Novel insights on different treatment of magnesium alloys: A critical review.

Magnesium alloys are extensively used for weight reduction in automotive and aircraft applications. This research presents the effect of heat and cryogenic treatment on aluminium-zinc-based Mg alloys. Both treatments can improve the mechanical and corrosion properties of the AZ series Mg alloy. The review deals with a broad understanding of the microstructure changes that occur during heat and cryogenic treatment of Mg alloy. The mechanical and corrosion characteristics of heat and cryogenic treated AZ31, AZ91, AZ63, and AZ80 Mg alloys are discussed. The essential strengthening mechanisms of heat and cryogenic treated AZ series Mg are discussed with microstructure changes. This review has also shown a few gaps in research on the selection of suitable pre- and post-treatment processes for Mg alloy. The effects on grain refinement and the formation of secondary phase particles are discussed in detail. The related crystallographic plane, twining, and dislocation changes are out of the scope of this review. Finally, the correlations of the above changes to mechanical properties are the directions of the future.

Maintaining neutral sagittal cervical alignment after football helmet removal during emergency spine injury management.

STUDY DESIGN: Descriptive laboratory study. OBJECTIVE: To determine whether the placement of padding beneath the occiput after helmet removal is an effective intervention to maintain neutral sagittal cervical spine alignment in a position comparable with the helmeted condition. SUMMARY OF BACKGROUND DATA: Current on-field recommendations for managing football athletes with suspected cervical spine injuries call for face mask removal, rather than helmet removal, because the combination of helmet and shoulder pads has been shown to maintain neutral cervical alignment. Therefore, in cases when helmet removal is required, recommendations also call for shoulder pad removal. Because removal of equipment causes motion, any technique that postpones the need to remove the shoulder pads would reduce prehospital motion. METHODS: Four lateral radiographs of 20 male participants were obtained (age = 23.6 ± 2.7 years). Radiographs of participants wearing shoulder pads and helmet were first obtained. The helmet was removed and radiographs of participants with occipital padding were obtained immediately and 20 minutes later and finally without occipital padding. Cobb angle measurements for C2-C6 vertebral segments were determined by an orthopedic spine surgeon blinded to the study's purpose. Intraobserver reliability was determined using intraclass coefficient analysis. Measurements were analyzed using a 1×4 repeated-measures analysis of variance and post hoc pairwise comparisons with Bonferroni correction. RESULTS: Intraobserver analysis showed excellent reliability (intraclass correlation = 1.0; 95% confidence interval [CI], 0.999-1.0). Repeated-measures analysis of variance detected significant differences (F(3,17) = 13.34; P < 0.001). Pairwise comparisons revealed no differences in cervical alignment (all measurements reported reflect lordosis) when comparing the baseline helmeted condition (10.1° ± 8.7°; 95% CI, 6.0-14.1) with the padded conditions. Measurements taken after removal of occipital padding (14.4° ± 8.1°; 95% CI, 10.6-18.2) demonstrated a significant increase in cervical lordosis compared with the immediate padded measurement (9.5° ± 6.9°; 95% CI, 6.3-12.7; P = 0.011) and the 20-minute padded measurement (6.5° ± 6.8°; 95% CI, 3.4-9.7; P < 0.001). CONCLUSION: Although face mask removal remains the standard, if it becomes necessary to remove the football helmet in the field, occipital padding (along with full body/head immobilization techniques) may be used to limit cervical lordosis, allowing safe delay of shoulder pad removal.