Spontaneous regression of calcified thoracic herniations: Can Hounsfield-units radiodensity have a predictive value?

Introduction Spontaneous regressions of calcified thoracic disc herniations (TDH) have been rarely described. Since now, no previous papers hypothesized that radiological factors could be able to predict the evolution of the herniation. This study shows that the radiodensity of the herniated material in herniations with spontaneous resolution might differ from that of operated herniations. Methods This is a retrospective study. A cohort of patients that underwent surgical removal of a calcified thoracic disc herniation has been compared to two cases conservatively treated and a case with spontaneous regression. CT scans were evaluated to compute the average radiodensity [in Hounsfield units (HU)] of the calcified components of the herniations. All the slices of the CT scans involving the calcification were evaluated in their axial images and in their coronal and sagittal reformations. Comparison of the slices radiodensity (spontaneously resolved versus surgically treated) was performed with the unpaired Student's t test. Results The mean density of calcification in the case with spontaneous regression was found to be 454 HU. In the control group of surgical cases observed, and the conservatively treated cases, the mean HU density showed higher values (respectively, 827 and 853 HU) (p < 0.01). Conclusion Qualitative differences between calcified TDH that resolve spontaneously or need surgical treatment might be shown by differences of radiodensity. This comparative study, in spite of the limitations due to small numbers, provides a new insight in the interpretation of the phenomenon of spontaneous resolution of calcified TDH. Graphic abstract These slides can be retrieved under Electronic Supplementary Material.