Measurement of knee cartilage thickness using MRI: a reproducibility study in a meniscectomized guinea pig model of osteoarthritis.

The in vivo precision (reproducibility) of quantitative MRI is of particular importance in osteoarthritis (OA) progression of small magnitude and response to therapy. In this study, three-dimensional high-resolution MRI performed at 7 T was used to assess the short-term reproducibility of measurements of mean tibial cartilage thickness in a meniscectomized guinea pig model of OA. MR image acquisition was repeated five times in nine controls (SHAM) and 10 osteoarthritic animals 3 months after meniscectomy (MNX), in vivo. The animals were then killed for histomorphometric assessment and correlation with the MRI-based measurements. Medial tibial cartilage thickness was measured on MR images using semi-automatic dedicated 3D software developed in-house. The reproducibility of measurements of cartilage thickness was assessed by five repeated MRI examinations with a short recovery delay between examinations (48 h). The computed coefficients of variation were 8.9% for the SHAM group and 8.2% for the MNX group. The coefficients of variation were compatible with expected thickness variations between normal and pathological animals. A positive agreement and significant partial correlation (Spearman r' = 0.74; P < 0.01) between the MRI and histomorphometric data was established. Three-dimensional high-resolution MRI is a promising non-invasive research tool for in vivo follow-up. This modality could be used for staging and monitoring therapy response in small-animal models of OA.

Knee cartilage thickness measurements using MRI: a 4(1/2)-month longitudinal study in the meniscectomized guinea pig model of OA.

OBJECTIVE: The aim of this study was to follow, over a 4(1/2)-month period, the medial tibia cartilage thickness on a meniscectomy (MNX) guinea pig osteoarthritis (OA) model and to compare with control animals, using three-dimensional high-resolution magnetic resonance imaging (3D HR-MRI). METHODS: MRI experimentations were performed in vivo at 7 T on guinea pig knee joints. 3D HR-MR images were acquired in 60 controls (SHAM) and 45 osteoarthritic animals (MNX) at four time-points (15, 45, 90 and 135 days) after surgery. Medial tibial cartilage thickness was measured from MRI images using in-house dedicated 3D software followed by a statistical analysis. At each time-point 15 SHAM and 15 MNX animals were sacrificed for histomorphometric assessments. RESULTS: No significant difference of mean cartilage thickness between the groups was found at early stage (D45) using MRI; however, significant differences were found between the groups at D90 (P<0.001) and D135 (P<0.001). Histomorphometry data confirmed the pathological status of the animals and was well correlated with MRI at D15 (r=0.79, P<0.01), D45 (r=0.67, P<0.01), and D135 (r=0.39, P<0.05) for SHAM, and at D45 (r=0.63, P<0.01), and D135 (r=0.81, P<0.01) for MNX. CONCLUSION: Medial tibial cartilage measurement based on HR-MR images enables the monitoring of longitudinal cartilage thickness changes. This technique showed significant differences between SHAM and MNX as from D90 after surgery. It could be used as a noninvasive and reproducible tool to monitor therapeutic response in this OA model.

Reliability of computed tomographic angiography in the diagnosis of brain death.

OBJECTIVE: This study examined the validity of cerebral computed tomographic (CT) angiography in the diagnosis of brain death (BD) compared with conventional cerebral angiography. METHODS: This prospective, monocentric study was performed over a 24-month period and included 43 patients, at least 18 years of age, with clinical criteria of BD. All patients underwent cerebral CT angiography and then cerebral angiography. To confirm BD, the CT scan had to show the absence of perfusion of A2 anterior cerebral artery segments (A2-ACA), M4 middle cerebral artery segments (M4-MCA), P2 posterior cerebral artery segments (P2-PCA), basilar artery, internal cerebral veins, and finally the great cerebral vein. Cerebral angiography showed cerebral blood flow arrest at the level of the foramen magnum for posterior circulation and carotid siphon for anterior circulation. RESULTS: For 30 patients, BD was confirmed by both examinations. For 13 patients, cerebral angiography confirmed BD, whereas CT angiography still showed cerebral perfusion; the divergence rate was 30.2%. CONCLUSIONS: CT angiography seems to be a promising exam to confirm BD. However, the divergence with cerebral angiography is significant mainly concerning A2-ACA, which are proximal. It may be possible to only use the absence of opacification of M4-MCA, P2-PCA, basilar artery, and venous blood return to remain in conformity with the French law. In all cases, the international medical community should obtain a consensus for the interpretation of CT angiography to use it extensively as a complementary exam for BD.

Calorimetric and FTIR study of the acid properties of sulfated titanias.

Titanium oxides of different surface areas were sulfated then calcined to convert the solid to a strong acid. The amount of sulfur retained by the solid and the thermal stability of the resulting sulfate are controlled by the dispersion of the initial oxide. The acid properties were determined by gravimetry at 383 K, calorimetry using ammonia adsorption at 353 K, and by quantitative analysis of the infrared spectra of pyridine retained after evacuation at 423 K. A good agreement was observed between the different determinations. At low coverage of ammonia, sulfated titanias show a much lower heat of adsorption, and the IR study of NH3 adsorption shows that the first doses of NH3 dissociate at the surface with the formation of OH species. The lower heat of adsorption is then attributed to the contribution of NH3 dissociation to the differential heat of adsorption. IR spectroscopy indicates that NH3 reacts with sulfates and may lead to the transformation of disulfate species into monosulfate species on sulfated titania dioxide. A band at ca. 3574 cm-1 has been assigned to nu(OH) of monosulfate species. This particular behavior makes it difficult to appreciate the initial acidity of these sulfated oxides.

Quantitative assessment of articular cartilage and subchondral bone histology in the meniscectomized guinea pig model of osteoarthritis.

OBJECTIVE: A new image analysis system was employed to quantify the main histological parameters reflecting osteoarthritic features, at the cartilage and bone levels, in the meniscectomized guinea pig model of osteoarthritis (OA). METHODS: Meniscectomized (MNX) and sham-operated (SH) guinea pigs were studied 1 and 3 months after partial meniscectomy at the medial side of the left knee (n=10 to 12 animals/group). The left proximal tibias were included in methylmethacrylate. Sections were cut and stained with safranin O or Goldner trichrome. Parameters were quantified using special programs of a Biocom image analyser. The following parameters were evaluated at the medial side of the tibia: cartilage thickness (CT); fibrillation index (FI); proteoglycan content ratio based on safranin O staining intensities (PC); chondrocyte density (CD); bone volume (BV) and subchondral bone plate thickness (SBPT). The degree of user interaction varied from manually tracing objects to almost complete computer automation. RESULTS: Meniscectomy resulted in significant variations of these reproducible histomorphometric parameters both after 1 month (FI: +522%, P<0.01) and 3 months (FI: +162%, P<0.001; PC: -36.7%, P<0.001; CD: -31.8%, P<0.001; SBPT: +8.7%, P<0.05) post-operation (results expressed as percentage variation of MNX vs SH). The linear correlation analysis including data from SH and/or MNX animals at the two grouped time points revealed significant r values, in particular between cartilage (CT) and subchondral bone parameters (SBPT) (r=-0.41, P<0.01). CONCLUSIONS: Contrary to scoring evaluation, this system allowed to show the time-dependent impact of the pathology with an early fibrillation of the medial tibial cartilage appearing as soon as 1 month post-surgery, and the close relationship between bone and cartilage parameters during the progression of OA.

[Allergy investigations after two cases of adverse reactions to a neuromuscular blocking agent and management for subsequent general anaesthesia]. / Bilan allergologique après un choc anaphylactique à un curare non dépolarisant: conduite à tenir pour une anesthésie ultérieure.

We report two cases of severe anaphylactic reactions to rocuronium. Diagnosis was confirmed by skin tests and specific IgE assay. Cross-reactivity to all neuromuscular blocking agents was investigated by intradermal tests and leucocyte histamine release test. Intradermal tests and leukocyte histamine release were negative for cisatracurium. The two patients had undergone a subsequent general anaesthesia using cisatracurium and did not present any adverse reaction.

[Evaluation of the learning curve of a new intubation technique: intubating laryngeal mask]. / Evaluation de l'apprentissage d'une nouvelle technique d'intubation: le ML-Fastrach.

OBJECTIVE: Assessment of the learning curve of a new device for blind orotracheal intubation: Intubating laryngeal mask. STUDY DESIGN: Prospective clinical study. METHODS: Ten persons practicing anaesthesia (specialist, fellow, nurse) underwent videotape learning and manikin training required with the device. Each person had to carry out a tracheal intubation in ten consecutive patients undergoing scheduled surgery. No patient presented history or clinical sign of difficult airway management. Results were expressed as mean +/- SD. Main percentages were provided with their 95% confidence interval; the percentage comparison were performed using Chi 2 test. The significance level for overall analysis was p < 0.05. RESULTS: One hundred patients were included. The overall success rate of tracheal intubation with the intubating laryngeal mask was 88%. An easy learning curve was obtained according to the low failure rate that was observed. No failure was noticed after eight procedures. Significant diminution of the delay for tube insertion was observed during the practice (3 +/- 1.30 min for the first procedure and 1.16 +/- 0.60 min for the tenth procedure). Circumstances of the oral intubation were improved with muscle relaxation. Finally, all failure with the intubating laryngeal mask were followed by successful intubation using direct laryngoscopy. CONCLUSION: The intubating laryngeal mask is a new device for blind orotracheal intubation with an easy learning curve in patients without difficulty in airway management, even for non-selected operators.

[Tracheal gas insufflation avoids hypercapnia in patients with severe head trauma and acute lung injury]. / L'insufflation trachéale de gaz permet d'éviter l'hypercapnie chez le traumatisé crânien grave avec syndrome de détresse respiratoire aiguë.

PURPOSE: The purpose of the ventilatory management of acute respiratory distress syndrome (ARDS) is to avoid any barotrauma to the lungs by decreasing the tidal volume at the expense of permissive hypercapnia. This hypercapnia is extremely dangerous for severe head trauma patients because it increases intracranial pressure. The solution could be the use of tracheal gas which insufflation (TGI) allows the reduction of arterial carbon dioxide tension (PaCO(2)) while controlling airway pressures. CLINICAL FEATURES: We report the cases of two patients with ARDS and severe head trauma. The decrease of tidal volume ( by 60 and 25% respectively) in association with tracheal gas insufflation allowed to reduce plateau airway pressure (<35 cm d'H(2)O) and PaCO(2) (in the first case by 23% and in the second case, by 11% for the second hour then by 24%), while intracranial pressure remained constant or was lowered (in the second case by 39% for the second hour). TGI consisted in insufflating fresh gas via a small catheter placed in the trachea (0(2) at 6 L*min(-1) in the first patient and 4 L*min(-1) in the second case). CONCLUSION: TGI appears to be an important component of ventilatory management when ARDS is associated with severe head trauma.

Evidence of early subchondral bone changes in the meniscectomized guinea pig. A densitometric study using dual-energy X-ray absorptiometry subregional analysis.

OBJECTIVE: Subchondral bone changes are thought to be an important aetiological element in the pathogenesis of osteoarthritis (OA). To confirm this hypothesis in the meniscectomized (MNX) guinea pig model, bone densitometry was performed in the subchondral bone of the distal femur. METHODS: MNX and sham-operated (SH) guinea pigs were studied 1 and 3 months after partial meniscectomy at the medial side of the left knee. Bone mineral density was measured at the lateral (BMD-L) and medial (BMD-M) sides of the distal femur using dual-energy X-ray absorptiometry (DXA). BMD-M was then compared to the bone volume evaluated by histomorphometry at the medial epiphyseal part of the proximal tibia (BV-M). RESULTS: One month after operation, in MNX animals left femur BMD-M was significantly lower than in the contralateral femur (-9%, P< 0.01) and than in the left femur of SH (-11%, P< 0.01). By contrast, 3 months after meniscectomy BMD-M was higher in the femur than in the contralateral femur (+4%, P< 0.05); BV-M tended to be higher on the left than on the right side (+4%, P< 0.06), and was significantly correlated with BMD-M at the 2 grouped time points: r=0.74 (P< 0.001). CONCLUSIONS: These data emphasize the usefulness of DXA as a simple tool to assess subchondral bone changes at the OA-affected side of the femur and reveal typical variations of bone metabolism in the initiation of OA pathology in the MNX guinea pig: early bone loss at the subchondral level followed by increased bone density.

Specific evaluation of localized bone mass and bone loss in the rat using dual-energy X-ray absorptiometry subregional analysis.

Dual-energy X-ray absorptiometry (DXA), together with the use of ultra-high resolution software, recently appeared as an accurate method for determining bone mineral density (BMD) in the rat. In order to assess the ability of this technique to detect changes in bone mass in the rat rapidly and precisely, we measured BMD at various sites of the femur using DXA subregional analysis. In particular, we studied the BMD of the metaphyseal part of the femur (M-BMD) rich in trabecular bone, and compared the values obtained with the cancellous bone volume measured by histomorphometry. In short-term ovariectomized animals (experiment 1), M-BMD was the only parameter to differentiate statistically between 10 ovariectomized (OVX) and 10 SHAM-operated (SHAM) rats (-11.2%, p < 0.01) 9 days after surgery. M-BMD still expressed the greatest variation between OVX and SHAM rats 42 days following ovariectomy (experiment 2) (-16.1%, p < 0.001 v -6.2%, p < 0.01 for the total femur BMD) and confirmed previous data demonstrating a greater loss of cancellous than cortical bone after cessation of ovarian activity. M-BMD was highly correlated with cancellous bone volume (BV) in normal (r = 0.82, p < 0.001, n = 30), OVX (r = 0.77, p < 0.001, n = 22) and SHAM (r = 0.88, p < 0.001, n = 21) rats.(ABSTRACT TRUNCATED AT 250 WORDS)