We're going to move with the accessory obturator nerve and anatomical study with relevance to anterior and lateral approaches to the lumbosacral spine. Matthew Allen Protas. Thank you, everybody. My name is Matthew Protas. I'm a third year medical student. It's a privilege to be here, to be able to talk with the professionals, and it's an honor. I'd like to start by at least saying why is it important to study accessory obturator nerve, especially coming from a peripheral nerves to neurosurgeon's perspective. Well, a lot of the, as you'll see from the studies, a lot of the studies that have been done are kind of ambiguous on the results, and they typically only study the plexus. They didn't look into the actual pathing of the nerve and its innervation. So what we did is we did a 20 cadaver study. We've evaluated 40 plexuses, and we did a complete literature review of the accessory obturator nerve to basically go over what I just spoke of. So as for its prevalence, it typically ranges from about 80% to 30%. From our study, we found that it was 30%. We found that this is because we used the technique of evaluating it from under the femoral vessels, which as it passes over the pubic ramus compared to the obturator nerve, which goes to the obturator canal. We thought that this technique was superior to just evaluating the plexus. As we'll see from a lot of the origin, there's a lot of variation. As for sidedness, in our study, we found that it was more common on the left side, but not by much. The largest study done by, which was done by Ketriatzis, I'm sorry if I'm butchering that name, was about more common on the left side. And for gender, it was about even about 13% for males and females. But as you can see from the literature, most of the studies have lower prevalences, which use the technique of mostly evaluating the plexus and not looking at the actual pathing to identify it. As for its origin, it most commonly comes from L3 and L4. In our study, we had a wide distribution of its origin. Some of it coming from the femoral nerve. Some of it coming from L2 and L3. As we see, there's many variations. And here are some schematics of the actual origin. As you can see, some of them coming from the trunk of the obturator nerve are especially hard to identify when you're looking just at the plexus for evaluations of accessory nerves. Here was just the study breakdown. As for the pathing, we found it to be 2 to 3 centimeters anterolateral to the obturator nerve, immediate to the psoas major. Using that for identification was also difficult due to its location around the general femoral nerve and the obturator nerve. And even the lateral femoral cutaneous nerve made it a little difficult to identify in this location. Embryologically, though, as it passes under the femoral vessels and over the pubic ramus compared to the regular obturator nerve, it was thought to be due that this wasn't due to the actual development of the bone, but the actual relevance is unclear of how this nerve goes over the pubic ramus instead of through the canal. This is thought to be due to the fact that this nerve should have been named the anterior femoral nerve, the accessory femoral nerve, instead of the accessory obturator nerve. And as we'll see from its function, it is consistent with that. As for its innervation, the three most common innervations were the hip joint, the pectineus muscle, and also anastomosing with the anterior branch of the obturator nerve. So previous studies have shown that it only will anastomose with the pectineus muscle about, innervate, sorry, innervate the pectineus muscle about 20% of the time. During our study, we found it to be about 80%, being on the dorsal medial side of the pectineus muscle. As for joining the anterior branch of the obturator nerve, it was only about 15% and posterior about 5% in literature. We found that to be similar with our research. Here's a schematic of its pathing and its innervations. And so as I've been talking about our experimental results as we've gone on, these are the exact results we found. We found it most common in L2 and L3, which is unusual. But as you can see, there is a wide range of actual origins. So using the actual plexus is a bad indication for finding its prevalence compared to actually looking under the femoral vessels. As for its average length to the superior pubic ramus, it was about 15 centimeters. Its diameter being about 1.2 millimeters, which I'll show you the in-cadaver pictures, it's very small. We found it to be more prevalent in males, which we had a very small amount of cadavers, so it's hard to make a causality on that. But we did find it to be more common on the left side, as for the terminal branches I've discussed already. So here's an actual cadaver image of the accessory obturator nerve. Seems a little better. As you can see, the psoas muscle is being retracted. You can see the accessory obturator nerve right here. How it can easily be destroyed during cadaveric manipulation. As for clinical relevance, there was a study in 2008 in which they were doing a TERT procedure, and they believed that because of inadequate anesthetic, the accessory obturator nerve wasn't properly anesthetized, causing contraction of the patient's leg, leading to life-threatening hemorrhage. As for cada ETL, they decided that the best way to actually prevent this injury is to plan for its presence no matter what. Even though the exact function is unknown, except for its innervation of the pectineus, and sometimes the abductus longus, it would still be important to properly anesthetize this, which the technique is to use, because the accessory obturator nerve is averaged about four centimeters from the pubic tubercle, a needle can be inserted there and properly anesthetized. I'd like to thank Wes Price and Angela Ortiz for the images, and I'd like to thank you all for your time and listening to my presentation. Thank you very much. Sorry for my cough. I've had a little bit of a cold all week. Any questions? Dr. Zegar? I have a question, but a comment. It's a nice anatomic study. You know, there is some evidence in animals, at least, that using a motor nerve graft would produce better motor results from a predominantly motor nerve using a sertile nerve, which is a sensitive nerve. So I'm just wondering if perhaps this should be something we learn to identify as a nerve. I've never looked for it. Maybe we should use that as our sertile nerve, so to speak, as our donor. But the problem is it's only present in 30% of cases. Well, actually, in apes, so part of the reason why they think that it develops is it has to do with chemotactic factors from the pectennius muscle. So in apes, they have a pectennius intermedius when it's being developed. So they think that what's happening is embryologically, the nerve is forming before the intermedius actually becomes the two parts, the anterior and posterior part of the pectennius muscle. So if we can maybe use ape cadavers, I'm not sure. Any other questions? Thank you very much. All right, thank you very much.

Matthew Protas

medical student

accessory obturator nerve

lumbosacral spine approaches

anatomical study