The investigation of bone damage processes is a crucial point to understand the mechanisms of age-related bone fractures. In order to reduce their impact, early diagnosis is key. The intricate ...architecture of bone and the complexity of multiscale damage processes make fracture prediction an ambitious goal. This review, supported by a detailed analysis of bone damage physical principles, aims at presenting a critical overview of how multiscale imaging techniques could be used to implement reliable and validated numerical tools for the study and prediction of bone fractures. While macro- and meso-scale imaging find applications in clinical practice, micro- and nano-scale imaging are commonly used only for research purposes, with the objective to extract fragility indexes. Those images are used as a source for multiscale computational damage models. As an example, micro-computed tomography (micro-CT) images in combination with micro-finite element models could shed some light on the comprehension of the interaction between micro-cracks and micro-scale bone features. As future insights, the actual state of technology suggests that these models could be a potential substitute for invasive clinical practice for the prediction of age-related bone fractures. However, the translation to clinical practice requires experimental validation, which is still in progress.
Abstract
Metallization of polymers using cold spray technology has reached wide consideration in recent years. However, an effective modeling approach to address the deposition phenomena able to ...assess bonding formation in polymer metallization is still lacking. This study aims to develop a finite element model to simulate the solid-state deposition of metallic particles on thermoplastic polymeric substrates. Single copper particle impact on the Polyether Ether Ketone substrate was modeled using the coupled Lagrangian–Eulerian approach. Emphasis was given to the polymer material properties and substrate thermal history to account for the sensitivity of the physical and mechanical properties of polymers to temperature. Experimental coating depositions were performed to select an optimized set of spray parameters while single-particle impact tests were conducted for model validation. The substrate temperature was measured using an infrared thermal camera and was used to model the sub-surface temperature gradient during gas spray exposure. The proposed numerical model is shown to be capable of predicting various impact features includi mechanical interlocking and the effect of particle velocity fluctuations and temperature gradients on the extent of bonding. Substrate heating was found to have a distinct effect on the correct prediction of particle bonding. The proposed model enables tuning the appropriate processing conditions for successful copper particle adhesion on PEEK polymeric substrates.
Dual Energy X-Ray Absorptiometry (DXA) is currently the most widely adopted non-invasive clinical technique to assess bone mineral density and bone mineral content in human research and represents ...the primary tool for the diagnosis of osteoporosis. DXA measures areal bone mineral density, BMD, which does not account for the three-dimensional structure of the vertebrae and for the distribution of bone mass. The result is that longitudinal DXA can only predict about 70% of vertebral fractures. This study proposes a complementary tool, based on Finite Element (FE) models, to improve the DXA accuracy. Bone is simulated as elastic and inhomogeneous material, with stiffness distribution derived from DXA greyscale images of density. The numerical procedure simulates a compressive load on each vertebra to evaluate the local minimum principal strain values. From these values, both the local average and the maximum strains are computed over the cross sections and along the height of the analysed bone region, to provide a parameter, named Strain Index of Bone (SIB), which could be considered as a bone fragility index. The procedure is initially validated on 33 cylindrical trabecular bone samples obtained from porcine lumbar vertebrae, experimentally tested under static compressive loading. Comparing the experimental mechanical parameters with the SIB, we could find a higher correlation of the ultimate stress, σULT, with the SIB values (R2adj = 0.63) than that observed with the conventional DXA-based clinical parameters, i.e. Bone Mineral Density, BMD (R2adj = 0.34) and Trabecular Bone Score, TBS (R2adj = -0.03). The paper finally presents a few case studies of numerical simulations carried out on human lumbar vertebrae. If our results are confirmed in prospective studies, SIB could be used-together with BMD and TBS-to improve the fracture risk assessment and support the clinical decision to assume specific drugs for metabolic bone diseases.
Integration of numerous prognostic variables not included in the conventional staging of retroperitoneal soft tissue sarcomas (RPS) is essential in providing effective treatment. The purpose of this ...study was to build a specific nomogram for predicting postoperative overall survival (OS) and disease-free survival (DFS) in patients with primary RPS.
Data registered in three institutional prospective sarcoma databases were used. We included patients with primary localized RPS resected between 1999 and 2009. Univariate (Kaplan and Meier plots) and multivariate (Cox model) analyses were carried out. The a priori chosen prognostic covariates were age, tumor size, grade, histologic subtype, multifocality, quality of surgery, and radiation therapy. External validation was performed by applying the nomograms to the patients of an external cohort. The model's discriminative ability was estimated by means of the bootstrap-corrected Harrell C statistic.
In all, 523 patients were identified at the three institutions (developing set). At a median follow-up of 45 months (interquartile range, 22 to 72 months), 171 deaths were recorded. Five- and 7-year OS rates were 56.8% (95% CI, 51.4% to 62.6%) and 46.7% (95% CI, 39.9% to 54.6%. Two hundred twenty-one patients had disease recurrence. Five- and 7-year DFS rates were 39.4% (95% CI, 34.5% to 45.0%) and 35.7% (95% CI, 30.3% to 42.1%). The validation set consisted of 135 patients who were identified at the fourth institution for external validation. The bootstrap-corrected Harrell C statistics for OS and DFS were 0.74 and 0.71 in the developing set and 0.68 and 0.69 in the validating set.
These nomograms accurately predict OS and DFS. They should be used for patient counseling in clinical practice and stratification in clinical trials.
Purpose
The relevance of the initial observational approach for desmoid tumors (DTs) remains unclear. We investigated a new conservative management treatment for primary abdominal wall DTs.
Methods
...Data were collected from 147 patients between 1993 and 2012. The initial therapeutic approaches were categorized as front-line surgery surgery group (SG),
n
= 41, 28 % and initial observation or medical treatment nonsurgery group (NSG),
n
= 106, 72 %. The cumulative incidence of the last strategy modification was estimated using competing risk methods with variable censoring times.
Results
Of the 147 patients, 143 were female (97 %). In the SG, 27 patients (66 %) required full-thickness abdominal wall mesh repair. In the NSG, 102 patients (96 %) underwent initial observation and four received medical treatment. In the NSG, the 1- and 3-year incidences of changing to medical treatment (no further changes during the follow-up) were 19 % 95 % confidence interval (CI) 11–28 and 25 % (95 % CI 17–35), respectively, and the 1- and 3-year incidences of a final switch to surgery were 14 % (95 % CI 8–22) and 16 % (95 % CI 9–24), respectively. An initial tumor size of >7 cm was associated with a higher strategy modification risk (
p
= 0.004). Of the 102 patients initially observed, 29 experienced spontaneous regression over a median follow-up period of 32 months. All second-intent resections were macroscopically completed, with R0 resections achieved in 82 % of patients.
Conclusions
This study supports an initial nonsurgical approach to abdominal wall DTs ≤7 cm, followed by surgery based on tumor growth in select cases.
The comprehension of trabecular bone damage processes could be a crucial hint for understanding how bone damage starts and propagates. Currently, different approaches to bone damage identification ...could be followed. Clinical approaches start from dual X-ray absorptiometry (DXA) technique that can evaluate bone mineral density (BMD), an indirect indicator of fracture risk. DXA is, in fact, a two-dimensional technology, and BMD alone is not able to predict the effective risk of fractures. First attempts in overcoming this issue have been performed with finite element (FE) methods, combined with the use of three-dimensional high-resolution micro-computed tomographic images. The purpose of this work is to evaluate damage initiation and propagation in trabecular vertebral porcine samples using 2D linear-elastic FE models from DXA images and 3D linear FE models from micro-CT images. Results show that computed values of strains with 2D and 3D approaches (e.g., the minimum principal strain) are of the same order of magnitude. 2D DXA-based models still remain a powerful tool for a preliminary screening of trabecular regions that are prone to fracture, while from 3D micro-CT-based models, it is possible to reach details that permit the localization of the most strained trabecula.
Graphical abstract
Purpose
To explore patterns of failure and postrelapse outcome of patients with retroperitoneal sarcoma primarily treated by extended resection.
Methods
All consecutive patients with primary ...retroperitoneal sarcoma, treated between January 2002 and December 2011 at two European sarcoma centers were included. Five-year overall survival (OS) and crude cumulative incidence (CCI) of local recurrence (LR) and distant metastases (DM) were calculated. Multivariate analyses for OS and CCI of LR and DM were performed. Postrelapse OS was investigated.
Results
A total of 377 patients were identified. Median follow-up from the time of primary surgery was 44 months interquartile range (IQR) 27–82. Five-year OS was 64 % 95 % confidence interval (CI) 0.588, 0710. CCI of LR and DM were 23.6 % (95 % CI 18.9, 29.4) and 21.9 % (95 % CI 17.6, 27.3), respectively. OS, CCI of LR and DM were 87, 18 % and 0 for well-differentiated liposarcoma; 54, 44 and 9 % for grade II dedifferentiated liposarcoma; 41,33, and 44 % for grade III dedifferentiated liposarcoma; 58, 5, and 55 % for leiomyosarcoma; and 85, 4, and 17 % for solitary fibrous tumor, respectively. Seventy-six patients developed LR. Median postrelapse follow-up was 27 months (IQR 10–58). Twenty-one patients (27 %) underwent a second surgical resection (complete in 18), while 55 (73 %) did not (22 multifocal, 17 inoperable, 16 other causes). Median postrelapse OS was 17 months (IQR 7–31). Well-differentiated liposarcoma histology and disease-free interval predicted postrelapse OS, while surgical resection did not.
Conclusions
When primary extended surgery limits LR, histologic subtype and grade determine the outcome. At recurrence, a second surgery is of limited benefit.
Introduction
Retroperitoneal soft tissue sarcomas (RPSs) are mesenchymal neoplasms. The prevalence of protein energetic malnutrition (PEM) and its impact in RPS patients who were candidates for ...surgery is unknown.
Materials and Methods
A prospective feasibility study enrolled 35 patients with primary RPS who were candidates for extended multivisceral resection. PEM was screened at enrollment. Preoperative high protein β-hydroxy-β-methyl butyrate oral nutritional support (ONS) was provided according to the degree of PEM. After surgery, nutritional support followed standard practice, targeting at least 1 g/kg/day protein and 20 kcal/kg/day caloric intake within the third postoperative day (POD). PEM was re-evaluated before surgery on POD 10, and at 4 and 12 months after surgery. Primary outcomes were the patient’s compliance to preoperative ONS and the physician’s compliance to postoperative nutritional targets.
Results
PEM was documented in 46% of patients at baseline; ONS met a 91% adherence (overall well tolerated). After ONS, PEM reduced to 38% (
p
= 0.45). The postoperative caloric target was reached on day 4.1 (standard error ± 2.7), with a protocol adherence rate of 52%. On POD 10, 91% of patients experienced PEM, the worsening of which was greater after resection of four or more organs (
p
= 0.06). At 4 and 12 months after surgery, almost all patients had fully recovered. A significant correlation between PEM at surgery and postoperative complications was found (
p
= 0.04).
Conclusions
Relevant PEM prevalence in RPS is documented for the first time. PEM correlates with greater morbidity. In this setting, preoperative ONS was feasible and well-tolerated. Disease-related factors for PEM and the ideal perioperative caloric target in the context of extended multivisceral resection need to be further investigated. Nutritional support should be included in enhanced recovery after surgery programs for RPS.
Trial Registry
ClinicalTrials.gov identifier: NCT03877588.
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