Purpose: To study sacral injuries and influencing factors after ultrasonic ablation of uterine fibroids no more than 30 mm from the sacrum.
Methods: A total of 406 patients with uterine fibroids who underwent percutaneous ultrasound ablation were analyzed retrospectively. All patients underwent contrast-enhanced magnetic resonance imaging (MRI) scans before and after high-intensity focused ultrasound. The abnormal signal intensity (low signal intensity on T1WI and high signal intensity on T2WI) on the postoperative MRIs was indicative of a sacral injury. The patients were divided into a sacrum injury group and a sacrum non-injury group. The relationship between fibroid characteristics, ultrasound ablation parameters, and injury was analyzed using univariate and multivariate analyses.
Results: There were 139 cases of sacral injury (34.24%). When the distance from the fibroid's dorsal side to the sacrum was 0-10 mm, the risk assessment showed that the danger of sacral injury increased by 1.85 times and 3.03 times compared with that at a distance of 11-20 or 21-30 mm. Furthermore, the risk of sacral injury increased by 1.89 times and 3.23 times when the therapeutic dose (TD) of a fibroid was >500 KJ compared with that of a fibroid with TD= 250-500 KJ and <250 KJ.
Conclusion: A distance of 10 mm or less and a TD of >500 KJ were significantly correlated with sacral injury. The distance from the fibroid's dorsal side to the sacrum and the TD were the main causes of injury to the sacrum. A distance of 10 mm or less and a TD of >500 KJ carried higher injury risks, while a distance of 21-30 mm and a TD of <250 KJ were the most appropriate circumstances to reduce the risk of sacral injury.
Keywords: High-intensity focused ultrasound (HIFU); magnetic resonance imaging; sacrum injury; ultrasound ablation; uterine fibroids.