Total meniscectomies are commonly thought to cause progressive degenerative arthrosis pathology in articular cartilage in a period of a few years because of alteration of the biomechanical environment including increased joint instability. This concern has lead to a preference for partial meniscectomies, although lateral partial meniscectomies sometimes lead to catastrophic results. We performed a three-dimensional finite element model of the human tibiofemoral joint to examine the effect of lateral meniscectomy on knee biomechanics. The results were compared to those from modeling a medial meniscectomy. Under axial femoral compressive loads, the peak contact stress and maximum shear stress in the articular cartilage increased 200% more after a lateral than a medial meniscectomy. These increased stresses could partly explain the higher cartilage degeneration observed after a lateral meniscectomy. ß

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The Finite Element Method (FEM) can be used to analyze very complex geometries, such as the pelvis, and complicated constitutive behaviors, such as the heterogeneous, nonlinear, and anisotropic behavior of bone tissue or the noncompression, nonbending character of ligaments. Here, FEM was used to simulate the mechanical ability of several external and internal fixations that stabilize pelvic ring disruptions. A customized pelvic fracture analysis was performed by computer simulation to determine the best fixation method for each individual treatment. The stability of open-book fractures with external fixations at either the iliac crests or the pelvic equator was similar, and increased greatly when they were used in combination. However, external fixations did not effectively stabilize rotationally and vertically unstable fractures. Adequate stabilization was only achieved using an internal pubis fixation with two sacroiliac screws.

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A retrospective review of complications with the gamma nail has been carried out in 152 patients with stable and unstable pertrochanteric fractures. Operative complications occurred in 10 patients. Screws penetrated the femoral neck in 3, immediate varus was associated with a short screw in 2, diaphyseal fractures occurred at the site of the distal screws in 3 and comminuted femoral fractures in 2. Fifteen patients (10.5%) died in hospital. At follow up, pseudarthrosis was present in 2 cases and fractures of the femoral shaft in 4. The incidence of complications could be reduced by using of shorter nails, less valgus angulation and by not introducing distal screws unless essential.

The main objective of this work is the evaluation, by means of the finite element method (FEM) of the mechanical stability and long-term microstructural modifications in bone induced to three different kinds of fractures of the distal femur by three types of implants: the Condyle Plate, the less invasive stabilization system plate (LISS) and the distal femur nail (DFN). The displacement and the stress distributions both in bone and implants and the internal bone remodelling process after fracture and fixation are obtained and analysed by computational simulation. The main conclusions of this work are that distal femoral fractures can be treated correctly with the Condyle Plate, the LISS plate and the DFN. The stresses both in LISS and DFN implant are high especially around the screws. When respect to remodelling, the LISS produces an important resorption in the fractured region, while the other two implants do not strongly modify bone tissue microstructure.

Generally, monitoring of hypoxemia has been always based on partial pressure of arterial oxygen to fraction of inspired oxygen ratio; recently it was confirmed a good correlation between this ratio and a non-invasive alternative ratio of oxygen saturation to fraction of inspired oxygen (SF ratio = SpO2/FiO2). The SF ratio has been studied and validated, especially in the intubated patients, however studies monitoring patients treated with non-invasive ventilation (NIV) are lacking. The aim of the study was to determine if the SF ratio is a reliable predictive factor for failure of NIV in pediatric patients diagnosed with hypoxemic acute respiratory failure due to pneumonia. A five year retrospective study with consecutive sampling of patients diagnosed with hypoxemic acute respiratory failure due to pneumonia, admitted to the pediatric intensive care unit in a university hospital and treated with NIV was conducted. Physiological and ventilator variables were collected before starting NIV and at 2, 8 and 12 hours of treatment, and the corresponding SF ratios calculated. Thirty-four patients were studied. NIV failed in seven patients. Significant differences in SF ratio were observed between the successful and unsuccessful patients at the onset, 2 and 12 hours of treatment. Multivariable analysis revealed the SF ratio at two hours to be an independent predictor of NIV failure (odds ratio = 0.96, 95% confidence intervals 0.93?0.99; P = 0.015). Area Under Receiver Operating Characteristic curve = 0.90 (95% confidence interval = 0.79 to 1.000), optimal cut off value for SF at 2 hours ? 189; sensitivity = 86%, specificity = 74%. In conclusion, the SF ratio of 189 or less at 2 hours of NIV seems to be useful for predicting NIV failure in this cohort.