Anterior Interosseous Nerve

00:01 level. One specific question in your exam will be the anterior interosseous nerve.

00:04 There’s something called the anterior interosseous nerve syndrome. You can get patients with anterior interosseous nerve compression. What’s anterior interosseous nerve? Where does it come from? What does it supply? The anterior interosseous nerve is the continuation of the median nerve. Very good, yeah.

00:23 As it extends beyond the cubital fossa, as it gets into the forearm, it kind of extends and supplies the flexors.

00:40 All the flexors? I think so, yeah, and it goes into the forearm and then it gives recurrent branches. Okay. You got pretty much that. The anterior interosseous nerve is a branch of the median nerve. That’s the first thing you need to remember, branch of the median nerve. One of the MCQ questions will be, as the median nerve comes into the forearm, it lies between the two heads of the pronator teres. It lies between the two heads of the pronator teres then it gives off an anterior interosseous branch which is also called the deep branch. That goes and supplies the flexor pollicis longus to the thumb, flexor digitorum profundus, and pronator quadratus. So the three deep muscles in the forearm are supplied by the anterior interosseous nerve.

01:33 Then your median nerve on its own continues in the forearm, and then it goes under the carpal tunnel. So that’s all you need to know about the anterior interosseous nerve syndrome. So in a patient with anterior interosseous nerve injury, the patient will have lots of normal function because the FCR is intact. So the patient will be able to flex their wrist. They’ll have some pronation because the pronator teres is working, but then they’ll have specific loss of function in the thumb, in the DIPJ, and the final pronator quadratus. So that is the anterior interosseous nerve syndrome.

02:10 Right. I’m just going to go back there now. The reason I brought it here is to get you an understanding of the all the nerves from the lateral cord, all the nerves from the medial cord. The only thing that’s remaining is the posterior cord. It’s very easy to remember the posterior cord. If you recall what we discussed, we've discussed only the anterior side of the arm and the forearm. So everything posterior is from the posterior cord.

02:44 So everything posterior, this much, the entire posterior aspect of the arm, posterior aspect of forearm, wrist, fingers, thumb, they’re all from the posterior cord. So it’s very easy to remember. If you just imagine all the nerves coming from the posterior cord, have to supply something posterior. Okay? What are the nerves from the posterior cord? Do you want to take that? Radial. Radial.

03:18 Axillary. Axillary, very good. And superior scapula.

03:23 Subscapular And inferior.

03:30 Upper and lower, fine, okay. Upper and lower, that’s fine, yup, very good. And one more.

03:33 Nerve to latissimus dorsi or also called the thoracodorsal nerve. So that is a mnemonic ulnar. So upper subscapular nerve, lower subscapular nerve, nerve to latissimus dorsi also called thoracodorsal nerve, axillary, and radial. So, we’ll go through each nerve. Upper subscapular nerve, what does it supply? Supraspinatus.

04:11 No. Anyone? Upper subscapular nerve, lower subscapular, what do these supply? The subscapular muscle. Subscapularis, okay. So imagine your scapula.

04:30 The scapula here, then the inside surface is the subscapularis. So the upper and the lower subscapular nerve supply the subscapularis. Nerve to latissimus dorsi, also called the thoracodorsal nerve as the name says, supplies the latissimus dorsi. So again, the posterior muscle. Axillary nerve supplies the deltoid. Radial nerve supplies all the muscles in the posterior surface of the arm and the forearm. So, radial nerve supplies the in-depth triceps, all the three heads of the triceps, all the forearm extensors, wrist extensors, finger extensors. They’re all the radial nerve.

05:14 Okay. So, that’s the spine of the scapula, supraspinatus, infraspinatus, what supply