Effectiveness of Initial Fixation of a Grasping Pin for Proximal Femoral Fractures

We developed a grasping pin with a hook for osteosynthesis of proximal femoral fractures and compared its performance with that of a lag screw. Cyclic compressive tests were performed to simulate cut-outs, and quasi-static torsion, tests were conducted to simulate rotational displacement in polyurethane model bones and femoral heads collected after hip replacement surgery, and cadaveric femoral heads. In the polyurethane model bones and femoral head collected after hip replacement surgery, implant displacement was increased in the cut-out simulation test in both the grasping pin group and lag screw group, deformation was less in the grasping pin group than in the lag screw group. In polyurethane bones and cadaveric bones, the grasping pins showed higher rotational resistance compared with the lag screws in the quasi-static torsion test because of the high compression force generated during implantation. In contrast, in the collected femoral head after hip replacement surgery model, the lag screws destroyed bone tissue, the lag screw group exhibited a higher rotational resistance and a lower risk of rotational displacement than the grasping pin model. The depth of cadaveric femoral heads was 60mm compared with 30mm for femoral heads obtained after surgery; therefore, the pins could be completely inserted up to the octagonal portion in the cadaveric bones, resulting in higher rotational resistance

Evaluation of image quality of pituitary dynamic contrast-enhanced MRI using time-resolved angiography with interleaved stochastic trajectories (TWIST) and iterative reconstruction TWIST (IT-TWIST)

Background: Time‐resolved angiography with interleaved stochastic trajectories (TWIST) is a keyhole imaging with frequent sampling of central k‐space data and view‐sharing for the peripheral k‐space of dynamic phases. IT‐TWIST is a technique to reconstruct images with a smaller temporal footprint using the same raw data obtained with TWIST by iterative reconstruction. Purpose: To compare image quality between TWIST and IT‐TWIST in 3D pituitary DCE‐MRI. Study Type: Retrospective observation study. Population: Fifty‐one patients (23 men, 28 women) who underwent 3D pituitary DCE‐MRI using TWIST between July 2016 and April 2017. Field Strength/Sequence: 3T/TWIST and IT‐TWIST. Assessment: Visual evaluation was conducted for image quality of delineation of the pituitary stalk and posterior lobe during the early arterial phase, cerebral white matter near the sella turcica, and the mass lesion. Bolus sharpness of the pituitary stalk, posterior lobe, and bilateral cavernous sinus was evaluated on the enhancement slope map calculated from TWIST and IT‐TWIST. Temporal stability of intensity of the nonenhanced area was evaluated on temporal standard deviation (SD) maps calculated from TWIST and IT‐TWIST. Statistical Tests: Paired t‐test or Wilcoxon rank‐sum test was used to test the differences between TWIST and IT‐TWIST in both visual evaluation and region of interest evaluation. Results: Scores of visual evaluations for IT‐TWIST were significantly better than those for TWIST (P < 0.001) in all items. Enhancement slope for IT‐TWIST was significantly higher than that for TWIST in posterior lobe, and right and left cavernous sinus (P < 0.001). Temporal SD for IT‐TWIST was significantly lower than that for TWIST in all items, with statistical significance (P < 0.001). Data Conclusion: IT‐TWIST yielded better visualization, and better enhancement slope, and less temporal SD compared with TWIST in 3D pituitary DCE‐MRI