Cerium (III) and (IV) containing mesoporous glasses/alginate beads for bone regeneration: bioactivity, biocompatibility and reactive oxygen species activity.

A very small number of biomaterials investigated for bone regeneration was reported as able to prevent the oxidative stress. In this study beads based on alginate hydrogel and mesoporous glasses (MG) containing different amounts of cerium oxides (Ce3+/Ce4+) exhibiting antioxidant properties were investigated as a good approach to mimic the action of antioxidant enzymes in our organism. The effect of cerium contents on the bioactivity and biocompatibility of beads were investigated. Moreover, the potential capability of Ce-containing MG to prevent the oxidative stress caused by the activity of reactive oxygen species (ROS) was here investigated for the first time. The increment of cerium oxide from 1.2, to 3.6 and 5.3 mol-% decreases the surface area and porosity of MG and increases the catalase mimetic activity after 168 h. Swelling tests in different cell culture media (D- and α-MEM) demonstrated the rehydration capability of beads. The presence of beads with the highest Ce-contents (3.6 and 5.3 %) improved the proliferation of pre-osteoblastic cells MC3T3-Cl cells. However, the cell differentiation decreased when increased the cerium content. Lactate dehydrogenase assays showed beads are cytocompatible materials. Moreover, oxidative stress tests with H2O2 showed a better response related to cell viability and the elimination of oxidant species when increased cerium content. Beads of glasses with 1.2 and 3.6 % of CeO2 are excellent candidates as bioactive scaffolds for bone regeneration capable of counteract the oxidative stress.

Cerium (III) and (IV) containing mesoporous glasses/alginate beads for bone regeneration: Bioactivity, biocompatibility and reactive oxygen species activity.

A very small number of biomaterials investigated for bone regeneration were reported as able to prevent the oxidative stress. In this study beads based on alginate hydrogel and mesoporous glasses (MG) containing different amounts of cerium oxides (Ce3+/Ce4+) exhibiting antioxidant properties were investigated as a good approach to mimic the action of antioxidant enzymes in our organism. The effect of cerium contents on the bioactivity and biocompatibility of beads were investigated. Moreover, the potential capability of Ce-containing MG to prevent the oxidative stress caused by the activity of reactive oxygen species (ROS) was here investigated for the first time. The increment of cerium oxide from 1.2, to 3.6 and 5.3 mol% decreases the surface area and porosity of MG and increases the catalase mimetic activity after 168 h. Swelling tests in different cell culture media (D- and α-MEM) demonstrated the rehydration capability of beads. The presence of beads with the highest Ce-contents (3.6 and 5.3%) improved the proliferation of pre-osteoblastic cells MC3T3-C1 cells. However, the cell differentiation decreased when increased the cerium content. Lactate dehydrogenase assays showed beads are cytocompatible materials. Moreover, oxidative stress tests with H2O2 showed a better response related to cell viability and the elimination of oxidant species when increased cerium content. Beads of glasses with 1.2 and 3.6% of CeO2 are excellent candidates as bioactive scaffolds for bone regeneration capable of counteract the oxidative stress.

In-vitro method for assessing femoral implant-bone micromotions in resurfacing hip implants under different loading conditions.

Although prosthesis-bone micromotion is known to influence the stability of total hip replacement, no protocol exists to investigate resurfacing hip implants. An in-vitro protocol was developed to measure prosthesis-bone micromotions of resurfaced femurs. In order to assess the effect of all loading directions, the protocol included a variety of in-vitro loading scenarios covering the range of directions spanned by the hip resultant force in the most typical motor tasks. Gap-opening and shear-slippage micromotions were measured in the locations where they reach the maximum value. The applicability of the protocol was assessed on two commercial designs and different head sizes. Intra-specimen repeatability and inter-specimen reproducibility were excellent (comparable with the best protocols for cemented hip stems). Results showed that the protocol is accurate enough to detect prosthesis-bone micromotions of the order of a few microns. Statistically significant differences were observed in relation to the direction of the applied force. Using the whole range of hip loads enabled detection of maximum micromotions for any design (the peak value could be different for different loading directions). Application of the protocol during a test to failure indicated that the system could track micromotion up to the last instant prior to failure. The protocol proposed is thus completely validated and can be applied for preliminary screening of new epiphyseal designs.

Predicting the subject-specific primary stability of cementless implants during pre-operative planning: preliminary validation of subject-specific finite-element models.

Pre-operative planning help the surgeon in taking the proper clinical decision. The ultimate goal of this work is to develop numerical models that allow the surgeon to estimate the primary stability during the pre-operative planning session. The present study was aimed to validate finite-element (FE) models accounting for patient and prosthetic size and position as planned by the surgeon. For this purpose, the FE model of a cadaveric femur was generated starting from the CT scan and the anatomical position of a cementless stem derived by a skilled surgeon using a pre-operative CT-based planning simulation software. In-vitro experimental measurements were used as benchmark problem to validate the bone-implant relative micromotions predicted by the patient-specific FE model. A maximum torque in internal rotation of 11.4 Nm was applied to the proximal part of the hip stem. The error on the maximum predicted micromotion was 12% of the peak micromotion measured experimentally. The average error over the entire range of applied torques was only 7% of peak measurement. Hence, the present study confirms that it is possible to accurately predict the level of primary stability achieved for cementless stems using numerical models that account for patient specificity and surgical variability.

On the biomechanical stability of cementless straight conical hip stems.

The aim of the present study was to investigation in vitro the effect of deficient bone-implant contact on the primary stability of a straight conical stem. Various possible deficient contact patterns were derived from surgical simulations. The effect of stair climbing loads on the bone-implant micromotion was firstly investigated using a finite element model and then an in vitro test aimed at assessing primary stability. It was found that if the surface features are prevented from biting dense bone in a few small but critical regions, stem primary stability is completely lost. These results suggest that the surface features used in the axisymmetric stem under investigation can be too sensitive to deficient contact conditions, and thus should be augmented with additional antirotational fins. Preliminary tests showed that a stem with the addition of such fins presents good primary stability in all tested conditions.

Device to measure intra-operatively the primary stability of cementless hip stems.

The primary stability of cementless prostheses is critical for the long-term outcome of the operation. Surgeons are currently driven only by their experience in evaluating the extent of stem stability achieved. The aim of the present work was to develop a new device that enables the stability of a cementless stem to be quantitatively assessed intraoperatively. The angle of the stem/femur rotation under torsion and the torque are acquired and compared in real-time to a pre-set threshold inferred from the literature. The device indicates whether the stem is stable or not. It was extensively tested and finally validated in vitro on cadaveric and composite femurs hosting different sizes of the same kind of prostheses, implanted with different levels of press-fitting. The overall accuracy (23%) takes into account not only the overall measurement error but also the variability due to differences in bone quality and stem press-fitting. This error was deemed sufficient to discriminate between stable and unstable implants.

[Bronchial epidermoid carcinoma with unusual disclosure]. / Carcinome épidermoïde bronchique de révélation inhabituelle.

Dissemination has often occurred before the diagnosis of bronchopulmonary cancer. Pancreatic metastases are exceptional and are very rarely the revealing manifestation. The authors report a case of a tumour of the pancreas which led to the discover of an bronchogenic epidermoid carcinoma. The relationship between these two tumours lead to the proposed hypothesis of pancreatic metastasis of a bronchogenic carcinoma. Although this situation is rare, the preoperative work-up for bronchogenic carcinoma should include computed tomography of the pancreas if the abdominal echography does not allow complete visualization of the pancreas in cases with suggestive digestive disorders. If a tumour is observed in the pancreas, scan-guided needle biopsy should be performed to enable the histological examination.

Particle spallation and plasticiser (DEHP) release from extracorporeal circuit tubing materials.

Particle spallation and plasticiser (DEHP) release from medical grade polyvinylchloride (PVC), co-extruded PVC-polyurethane (PIVIPOL)R and an experimentally produced co-extruded PVC-ethylene vinyl acetate (EVA) has been studied when used with manually occluded and self-occluding peristaltic pumps over a six hour pumping period. The shore hardness of the tubings studied were similar but the luminal coating thickness differed (0.2 mm polyurethane, 0.99 mm EVA). The pattern of particle release was similar for all materials on the pump type used with the majority of particles released being less than 5 microns in diameter. The number of particles greater than 5 microns released was independent of the tubing material but depended on the pump type. Particle release with self-occluding pumps was significantly higher (p less than 0.001) than for the manually occluded pump. Scanning electron microscopy indicated that the particles released originate from the repeated compression and flexing of the insert during pumping which leads to material structural failure. The higher release observed in the case of self-occluding pumps is suggestive of over-occlusion by the springs utilised in the pump. DEHP release (ppm) over a six hour period while perfused at 300 ml/min was significantly reduced for co-extruded tubing (0.56 +/- 0.05 mg (PVC-polyurethane) and 0.12 +/- 0.04 mg (PVC-EVA) compared with PVC (0.74 +/- 0.05 mg).

Adequacy of haemodiafiltration.

In this study we have evaluated the influence of blood and ultrafiltration flow rate on the performance of five different high-flux membrane dialysers during haemodiafiltration. On the basis of clearance data we optimised the haemodiafiltration schedule of six uraemic patients to maintain an adequate midweek blood urea nitrogen concentration, while reducing the treatment time from 285 +/- 23 min to 210 min. After a follow-up of 6 months, we observed no difference in the clinical tolerance or in the biochemical parameters, compared to those found during the preceding haemodialysis period. Our data confirm the suggestions of other authors that haemodiafiltration is an effective alternative to conventional haemodialysis.