Obturator Internus 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 transperineal approach to intrapelvic OI injections.
Origin of Obturator Internus Muscle
- It arises from the inner surface of the anterolateral wall of the pelvis, where it surrounds the greater part of the obturator foramen, being attached to the inferior pubic ramus and ischium, and at the side to the inner surface of the hip bone below and behind the pelvic brim, reaching from the upper part of the greater sciatic foramen above and behind to the obturator foramen below and in front.
- It also arises from the pelvic surface of the obturator membrane except in the posterior part, from the tendinous arch which completes the canal for the passage of the obturator vessels and nerve, and to a slight extent from the obturator fascia, which covers the muscle.
- The fibers converge rapidly toward the lesser sciatic foramen, and end in four or five tendinous bands, which are found on the deep surface of the muscle; these bands are reflected at a right angle over the grooved surface of the ischium between its spine and tuberosity. The tendon inserts on the greater trochanter of the proximal femur.
Nerve Supply of Obturator Internus Muscle
- Obturator internus is innervated by the nerve to obturator internus, derived from spinal roots L5 and S1.
Blood Supply
- The blood supply of obturator internus is mainly provided by branches of the obturator artery.
- However, the extra pelvic portion of the muscle can also receive arterial blood from the Gellar branches of the internal pudendal artery.
Function
- Due to their attachment on the greater trochanter of the femur, obturator internus and the Gemelli’s muscles act as external (lateral) rotators of the extended thigh. They also abduct the flexed thigh.
- In addition to this prime mover role, the obturator internus muscle, along with the other short muscles of the hip (piriformis, superior and inferior Gemelli, pectineus, quadratus femoris, and obturator externus), acts as an important postural muscle, providing stability to the hip joint, particularly when the thigh is flexed.
- Due to their attachment on the greater trochanter of the femur, obturator internus and the Gemelli’s muscles act as external (lateral) rotators of the extended thigh. They also abduct the flexed thigh.
- In addition to this prime mover role, the obturator internus muscle, along with the other short muscles of the hip (piriformis, superior and inferior Gemelli, pectineus, quadratus femoris, and obturator externus), acts as an important postural muscle, providing stability to the hip joint, particularly when the thigh is flexed.