The progression of local cartilage surface damage toward early stage osteoarthritis (OA) likely depends on the severity of the damage and its impact on the local lubrication and stress distribution ...in the surrounding tissue. It is difficult to study the local responses using traditional methods; in situ microtribological methods are being pursued here as a means to elucidate the mechanical aspects of OA progression. While decades of research have been dedicated to the macrotribological properties of articular cartilage, the microscale response is unclear. An experimental study of healthy cartilage microtribology was undertaken to assess the physiological relevance of a microscale friction probe. Normal forces were on the order of 50 mN. Sliding speed varied from 0 to 5 mm/s, and two probes radii, 0.8 and 3.2 mm, were used in the study. In situ measurements of the indentation depth into the cartilage enabled calculations of contact area, effective elastic modulus, elastic and fluid normal force contributions, and the interfacial friction coefficient. This work resulted in the following findings: (1) at high sliding speed (V = 1-5 mm/s), the friction coefficient was low (μ = 0.025) and insensitive to probe radius (0.8-3.2 mm) despite the fourfold difference in the resulting contact areas; (2) the contact area was a strong function of the probe radius and sliding speed; (3) the friction coefficient was proportional to contact area when sliding speed varied from 0.05 to 5 mm/s; (4) the fluid load support was greater than 85% for all sliding conditions (0% fluid support when V = 0) and was insensitive to both probe radius and sliding speed. The findings were consistent with the adhesive theory of friction; as speed increased, increased effective hardness reduced the area of solid-solid contact which subsequently reduced the friction force. Where the severity of the sliding conditions dominates the wear and degradation of typical engineering tribomaterials, the results suggest that joint motion is actually beneficial for maintaining low matrix stresses, low contact areas, and effective lubrication for the fluid-saturated porous cartilage tissue. Further, the results demonstrated effective pressurization and lubrication beneath single asperity microscale contacts. With carefully designed experimental conditions, local friction probes can facilitate more fundamental studies of cartilage lubrication, friction and wear, and potentially add important insights into the mechanical mechanisms of OA.
Abstract Interstitial fluid pressurization, a consequence of a biphasic tissue structure, is essential to the load bearing and lubrication properties of articular cartilage. Focal tissue degradation ...may interfere with this protective mechanism, eventually leading to gross degeneration and osteoarthritis. Our long-term goal is to determine whether local contacts can be used as a means to probe local tissue integrity and functionality. In the present work, Hertzian rate-controlled microindentation was used as a model of the more complicated sliding system to directly determine the effects of contact radius and deformation rate on interstitial load support. During localized contact between a steel spherical probe and bovine articular cartilage, the equilibrium and non-equilibrium responses were well-fit by the Hertz model ( R2 >0.998) with a mean equilibrium contact modulus of 0.93 MPa. The effective contact modulus and fluid load fraction were independent of indentation depth, contact radius, and normal force; both increased monotonically with indentation rate. At 21 μm/s indentation rate, the cartilage was effectively stiffened by 6-fold with the fluid pressure supporting 85% of the contact force. The results motivated a simple analytical model that directly links the tribomechanical response (including fluid load support) and the Peclet number to measurable material properties and controllable experimental variables. This paper demonstrates that tribological contacts can be used to probe local functional properties. Such measurements can add important insights into the roles of focal tissue damage and impaired local functionality in the pathogenesis of osteoarthritis.
Tractography of the facial nerve based on single-shell diffusion MR imaging is thought to be helpful before surgery for resection of vestibular schwannoma. However, this paradigm can be vitiated by ...the isotropic diffusion of the CSF, the convoluted path of the facial nerve, and its crossing with other bundles. Here we propose a multishell diffusion MR imaging acquisition scheme combined with probabilistic tractography that has the potential to provide a presurgical facial nerve reconstruction uncontaminated by such effects.
Five patients scheduled for vestibular schwannoma resection underwent multishell diffusion MR imaging (b-values = 0, 300, 1000, 2000 s/mm
). Facial nerve tractography was performed with a probabilistic algorithm and anatomic seeds located in the brain stem, cerebellopontine cistern, and internal auditory canal. A single-shell diffusion MR imaging (b-value = 0, 1000 s/mm
) subset was extrapolated from the multishell diffusion MR imaging data. The quality of the facial nerve reconstruction based on both multishell diffusion MR imaging and single-shell diffusion MR imaging sequences was assessed against intraoperative videos recorded during the operation.
Single-shell diffusion MR imaging-based tractography was characterized by failures in facial nerve tracking (2/5 cases) and inaccurate facial nerve reconstructions displaying false-positives and partial volume effects. In contrast, multishell diffusion MR imaging-based tractography provided accurate facial nerve reconstructions (4/5 cases), even in the presence of ostensibly complex patterns.
In comparison with single-shell diffusion MR imaging, the combination of multishell diffusion MR imaging-based tractography and probabilistic algorithms is a more valuable aid for surgeons before vestibular schwannoma resection, providing more accurate facial nerve reconstructions, which may ultimately improve the postsurgical patient's outcome.
Background
COVID-19 pandemic is thought to have changed the epidemiology of some pediatric neurosurgical disease: among them are the intracranial complications of sinusitis and otitis (ICSO). ...According to some studies on a limited number of cases, both streptococci-related sinusitis and ICSO would have increased immediately after the pandemic, although the reason is not clear yet (seasonal changes versus pandemic-related effects). The goal of the present survey of the European Society for Pediatric Neurosurgery (ESPN) was to collect a large number of cases from different European countries encompassing the pre-COVID (2017–2019), COVID (2020–2021), and post-COVID period (2022–June 2023) looking for possible epidemiological and/or clinical changes.
Material and methods
An English language questionnaire was sent to ESPN members about year of the event, patient’s age and gender, presence of immune-deficit or other favoring risk factors, COVID infection, signs and symptoms at onset, site of primary infection, type of intracranial complication, identified germ, type and number of surgical operations, type and duration of medical treatment, clinical and radiological outcome, duration of the follow-up.
Results
Two hundred fifty-four cases were collected by 30 centers coming from 14 different European countries. There was a statistically significant difference between the post-COVID period (129 children, 86 cases/year, 50.7% of the whole series) and the COVID (40 children, 20 cases/year, 15.7%) or the pre-COVID period (85 children, 28.3 cases/year, 33.5%). Other significant differences concerned the presence of predisposing factors/concurrent diseases (higher in the pre-COVID period) and previous COVID infection (higher in the post-COVID period). No relevant differences occurred as far as demographic, microbiological, clinical, radiological, outcome, morbidity, and mortality data were concerned. Paranasal sinuses and middle ear/mastoid were the most involved primary site of infection (71% and 27%, respectively), while extradural or subdural empyema and brain abscess were the most common ICSO (73% and 17%, respectively). Surgery was required in 95% of cases (neurosurgical and ENT procedure in 71% and 62% of cases, respectively) while antibiotics in 99% of cases. After a 12.4-month follow-up, a full clinical and radiological recovery was obtained in 85% and 84% of cases, respectively. The mortality rate was 2.7%.
Conclusions
These results suggest that the occurrence of ICSO was significantly increased after the pandemic. Such an increase seems to be related to the indirect effects of the pandemic (e.g., immunity debt) rather than to a direct effect of COVID infection or to seasonal fluctuations. ICSO remain challenging diseases but the pandemic did not affect the management strategies nor their prognosis. The epidemiological change of sinusitis/otitis and ICSO should alert about the appropriate follow-up of children with sinusitis/otitis.
We report our preliminary experience concerning the use of thrombin-gelatin hemostatic matrix to strengthen the final hemostasis after posterior fossa low-grade tumor surgery in children. To our ...knowledge, this is the first report regarding the use of hemostatic matrix in pediatric neurosurgery.
Between 2012 and 2016, twenty-three patients underwent posterior fossa surgery for low-grade gliomas in our department. The mean age was 6.35 years; 12 patients were female and 11 male. Histology revealed pilocytic astrocytoma in 15 cases, ependymoma in 7 cases, and gangliocytoma in 1 case. At the end of the surgery, effective hemostasis was achieved using standard methods and, in order to strengthen the final hemostasis, we used a thrombin-gelatin hemostatic matrix. In all of the cases a postoperative MRI was performed within 24 after the surgery; during hospitalization the patients underwent a clinical evaluation. Moreover, blood samples were taken to evaluate inflammatory parameters, hemoglobin, and sodium, and kidney and liver tests were performed according to the standard protocol.
The postoperative MRI did not show any complications imputable to the matrix. Dur ing radiological and clinical follow-up none of the patients showed any delayed complications related to the matrix.
In our practice we found thrombin-gelatin hemostatic matrix sealant to be a valid and safe tool for strengthening hemostasis in pediatric low-grade posterior fossa surgery.
In addition to qualitative information, specific quantitative psychiatrics tests (regarding anxiety and depression) and objective psychological tests specific to cancer populations were used to ...compare psychological variables in two groups of metastatic cancer patients treated with chemotherapy. The study also recorded 24 possible symptoms (somatic and psychic) allowing the self-evaluation of individual quality of life. The evaluation was performed at 7 different times (from before the beginning of treatment up to the 6th course). In comparison to traditional treatment, the results showed a better psychosocial adaptation for patients receiving chronoprogrammed administration of anticancer medication, with better social relations, less feelings of loss of independence, less anxiety, depression, and somatic discomfort.
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