A first report of thyroid cartilage fracture resulting from laryngoscopy and intubation has been published. An elective surgery patient underwent paralysis with 60 mg rocuronium after which ‘laryngoscopy and intubation attempts with a Macintosh 3 blade, Miller 2 blade, stylet, and vigorous external laryngeal manipulation yielded only Cormack Lehane grade 3 views of the larynx‘. Intubation was eventually achieved with a Glidescope, but it was noted that ‘external laryngeal manipulation was applied as forcefully as the assistant could perform the maneuver‘.
The author suggests the fracture could either have resulted from the external laryngeal manipulation during laryngoscopy or from the rigid curved stylet used with the Glidescope. Whichever it was, their take home advice is sound:

Even during difficult laryngoscopies, gentle manipulations are best

I would add to this – do the ELM yourself – in other words, bimanual laryngoscopy.
Laryngoscopy Complicated by Thyroid Cartilage Fracture
Anesthesiology. 2010 Oct;113(4):993-4