Gross anatomy observation: The trunk of the obturator nerve passes through the obturator externus muscle
about 3 cm inferiolaterally to the pubic tubercle and divides into anterior and posterior branches, both of which travel superficial (anterior branch) and deep (posterior branch) to the adductor brevis muscle.
In this view, the target interfascial plane is seen deep in relation to the pectineus muscle separating it from the obturator externus muscle (Figure 3(b)).
The anterior and posterior branches of the obturator nerve, or the common obturator nerve, run between the pectineus and obturator externus muscles immediately after the nerve emerges from the obturator canal (Figure 1(a)).
Taha reported that ultrasound-guided injection of local anesthetic into the interfascial plane between the pectineus and obturator externus muscles successfully produces blockade of both the anterior and posterior branches of the obturator nerve .
MRI revealed high grade right obturator internus and obturator externus muscle
strain involving the attachments to the obturator ring and ischium (Figure 2).
It passes through the following structures in the following order: gracilis, adductor brevis muscle, obturator externus muscle
, obturator membrane, and beneath or through the obturator internus muscle and periurethral endopelvic connective tissue; it finally exits through the opened vagina.
There was herniation of a bowel loop of length 3.5 cm through left obturator foramen extending inferiorly between pectineus muscle anteriorly and obturator externus muscle posteriorly, suggestive of obturator hernia (Figures 3, 4(a), and 4(b)).
CT imaging of bowel herniating through the obturator foramen and lying between the pectineus muscle anteriorly and obturator externus muscle posteriorly is diagnostic.
After preparation of the space between the anteroinferior capsule and the psoas tendon, the ischium is approached proximal to the obturator externus muscle
. This is important because the medial femoral circumflex artery runs distal to this muscle.
The obturator externus muscle was carefully removed from its origin and the contents of the obturator canal were dissected out.
The obturator externus muscle is the deepest muscle of the superomedial part of the thigh.
However, the first ischial cut can be easily performed prior to repositioning through the lateral incision, between the inferior gemellus and obturator externus muscles
, with optimal visual control of the sciatic nerve.