Cadaveric Spinal Surgery Simulation: A Comparison of Cadaver Types.

Study Design Single-blinded study. Objective To assess the suitability of three types of cadaver for simulating pedicle screw insertion and establish if there is an ideal. Methods Three types of cadaver-Thiel-embalmed, Crosado-embalmed, and formaldehyde-embalmed-were draped and the spines exposed. Experienced surgeons were asked to place pedicle screws in each cadaver and give written questionnaire feedback using a modified Likert scale. Soft tissue and bony properties were assessed, along with the role of simulation in spinal surgery training. Results The Thiel cadaver rated highest for soft tissue feel and appearance with a median score of 6 for both (range 2 to 7). The Crosado cadaver rated highest for bony feel, with a median score of 6 (range 2 to 7). The formaldehyde cadaver rated lowest for all categories with median scores of 2, 2.5, and 3.5, respectively. All surgeons felt pedicle screw insertion should be learned in a simulated setting using human cadavers. Conclusion Thiel and Crosado cadavers both offered lifelike simulation of pedicle screw insertion, with each having advantages depending on whether the focus is on soft tissue approach or technical aspects of bony screw insertion. Both cadaver types offer the advantage of long life span, unlike fresh frozen tissue, which means cadavers can be used multiple times, thus reducing the costs.

Constraints on neutron star crusts from oscillations in giant flares.

We show that the fundamental seismic shear mode, observed as a quasiperiodic oscillation in giant flares emitted by highly magnetized neutron stars, is particularly sensitive to the nuclear physics of the crust. The identification of an oscillation at approximately 30 Hz as the fundamental crustal shear mode requires a nuclear symmetry energy that depends very weakly on density near saturation. If the nuclear symmetry energy varies more strongly with density, then lower frequency oscillations, previously identified as torsional Alfvén modes of the fluid core, could instead be associated with the crust. If this is the case, then future observations of giant flares should detect oscillations at around 18 Hz. An accurate measurement of the neutron-skin thickness of lead will also constrain the frequencies predicted by the model.