Sacral Muscle Injuries Post-High-Intensity Focused Ultrasound Ablation for Uterine Fibroids: MRI Evaluation and Influencing Factors

Abstract

Objective: To explore the manifestations of magnetic resonance (MR) imaging-detected muscle injuries around the sacrum following uterine fibroid ablation using ultrasound-guided high-intensity focused ultrasound (USgHIFU) and the factors influencing these injuries. Materials and Methods: A retrospective analysis was conducted on 555 patients with uterine fibroids who underwent USgHIFU ablation therapy. Based on their postoperative MR images, patients with muscle injuries around the sacrum were identified, and the specific locations of these muscles were recorded. The severity of muscle injuries around the sacrum was evaluated imitating the semi-quantitative assessment system for paraspinal muscle infiltration. Thus, the severity of muscle injury was stratified into five groups for comparison of fibroid characteristics and HIFU treatment parameters among the groups. Both univariate and multivariate analyses were employed to analyze all results. Results: Among the 555 patients with uterine fibroids who underwent USgHIFU ablation therapy, 226 patients (40.7%, 226/555) exhibited muscle injuries around the sacrum. Piriformis muscle injury was particularly prevalent, accounting for 97.3% (220/226) of cases, including 20 cases with concurrent gluteus maximus muscle injury. Only 6 cases involved isolated gluteus maximus muscle injury, while no injuries to other muscles were reported. Multivariate analysis revealed that uterine position, fibroid location, T2 signal intensity and HIFU treatment intensity were significantly associated with the severity of piriformis muscle injury (p < 0.05). Conclusion: Following USgHIFU ablation therapy for uterine fibroids, a part of patients may experience muscle injuries around the sacrum, including the piriformis and gluteus maximus muscles, with piriformis muscle injury being the most common. Patients with retroverted uterus, posterior wall fibroids, fibroids with higher T2 signal intensity, and high HIFU treatment intensity may experience more severe piriformis muscle injury postoperatively.