For this video in the series on examination of the injured hand, we're going to be discussing um examination of the extensor tendons. So when one is examining the extensors, it's important to remember the anatomy. So you can see this young lady's allowing me to put some pen marks here. You can see you got the long extensors to the fingers and as it goes across here you then have contributions from the lumbricals and the interosia and it forms like a hood over the proximal fings and this interestingly separates into three and you've got one central bit that inserts into the base of the middle fing. This is called the central slip. And then you got a little band on either side. Then it combines and it inserts onto the base of the distal fings. So one extensor contributions from other muscles and then it splits into three. That's fairly complex sort of um thing. Now the long extensor is responsible for extension at the MCP joint. So if a person's got an injury to the hand and they're unable to extend at the metacarpalangial joint, they've injured the long extensor. If they're unable to extend at the middle falank, it means that they have injured the central slit. Now, interestingly, because of the combination of all of these together, you can have an injury to the central slip, but still be able to extend at the um PIP joint because you can have secondary pull from extending at the DIPG. And the way to tell whether the central slip is injured when that scenario occurs is by doing the Elson test. And we have a separate video because the Elson test is a little bit more involved. If somebody has an injury to the central slip, they may get a butonius deformity which is inability to extend at the PIPJ and a hyperextension at the DIPJ. So compensatory. So the finger looks bent here and hyperextended here. Now if somebody's got an injury to the um the extensor as it distal to the central slip then they have an inability to extend at the DIPG and that is called a mallet finger and the mallet finger is when you have you get a droop like that and unable to unable to actively extend it and when you have a mallet finger you can have a compensatory situation with the proxim fings which is a swan nicking essentially you have a droop here and you have a hyper extension here but an an acute thing you you tend not to get the the demonstration of the um swan nicking so that in a nutshell is examination of the hand in's um paper he describes the um test to be done by putting the hand at the edge of a table and keeping the PIPJ flex and then checking the DIPJ to see if it's floppy or if they can um extend it. That can be quite difficult to do in terms of the access really. So this is a modification where you can get the patient's hand up like that and you essentially flex and keep in flexion the PIPJ and then ask the patient to try to extend the distal interfallangial joint and see if it's floppy or if they can actually tighten it up. If the central slip is intact then this will be floppy. Okay. And they won't be able to extend it. Right? If the central slip has been divided, they will be able to um extend that and this floppiness would be there. It will be a lot more tense. Okay, good. The another modification is to actually get the patient to put the in fact yeah your hands together. Let let me do it from myself actually. Another modification is to get the patient to put the two fingers like that. So you have flexion at the PIPG and get them to then try to push the two nails together and if you have one side that is the central slip has been injured they will to extend a bit more and you have an asymmetrical. So I'm pushing this to demonstrate what can happen. You can see you're symmetrical because neither of my central sips have been injured and I cannot extend actively at the DIPG once the PIPG has been flexed.