Manual strangulation: experimental approach to the genesis of hyoid bone fractures

Discovery of a fracture of the hyoid bone during forensic autopsy is a feature that raises suspicions of constriction of the neck. Studies have shown the influence of gender and build of the individual on the morphology of this bone. Our aims were to confirm these findings and to develop an experimental protocol for simulating manual strangulation in order to determine the force required to fracture the hyoid bone and the influence of anthropometric parameters on this force. A total of 77 intact hyoid bones were obtained, scanned, modeled, measured and embedded in resin. Using a hydraulic press, we applied force to the distal extremity of the greater horn. The relationships between the parameters of sex, weight and height of the subject, anteroposterior length of the hyoid, width between the greater horns, angle, fusion of the greater horns and force applied were analyzed. Our study confirmed sexual dimorphism, shown by greater length in males (>37.8 mm) than in females, and a larger angle in females (a shorter bone with a width>43.7 mm and an angle>31°01). The study confirmed the positive correlation between the length of the hyoid and the weight and height of the subject (p<0.05). Sixty-seven of the 77 hyoid bones fractured during the experiment (87% fracture rate). Of the fractures, 48% occurred at the junction between the body and the greater horns, 49% in the greater horns (mean distance from the distal extremity of the horn 17.33±4.37 mm), and 3% in the median part of the body. No significant association was found between gender and type of fracture, or between fusion or non-fusion of the horn (p>0.05). Fused bones were not more susceptible to fracture than non-fused bones. Fracture occurred at a mean force of 30.55 N (±18.189). Multiple linear regression showed a significant negative correlation between force required for fracture and age, weight and height of the subject, anteroposterior length and angle. The younger the individual, the slighter their build, the longer the bone and the smaller the angle, the greater the force required to fracture the hyoid bone.