Stimulating effect of implant loading on surrounding bone. Comparison of three numerical models and validation by in vivo data

A number of algorithms have been proposed to model the adaptive behavior of bone under load. However, the predictions of several models have neither been compared nor have they been systematically related to in vivo data. To this end, the stress states of loaded implant-bone interfaces were analyzed before and after osseointegration using finite element (FE) techniques. In a preliminary step, an FE mesh of a cylindrical implant encased in a cancellous core surrounded by a cortical layer was constructed, and the stresses and strains that developed at the interface were determined. The implant was loaded with 100 N vertical and 30 N lateral loads. Using this structure, the peak compressive and tensile stresses were determined. Then bone remodeling predictions were assessed using three different models: von Mises equivalent strain, strain energy density and effective stress. Finally, a systematic search of the literature was conducted to relate the numerical predictions to existing in vivo data. The FE simulations led to the following conclusions: (1) calculated compressive stresses were lower than the ultimate compressive stresses of cortical and cancellous bone. (2) Calculated tensile stresses were generally superior to experimental data on the tensile strength of the bone-implant interface. (3) With one exception, the predictions of all models were homogeneously grouped on the stimulus scales. (4) The predictions of the models as to bone gain or loss were not consistent and at times contradictory. It is hypothesized that this effect is linked to a lazy zone that is too narrow. With respect to the application of the numerical models to in vivo data, peak strains and strain energy densities were consistent with in vivo data. No in vivo data were found that supported effective stress as a stimulus.     

Macular serous detachment revealing acute lymphoblastic leukemia

BACKGROUND: Leukemias are a group of malignant diseases caused by immature hematopoietic cells proliferating in the blood marrow. Some manifestations result from ocular-orbital involvement, which usually occurs through the central nervous system. Other manifestations stem from vasculopathy and/or hemorheologic disorders (anemia, thrombocytopenia, hyperviscosity). OBSERVATION: We report a case of a 42-year-old women presenting with loss of vision caused by serous macular detachment. The investigations showed the diagnosis of acute lymphoblastic leukemia. Steroids and chemotherapy led to complete remission with normal visual acuity during a follow-up of 29 months. DISCUSSION: Ocular involvement is seen in 28%-80% of leukemia cases. The most obvious findings are the presence of retinal hemorrhages, which are most commonly located in the posterior pole. The intraretinal hemorrhage may contain a white component that usually is a white dot in the center of the hemorrhage, but other clinical features are described. Serous detachment of the neuroepithelium is seldom reported, and can be the first symptom of the disease. Other ocular findings include infiltrative involvement of the chorioretina, anterior segment involvement, and orbital location. Ocular location is estimated to be an equivalent of central nervous system involvement, and subsequently requires adequate treatment (steroids, chemotherapy and radiotherapy of the central nervous system). CONCLUSION: Ocular manifestations of leukemia are frequent but rarely reveal the disease. Serous detachment is rarer. However, the diagnosis of leukemia should be considered in case of pigmentary epithelium involvement.     

Inflammatory pseudotumor of the lacrimal gland. Apropos of 2 cases]

BACKGROUND: Inflammatory pseudotumors of the orbit are relatively common accounting for 12 to 15% of all orbital diseases. Lacrimal gland location is exceptional. CASE REPORTS: We report 2 patients aged 30 and 25 years who underwent surgery for an isodense tumor of the lacrimal gland. Immunohistochemistry revealed an inflammatory pseudotumoral process. Both patients are recurrence-free 2 years follow-up. DISCUSSION: Inflammatory pseudotumors of the orbit, particularly those located in the lacrimal gland still raise unresolved questions concerning the pathogenesis, diagnosis and treatment. CONCLUSION: Lacrimal gland localizations of inflammatory pseudotumors must be recognized due to difficulties in diagnosis and therapeutic management.     

Validation of the neutrophil-to-lymphocyte ratio as a new simple biomarker of adult onset Still’s disease: A STROBE-Compliant prospective observational study

This study was performed to investigate the role of neutrophil-to-lymphocyte ratio (NLR) in the diagnosis of adult onset Still disease (AOSD) and its performance to improve the sensitivity of the classifications criteria (Yamaguchi and Fautrel Classifications).We conducted a multicenter prospective nationwide case-control study in Internal medicine, Rheumatology and Infectious disease departments, to include successively patients with suspected AOSD (2 or more major criteria of Yamaguchi or Fautrel classifications). All clinical and biological features were collected in a consensual and standardized clinical assessment at baseline and during follow-up. A receiving operating characteristic (ROC) curve was used to reassess the cutoff value of NLR. After determination of the cutoff value for NLR by ROC curve, 2 composite sets (Yamaguchi classification + NLR as a major criterion and Fautrel classification + NLR as a major criterion) were performed and evaluated.One hundred sixty patients were included, 80 patients with AOSD and 60 controls with different diagnoses. Twenty patients with incomplete data were excluded. The cutoff value for NLR equals 4 (area under the curve, AUC: 0.82). The NLR was ≥ 4 in 93.7% (75/80) of AOSD patients with a sensitivity of 93.8% and specificity of 61.7%. The association of NLR as a major criterion with the classification of Yamaguchi or Fautrel improved their sensitivity, respectively for Fautrel (76.3% to 92.5%, P = .004) and Yamaguchi (78.8% to 90%, P = .05).This study validates the NLR as a good simple biomarker of AOSD with a cutoff value of 4 and high sensitivity (93.8%). The addition of NLR (NLR ≥ 4) as a major criterion to the classifications (Yamaguchi and Fautrel) improved significantly their sensitivity and accuracy.     

18F-NaF positron emission tomography/computed tomography in voriconazole-induced periostitis

Clinical Rheumatology -     

Fatigue resistance of ITI implant-abutment connectors -- a comparison of the standard cone with a novel internally keyed design

The Straumann Company has recently supplemented its standard 'morse-taper' configuration with an octagonal internal key. During the restorative phase of implant treatment, this additional feature was designed to ensure positional duplicability between the laboratory and the clinical environments. It was, however, unclear whether this keying mechanism would decrease the mechanical strength of the connection between the implant and the abutment. This applies to keyed male and female parts but also to combinations of the new and the standard designs. Specially constructed specimens analogs representing all three combinations were fitted with a T-shaped bar, preangled to 15 degrees and subjected to vertical force applications provided by a servohydrolic fatigue tester. The loading frequency was 2 Hz and the maximum cycle number was 106. The data were evaluated using the staircase technique. The specimens were also modeled and analyzed numerically using finite element procedures. The samples' failure locations were recorded and the displacement vs. cycle number plots were patterned in four groups. The fatigue tests and staircase analysis showed no difference in mechanical resistance between the standard and the internally keyed connectors. The finite element models revealed a stress concentration located at the apical edges of the octagonal connector. However, it appeared that this phenomenon was based on computational rather than mechanical grounds. The locations of the failure sites were distributed randomly across the structures, thereby indicating the absence of a locus of minor resistance. The patterns of the displacement vs. cycle number could not be attributed to specific combinations between the standard and the internally keyed designs. It was concluded that both connectors are equal in their mechanical resistance to bending and torquing forces.     

Rehabilitation after ischemic stroke in the elderly

The aim of the rehabilitation after stroke is the recovery of the best functioning, by stimulation of cerebral plasticity and functional compensation while preventing complications. The capacity of recovery in the ageing subject depends on previous physiological and psychological status, previous medical history, specially previous brain lesions, and stroke severity. Rehabilitation is best to be conducted in specialised Physical and Medicine Rehabilitation Units, in which the functional and vital prognosis is improved by specialised interdisciplinary teams. Its goal is to obtain the best autonomy possible in the usual environment. Age by itself should not be a criteria for admission in such units.     

5-HT2 receptors in the nucleus tractus solitarius: characterisation and role in cardiovascular regulation in the rat

The effects of the local application of drugs acting on 5-HT₂ receptors in the nucleus tractus solitarius (NTS) on the heart rate and blood pressure were investigated in normal and nodose ganglionectomized anaesthetized rats. The unilateral micro-injection of an agonist such as 2,5-dimethoxy-3-bromo-amphetamine (DOB) (0.1–0.5 pmol) or 2,5-dimethoxy-3-nitroamphetamine (DON) (0.1–0.5 pmol) produced a dose-dependent hypotension and bradycardia in both intact and ganglionectomized animals. These cardiovascular effects were similar to those observed after the unilateral micro-injection of low doses (pmol) of 5-HT, and could be prevented by the prior micro-injections of the 5-HT₂ antagonists ketanserin, ritanserin and piremperone. These findings support the hypothesis that 5-HT₂ receptors within the NTS play a role in the reflex regulation of blood pressure. In addition, it was also observed that the micro-injection of subthreshold doses of 5-HT or DOB significantly enhanced the hypotension and bradycardia produced by the unilateral micro-injection of N-methyl-d-aspartate (NMDA). The potentiation of NMDA depressor effects by 5-HT or DOB could be totally prevented by ketanserin or piremperone, suggesting that 5-HT acting upon 5-HT₂ receptors in the NTS may intervene in the reflex control of blood pressure by modulating the glutamatergic transmission.