Optimal drilling at femoral head-neck junction for treatment of the femoral head necrosis: Experimental and numerical evaluation.

BACKGROUND: Advanced core decompression (ACD) is a relative new technique for treatment of early stages of avascular femoral head necrosis. Although it is a promising treatment option, there is a need to modify this technique for achieving higher hip survival rates. An idea was to combine this technique with the lightbulb procedure in order to get a complete removal of the necrosis. This study aimed at evaluating the fracture risk of the femora treated by the combined Lightbulb-ACD technique as the basis for clinical application. METHODS: Subject-specific models were generated from CT scan data of five intact femora. Several treated models were then created from each intact bone and simulated during normal walking activity. Biomechanical testing was additionally performed on 12 pairs of cadaver femora to confirm the simulation results. FINDINGS: The finite element results revealed that the risk factor of the treated models with a 8 mm-drill increased, but was not significantly greater than that of their corresponding intact models. However, for the femur treated with a 10 mm-drill, the risk factor increased significantly. Fracture always initiated on the femoral neck, i.e. it was either subcapital or transcervical fracture. Our biomechanical testing results correlated well with the simulation data which confirmed the usefulness and effectiveness of the bone models. INTERPRETATION: The combined Lightbulb-ACD technique using a 10 mm drill increased the fracture risk of femur postoperatively. A drill of up to 8 mm at the anterior head-neck junction did not however lead to the weakening of the femur so that full load bearing may be possible.

Layer-Specific Damage Modeling of Porcine Large Intestine under Biaxial Tension.

The mechanical behavior of the large intestine beyond the ultimate stress has never been investigated. Stretching beyond the ultimate stress may drastically impair the tissue microstructure, which consequently weakens its healthy state functions of absorption, temporary storage, and transportation for defecation. Due to closely similar microstructure and function with humans, biaxial tensile experiments on the porcine large intestine have been performed in this study. In this paper, we report hyperelastic characterization of the large intestine based on experiments in 102 specimens. We also report the theoretical analysis of the experimental results, including an exponential damage evolution function. The fracture energies and the threshold stresses are set as damage material parameters for the longitudinal muscular, the circumferential muscular and the submucosal collagenous layers. A biaxial tensile simulation of a linear brick element has been performed to validate the applicability of the estimated material parameters. The model successfully simulates the biomechanical response of the large intestine under physiological and non-physiological loads.

Hip joint mechanics in patients with osteonecrosis of the femoral head following treatment by advanced core decompression.

BACKGROUND: Osteonecrosis of the femoral head is a serious disease which, if left untreated, leads to destruction of the affected hip joint. For treatment of early stages of this disease, core decompression is the most common procedure. This study investigated the influence of the necrotic lesion and core decompression on the stress pattern in the hip joint using finite element analysis. METHODS: Subject-specific models were generated from CT scan data of 5 intact hips. For each intact hip, twelve affected hip models were created by imposing a necrotic lesion in the femoral head, and four treated models were then created from four affected ones with central lesion, respectively. Treated models were created by supposing that the defect zone and the drill canal were filled with a bone substitute. Totally 105 hip models from three groups (intact, affected and treated) were simulated during normal walking activity. FINDINGS: Necrotic lesion modified the stress distribution within the femoral head. Peak stress increased significantly up to 186% in mean in hips with a large lesion indicating an increased risk of femoral head collapse. Additionally, the presence of a medium to large necrosis altered significantly stress values (P < 0.05) and pattern in the articular cartilage. Our study revealed that advanced core decompression can recover normal cartilage stress values and pattern in treated joint. INTERPRETATION: The presence of a large lesion increased the risk of femoral head collapse. Advanced core decompression with bone grafts can restore normal cartilage mechanics in hip postoperatively.

A literature review on large intestinal hyperelastic constitutive modeling.

Impacts, traumas and strokes are spontaneously life-threatening, but chronic symptoms strangle patient every day. Colorectal tissue mechanics in such chronic situations not only regulates the physio-psychological well-being of the patient, but also confirms the level of comfort and post-operative clinical outcomes. Numerous uniaxial and multiaxial tensile experiments on healthy and affected samples have evidenced significant differences in tissue mechanical behavior and strong colorectal anisotropy across each layer in thickness direction and along the length. Furthermore, this study reviewed various forms of passive constitutive models for the highly fibrous colorectal tissue ranging from the simplest linearly elastic and the conventional isotropic hyperelastic to the most sophisticated second harmonic generation image based anisotropic mathematical formulation. Under large deformation, the isotropic description of tissue mechanics is unequivocally ineffective which demands a microstructural based tissue definition. Therefore, the information collected in this review paper would present the current state-of-the-art in colorectal biomechanics and profoundly serve as updated computational resources to develop a sophisticated characterization of colorectal tissues.

The protective effect of rural life on mite sensitization disappears among urban migrants in the South of Vietnam.

BACKGROUND: Rapid urbanization combined with rural migration to urban areas in southern Vietnam could be risk factors for allergen sensitization, contributing to chronic respiratory diseases (CRD). We aimed to evaluate the prevalence of mite sensitization and its relation to house dust characteristics among rural and urban native and migrating populations with CRD. METHODS: Rural (n = 19) and urban (n = 46) dwellings were defined on the basis of a home typology. Controls were western Belgian houses (n = 14). Besides the house characteristics, both endotoxin and mite allergens were measured in the settled dusts. The sensitization to mite allergens was defined by positive skin prick test (SPT) and concentration of specific IgE (sIgE)≥ 0.7 U/mL. The prevalence of mite sensitization was evaluated among 610 patients with CRD and compared according to both their home types and places of birth and residences. RESULTS: The concentration of endotoxin (but not mite allergen) was higher in rural compared to urban dusts (440 (95%CI: 314-566) versus 170 (95%CI: 115-226) EU/mg; p < 0.0001). The prevalence of positive sIgE to Der p1 and Der p2 was significantly lower in rural (9% and 5%) compared to urban (15% and 9%) population, consistent with the positive SPT to mite (14% and 21%, respectively). Among the urban migrants, the risk of mite sensitization (SPT) was higher compared to the rural natives (OR: 1.79 (1.02-3.15), p < 0.05) and not different to the urban ones (OR: 1.35 (0.82-2.23) p NS). CONCLUSION: In Vietnam, associated with higher endotoxin (but not allergen) dust concentrations, the risk of mite sensitization was lower in rural compared to the native urban population, but this protective effect could disappear among rural to urban migrants.

Geometric analysis of an expandable reamer for treatment of avascular necrosis of the femoral head.

"Advanced core decompression" (ACD) is a treatment option for osteonecrosis of the femoral head (ONFH) that aims at complete removal of the necrotic tissue using a percutaneous expandable reamer and refilling of the head with an osteoconductive bone-graft substitute. The objective of this study was to evaluate if the success of ACD depends on the amount of necrotic tissue remaining after the procedure and how efficiently the necrotic tissue can be removed with the current reamer. Three-dimensional models of proximal femora including ONFH were generated from the preoperative MRIs of 50 patients who underwent ACD. Best-case removal was calculated by geometrical analysis. In 28 of 50 cases, postoperative MRI was used to determine how much necrotic tissue had been removed. Prognostic values and correlations were evaluated in order to assess success or failure of the treatment. The amount of preoperative and remaining necrosis correlates significantly with treatment failure. The larger both volumes are, the more likely it is that treatment will fail. In patients with remaining necrosis of less than 1000 mm(3), no treatment failure was observed. The amount of necrosis actually removed differed significantly from the amount calculated as the best possible result. Simulation of the removal procedure showed that complete removal is not possible. These results led to the conclusion that the success of ACD depends on the amount of necrotic tissue remaining in the femoral head after the procedure. Modifications to the instrument are necessary to increase the amount of necrotic tissue that can be removed.

Effect of antibiotics on callus regeneration during transformation of IR 64 rice.

We report here the effect of antibiotics on the regeneration potential of recalcitrant indica rice cultivar, IR64. Different protocols reporting high-efficiency agro-bacterium-mediated transformation of mature seed-derived regenerative calli were used and compared. The putative transgenic (T0) plants were analyzed for integration of the transgene through polymerase chain reaction and Southern blotting analyses. It was observed that the high-efficiency transformation of scutellar-derived regenerative calli could be obtained by using maltose as a carbon source and increased quantity of 2,4-D on a medium containing a higher concentration of gelling agent. The percentage of regeneration is greatly affected by the presence of antibiotics.