A finite element model to simulate femoral fractures in calves: testing different polymers for intramedullary interlocking nails.

OBJECTIVE: To verify if the finite element method can correctly estimate the performance of polyacetal and polyamide 6 intramedullary nails in stabilizing a femoral fracture in calves and to estimate the performance of a polypropylene nail in same conditions. STUDY DESIGN: Computational and experimental study. SAMPLE POPULATION: Finite element models (FEMs). METHODS: Based on a 3-dimensional finite element method (FEM) of the femoral diaphysis, 3 models were constructed to simulate an oblique simple fracture stabilized by an intramedullary nail composed of 1 of 3 distinct polymers. Models were tested under 6 loading conditions that simulated a static calf or a calf in different walking phases. Maximum bone and implant stresses were compared to yield and rupture stresses of specific materials. RESULTS: Under static conditions, all polymers were resistant to critical deformation and rupture because maximum von Mises stresses were lower than the respective yield and rupture stresses. However, during walking, maximum stresses exceeded the yield and rupture limits of the polymers, in agreement with a previous in vivo study, which used polyacetal and polyamide nails. CONCLUSIONS: FEM correctly estimated that polyacetal and polyamide 6 nails would fail to immobilize an oblique femoral diaphyseal fracture in calves that were allowed to walk freely during the early postoperative period. FEM can be useful in the development of new bovine orthopedic devices.

Evaluation of polycyclic aromatic hydrocarbons in asphalt binder using matrix solid-phase dispersion and gas chromatography.

A method developed for the extraction and analysis of polycyclic aromatic hydrocarbons (PAHs) in the asphalt binder using a matrix solid-phase dispersion (MSPD) and gas chromatography is presented. The MSPD method was proposed as a rapid and easy approach to determining PAHs present in the maltenic phase of asphalt binder extracted through a mechanical shaking and sonication of the material. The recovery rates ranged from 62.77-89.92% (shaking) and from 56.54-93.6% (sonication) with relative standard deviations lower than 8.8%. The study shows that the recovery rates using shaking and sonication extractions are not significantly different at the p < 0.05 level. The limits of detection and quantification ranged from 0.7-1.8 mg/kg and 2.2-5.6 mg/kg, respectively. The proposed analytical method was applied to determine PAH levels in an asphalt binder from Brazil. The main PAHs found were BbF, BaP, Per, IncdP, DahA, and BghiP, with average concentrations of 10.2-20.7 mg/kg, but the PAHs Ace and Acy were not detected. However, Nap, Fl, Phen, Ant, Flr, Pyr, Chry, BaA, and BkF were present in average concentrations amounting to less than 10 mg/kg. The results showed that the MSPD method is potentially a valuable tool for the determination of PAHs in the asphalt binder.

The anatomical relationship between the position of the auriculotemporal nerve and mandibular condyle.

Head, neck, face, and ear pains are commonly associated with disorders of the temporomandibular joint (TMJ). Several theories have been proposed regarding the functional relationship of the TMJ and the associated structures, and how they might contribute to certain painful conditions. This study was conducted to determine the anatomic relationship of the auriculotemporal nerve to the middle meningeal artery and the mandibular condyle. Forty human cadaver temporomandibular joints were dissected to locate the precise position of the auriculotemporal nerve to the mandibular condyle. The study findings revealed a significant variation in the relationship of the auriculotemporal nerve to the middle meningeal artery. The auriculotemporal nerve was found to be between 10-13 mm inferior to the superior surface of the condyle and 1-2 mm posterior to the neck of the condyle. The nerve was not found to be in a position that would likely create an entrapment with adjacent tissues. These findings may assist the clinician to locate the most appropriate injection site for an auriculotemporal nerve block.