Intrapelvic Obturator Internus Muscle Injections: A Novel Fluoroscopic Technique

Abstract

The obturator internus (OI) muscle is important in adult chronic noninfectious pelvic, perineal, gluteal, and retrotrochanteric pain syndromes. Evaluation and management of these patients’ pain can be challenging because of the complex anatomy of this region, broad differential diagnosis, and lack of specific physical examination findings. Consequently, several clinicians have advocated the use of image guided injections to assist in the accurate diagnosis of OI-related symptoms and provide symptomatic relief to affected patients. We present 2 case series describing a novel fluoroscopically guided contrast controlled transpectineal approach to intrapelvic OI injections. Unlike prior fluoroscopically guided OI injection techniques, the approach described in the present 2 cases utilized multiple standard pelvic views, thus facilitating optimal needle positioning in three-dimensional space. This technique utilized standard fluoroscopic pelvic views to accurately measure needle depth within the pelvic cavity permitting the bulk of the OI to be injected in a controlled and safe fashion. The first patient underwent a left intrapelvic OI muscle injection with bupivacaine 0.25% and 40 mg methylprednisolone. The average pre- and postprocedural visual analog pain scale scores were 5 out of 10 and 2 out of 10, respectively, with a self-reported 75% pain reduction. The second patient underwent a right intrapelvic OI muscle injection with bupivacaine 0.25% and 40 mg methylprednisolone. The average pre- and postprocedural visual analog scale scores were 8 out of 10 and 1 out of 10, respectively, with a self-reported 90% pain reduction. Larger scale studies should be undertaken to evaluate the therapeutic efficacy and generalized accuracy of this technique. Key words: Obturator internus muscle, pelvic, perineal, gluteal, retrotrochanteric pain, fluoroscopic, transpectineal