments, we considered a different artery - the porcine common carotid that allowed longer and larger diameters.

Verified and validated finite element analyses of humeri.

Background: Although ~200,000 emergency room visits per year in the US alone are associated with fractures of the proximal humerus, only limited studies exist on their mechanical response. We hypothesise that for the proximal humeri (a) the mechanical response can be well predicted by using inhomogeneous isotropic material properties, (b) the relation between bone elastic modulus and ash density (E(ρash)) is similar for the humerus and the femur, and may be general for long bones, and (c) it is possible to replicate a proximal humerus fracture in vitro by applying uniaxial compression on humerus׳ head at a prescribed angle.

Methods: Four fresh frozen proximal humeri were CT-scanned, instrumented by strain-gauges and loaded at three inclination angles.

Uncertainty quantification for personalized analyses of human proximal femurs.

Computational models for the personalized analysis of human femurs contain uncertainties in bone material properties and loads, which affect the simulation results. To quantify the influence we developed a probabilistic framework based on polynomial chaos (PC) that propagates stochastic input variables through any computational model. We considered a stochastic E-ρ relationship and a stochastic hip contact force, representing realistic variability of experimental data.

The physiologic and histologic properties of the distal internal thoracic artery and its subdivisions.

Objective: We compared the flow rates, reactivity, and morphology of the distal internal thoracic artery and its branches, the superior epigastric and musculophrenic arteries, to test their applicability as possible conduits in coronary artery bypass grafting surgeries.

Methods: Skeletonized internal thoracic artery and subdivisions of patients undergoing coronary artery bypass grafting were studied intraoperatively (n = 100) for flow and length measurements and in vitro in organ baths (n = 58) for active response to norepinephrine. Quantitative microscopic analysis of the muscle density and degree of intimal hyperplasia was performed.

Stochastic description of the peak hip contact force during walking free and going upstairs.

Uncertainty quantification for the response of a patient specific femur is mandatory when advocating finite element (FE) models in clinical applications. Reliable stochastic descriptions of physiological hip contact forces are an essential prerequisite for such an endeavor. We therefore analyze the in-vivo available data of seven individuals from HIP98 and OrthoLoad with the objective of characterizing the variability of the peak hip contact force magnitude and two corresponding spatial angles (in sagittal and frontal plane) during walking free and going upstairs.

Predicting the stiffness and strength of human femurs with real metastatic tumors.

Background: Predicting patient specific risk of fracture in femurs with metastatic tumors and the need for surgical intervention are of major clinical importance. Recent patient-specific high-order finite element methods (p-FEMs) based on CT-scans demonstrated accurate results for healthy femurs, so that their application to metastatic affected femurs is considered herein.

Methods: Radiographs of fresh frozen proximal femur specimens from donors that died of cancer were examined, and seven pairs with metastatic tumor were identified.

Experimental evidence of the compressibility of arteries.

A definitive answer to the question whether artery walls are incompressible is to our opinion not yet categorically provided. Experimental-based evidence on the level of compressibility in artery walls is not easily achieved because of the difficulties associated with the measurement of very small differences in volumes under physiological pressure in these biological tissues. Past experiments aimed at addressing the question considered different species, different arteries, the experimental devices were not accurate enough and a statistical analysis of the results was missing.

Patient-specific FE analyses of metatarsal bones with inhomogeneous isotropic material properties.

The mechanical response of human metatarsal bones is of importance in both research and clinical practice, especially when associated with the correction of Hallux Valgus. Verified and validated patient-specific finite-element analysis (FEA) based on CT scans developed for human femurs are extended here to the first and second metatarsal bones. Two fresh-frozen metatarsal #1 and five metatarsal #2 bones from three donors were loaded in-vitro at three different angles.

Toward verified and validated FE simulations of a femur with a cemented hip prosthesis.

Background: Verified and validated CT-based high-order finite element (FE) methods were developed that predict accurately the mechanical response of patient-specific intact femurs. Here we extend these capabilities to human femurs undergoing a total hip replacement using cemented prostheses.

Methods: A fresh-frozen human femur was CT-scanned and thereafter in vitro loaded in a stance position until fracture at the neck.

Prediction of the mechanical response of the femur with uncertain elastic properties.

A mandatory requirement for any reliable prediction of the mechanical response of bones, based on quantitative computer tomography, is an accurate relationship between material properties (usually Young's modulus E) and bone density ρ. Many such E-ρ relationships are available based on different experiments on femur specimens with a large spread due to uncertainties. The first goal of this study is to pool and analyze the relevant available experimental data and develop a stochasticE-ρ relationship.