Modeling of safe window for percutaneous thoracic sympathectomy

Despite the many benefits of percutaneous thoracic sympathectomy, it also has serious complications such as pneumothorax. This study was conducted in order to determine the safe percutaneous entering window and angles for the needle during T2 and T3 thoracic sympathectomy avoiding pneumothorax.

Transverse section of CT images that crosses at the middle of the T2 or T3 vertebral body was selected. Medial and lateral imaginary lines were drawn from the dorsoventrally midpoint on the lateral surface of the vertebral body (v) to the skin. The medial one was drawn to the skin medially as much as possible tangent to the vertebral body (vM). The lateral one was drawn to the skin tangent to parietal pleura (vL). c was defined as the point where the midsagittal line meets the skin. The distance cM and cL, the angle aM and aL made between the midsagittal line and vM or vL lines were measured. To determine the relations between patients' covariates and measured data, mixed-effect population analysis was performed for the cL, aL, and vL.

In males, the mean values of cL were 85.3 and 79.2 mm for T2 and T3, respectively. In females, they were 71.5 and 63.7 mm for T2 and T3, respectively. Population analysis revealed that cL was best described with age, weight, gender covariates, and interindividual variability. The aL was best described with BMI and gender covariates.

The covariates' relationship and interindividual variability resulting from the mixed-effect analysis enhanced individual prediction for safe widows.