“Jonathan Arden, president of the National Association of Medical Examiners, said a hyoid can be broken in many circumstances, but is more commonly associated with homicidal strangulation than suicidal hanging”
Improvised prison suicide hanings are likely not to be similar to your garden variety suicidal hanging.
There’s some research on the subject:
Abstract
OBJECTIVE:
To analyze the frequency of hyoid bone and thyroid cartilage fractures caused by suicidal hanging in Thai people and compare the different methods of visualizing the those fractures. Results could be used for forensic purposes.
MATERIAL AND METHOD:
A prospective study of hyoid bone and thyroid cartilage fractures in Thai people who died from suicidal hanging between November 2008 and August 2009. The authors confirmed suicides, based on history, crime scene investigation, autopsy reports, and other police information, visual and palpatory examination, and stereomicroscopy with or without 1% Toluidine. Neck dissection was performed following the protocol of Prinsloo and Gordon. Results and data analysis were performed via SPSS version 16.
RESULTS:
Twenty male cases of suicidal hanging were reviewed. Fractures of the hyoid bone and/or thyroid cartilage were found in five cases (25%). Two cases ofthe hyoid bone fracture, two cases of thyroid cartilage fracture, and one case was both bone fractures. Mean age of all cases, non-fracture, and fracture cases were 42.40, 35.93, and 61.80 years, respectively The knot was at the back of the neck in most cases (12 cases, 60%) and at the left, front, and right in four, two, and two cases, respectively. However there was no relation between location ofthe knot at the neck and fractures of hyoid bone and thyroid cartilage (p=1). Incomplete and complete hanging were found in 11 and nine cases. Five cases with fractures of the hyoid bone and/or thyroid cartilage were incomplete hanging. The visual and palpatory examination did not detect the fracture of hyoid bone in all 20 cases but stereomicroscopy and stereomicroscopy with Toluidine blue stain detected fracture in three cases. For detecting thyroid cartilage fractures, all three methods had the same result.
CONCLUSION:
Fractures of the hyoid bone and thyroid cartilage in 25% of Thais who died of suicidal hanging were related with older ages and incomplete hanging but not related with location of the knot. The stereomicroscopic method is fast and effective in detecting fractures of the hyoid bone and thyroid cartilage.
https://www.ncbi.nlm.nih.gov/pubmed/20973326