A Novel Coaxial Transosseous Technique for Ganglion Impar Block in Radiation-Induced Sacrococcygeal Fusion.

Perineal pain in patients with pelvic malignancies, such as rectal cancer, can be debilitating and significantly impair quality of life. The ganglion impar block (GIB) is an established interventional technique for managing such pain. However, anatomical changes following pelvic radiotherapy, particularly sacrococcygeal fusion, may render conventional approaches to GIB ineffective or unsafe. We report the case of a 41-year-old male with locally advanced rectal cancer and radiation-induced sacrococcygeal fusion who presented with severe, refractory perineal pain. Pain was poorly controlled despite systemic opioids and adjuvant analgesics, and conventional trans-sacrococcygeal GIB attempts under fluoroscopy failed due to the inability to traverse the fused joint. A novel coaxial transosseous technique was employed. A large-bore (21G) needle was used in a rotatory fashion to drill through the ossified sacrococcygeal joint. Subsequently, a 27G spinal needle was introduced coaxially through the first needle, facilitating precise placement and administration of therapeutic agents under fluoroscopic guidance. The patient reported significant and sustained pain relief. Post-procedure, the patient experienced substantial pain reduction (Numerical Rating Scale 8/10 to 2/10), improved defecation-related symptoms, and enhanced functional status. No procedural complications were observed. Follow-up at one week confirmed ongoing analgesic benefit with reduced opioid requirements. The coaxial transosseous GIB is a safe, effective, and innovative technique for managing refractory perineal pain in patients with radiation-induced sacrococcygeal fusion. It offers a viable alternative when conventional approaches fail and warrants further evaluation through prospective studies.