ABSTRACT
Objective To investigate mechanical properties of the thoracic spine fixed with pedicle screws that were placed using a “funnel technique”. MethodFourteen thoracic spinal segments (T6 to T10) were collected from adult cadavers. These specimens were divided into two groups, 7 in each, and fixed with pedicle screw using funnel and Magerl techniques. The displacement stiffness of the spinal segment and the pull out strength of the pedicle screw were tested for intact and fixed spinal specimens. The displacement stiffness was measured from different loading directions, including axial compression, anterior flexion, posterior extension, lateral bending and axial torsion. ResultsCompared to the intact spine segments, the displacement stiffness is significantly increased (P＜0.05) at all directions in the segments fixed with either funnel or Magerl technique; however, there is no significant difference between the groups fixed with different technique. The screw pull out strength is significantly decreased (P＜0.05) in spine segments fixed with Funnel technique compared to those fixed with Magerl technique. ConclusionsSince funnel technique removed a portion of bone from the posterior side of the vertebral pedicle, it can raise the accuracy and safety for the placement of pedicle screw. Although this technique does not affect the stiffness of fixed spinal segment, it may decrease the anchor strength of pedicle screw. Accordingly, we recommend that the funnel technique can be considered as a complement method for the fixation of vertebral fracture using pedicle screws.
ABSTRACT
<p><b>BACKGROUND</b>Transparent dressings are commonly used to cover central venous catheter sites. However, it has been suggested that they might not allow adequate moisture vapor transmission, resulting in local moistness that promotes bacterial growth. We compared the moisture vapor transmission rates (MVTRs) of different, currently used transparent and traditional gauze dressings. We aimed to determine the MVTRs at different temperatures and humidities.</p><p><b>METHODS</b>The dressings were used to seal 50-ml plastic centrifuge tubes containing 20 ml deionized water: Tubes in group 1 were covered with 12 layers of ordinary gauze, group 2 with IV3000, group 3 with OPSITE FLEXIGRID, group 4 with 3M HP Tegaderm, and group 5 with 3M Tegaderm. The tubes were placed upright in an artificial climate cabinet, so that the dressings were not touching the water, in order to simulate the conditions of medical dressings in contact with the skin. The average MVTRs were determined under different conditions. MVTRs were also determined with tubes from groups 2 - 5 laid on their sides, allowing the dressings to touch the water, so simulating contact of the dressings with sweating skin, or wounded skin with exudates. We also calculated the dressings' self-reactive abilities by comparing their MVTRs in contact with the water surface with those when not in contact with the water surface.</p><p><b>RESULTS</b>Group 1 demonstrated the highest MVTR, followed by groups 2, 4, 3 and 5 under conditions simulating contact of the dressings with normal skin at the following temperatures and humidities: 20 degrees C/30%, 20 degrees C/60%, 20 degrees C/90%, 37 degrees C/30%, 37 degrees C/60% and 37 degrees C/90%. When the relative humidity (RH) increased, the MVTRs decreased. The MVTRs differed significantly among different dressings and RHs: At high temperature (37 degrees C) and high humidity (90%), the MVTR of the transparent dressings in group 2 was higher than that of group 1 (P < 0.01). The reactive MVTR was highest in group 2 (10.2 - 16.3 times > MVTR) while that of group 4 was second highest (2.6 - 9.6 times > MVTR).</p><p><b>CONCLUSIONS</b>RH and temperature had significant effects on the MVTRs of different dressings. The IV3000 transparent dressing used in group 2 was as effective as ordinary gauze. These results suggest that increased infection rates due to low MVTRs might not be a problem. The clinical implications of these observations for catheter-related infections need to be further investigated in multicenter studies.</p>