It was reported that the XYZ/2 technique (using length, width and height of hematoma) is a simple and reliable method of estimation of chronic subdural hematoma volume. Two subtypes of techniques enable to adequately estimate, it is unclear which is more accurate. Computer-assisted volumetric analysis is widely considered the gold standard for CSDH volumetric analysis. It is important to consider the stability of analyses between examiners, because individual, decision-making differences may be relevant to the analysis, as hematoma margin and length are hand-operated. In this study, we investigated potential measurement biases of three neurosurgeons and analyzed the validity of the XYZ/2 technique by comparing it to the gold standard method.

We retrospectively analyzed CT scans that indicated the need for an operation in 50 patients with CSDH in our department. Three neurosurgeons measured and calculated CSDH volumes independent of one another. We investigated potential measurement biases of three neurosurgeons and analyzed the validity of the XYZ/2 technique by comparing it to the gold standard method. The XYZ/2 technique includes the “maximal method” that uses the maximum length and maximum width of a slice to determine volume, and the “central method” that uses only the central slice to measure length and width.

ICCs for the gold standard, central method, and maximal method were 0.945, 0.916, and 0.844, respectively, all of which indicated excellent reliability. For all examiners, the differences in calculation from gold standard and central method were not statistically significant (P>0.05). The estimations of CSDH volume calculated by the maximal method were significantly greater than the estimates calculated by the gold standard (P<0.05).

This study proves that the XYZ/2 technique is a simple and reliable method of estimating CSDH volume. The “central method” in particular yielded similar results to that of the gold standard method.