An in vitro investigation of peak insertion torque values of six commercially available mini-implants

This study compared peak insertion torque values of six commercially available self-drilling mini-implants [Mini Spider? screw (1.5 × 8 mm), Infinitas? (1.5 × 9 mm), Vector TAS? (1.4 × 8 mm), Dual Top? (1.6 × 8 mm), Tomas Pin? (1.6 × 8 mm), and Ortho-Easy? (1.7 × 6, 8, and 10 mm)]. Twenty implants each were drilled into acrylic rods at a speed of 8 rpm using a motorized torque measurement stand, and the values were recorded in Newton centimetres (Ncm). A further 20 Ortho-Easy? implants with a length of 6 and 10 mm were tested at 8 rpm; 20 implants of 6 mm length were also tested at 4 rpm. Kaplan-Meier estimates of the peak torque values were compared using the log-rank test with multiple comparisons evaluated by Sidak's test. There were significant differences in the maximum torque values for different mini-implants with the same length. The Mini Spider? screw and Infinitas? showed the lowest average torque values (6.5 and 12.4 Ncm) compared with Vector TAS?, Dual ToP?, Tomas Pin?, and Ortho-Easy? (30.9, 29.4, 25.4, and 24.8 Ncm, respectively). There was no correlation between the diameter of the implants and torque values. The Tomas Pin? showed the largest standard deviation (7.7 Ncm) and the Dual Top? implant the smallest (0.6 Ncm). Different insertion speeds did not result in significant differences in peak torque values but the 6 mm mini-implants showed significantly higher torque values than the 8 and 10 mm implants. Using a 'torque limiting' screwdriver or pre-drilling cortical bone to reduce insertion, torque appears justified for some of the tested implants.     

Quantitative Analysis of the Effect of Iterative Reconstruction Using a Phantom: Determining the Appropriate Blending Percentage

Purpose

To investigate the optimal blending percentage of adaptive statistical iterative reconstruction (ASIR) in a reduced radiation dose while preserving a degree of image quality and texture that is similar to that of standard-dose computed tomography (CT).

Materials and Methods

The CT performance phantom was scanned with standard and dose reduction protocols including reduced mAs or kVp. Image quality parameters including noise, spatial, and low-contrast resolution, as well as image texture, were quantitatively evaluated after applying various blending percentages of ASIR. The optimal blending percentage of ASIR that preserved image quality and texture compared to standard dose CT was investigated in each radiation dose reduction protocol.

Results

As the percentage of ASIR increased, noise and spatial-resolution decreased, whereas low-contrast resolution increased. In the texture analysis, an increasing percentage of ASIR resulted in an increase of angular second moment, inverse difference moment, and correlation and in a decrease of contrast and entropy. The 20% and 40% dose reduction protocols with 20% and 40% ASIR blending, respectively, resulted in an optimal quality of images with preservation of the image texture.

Conclusion

Blending the 40% ASIR to the 40% reduced tube-current product can maximize radiation dose reduction and preserve adequate image quality and texture.     

Effect of soft tissue thickness over the posterior border of the vertebral body and disc space on cage placement during posterior lumbar interbody fusion: A cadaveric study

In the present study, we investigated whether there is a difference between visual depth (VD) and radiological image depth (RD) of cages (i.e., structural interbody support devices) placed in disc spaces during posterior lumbar interbody fusion and whether soft tissues covering the posterior border of the vertebral body and associated disc space are the cause of any observed differences. Using digital calipers, cages were inserted at a depth of 5 mm from the soft tissues covering the posterior border of the vertebral body and disc space under direct vision; this depth was defined as VD. After insertion, RD was measured in triplicate. The reliability of RD measurements was evaluated using an intraclass coefficient test. To identify the cause of differences between VD and RD, the thicknesses of soft tissues were measured microscopically. A total of 40 lumbar intervertebral disc spaces with cages were evaluated. The mean RD of cages was 3.12 mm, while the mean difference between the VD and RD of cages (DVRD) was 1.91 mm. On histological examination, the mean thickness of the soft tissue was 2.02 mm. Comparative analysis between histological values and DVRD showed no statistical difference (P = 1.14, 1.55, 0.06). There was a significant difference between VD and RD during cage placement, and soft tissue structure appeared to be responsible for the DVRD of inserted cages. Therefore, cages should be inserted deeper to account for differences between visual and radiological image depths. Clin. Anat. 25:1066–1073, 2012. © 2012 Wiley Periodicals, Inc.     

Update: mechanisms by which magnesium modulates intracellular potassium.

The objective of this study was to investigate the relative bioavailability (BV) of beta-carotene (BC) and alpha-carotene (AC) from different extracts of carrots utilizing the ferret model.

Five groups of animals (n = 6) were provided free access to a carotenoid-free, vitamin A-adequate diet and tap water for 2 weeks, then for 3 consecutive days 10 mg of BC was provided in 30–40 mL of one of the following fluids as partial replacement for tap water along with diet: 1) commercial BC beadlets dispersed in distilled water (control), 2) non-heated carrot juice, 3) heated carrot juice, 4) non-heated isolated carrot chromoplasts, or 5) heated carrot chromoplasts. The animals were killed and samples of blood and tissues (liver, adrenal, lung, kidney, spleen) were collected and analyzed for AC and BC concentrations.

The tissue analysis of BC concentrations indicated that BC-beadlet-supplemented animals had significantly higher BC concentrations than other groups (p<0.01). Carrot chromoplast-supplemented animals had significantly higher tissue BC and AC concentrations than carrot juice-supplemented animals. Heat treatment tended to reduce the relative BV of carotenoids but the differences between heated and non-heated juices or isolated carrot chromoplasts were not significantly different.

These results suggest that the food matrix, probably pectin-like fibers, and the crystalline form of carotenoids in carrot chromoplast are the primary factors that reduce the relative BV of carotenoids from carrot juice.     

Intravenous magnesium—potential hazard of inadequate mixing.

Failure to mix 24.5 mM of magnesium, added as 50% MgSO4 in 1 liter of intravenous fluid, results in a high concentration of Mg in the initial 10-cc aliquot: 1,145.7 mM/liter. Adequate dispersion can be obtained after three inversions. We conclude that because of the extremely high concentrations of Mg that can result if no mixing is done, it is imperative that hospital personnel ensure that added Mg is adequately dispersed in intravenous fluid prior to administration. A method of signalling the inadequacy of mixing is to color code additives with a harmless dye to alert personnel to the problem of inadequate dispersement.