Dislocation and ligament injuries of the thumb. So the thumb's a little bit different in terms of the anatomy compared to the digits. So that's why we sort of split this up. My disclosures haven't changed in the last 20 minutes. So in terms of outline, we'll start from the CMC joint and work our way up to the IP joint. So in terms of the CMC joint, very common, especially for basilar thumb joint arthritis. And what's the issues here? Well, the two bones are the trapezium and the base of the metacarpal. And essentially, they give you minimal stability of the CMC joint. Landmark study by Dr. Cooney was demonstrating when you pinch between the thumb and the index finger, the force is magnifold, 12-fold at the CMC joint. And there's a test question if we get time that will go through that. So in terms of the two bones, you have the trapezium. In the coronal plane, it's convex. And in the sagittal plane, it's concave. So naturally, the metacarpal base reciprocates that. And the key thing here is that because of this joint, you allow motion along three axial planes. So it's a high-degree motion at the CMC joint. And that will lend into the treatment, for example, of an epibasal fracture that we'll discuss in a second. So primarily, stability of the joint is static and dynamic stabilizers. And the ligaments are the primary static stabilizers of the CMC joint. There are 16, or some people say 17, ligaments of the thumb for the test. You really only need to know two, thank God. So you have the volar ligament, or the oblique ligament. And the reason why I put this in here is because they do ask you about, there's two portions of it. There's the deep and the superficial part. And what they do, it's a sneaky question out there, is that which one is taught in which position. So the deep part of the ligament is taught in wide abduction and extension. And the superficial part is taught in pronation and extension. The primary ligament to preventing dorsal instability of the CMC joint is the dorsal radial ligament. And we'll go into some studies just showing that in a second. But put that back in your memory. Primary restraint to dorsal instability is the dorsal radial ligament. I'll also mention the dynamic stabilizers. These are essentially the thenar muscles. The most important here is the first dorsal intraossei. It's been some work by Julie Adams looking at the role of strengthening the first dorsal intraossei for early CMC joint instability. So that's why the first dorsal intraossei is mentioned. So inherently, you have an unstable joint. And how do you make this stable? And so that's sort of given by this screw-home mechanism. So during thumb opposition, essentially you get internal rotation of the thumb metacarpal. And the dorsal radial ligament, remember I mentioned that ligament, that tightens. And in doing so, you're converting a relatively incongruent unstable joint into a relatively stable joint. And during this whole process of this screw-home mechanism, the volar beat ligament remains relatively lax. So it's the dorsal radial ligament is the one that tightens. In terms of the instabilities, the majority of these in the thumb, as in the digits, are dorsal. And so what tends to happen is that the volar ligaments tend to remain stout. The dorsal ligaments are thin, apart from the dorsal radial ligament. But this is the ligament that's injured, giving you dorsal instability. In terms of x-rays, you wanna get a true Roberts view, and also potentially a thumb stress view to see that degree of instability, if, for example, the CMC joint is reduced. And in terms of treatment, I wish I could give you level one evidence out there, but unfortunately, if you look at our literature, it's most about case reports. So I'll try and summarize the sort of take-home principles from this. So this was a study by Watt and Hooper, who had 12 patients who had a dislocation of the CMC joint, all dorsal, and then they underwent closed reduction. If they were stable, they were placed into a cast. If they're unstable, they had closed reduction percutaneous pinning. And essentially, what they noticed was that you had poor results if there was a delay in diagnosis, but despite even the ones that are being stable were casted, you can see that five patients of these, so just under half, had persistent instability. So this is what the biggest complication is of this injury. And you can treat this with an Eaton reconstruction, where you're taking a distally-based strip of the FCR, and instead of, for example, doing an LRTI, where you take out the trapezium, you leave the trapezium intact, but you take the distally-based strip of the FCR and weave it through a drill hole at the base of the thumb metacarpal to give you stability. This is a study of four patients. As I said, these are rare injuries, so it's basically case reports, who all underwent closed reduction. And you can see that three or four of these needed to be open. One was treated with closed reduction percutaneous pinning. The ones that were open, that's where the dorsal radial ligament injury was discovered. And in terms of treatment, you can see 75% were asymptomatic, but of those, you can still see two or four had dorsal CMC subluxation. So residual instability is a common theme of what's the biggest complication of these injuries. Study by Tom Trumbull, looking at closed reduction percutaneous pinning with that ligament reconstruction, the FCR one that I just mentioned. Essentially, he noted that when he did a ligament reconstruction using the FCR, he had better strength, less arthrosis, but all of these patients had a degree of instability. So that's what they'll test you on in this injury if they're asking what's the long-term sequelae of these injuries. In terms of fracture dislocations, the epibasal fracture is an extra-articular fracture. And because there's so much motion at the CMC joint, these are relatively forgiving in terms of when you need to operate. And essentially, rule of thumb is that when the deformity is greater than 30 degrees, you have apex dorsal deformity. When it's greater than 30 degrees, it's relatively well-tolerated. Any more than that, then you start getting compensatory MCP joint, not CMC, MCP joint hyperextension. So non-operative treatment, less than 20 to 30 degrees of apex dorsal angulation is tolerated. Any more than that, and that's when you operate. There's a question on there named what's the reduction maneuver? And my mnemonic for this is TAPE. Essentially, on the distal phalanx, sorry, on the distal metacarpal, it's traction, abduction, pronation, and extension. That's the reduction maneuver, and then you can do your treatment. So the mnemonic here is TAPE. You'll see a question come up, and that's where the answer is. So in terms of Bennett fractures, this is a fractured dislocation. And so the key part here is we talked about those stout volar ligaments, and it's the volar oblique ligament that essentially keeps that fracture fragment reduced. So what's the dislocated part? Essentially, it's the thumb metacarpal that is being pulled by the abductor pollicis longus. That's the primary deforming force is what's causing the dislocation. Most of these you can reduce and do a closed reduction percutaneous pinning. The reduction maneuver is the same. If you're gonna have to fix them, and we'll talk about a next fracture next, is the Wagner approach, which is essentially an incision through the glabrous part of the palm. And the structure that's at risk, number one, is the dorsal sensory branch of the radial nerve. So that's the structure at risk through the Wagner approach if you're gonna open these. Rolando fracture is a comminuted intraarticular fracture. If you're gonna open them, again, a Wagner approach. These are not really amenable to closed reduction percutaneous pinning. It's either an X fix to distract it because it's too comminuted, or a Wagner approach for open reduction internal fixation. Okay, moving on, MCP joint. So again, all the joints in the hand considered to be a box. So you have the radial on the collateral ligament, and we'll go into nuances of their anatomy in a second. You have the dorsal capsule and the volar plate. But you also have dynamic stabilizers, and these are essentially the intrinsic and the extrinsic muscles that run along the thumb. And the primary dynamic stabilizer of the thumb MCP joint is the adductor pollicis. Okay, and that's the primary intrinsic stabilizer dynamically. In terms of the collateral ligament, it's divided into true and accessory like all of these ligaments. The true runs in an oblique manner from the metacarpal head to the volar aspect to the proximal phalanx. The accessory ligament is more superficial and blends into the volar plate and the ulnar sesamoids. The primary role is to resist valgus force, but it has a secondary role. Number one, to resist MCP joint subluxation, but also to resist supination of the MCP joint. So how do you test them? So in full extension, essentially you're testing the volar plate, and if you're testing the volar plate, you have to be testing the accessory collateral ligament as it inserts there. In 30 degrees of flexion, so remember the MCP joint, you flex at 90 degrees. For the thumb, the difference here is that you flex it at 30 degrees, and that's where you're testing the true ulnar collateral ligament and the dorsal capsule. In terms of the nomenclature, there's two main types. There's skier's thumb, which is an acute injury. Gamekeeper's thumb is an attenuation. It's more of a chronic injury. My mnemonic here is PRS, plastic reconstructive surgery. So that's my mnemonic here. When you injure the ulnar collateral ligament, what happens to the proximal phalanx? Well, the proximal phalanx rotates and supinates around the intact radiocollateral ligament, okay? So that's where PRS. Proximal phalanx supinates around the intact radiocollateral ligament. There's no easy other way to remember it, so that's how I remembered it. Okay, so in terms of history, skier's thumb, again, is acute injury. Gamekeeper's thumb, you're thinking more of a chronic pain and an attenuation. Edema, well, you know, that's important because if you have a presence of a palpable lump, you need to start thinking, in the test question, if they talk about a palpable lump, start thinking about a possible stenolesion. When you're examining these patients, examine the uninjured side. That's just more of a practical tip. That's their natural control. And in terms of the test, this is what I put these numbers down. When you've injured the true ulnar collateral ligament, so there's no endpoint, it's when you basically get greater than 35 degrees of laxity and 30 degrees of flexion. 30 degrees of flexion, you're testing the true ulnar collateral ligament, greater than 35 degrees, or greater than 15 degrees difference compared to the uninjured side. There is a paper out there about the role of intraarticular lidocaine injections. Basically shows that it really improved the ability to diagnose a true ulnar collateral ligament when you anesthetize the joint. In terms of gradation of injury, I put this in because this leads into the treatment. There's three types of gradations. Grade one, where there's a sprain, but there's a good endpoint. Grade two, where there's a slight increase in laxity, but you still have a solid endpoint. And grade three, essentially that there's no endpoint and you've got a true ulnar collateral ligament injury. This is an important slide in terms of location of rupture. The majority of ruptures on the ulnar side occur distally. And it's the opposite on the radial side. And the reason for this is as you go distally, the ulnar collateral ligament thins and is not as wide as it is proximally. So majority of ruptures on the ulnar side are distal. In terms of imaging, plane x-rays are important to get to look out for an avulsion fracture. But don't think that if you get an avulsion fracture that the ulnar collateral ligament is necessarily attached to that. There was this study by Hinterman actually showing that you can have an avulsion fracture, but you can also have a condition where the ligament also is off that avulsion fracture. So most of us are thinking, well, the avulsion fracture will scar down, the ligament's attached to that. That's not necessarily the case. And so that's why I put that caveat in there. Ultrasound is operator dependent. And so really, if you're gonna get a test, it'll be an MRI, essentially to look out for a stenolesion. In terms of treatment, if you have a partial tear, I think casting and splinting, the outcomes are pretty good. If you have an avulsion fracture, this is a study by Kutz of 20 patients, sorry, 30 patients that were treated in a cast. And all of these patients actually did pretty well with an avulsion fracture. But then in another study by Dinowitz, all of these patients had an avulsion fracture, but more than two millimeters of displacement. And this is the reason why an operative indication where the number of two millimeters comes important. You'll see that all were treated in a cast, all were unstable, all needed surgical fixation. So in terms of surgical indications for ulnar collateral ligament, it's where you have a complete tear, a stenolesion, or displaced avulsion fracture. In terms of treatment options, I'll sort of run through them quickly. Again, multiple case reports, no level one evidence. Couple of pearls, when you're placing your anchors or your drill holes, make sure they're in an anatomical footprint. So on the proximal phalanx, it's on the volar side. And on the metacarpal head, it's on the dorsal side to recreate that obliquity of the collateral ligaments. Study looking at sutures versus suture anchors essentially showed that the suture anchor population did better. It's not really surprising because the suture anchor patients mobilized much quicker than the other patients. But when followed out long-term, really no difference between the two cohorts. Tension band fixation out of our institution by Dr. Cozen and Bishop, essentially seven patients who had a displaced more than two millimeters of displacement were fixed, did well. So try to come up with this table of how to sort of break it down in your mind. Essentially, when there's complete instability or a displaced fracture fragment of more than two millimeters or it's rotated, you wanna fix them. If you have a stress evidence of instability, again, you wanna fix. Anything else, try non-operative treatment first. Now, that was the acute. Moving on to chronic, many different types of treatments from primary repair all the way to arthrodesis. When you look at the literature for primary repair, there's really not much out there. This is the only study that I could find, and you could see this was back in the 90s, where they had two primary repairs of this cohort of 33 patients. Dealer's choice what you take out from that, so I don't think they'll ask you that on the test. It's too controversial. But what they may ask you is dynamic tendons transfers, and the main transfer out there is an adductor advancement, and this is by Niveza, where they essentially took the adductor and advanced it to the proximal phalanx. Remember, we talked about the adductor being an important dynamic secondary stabilizer. Well, this is where this plays into role, and you'll see that three quarters of the patients actually did pretty well with this treatment. I think most of us now, with the advent of biotinodesis screws and better graft choices, are using some form of tendon reconstruction, many different types of grafts, many different types of weaves. Because there's so many different types, they're not gonna ask you that in the test. This was a study just looking at some literature of 38 patients treated with a free palmaris longus graft. Patients did well, but when they fail, what's the bailout? And this is what might come up in the test. Well, the answer is an arthrodesis. And the arthrodesis is also when you're doing it for an arthritic MCP joint. And I mentioned why they might ask you this in the test, because there's a question out there more for treatment of basilar thumb joint, and when you fuse the MCP joint of the thumb, what do patients lack? And what they lack is flexion and adduction of the thumb. So that's the answer there. So that's why I put it in this series. Okay, radiocollateral ligament. The anatomy on the radial side differs from the ulnar side. Number one, the abductor pollicis brevis muscle is there. It tends to be wider than the adductor, so there's a less risk of having a stenolesion on the radial side, but you can get stenolesions on the radial side. There have been case reports on that. Doubt they'll ask you that, but just an FYI. We talked about where you get tears on the ulnar side. Most of the tears are distally. On the radial side, it's the converse, it's proximally. The reason is because on the radial side, the ligament is wider distally than it is proximally. Again, you have the true ligament that runs in that oblique manner, and you have the accessory ligament that is more volar and blends into the volar plate. Mechanisms of injury is forced adduction. In terms of getting a complete tear, similar to what we've talked about on the ulnar collateral ligament, greater than 35 degrees of laxity and 30 degrees of flexion, or more than 15 degrees compared to the uninjured side. In terms of imaging, you want to get plane radiographs. And we talked about what happens on the ulnar side. The proximal phalanx supinates around the intact radial collateral ligament. But on the radial side, what happens when you injure the radial collateral ligament, the proximal phalanx pronates around the intact ulnar collateral ligament. And it's sort of a bit of a word salad, but it's a very easy test question to make, so that's why I put it in there. Gradation of injury, it's a stage one to stage three that we've talked about on the ulnar side, grade one, where you have a firm end point, grade three, that there's no end point and complete laxity. In terms of treatment for partial tears, can you treat them in the cast? On the ulnar side, you routinely do, but what about on the radial side? You can try it, but the concern there is that the problem on the radial side is that the pull of the adductor and the EPL, they're so strong, they'll tend to stretch out your radial-sided, if you're gonna treat them in the cast, or repair. So most people try and advocate surgery for a complete tear because of the strong deviating forces of the adductor and the EPL. One of the pearls are to make sure your anchors are in the right position. Remember, you wanna go in a bleak manner from the dorsal aspect to the metacarpal to the volar aspect to the proximal phalanx. And also to transfix the MCP joint with a K-wire just because the ulnar-sided pull is so strong. And so I don't think they'll ask you that in a test, it's just a technical tip. In terms of chronic injuries, again, these tend to be more of a reconstruction with biotinidesis screws or if it's an arthritic to fuse the joint. This is in your handout. The reason why I put it in your handout is not for you to learn from this, it's just to show you that the quality of the literature is so poor that I doubt that they'll ever ask you about the treatment of a chronic radiocollateral ligament because there's no real agreement in what the definition of acute and chronic is and there's a discrepancy in terms of if it's less than three weeks or greater than three weeks. In my mind, greater than three weeks is still acute. So that's why I doubt that they'll ask you that but I put it in your handout just for completion. In terms of thumb MCP joint dislocations, so moving on in terms of most of them are dorsal. Again, similar to the PIP joint that we talked about, the volar plate, you wanna watch out for this. So you can see in this x-ray, the sesamoids are interposed. So that's gonna be an irreducible dislocation and you'll need to open that. You're not gonna get that reduced closed because the volar plate has been pulled in with the sesamoids. If they're not there, you can reduce these but if not, you need to open them. If you do get a closed reduction of a simple dislocation, make sure you check for collateral ligament instability because it's not infrequent that the collateral ligaments are injured, especially the ulnar collateral ligament and if you have a grade three injury, you'll repair it. There's a test question out there of a patient had a thumb MCP joint dislocation that was reduced. What's the next thing you check for? Well, one of the things that you wanna check for is collateral ligament stability. And lastly, thumb IP joint dislocations, very rare. If they're gonna dislocate, they tend to be dorsal. They tend to get this volar skin tear. Most of these tend to be closed reduction is possible but you may need to open them, especially if you have a large avulsion fracture or the FPL is a vol stuff. Time for any question? No, okay, thank you.

dislocation

ligament injuries

thumb

CMC joint

anatomy