Intradiscal vacuum phenomenon on postmortem kinetic computed tomography of the cervical spine suggests intact...

Anterior disc space widening (ADSW), defined in this study as an autopsy-based category of cervical discoligamentous injury, is difficult to diagnose on postmortem computed tomography. The vacuum phenomenon (VP) has been debated as a trauma-related finding, and several studies have suggested that its presence may indicate ADSW. However, VP generation requires a negative-pressure environment and may not occur in structurally disrupted disc spaces.

We retrospectively evaluated 395 cases that underwent autopsy and postmortem kinetic CT of the cervical spine, including neutral and extension series. VP was defined as intervertebral gas with attenuation values below -100 HU. The prevalence of VP was analyzed in relation to cervical positioning, degeneration, and the presence or absence of ADSW.

The prevalence of VP increased significantly from the neutral to the extended position and was consistently higher in degenerated spines, indicating a posture-dependent, degeneration-related phenomenon. In contrast, no clear positive association with ADSW was observed on neutral imaging, and ADSW showed a tendency toward lower VP prevalence in the extended position and among newly appearing VP after positional change. Bayesian logistic regression analysis demonstrated a high posterior probability that the odds ratio for VP occurrence was less than 1 in the presence of ADSW.

These findings indicate that VP reflects degenerative negative-pressure states rather than traumatic disc separation. Accordingly, VP should not be regarded as a marker of traumatic injury but may serve as supportive evidence against ADSW in forensic practice, particularly when evaluated on postmortem kinetic CT.