Hi Linh,
They are a few good topics,
I will get around to making material on them,
but for now some comments:
The Lacunar ligament is not a structure I see with ultrasound but I know where it lives and I can see if it fails.
Imagine the apex of a triangle being made by the inguinal ligament and the anterior surface of the pectinous muscle (with the bony iliopectineal eminence beneath it). This triangular area is where the lunar ligament lives and when it fails peritoneal content can pass deep to the inguinal ligament and superficial to the pectinous muscle through the defect. So it is sort of a really medially placed femoral hernia just lateral to the pubic tubercle.
The pubic aponeurosis is the combined collagen anterior to the symphysis pubis. It has contributions from the right and left inguinal legs, conjoint tendons, rectus abdominus and the adductor longus from below. So that is 8 structures in total and they all blend together interdigitating anterior to the symphysis pubis forming the pubic aponeurosis.
The conjoint tendon is the collagen from transversus abdominus and internal oblique (which make the posterior wall of the intgional canal) then blend with the pubic aponeurosis just medial to the attachment of the inguinal ligament. If you scan the right pubic tubercle for example and have the transducer straight sagittal pointing towards the patients chin you will see the rectus abdominus tendon blending into the pubic aponeurosis with the pyramidalis muscle sitting anterior to it. If you then slide the transducer to the lateral edge of the pubic tubercle and then rotate the transducer slightly anticlockwise so the probe is pointing to the patients ipsilateral shoulder tip you will see another structure that looks similar to the rectus abdominus tendon, but this time it is the conjoint tendon.
The conjoint tendon is much talked about, however I don’t personally see many cases where it looks abnormal sonographically. It certainly makes up part of my athletic pubalgia examination.
The pyramidalis is on no concern to me. It can be of varying sizes as an anatomical variation between individuals and it can be absent congenitally. It is always a fairly small muscle so doesn’t have a lot of strength.
You see it anterior to the rectus abdominus tendons and distal muscle bellies and it is triangular in shape. I have never seen this published, but I observe the tendon of rectus abdominus being longer in patients with a larger pyramidalis and the rect and tendon is shorter (with a longer muscle extension) in patients with an absent pyramidalis.
The obturator nerve can indeed be a source of pain in the upper inner thigh area.
I don’t see an abnormal nerve sonographically, however we do see where the nerve runs.
If you scan sagittal just lateral to the edge of the pubic tubercle you will see the pectinous muscle originating from the iliopectineal eminence. Deep to this muscle is the obturator externes muscle and the 2 branches of the obturator nerve run 1: between pectinous and obturator externes and 2: immediately deep to obturator externus. You can see the adjacent artery with colour Doppler. Both of these locations can be injected under ultrasound guidance.
Steve