Finite Element Analysis of Insertion Angle of Absorbable Screws for the Fixation of Radial Head Fractures.

OBJECTIVE: To investigate the biomechanical effects of different insertion angles of absorbable screws for the fixation of radial head fractures. METHODS: The finite element models used to simulate the fractures were created based on CT scans. Two absorbable screws were used to fix and maintain the stability of the fracture, and the angles between the screws were set to 0°, 15°, 30°, 45°, 60°, 75°, and 90°. A downward force of 100 N was applied at the stress point, which was coupled with the surface, and the distal radius was limited to six degrees of freedom. The direction and location of the applied force were the same in each model. The values of the von Mises stress and peak displacements were calculated. RESULTS: Under the applied load and different screw angles, the maximum von Mises stress in the screws was concentrated on the surface contacting the fracture surfaces. The maximum von Mises equivalent stress in the screw decreased when the angle increased from 0° (19.54 MPa) to 45° (13.11 MPa) and increased when the angle further increased to 90° (24.63 MPa). The peak displacement decreased as the angle increased from 0° (0.19 mm) to 45° (0.15 mm) and increased when the angle further increased to 90° (0.25 mm). CONCLUSION: The computational stress distribution showed that fixation with absorbable screws is safe for patients. Moreover, the minimum von Mises stress and displacements were generated when the angle between the screws was 45°; hence, this setting should be recommended for Mason type II radial fractures.

Genome-based analysis of the type II PKS biosynthesis pathway of xanthones in Streptomyces caelestis and their antifungal activity.

The ethyl acetate extract from the liquid fermentation of S. caelestis Aw99c exhibited high and broad antifungal activities against plant pathogenic fungi. Bioassay guide fractionation led to the discovery of two xanthones, citreamicin ε and θ. The draft genome sequence of S. caelestis Aw99c was analyzed by a similarity-based approach to elucidate the pathway for the citreamicins. A 48 kb citreamicin (cit) gene cluster with 51 open reading frames encoding type II polyketide synthases and unique polyketide tailoring enzymes was proposed based on the genome analysis and the chemical structure derivation. In vitro antifungal assay showed that citreamicin ε exhibited significant growth inhibition against the plant pathogenic fungi with MIC values ranging from 1.56 to 12.5 µM. The cellular structural change of M. grisea treated with citreamicin ε was detected by SEM and the result showed that citreamicin ε caused disruptive surface of the mycelia.