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ABSTRACT The principal subject matter of this work is the application of laser-induced breakdown spectroscopy for the multi-elemental analytical characterization of different qualities of solid silicon. The physical process upon which the technique is based is the temporally resolved observation of emission spectra emitted by a micro-plasma generated by a laser focused on the surface of a given sample. The optimal environmental parameters such as the composition of the buffering gas for the identification and measurement of several metallic, non-metallic, and dopant impurities were determined. Particular attention was given to boron. A detection limit of 2.10−4 mg/g of boron was found using a calibration curve, which was made in the range of 1 to 100 ppmw. Silicon samples from different production techniques (4C and directional solidification), which permit the segregation of different impurities along the length of the silicon ingot were analyzed using laser-induced breakdown spectroscopy. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ar+H2 RF thermal plasma spraying is used to melt, purify and hydrogenate metallurgical silicon particles in order to elaborate a thin layer for photovoltaïcs applications. Hydrogenation and purification phenomena have been analysed by a spectroscopic diagnostic. Transitions of excited argon, hydrogen and silicon detected have been used to calculate the electronic density, electronic temperature and silicon vapor content in the plasma flow. [ABSTRACT FROM AUTHOR]

the residence time of the particles in reactive thermal plasma governs mechanisms occuring at high temperature. (solid → liquid, liquid → vapor and oxydation Si[sub1] + O[subg] → Si O[subg] ). The goal is to control the process of particles purification with a partial evaporation in order to have a good yield of manufacture of ultra-pure silicon. In this study, it is evaluated from L-D.A. measurements, which provide the particle velocity. Experimental measurements by optical Emission Spectroscopy (O.E.S.), confirm the gas temperature range surrounding the particle, down stream all along the 30 cm trajectories. The most remarkable result of particle velocity obtained from L.D.A. measurements on one hand, and particle velocity obtained from modeling calculation and ab-initio numerical calculation on the other hand are in a good fitting, which confirm particles residence time τ[subPart]. along 30 cm trajectory. [ABSTRACT FROM AUTHOR]

The hydrogenation of silicon material proves great advantages concerning its photovoltaic properties and secure a key for the elimination of crystalline defects during the basaltic growth of the crystal. In our process, silicon particles are hydrogenated in the thermal plasma torch at atmospheric pressure. So, the aim of this work is to characterise the physical properties of the plasma flow in order to understand the interaction appearing between particles and hydrogenated plasma flow during the treatment. Highly excited states of atomic hydrogen, responsible of the silicon hydrogenation, have been detected in the plasma. These atomic hydrogen lines have been used to determine the electronic density on the plasma axis. Electronic temperature of different plasma mixture have been obtained by the Boltzmann plot method. [ABSTRACT FROM AUTHOR]

Magnesium alloys present a compelling prospect for absorbable implant materials in orthopedic and trauma surgery. This study evaluates an ultra-high purity, lean magnesium-calcium alloy (X0), both with and without plasma electrolytic oxidation (PEO) surface modification, in comparison to a clinically utilized WE43 magnesium alloy. It is shown that the mechanical properties of X0 can be tuned to yield a high-strength material suitable for bone screws (with an ultimate tensile strength of 336 MPa) or a ductile material appropriate for intraoperatively deformable plates (with an elongation at fracture of 24 %). Four plate-screw combinations were implanted onto the pelvic bones of six sheep without osteotomy for 8 weeks. Subsequent analysis utilized histology, micro-computed tomography, and light and electron microscopy. All implants exhibited signs of degradation and hydrogen-gas evolution, with PEO-coated X0 implants demonstrating the least volume loss and the most substantial new-bone formation on the implant surface and surrounding cancellous bone. Furthermore, the osteoconductive properties of the X0 implants, when uncoated, exceeded those of the uncoated WE43 implants, as evidenced by greater new-bone formation on the surface. This osteoconductivity was amplified with PEO surface modification, which mitigated gas evolution and enhanced osseointegration, encouraging bone apposition in the cancellous bone vicinity. These findings thus indicate that PEO-coated X0 implants hold substantial promise as a biocompatible and absorbable implant material., Competing Interests: LB and JFL are shareholders of Kairos Medical AG, an ETH Zurich spin-off working on absorbable magnesium-based implants. LB is currently employed by the company. This study and analysis was performed before its foundation., (© 2024 The Authors.)

Background: Imaging biomarkers are emerging as non-invasive predictors of cancer prognosis and clinical outcome. We assessed tumor-specific ("radiomics") and body composition imaging features ("morphomics") extracted from baseline pre-treatment CT for prediction of recurrence in patients with stage III colorectal cancer (CRC)., Methods: Patients with newly diagnosed stage III CRC were enrolled in this prospective observational study. Patients with available preoperative scans were included (N = 101). The tumor, if visible, was manually segmented and first-order radiomics features were extracted with a commercially available software. The morphomics features (reflecting muscle, fat, and bone characteristics) were extracted in a standardized fashion using a proprietary software and the values were adjusted and normalized based on a reference standard. Time to recurrence was the final outcome. Correlation between demographics, clinical features, radiomics, and morphomics features and outcome were assessed using univariate and multivariate tests as well as Kaplan-Meier and log-rank tests., Results: Morphomic analysis was performed in all 101 patients. 60 patients had discrete tumors suitable for radiomics analysis. These patients had lower ECOG score (p < 0.05), more muscle mass (p > 0.05), and lower fat density (p > 0.05) compared to the patients in whom radiomics analysis could not be performed. Pathological stage (HR: 2.69; p = 0.03), CEA level after surgery (HR: 1.11 for 1 ng/mL; p < 0.005), bone mineral density (HR: 1.01 for 1 Hounsfield Unit; p < 0.01), and tumor skewness (HR: 0.33 for 1 unit; p < 0.05) had association with recurrence based on both univariate and multivariate analyses. A model using Cox's regression analyses was able to divide the patients into low-, medium-, and high-risk for recurrence., Conclusions: Both radiomics and morphomics features were independently associated with the risk of CRC recurrence and, when combined, each contributed valuable information to explain risk of recurrence., Trial Registration: Clinical trial.gov NCT02842203. Patient recruitment occurred between 22/07/2016 and 18/03/2020., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: To determine the comparative accuracy and precision of routine magnetic resonance imaging (MRI) versus magnetic resonance (MR) arthrogram in measuring labral tear size as a function of time from a shoulder dislocation., Methods: We retrospectively evaluated consecutive patients who underwent primary arthroscopic stabilization between 2012 and 2021 in a single academic center. All patients completed a preoperative MRI or MR arthrogram of the shoulder within 60 days of injury and subsequently underwent arthroscopic repair within 6 months of imaging. Intraoperative labral tear size and location were used as standards for comparison. Three musculoskeletal radiologists independently interpreted tear extent using a clock-face convention. Accuracy and precision of MR labral tear measurements were defined based on location and size of the tear, respectively. Accuracy and precision were compared between MRI and MR arthrogram as a function of time from dislocation., Results: In total, 32 MRIs and 65 MR arthrograms (total n = 97) were assessed. Multivariate analysis demonstrated that intraoperative tear size, early imaging, and arthrogram status were associated with increased MR accuracy and precision (P < .05). Ordering surgeons preferred arthrogram for delayed imaging (P = .018). For routine MRI, error in accuracy increased by 3.4° per day and error in precision increased by 2.3° per day (P < .001) from time of injury. MR arthrogram, however, was not temporally influenced. Significant loss of accuracy and precision of MRI compared with MR arthrogram occurred at 2 weeks after an acute shoulder dislocation., Conclusions: Compared with MR arthrogram, conventional MRI demonstrates time-dependent loss of accuracy and precision in determining shoulder labral tear extent after dislocation, with statistical divergence occurring at 2 weeks., Level of Evidence: Level II, retrospective radiographic diagnostic study., Competing Interests: Disclosures The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: T.C. reports a relationship with Sustain Surgical that includes board membership and equity or stocks, has a patent pending to the Hospital for Special Surgery. B.L. reports a relationship with Mid-Atlantic Surgical Systems that includes funding grants. A.L. reports a relationship with Arthrex and Stryker that includes consulting or advisory, funding grants, and speaking and lecture fees; a relationship with Mid-Atlantic Surgical Systems that includes funding grants; and is an Editorial Board member of Arthroscopy. All other authors (S.C., J.G., A.C., C.A., S.D., R.R., M.C., N.D., J.H.) declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Full ICMJE author disclosure forms are available for this article online, as supplementary material., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

In large animal studies, the mechanical reintegration of the bone fragments is measured using postmortem physical testing, but these assessments can only be performed once, after sacrifice. Image-based virtual mechanical testing is an attractive alternative because it could be used to monitor healing longitudinally. However, the procedures and software required to perform finite element analysis (FEA) on subject-specific models for virtual mechanical testing can be time consuming and costly. Accordingly, the goal of this study was to determine whether a simpler image-based geometric measure-the torsion constant, sometimes known as polar moment of inertia-can be reliably used as a surrogate measure of bone healing in large animals. To achieve this, postmortem biomechanical testing and microCT scans were analyzed for a total of 33 operated and 20 intact ovine tibiae. An image-processing procedure to compute the attenuation-weighted torsion constant from the microCT scans was developed in MATLAB and this code has been made freely available. Linear regression analysis was performed between the postmortem biomechanical data, the results of virtual mechanical testing using FEA, and the torsion constants measured from the scans. The results showed that virtual mechanical testing is the most reliable surrogate measure of postmortem torsional rigidity, having strong correlations and high absolute agreement. However, when FEA is not practical, the torsion constant is a viable alternative surrogate measure that is moderately correlated with postmortem torsional rigidity and can be readily calculated., (© 2024 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Background: Muscle edema formation and inflammatory processes are early manifestations of acute rotator cuff lesions in sheep. Histological analysis of affected muscles revealed edema formation, inflammatory changes, and muscle tissue disruption in MRs., Hypothesis: Edema contributes to inflammatory reactions and early muscle fiber degeneration before the onset of fatty infiltration., Study Design: Controlled laboratory study., Methods: Osteotomy of the greater tuberosity, including the insertion of the infraspinatus tendon, was performed on 14 sheep. These experimental animal models were divided into 2 groups: a nontrauma group with surgical muscle release alone (7 sheep) and a trauma group with standardized application of additional trauma to the musculotendinous unit (7 sheep). Excisional biopsy specimens of the infraspinatus muscle were taken at 0, 3, and 4 weeks., Results: Edema formation was histologically demonstrated in both groups and peaked at 3 weeks. At 3 weeks, signs of muscle fiber degeneration were observed. At 4 weeks, ingrowth of loose alveolar and fibrotic tissue between fibers was detected. Fatty tissue was absent. The diameter of muscle fibers increased in both groups, albeit to a lesser degree in the trauma group, and practically normalized at 4 weeks. Immunohistology revealed an increase in macrophage types 1 and 2, as well as inflammatory mediators such as prostaglandin E2 and nuclear factor kappa-light-chain-enhancer of activated B cells., Conclusion: Early muscle edema and concomitant inflammation precede muscle fiber degeneration and fibrosis. Edema formation results from tendon release alone and is only slightly intensified by additional trauma., Clinical Relevance: This study illustrates that early edema formation and inflammation elicit muscle fiber degeneration that precedes fatty infiltration. Should this phenomenon be applicable to human traumatic rotator cuff tears, then surgery should be performed as soon as possible, ideally within the first 21 days after injury., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded by a grant from FORE (Foundation for research and teaching in the field of orthopaedic surgery, trauma, sports medicine, and imaging of the musculoskeletal system; grant No. FORE 2023-32). A.L. has received consulting fees from Arthrex, Medacta, Enovis, and Stryker and royalties from Stryker and Medacta; and is the founder of FORE, Med4Cast, and BeeMed. K.W. has received consulting fees from Zimmer Biomet. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

None., Competing Interests: Declaration of Competing Interest The authors have no conflicts of interest to disclose., (Copyright © 2023. Published by Elsevier Inc.)

The goal of this study was to develop an image analysis algorithm for quantifying the effects of remodeling on cortical bone during early fracture healing. An adaptive thresholding technique with boundary curvature and tortuosity control was developed to automatically identify the endocortical and pericortical boundaries in the presence of high-gradient bone mineral density (BMD) near the healing zone. The algorithm successfully segmented more than 47,000 microCT images from 12 healing ovine osteotomies and intact contralateral tibiae. Resampling techniques were used to achieve data dimensionality reduction on the segmented images, allowing characterization of radial and axial distributions of cortical BMD. Local (transverse slice) and total (whole bone) remodeling scores were produced. These surrogate measures of cortical remodeling derived from BMD revealed that cortical changes were detectable throughout the region covered by callus and that the localized loss of cortical BMD was highest near the osteotomy. Total remodeling score was moderately and significantly correlated with callus volume and mineral composition ( r > 0.64, p < 0.05), suggesting that the cortex may be a source of mineral needed to build callus., Competing Interests: Declaration of Interest Statement The authors have no conflicts of interest relevant to this work.

Background: Arthroscopic repair of large rotator cuff tendon tears is associated with high rates of retear. Construct failure often occurs at the suture-tendon interface. Patch augmentation can improve mechanical strength and healing at this interface., Purpose: To introduce a novel technique for suture-free attachment of an overlaid patch and evaluate its biomechanical strength and biological performance., Study Design: Descriptive and controlled laboratory studies., Methods: An established ovine model of partial infraspinatus tendon resection and immediate repair was used. After a nonwoven polyethylene terephthalate patch was overlaid to the resected tendon, a barbed microblade was used to draw fibers of the patch directly into the underlying tissue. In vivo histological assessment of healing was performed at 6 and 13 weeks after implantation. Ex vivo models were used to characterize primary repair strength of the suture-free patch fixation to tendon. Additional ex vivo testing assessed the potential of the technique for patch overlay augmentation of suture-based repair., Results: The in vivo study revealed no macroscopic evidence of adverse tissue reactions to the interlocked patch fibers. Histological testing indicated a normal host healing response with minimal fibrosis. Uniform and aligned tissue ingrowth to the core of the patch was observed from both the tendon and the bone interfaces to the patch. There was no evident retraction of the infraspinatus muscle, lengthening of the tendon, or tendon gap formation over 13 weeks. Ex vivo testing revealed that direct patch interlocking yielded tendon purchase equivalent to a Mason-Allen suture (150 ± 58 vs 154 ± 49 N, respectively; P = .25). In an overlay configuration, fiber interlocked patch augmentation increased Mason-Allen suture retention strength by 88% (from 221 ± 43 N to 417 ± 86 N; P < .01) with no detectable difference in repair stiffness., Conclusion: Testing in an ovine model of rotator cuff tendon repair suggested that surgical interlocking of a nonwoven medical textile can provide effective biomechanical performance, support functional tissue ingrowth, and help avoid musculotendinous retraction after surgical tendon repair., Clinical Relevance: The novel technique may facilitate patch augmentation of rotator cuff repairs.

Cytotherapies are often necessary for the management of symptomatic large knee (osteo)-chondral defects. While autologous chondrocyte implantation (ACI) has been clinically used for 30 years, allogeneic cells (clinical-grade FE002 primary chondroprogenitors) have been investigated in translational settings (Swiss progenitor cell transplantation program). The aim of this study was to comparatively assess autologous and allogeneic approaches (quality, safety, functional attributes) to cell-based knee chondrotherapies developed for clinical use. Protocol benchmarking from a manufacturing process and control viewpoint enabled us to highlight the respective advantages and risks. Safety data (telomerase and soft agarose colony formation assays, high passage cell senescence) and risk analyses were reported for the allogeneic FE002 cellular active substance in preparation for an autologous to allogeneic clinical protocol transposition. Validation results on autologous bioengineered grafts (autologous chondrocyte-bearing Chondro-Gide scaffolds) confirmed significant chondrogenic induction ( COL2 and ACAN upregulation, extracellular matrix synthesis) after 2 weeks of co-culture. Allogeneic grafts (bearing FE002 primary chondroprogenitors) displayed comparable endpoint quality and functionality attributes. Parameters of translational relevance (transport medium, finished product suturability) were validated for the allogeneic protocol. Notably, the process-based benchmarking of both approaches highlighted the key advantages of allogeneic FE002 cell-bearing grafts (reduced cellular variability, enhanced process standardization, rationalized logistical and clinical pathways). Overall, this study built on our robust knowledge and local experience with ACI (long-term safety and efficacy), setting an appropriate standard for further clinical investigations into allogeneic progenitor cell-based orthopedic protocols.

Background: The cause, extent, and role of muscle edema for muscle degeneration are unknown and not considered in the current literature. In vivo experiments were designed to prove muscle edema formation in the early period in a sheep model of acute rotator cuff tears., Hypothesis: Muscle edema occurs after tendon release with or without additional stretching trauma and may be associated with muscle retraction and subsequent muscle degeneration., Study Design: Controlled laboratory study., Methods: A sheep model with acute release of the infraspinatus tendon was used. An osteotomy of the greater tuberosity, including the insertion of the infraspinatus tendon, was performed in 14 sheep. To demonstrate presence of edema, magnetic resonance imaging scans were performed at 0, 2, and 4 weeks using T1-weighted, T2-weighted, proton density-weighted, and Dixon sequences. Excisional biopsy specimens were taken at 0, 3, and 4 weeks (histological results will be reported in a later publication). Two injury models were created: a nontrauma group that consisted of muscle release alone and a trauma group that included additional standardized traction to the musculotendinous unit. Evaluation of T1- and T2-weighted images included calculation of pennation angle, muscle fiber length, signal intensity (edema), and muscle volume. Muscle wet weight and volume were measured at sacrifice., Results: Edema formation was shown in all sheep and slightly more pronounced in the trauma group, where muscle intensity increased significantly between time point 0 (200 Grey Value (GV)) and weeks 2, 3, and 4 (300 GV). Edema formation started early after tendon release with a plateau between 3 and 4 weeks. Deterioration of muscle fiber bundles began also after tendon release with a peak at 4 weeks. Muscle volume decreased steadily over time., Conclusion: Muscle edema appeared early after rotator cuff tendon release, was more pronounced in the trauma group, and reached a plateau after 3 to 4 weeks. Muscle fatty content decreased within the short period of 4 weeks owing to a dilution effect. Muscle edema seems to be an essential factor in cuff tears and subsequent muscle retraction and degeneration., Clinical Relevance: This study demonstrates a new type of muscle edema of retraction and describes the characteristics of edema associated with a retracted rotator cuff tear.

Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Bone fractures commonly repair by forming a bridging structure called callus, which begins as soft tissue and gradually ossifies to restore rigidity to the bone. Virtual mechanical testing is a promising technique for image-based assessment of structural bone healing in both preclinical and clinical settings, but its accuracy depends on the validity of the material model used to assign tissue mechanical properties. The goal of this study was to develop a constitutive model for callus that captures the heterogeneity and biomechanical duality of the callus, which contains both soft tissue and woven bone. To achieve this, a large-scale optimization analysis was performed on 2363 variations of 3D finite element models derived from computed tomography (CT) scans of 33 osteotomized sheep under normal and delayed healing conditions. A piecewise material model was identified that produced high absolute agreement between virtual and physical tests by differentiating between soft and hard callus based on radiodensity. The results showed that the structural integrity of a healing long bone is conferred by an internal architecture of mineralized hard callus that is supported by interstitial soft tissue. These findings suggest that with appropriate material modeling, virtual mechanical testing is a reliable surrogate for physical biomechanical testing., (© 2022. The Author(s).)

Osteoarthritis (OA) is the most prevalent joint disorder, causing pain and disability predominantly in the aging population but also affecting young individuals. Current treatments are limited to use of anti-inflammatory drugs to alleviate symptoms or degenerated joint replacement by a prosthetic implant at the end stage of the disease. We hypothesized that degenerative cartilage defects can be treated using nasal chondrocyte–based tissue-engineered cartilage (N-TEC). We demonstrate that N-TEC maintained cartilaginous properties when exposed in vitro to inflammatory stimuli found in osteoarthritic joints and favorably altered the inflammatory profile of cells from osteoarthritic joints. These effects were at least partially mediated by down-regulation of the WNT (wingless/integrated) signaling pathway through sFRP1 (secreted frizzled-related protein-1). We further report that N-TEC survive and engraft in vivo in ectopic mouse models reproducing a human osteochondral OA tissue environment, as well as in sheep articular cartilage defects that mimic degenerative settings. Last, we tested the safety of autologous N-TEC for the treatment of osteoarthritic cartilage defects in the knees of two patients with advanced OA (Kellgren and Lawrence grades 3 and 4) who were otherwise considered for unicondylar knee arthroplasty. No adverse reactions were recorded, and patients reported reduced pain as well as improved joint function and life quality 14 months after surgery. Together, our findings indicate that N-TEC can directly contribute to cartilage repair in osteoarthritic joints. A suitably powered clinical trial is now required to assess its efficacy in the treatment of patients with OA.

Finite element analysis with models derived from computed tomography (CT) scans is potentially powerful as a translational research tool because it can achieve what animal studies and cadaver biomechanics cannot-low-risk, noninvasive, objective assessment of outcomes in living humans who have actually experienced the injury, or treatment being studied. The purpose of this study was to assess the validity of CT-based virtual mechanical testing with respect to physical biomechanical tests in a large animal model. Three different tibial osteotomy models were performed on 44 sheep. Data from 33 operated limbs and 20 intact limbs was retrospectively analyzed. Radiographic union scoring was performed on the operated limbs and physical torsional tests were performed on all limbs. Morphometric measures and finite element models were developed from CT scans and virtual torsional tests were performed to assess healing with four material assignment techniques. In correlation analysis, morphometric measures and radiographic scores were unreliable predictors of biomechanical rigidity, while the virtual torsion test results were strongly and significantly correlated with measured biomechanical test data, with high absolute agreement. Overall, the results validated the use of virtual mechanical testing as a reliable in vivo assessment of structural bone healing. This method is readily translatable to clinical evaluation for noninvasive assessment of the healing progress of fractures with minimal risk. Clinical significance: virtual mechanical testing can be used to reliably and noninvasively assess the rigidity of a healing fracture using clinical-resolution CT scans and that this measure is superior to morphometric and radiographic measures., (© 2020 Orthopaedic Research Society. Published by Wiley Periodicals LLC.)

Mechanoregulatory models have been used to predict the progression of bone fracture healing for more than two decades. However, many published studies share the same fundamental limitation: callus development proceeds within a pre-defined domain that both restricts and directs healing and leads to some non-physiologic healing patterns. To address this limitation, we added two spatial proximity functions to an existing mechanoregulatory model of fracture healing to control the localization of callus within the healing domain. We tested the performance of the new model in an idealized ovine tibial osteotomy with medial plate fixation using three sizes of healing domains and multiple variations of the spatial proximity functions. All model variations produced outward callus growth and bridging weighted toward the far cortex, which is consistent with in vivo healing. With and without the proximity functions, there were marked differences in the predicted callus volume and shape. With no proximity functions, the callus produced was strongly domain dependent, with a 15% difference in volume between the smallest and largest initialization domains. With proximity function control, callus growth was restricted to near the fracture line and there was only 2% difference in volume between domain sizes. Superimposing both proximity functions - one to control outward growth and one representing a decay in periosteal activity away from the fracture - produced a predicted callus size that was within the physiologic range for sheep and had a realistic morphology when compared with fluorescent dye co-localization with calcium deposition over time and histology., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Diverse cell therapy approaches constitute prime developmental prospects for managing acute or degenerative cartilaginous tissue affections, synergistically complementing specific surgical solutions. Bone marrow stimulation (i.e., microfracture) remains a standard technique for cartilage repair promotion, despite incurring the adverse generation of fibrocartilagenous scar tissue, while matrix-induced autologous chondrocyte implantation (MACI) and alternative autologous cell-based approaches may partly circumvent this effect. Autologous chondrocytes remain standard cell sources, yet arrays of alternative therapeutic biologicals present great potential for regenerative medicine. Cultured human epiphyseal chondro-progenitors (hECP) were proposed as sustainable, safe, and stable candidates for chaperoning cartilage repair or regeneration. This study describes the development and industrial transposition of hECP multi-tiered cell banking following a single organ donation, as well as preliminary preclinical hECP safety. Optimized cell banking workflows were proposed, potentially generating millions of safe and sustainable therapeutic products. Furthermore, clinical hECP doses were characterized as non-toxic in a standardized chorioallantoic membrane model. Lastly, a MACI-like protocol, including hECPs, was applied in a three-month GLP pilot safety evaluation in a caprine model of full-thickness articular cartilage defect. The safety of hECP transplantation was highlighted in xenogeneic settings, along with confirmed needs for optimal cell delivery vehicles and implantation techniques favoring effective cartilage repair or regeneration.

Purpose of Review: This review discusses imaging modalities for fracture repair assessment, with an emphasis on pragmatic clinical and translational use, best practices for implementation, and challenges and opportunities for continuing research., Recent Findings: Semiquantitative radiographic union scoring remains the clinical gold standard, but has questionable reliability as a surrogate indicator of structural bone healing, particularly in early-stage, complex, or compromised healing scenarios. Alternatively, computed tomography (CT) scanning enables quantitative assessment of callus morphometry and mechanics through the use of patient-specific finite-element models. Dual-energy X-ray absorptiometry (DXA) scanning and radiostereometric analysis (RSA) are also quantitative, but technically challenging. Nonionizing magnetic resonance (MR) and ultrasound imaging are of high interest, but require development to enable quantification of 3D mineralized structures. Emerging image-based methods for quantitative assessment of bone healing may transform clinical research design by displacing binary outcomes classification (union/nonunion) and ultimately enhance clinical care by enabling early nonunion detection.