Accuracy Assessment of Using Rapid Prototyping Drill Templates for Atlantoaxial Screw Placement: A Cadaver Study.

Purpose. To preliminarily evaluate the feasibility and accuracy of using rapid prototyping drill templates (RPDTs) for C1 lateral mass screw (C1-LMS) and C2 pedicle screw (C2-PS) placement. Methods. 23 formalin-fixed craniocervical cadaver specimens were randomly divided into two groups. In the conventional method group, intraoperative fluoroscopy was used to assist the screw placement. In the RPDT navigation group, specific RPDTs were constructed for each specimen and were used intraoperatively for screw placement navigation. The screw position, the operating time, and the fluoroscopy time for each screw placement were compared between the 2 groups. Results. Compared with the conventional method, the RPDT technique significantly increased the placement accuracy of the C2-PS (p < 0.05). In the axial plane, using RPDTs also significantly increased C1-LMS placement accuracy (p < 0.05). In the sagittal plane, although using RPDTs had a very high accuracy rate (100%) in C1-LMS placement, it was not statistically significant compared with the conventional method (p > 0.05). Moreover, the RPDT technique significantly decreased the operating and fluoroscopy times. Conclusion. Using RPDTs significantly increases the accuracy of C1-LMS and C2-PS placement while decreasing the screw placement time and the radiation exposure. Due to these advantages, this approach is worth promoting for use in the Harms technique.

[Residues and risk assessment of polycyclic aromatic hydrocarbons in the surface sediments and marine organisms from Dapeng Bay, Shenzhen].

In order to assess contamination by polycyclic aromatic hydrocarbons (PAHs), surface sediments and marine organism samples of fish, shrimp and shellfish were collected from the Dapeng Bay, Shenzhen in October 2011. Concentrations fof sixteen priority PAHs were determined by gas chromatography and mass spectrometry (GC-MS). The total concentrations of PAHs (Sigma PAHs ) ranged from 216. 56 ng.g-1 to 1 314. 92 ng.g-1 dry weight in sediment samples and from 70. 88 ng.g-1 to 251.90 ng.g-1 wet weight in biological samples, respectively. The mean concentration was the highest in fish (171.52 ng.g-1 ), followed by mussel (134.75 ng.g-1) and shrimp (123.35 ng.g-1) in the studied marine organisms. Compared with those in other water bodies around the world, PAHs pollution in the studied area was at medium level. The dominant fraction in the surface sediments was the 4-ring PAHs. Identification of PAH sources suggested that PAHs in Dapeng Bay were likely originated from both pyrolytic and petrogenic sources. The most abundant PAHs were 3-ring PAHs in the tissues of organisms, which may be governed by their feeding behaviors, habitats, and bioavailability of PAHs. Ecological risk assessment indicated that PAHs in surface sediments might have adverse impacts on local ecosystem. Health risk analysis revealed that the potency equivalent concentrations of BaP to the total PAHs in marine organisms from Dapeng Bay were relatively high and may cause some concerns on human health by consumption.