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At-Hook

The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Tracey P Bastrom – 1st expert on this subject based on the ideXlab platform

  • evaluation of proximal junctional kyphosis in adolescent idiopathic scoliosis following pedicle screw hook or hybrid instrumentation
    Spine, 2010
    Co-Authors: Melvin D Helgeson, Suken A Shah, Peter O Newton, David H Clements, Randal R Betz, Michelle C Marks, Tracey P Bastrom

    Abstract:

    Study Design. Retrospective review. Objective. To compare the incidence of and risk factors for proximal junctional kyphosis (PJK) in adolescent idiopathic scoliosis (AIS) following posterior spinal fusion using hook, pedicle screw, or hybrid constructs. Summary of Background Data. Proximal junctional kyphosis is a recently recognized phenomenon in adults and adolescents after AIS surgery. The postoperative effect on PJK with the use of hooks, hybrid constructs, or screws has not been compared in a multicenter study to date. Methods. From a multicenter database, the preoperative and 2-year follow-up radiographic measurements from 283 patients with AIS treated with posterior spinal fusion using hooks (group 1, n = 51), hybrid constructs (group 2, n = 177), pedicle screws (group 3, n = 37), and pedicle screws with hooks only at the top level (group 4, n = 18) were compared. Results. The average proximal level kyphosis at 2 years after surgery was 8.2° (range ―1 to 18) in the all screw constructs, representing a significant increase when compared with hybrid and all hook constructs, 5.7° (P = 0.02) and 5.0° (P = 0.014), respectively. Conversely, average postoperative T5―T12 kyphosis was significantly less (P = 0.016) in the screw group compared with the all hook group. Of potential interest, but currently not statistically significant, was the trend towards a decrease in proximal kyphosis in constructs with all pedicle screws except hooks at the most cephalad segment, 6.4°. The incidence of PJK (assuming PJK is a kyphotic deformity greater than 15°) was 0% in group 1, 2.3% in group 2, 8.1% in group 3, and 5.6% in group 4 (P = 0.18). Patients with PJK had an increased body mass index compared with those who did not meet criteria for PJK (P = 0.013). Conclusion. Adjacent level proximal kyphosis was significantly increased with pedicle screws, but the clinical significance of this is unclear. A potential solution is the substitution of hooks at the upper-instrumented vertebrae, but further investigation is required.

Seon Hyo Kim – 2nd expert on this subject based on the ideXlab platform

  • a new mechanism of hook formation during continuous casting of ultra low carbon steel slabs
    Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
    Co-Authors: Joydeep Sengupta, Brian G Thomas, Ho Jung Shin, Go Gi Lee, Seon Hyo Kim

    Abstract:

    The initial stages of solidification near the meniscus during continuous casting of steel slabs involve many complex inter-related transient phenomena, which cause periodic oscillation marks (OMs), subsurface hooks, and related surface defects. This article presents a detailed mechanism for the formation of curved hooks and their associated OMs, based on a careful analysis of numerous specially etched samples from ultra-low-carbon steel slabs combined with previous measurements, observations, and theoretical modeling results. It is demonstrated that hooks form by solidification and dendritic growth at the liquid meniscus during the negative strip time. Oscillation marks form when molten steel overflows over the curved hook and solidifies by nucleation of undercooled liquid. The mechanism has been justified by its explanation of several plant observations, including the variability of hook and OM characteristics under different casting conditions, and the relationships with mold powder consumption and negative/positive strip times.

Olsen Peter – 3rd expert on this subject based on the ideXlab platform

  • Consumer Behavior & Marketing Strategy
    Dana, 2009
    Co-Authors: Olsen Peter

    Abstract:

    This book is a strategic look at consumer behavior in order to guide successful marketing activities. The Wheel of Consumer Analysis is the organizing factor in the book. The four major parts of the wheel are consumer affect and cognition, consumer behavior, consumer environment, and marketing strategy.