Axis ring fractures due to simulated head impacts

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Trauma Research

Background:

• Investigating the mechanisms behind axis ring fractures resulting from simulated head impacts.
• Focusing on injuries to the upper cervical spine (occiput through C3).

Purpose of the Study:

• To determine the mechanisms of axis ring fractures in simulated head impacts.
• To analyze the relationship between impact location and fracture patterns.

Main Methods:

• Utilized a human upper cervical spine specimen (occiput-C3) mounted on a surrogate torso and head.
• Divided 13 specimens into three impact groups: midline forehead, lateral forehead, and lateral head.
• Documented injuries using post-impact fluoroscopy and anatomical dissection; analyzed peak load and acceleration timing.

Main Results:

• Five of 13 specimens sustained axis ring fractures, most commonly from upper left lateral forehead impacts.
• Peak neck loads averaged 1761.2N, with fractures occurring within 50 ms.
• Initial force and acceleration peaks occurred significantly earlier (18.0-22.8 ms) than absolute force peaks.

Conclusions:

• Observed asymmetrical axis ring fractures involving facets, laminae, vertebral body, pars interarticularis, and pedicles.
• Fracture patterns correlated with the axis's morphology as a transitional vertebra.
• Understanding fracture mechanisms can guide optimal reduction and stabilization techniques.