 MRI in finger injuries is a slightly tricky topic but once you have good quality images things become pretty easy. How to obtain good quality images we have already discussed in the previous video on MRI finger anatomy. So, in today's session we will have a quick revision of the finger anatomy. For all those who want to look at the detailed discussion of the MRI finger anatomy you can look at the previous video. After the anatomy we will look at the different mechanisms of injuries of different soft tissue structures followed by abnormal MRI appearances in these finger injuries and last we will look at how to report these injuries. Now this is very important there are certain points that you need to mention in your report which will add value to your report so that it is appreciated by the orthopods and you get an edge above your peers. So in today's session for every injury we will discuss a checklist of the points that you need to mention in your report. So let's begin with the anatomy like any other joint you have OSHA structures, the joint and the cartilage within the joint and you have soft tissue structures. Now since we are predominantly concentrating on MRI appearances of these injuries we will look at the soft tissue injuries in today's session. So soft tissue structures can be divided into three compartments that is the volar, dorsal and lateral compartments. The volar compartment, the first structure is the volar plate which is the deepest structure, superficial to that you have the flexor tendons and then you have the pulleys. In the dorsal compartment there is extensor tendon and superficial to that you have the sagittal band. So actually you have the entire extensor hood but the sagittal band is the most important and lateral compartment you have the radial and the ulnar collateral ligaments. In the tendons you have flexor tendons and extensor tendons. Now there are two flexor tendons, the superficial one is the flexor-digitorum superficialis and then the deeper one is the flexor-digitorum profondus. Whereas in the extensor tendons you have something called extrinsic tendon which arise in the forearm or outside the hand and insert onto the fingers whereas intrinsic tendons are those which arise within the hand and insert onto the fingers. So the extrinsic tendons are extensor-digitorum, extensor-indices, extensor-digitimini, whereas the intrinsic tendons are interocial and the nubrikes. Now let's look at the diagrammatic representation of all these three compartments to understand the anatomy better. So as you can see this is the coronal image of the finger and this is the sagittal image and this is the dorsal aspect and this is the volar aspect. So in the volar compartment the deepest structure is the volar plate which are triangular structures, have a broad base attachment towards the distal, have a distal broad base attachment and a proximal narrow attachment which is by the ligaments called as checkerine ligaments. Then you have the flexor-digitorum superficialis tendon. Now this tendon if you see it splits into two parts and has two separate attachments on the proximal aspect of the middle phalange and if you see this has a tunic fork-shaped appearance. So this splitting into two tendons occurs at the level of the proximal phalange. Then you have the flexor-digitorum profundus tendon. Now this does not split into two, it has a single attachment at the base of the distal phalange and if you see over here, as I told you before the profundus tendon is a deeper tendonus and the superficialis as name suggests is a superficial tendon. But at the level of the mid part of the proximal phalange where the superficialis splits into two slips the profundus passes through the gap between the two slips and becomes superficial. So after the mid part of the proximal phalange the profundus is a superficial tendon whereas superficialis is a deeper tendon and the superficialis will attach to the proximal aspect of middle phalange by two separate attachments whereas the profundus will attach by a single attachment to the base of the distal phalange and overlying these flexor tendons you have the pulleys. Now pulleys are annular and cruciform pulleys but the annular pulleys are more important and they are 5 in number that is A1 to A5 of which the odd number pulleys are at the level of the joints whereas the even number pulleys are at the level of the shafts of the bone. On the dorsal aspect you have the extensor tendon which is this is the extrinsic extensor tendon and of this extensor tendon divides into three slips the central one is the central slip and the two lateral ones are the lateral slips or the lateral bands. The central slip goes and attaches to the base of the middle phalange whereas there are two more tendons that is the intrinsic tendons which come from the intrinsic muscles and they go and merge with the lateral bands to form the con joint tendon. So these are the two con joint tendons now the two con joint tendons merge together to form a single tendon at the level of the distal inter phalangeal joint and they attach to the base of the distal phalange and this is nothing but the terminal extensor tendon and overlying these extensor tendon to support them you have the extensor hood of which the most important is the sagittal band which is at the level of the head of the metacarpal the last is the lateral compartment and it comprises of the radial and ulnar collateral ligaments. Finger injuries can be classified in a simple way as per the compartments so the dorsal compartment will consist of extensor tendon injuries and sagittal band injuries the volar compartment comprises of flexor tendon pulleys and volar plate injuries and lateral compartment consists of collateral ligament injuries. First we will look at the extensor tendon injuries now extensor tendon injuries can happen at multiple levels but the common one is at the distal phalangeal base attachment and the middle phalangeal base attachment and these are nothing but the closed tendon injuries so the distal phalangeal base attachment injury is known as the ballet finger or the baseball finger baseball finger because it happens when playing baseball or different other ball games ballet finger because whenever there is a tear of the distal extensor tendon the distal inter phalangeal joint goes into flexion and the appearance is similar to a mallet which is nothing but a hammer. Next is middle phalangeal base attachment a central slip injury and this eventually leads to boutonniere deformity how that happens we will look in the slides ahead. So now the mechanism of mallet finger as I told you that it happens in ball games like basketball and baseball this is a ball and when it comes and hits the tip of the finger the distal phalange is forced into extreme flexion and this results into the tear of the distal extensor tendon. Now when this distal extensor tendon tear is not treated or is not addressed eventually it results into swan neck deformity. So now as you will see whenever there is a distal extensor tendon tear there is flexion at the distal inter phalangeal joint. So there is a flexion at the distal inter phalangeal joint and this exerts tension on the proximal inter phalangeal joint and that joint goes into hyper extension. So swan neck deformity is nothing but hyper flexion at the distal joint and hyper extension at the proximal joint and this will happen if the distal extensor tendon injury is not treated on time. So here you can see this is a normal patient and you can very well see the distal extensor tendon attaching to the base of the distal phalange whereas here you can see that there is a tear of the distal phalangeal base attachment and in fact there is a gap the tendon is retracted and there is a gap of this much between the attachment and the tone end of the tendon. On the actual images this is your volar compartment with the flexor tendons and this is your extensor compartment and you can see the extensor tendon nicely. The central slip is not visualized because it is already attached to the base of the middle phalangeal. So as you go distally you can still appreciate the two lateral slips further you cannot see a tendon on this side and this side also the tendon appears very frimsy and here you cannot appreciate any tendon. So this is at the level of the tendon attachment to the base and you cannot appreciate any tendon that is attaching to the base of the distal phalangeal. This is a normal patient where you can see a jet black tendon that is attaching to the base of the distal phalangeal. So this is a mallet finger and this is a osceus evulsion. So this is also a mallet finger where there is a osceus evulsion at the base of the distal phalangeal. Osceus evulsions are better appreciated on lateral views of the x-rays or on a sagittal view of the CT. So with this we come to something called as extensor tendon zones. Now these zones were made so that whatever the radiologist is reporting and whatever the orthopod is understanding from the report they both are at the same page and hence to simplify our reporting these zones were created. So extensor tendon zones one thing to remember is thumb has a different classification of the zones as compared to the finger the thumb is labeled with T in the beginning. So today we will only discuss the finger zones. The finger zones are 1 to 8 on the extensor compartment and the key to remember is the odd number zones that is 1, 3, 5 and 7 they are at the level of the joints whereas the even number zones that is 2, 4, 6, 8 they are at the level of the shafts of the bone. So you need to mention the zone in which the injury has occurred that is important and you can also mention the zone in which the retracted tendon is lying. So the orthopod can understand exactly what is the gap between the two. Now this is a lateral slip injury and as I told you that along the shafts you have the even number zone and so lateral slip injury is nothing but the zone 2 injury. So here you can see that the lateral slip is intact and here you can see that again there is a disruption and you can see some tendon over here and you can see the other tendon edge on this side. So this is the gap between the torn tendon edge and here now at this level you can appreciate the lateral slip very nicely. Again the central slip has already attached to the base of the middle phallus. As you go distilly you can see that the ulnar lateral slip is intact but the radian lateral slip is not well visualized. So here there is a tear of the radian lateral slip and again distilly you can appreciate both the lateral slips very nicely. With this we come to the central slip injury. Now central slip injuries again they happen when there is a injury along the dosage of the finger but this time at the level of the proximal inter phallus joint or when the proximal inter phallus joint is forced into sudden hyper flexion. So with that there is a central slip tear. Now it is very important to identify the central slip injuries on MRI because often they are difficult to diagnose clinically and why is that so whenever there is a distal extensor tendon injury or mallet finger so whenever there is a complete tear of that tendon there is complete loss of extension at the distal inter phallus joint and that can be easily diagnosed on clinical examination. But with central slip injuries as you can see that the lateral slips are still crossing the proximal inter phallus joint. So the patient only has mild extension lack or extension weakness against resistance which can be difficult to diagnose clinically unless a high suspicion is kept in mind and the patient is actively examined for it. Therefore it is very important for us radiologists to make sure that we report the central slip injuries. Now what happens if the central slip injury is missed? So eventually because of the unopposed action of the flexors the proximal inter phallus joint will go into flexion. The lateral slips will shift more volarly and this will exert a tension on the distal inter phallus joint and as a result the distal inter phallus joint will go into hyper extension. So this is exactly opposite of what we have seen in this one leg deformity. Here the distal joint is in hyper extension whereas the proximal joint is in hyper flexion and this is known as boutonniere deformity. Now central slip injury will be a zone 3 injury because it is at the level of the joint so an odd number and here you can see that this is your normal central slip which is attaching to the base of the middle phallus. Whereas here you can see that there is a complete tear of the central slip injury. There is very minimal attraction in this particular patient. On the actual images again you can appreciate both the lateral slips. So here this is your first lateral slip and this is your second lateral slip. So you can appreciate the lateral slips also and you can also appreciate the central slip. Now as you come distally you can again appreciate the lateral slip. The central slip looks bad. Further distally at the level of the tear you can see that you cannot appreciate a central slip in this particular patient and even at the middle phalangeal base attachment you cannot appreciate a tendon that is attaching to the phallus. But you can see the two lateral slips very nicely. So this is a central slip injury. Now here you can appreciate that the cortex is missing at the base of the middle phallus. So this is nothing but the oceus evulsion at the central slip attachment. And this small bone piece can be appreciated over here. So this is your bone piece which is evalced off from the middle phallus base. And you can see the tendon itself is intact and is attached to the bone piece. And here on the ancient images you will appreciate that there is a defect in the bone and there is a bone piece which is edematous. Now oceus evulsions can be better appreciated on as I told you lateral views of the radiogram and surgical views of the CT. So this is a surgical view of the CT of the same patient where you can see the oceus piece very nicely. Now in this patient you can see that the tendon is very attenuated. It is not a healthy tendon that is attaching to the base of the middle phallus. And if you will see the entire finger this patient has actually started to develop a flexion deformity at the proximal joint and the extension deformity at the distal joint. So this is nothing but central slip injury which has been there for a longer period of time and now has resulted into boutonniere deformity. Now why do you call it as a boutonniere deformity? When you button a shirt the button goes through the shirt and attaches. Similarly you can see assume that the lateral bands are nothing but the hole and the joint is actually button holding through the gap between the lateral bands and hence it is called as boutonniere deformity. Now we look at the entire spectrum of extensive tendon injuries. So this is your normal extensive tendon, the normal attachment, distal, the lateral slips and the normal central slip attachment. This patient has a distal terminal tendon injury. This one has a lateral slip injury but you can see the terminal attachment very nicely. This one you can see the lateral slips and the terminal attachment is good but the central slip is torn. Here there is an osceus evulsion at the central slip attachment and this patient has now started to develop a boutonniere deformity. You can also have osceus evulsions happening at the distal attachment which again will be better seen on a radiograph or a CT. The checklist that you need to use when you're reporting such cases so which tendon is torn, what exactly is the site of injury so you can either give the exact distance from the insertion but more important is to mention the zone in which the injury has occurred whether it's a partial or a full thickness tear, the extent of tendon retraction so you can again describe where the tendon is lying or whether the tone edge of the tendon is lying or you can also mention the zone in which the torn tendon is lying. The exact gap between the two tendons because that is very important for a surgeon to decide the type of surgery that he needs to do. The length of the distal stump in case of zone 1 injuries the tendon quality of the torn end. Again this is very important because if it is a poor quality tendon if the tear is chronic, if the gap is too much the surgeon will not consider tendon repair as the treatment but the surgeon will rather consider tendon transfer. So he needs to know the gap to decide whether you need a surgical management or a conservative management and to decide what kind of surgical management. Again bony avulsion, so you need to mention both the size and the percentage of articular surface involved because a larger articular surface involvement the surgeon will have to use a surgical method as a mode of treatment but if the articular surface involvement or if the auspicious piece is small he can use the conservative management. If there is any associated joint subluxation or if there are any other associated soft tissue injuries. So this is a sample report that you can use whenever you see an extensive tendon injury so full thickness whichever finger is involved extends a digital tendon tear at the insertion of the base of the distal phalanx in zone 1 with retraction of the tendon by 0.5 centimeter so it is nothing but this gap this flimsy black structure that you see that is nothing but the tendon sheath it is not the tendon no distal tendon stump is noted at the insertion and the torn tendon is showing moderate degeneration so this is the healthy tendon which is jet black in color here you can see it is bulky and a bit degenerative so this is the complete report the surgeon knows exactly what needs to be done for this patient now first we look at the flexor tendon injuries and then we look at the other dorsal compartment injuries in flexor tendon injuries the most common is the transaction or the open wound injuries in close flexor tendon injuries the most common is the FTP or the flexor digitorum profanta syndrome it is commonly seen in rugby and football which are nothing but contact spots it is also called as rugby finger because it happens while playing rugby and it is also known as jersey finger not because it was diagnosed in new jersey but because in contact spots like rugby you can see as the sportsman is trying to tackle the jersey of another sportsman there is extreme possible contraction in the forearm and flexion of the fingers to hold the jersey the other sportsman simultaneously is trying to get away as a result of which an opposite force is exerted on the flexed fingers and this results into the FTP injury commonly the ring finger is involved because it is hypothesized that the ring finger is predominantly involved in any grasp so the mechanism of FTP injury is where you can see that the finger is in flexion and a flexion force is exerted simultaneously a opposite hyperextension force is exerted because the player is trying to get away and when this force becomes more the distal enterfalangeal joint goes into extreme hyperextension and results into the FTP tear which is also called as jersey finger now in the FTP injury it is the zoned one injury why we will discuss it in the next few slides so here you can see that the insertion of the tendon is intact but at the level of the middle phalange there is a tear and this is the gap between the torn tendon ends so this superficial tendon is the FTP tendon and the deeper one is the FDS tendon because we are distal to the level of the proximal phalanges on the axial images we can appreciate that the FDS tendon look intact the FTP tendons have a longitudinal split within them and as you go distally you can see the FDS tendons but the FTP tendons are not visualized here you can see the FDS tendon inserting onto the bone you can very well appreciate the pulley but the FTP tendons are missing so in this gap region you can see an empty pulley and then again you can appreciate the FTP tendon with a longitudinal split and the insertion of the FTP tendon is intact so this brings us to the flexor tendon zones which are less in number as compared to the extensor tendon zones and again the thumb zones are separate so in the finger the zone one is up to the FDS insertion zone two is up to the distal parma crease zone three is up to the distal aspect of the or the distal edge of the transverse carpal ligament zone four is the carpal tunnel and zone five is proximal to the transverse carpal ligament so this is the same checklist that we have used for the extensor tendons the same things you also need to report for the flexor tendon next let us look at the flexor tendon transaction injury or the open injury so here you can see that there is complete transaction of both FDS and FTP tendon there is a fluid filled gap between and the gap you can measure the gap like this and you can mention it in the report now on the actual images you can see that as you go from distal to proximal the tendon is visualized then what you can see is the tendon sheet with fluid filled gap within again the same you can see the fluid filled gap and the other tendons look normal so at this level you can see that there is a balled up or a coiled up tendon that is visualized both on the coronal and the asian images now this is important to report because this means that there is extra length to the tendon and this is very important for the surgeon to know normally the surgery involves a repair and whenever there is a large gap bringing the two ends together and suturing will create a lot of tension in the tendon so whenever there is a large gap between the two tendon ends the surgeon would prefer tendon transfer that is he will utilize some other tendon of the body rather than a pure tendon repair but if we mention in the report that there is a balled up tendon the surgeon knows that there is extra length to the tendon than what is visualized and he will consider tendon repair as a form of operation for the patient so this is a zone 2 injury which as we have discussed the injury has happened distal to the distal pama crease level so you can mention the level of injury that it is in the zone 2 you can mention the zone in which the tendon is lying which is zone 3 and the gap between the tendons so this is how we will create a report of this particular patient where you can say that there is a full thickness FDS FTP tear at the level of the metacarpophalangeal joint in zone 2 retraction up to zone 3 yielding a gap of 2.7 cm the important thing is to mention that the tendon edge is coiled and that it is showing some degeneration and the distal tendon edge is looking healthy next we look at the sagittal band injury so it occurs at the metacarpophalangeal joint the mechanism is where there is a direct blow along the dorsal aspect of the MCP joint or the MCP joint goes into sudden hyperflexion complete tears will result into extensive tendon dislocations and important thing to keep in mind is that the tendon dislocates to the opposite side so if you see this is your extensor tendon these are the two sagittal bands which on the volar aspect go and attach to the volar plate so whenever there is a tear of the sagittal band the other sagittal band has an unimposed effect and it pulls the tendon towards itself so the tendon dislocation happens on the opposite side just like what you see in a stroke patient where the mouth deviates to the opposite side so here at the level of the metacarpophalangeal joint you can see that this sagittal band which is the radial sagittal band is normal and the ulnar sagittal band you see it is not completely torn but it has an intermediate grade injury where the band itself is thickened hyper intense signal is there within it and there is soft tissue edema around it so whenever you see a complete fluid signal you know that it is a complete tear rest you can grade it into low intermediate and high grade injuries depending upon the appearance and eyeballing so what things you need to mention in the report which band is involved the grade of injury is there any extensor tendon subluxation or dislocation what is the status of the tendon itself whether it is torn, longitudinal splits or tendonosis and what are the other soft tissue injuries next we come to pulley injuries so A2 and A4 pulley which are along the shaft of the bone they are the most prone to injuries A2 pulley injury is particularly more common in rock climbers and therefore it is also called as a rock climber finger so whenever the PIP joint goes into extreme flexion it puts a lot of load on the A2 pulley before we discuss the mechanism let's look at the job of the pulley so the job of the pulley is to keep the tendon in opposition with the bone when the finger goes into flexion so whenever there is one pulley injury the tendon would still remain close to the bone because the other pulleys are intact but when multiple pulleys are injured what happens is bow stringing where the gap between the tendon and the underlying bone so this gap increases and this is called as bow stringing and you can label it bow stringing when the gap becomes more than 3 millimeters so let's discuss because I have a short discussion on the grip that I use in rock climbing so open hand grip where the PIP joint is not much in flexion this is the most preferred grip but sometimes the rock climber needs to use a full grip grip in order to put extra load on the fingers so whenever you want to use the full grip grip always try to use the thumb opposition because whenever you oppose the thumb on the fingers the amount of tension that is exerted on the tendons and the pulleys is reduced and hence the chances of pulley injuries are less as compared to only full grip grip so for all the rock climbers out there and for all the people who are interested in rock climbing make sure you use the open hand grip or the full grip grip with thumb opposed not just the full grip grip next is these are the sagittal images of the MRI where you can see that there is a pulley injury and there is resultant bow stringing so here this is the gap this gap is increased and on actual images what you will appreciate is here this is the level of the A2 pulley so you can see the proximal aspect of A2 pulley is thickened but not completely toned but there is some increase in the gap as you go distilly you can see that there is a complete tear of the A2 pulley here also there is a complete tear of the A2 pulley and there is marked increase in the gap between the bone and the tendons at the level of the A3 pulley so now you are at the level of the joint you can see that again there is a larger gap and the bone is and the pulleys are toned A4 pulley you can appreciate that the pulley is not completely toned but it is a high grade injury so this particular patient three pulleys are injured and it has resulted into bow stringing now in this patient there was an isolated A2 pulley injury where the pulley was not completely toned but it had a high grade injury and what you see is that there is minimal increase in gap between the bone and the tendons and there is no bow stringing against the previous patient where you can see that the gap is way much and this is nothing but bow stringing so you need to mention the pulleys which are involved with what grade of injury it is whether there is bow stringing or not status of the flexed tendons themselves and what are the other associated soft tissue injuries next we come to Volare plate injuries the Volare plate injuries are more common at the distal broad base attachment of the pulley the proximal attachment is by the slender checkering ligaments and injury of the proximal attachment is less common again you can grade the injuries into low grade injuries partial tear, complete tear and another thing is nauseous evulsions important thing to keep in mind is Volare plate injuries can be associated with fracture dislocations and most commonly they involve the proximal interferogen joint so mechanism this is the sagittal view of the finger and these are the volare plates so whenever there is a hyper extension injury that happens at the joint it will result into a Volare plate injury now this patient you can see that there is nauseous evulsion at the base of the middle phallic at the attachment of the Volare plate so the plate is well attached to this nauseous piece and there is an nauseous evulsion another thing to keep to see is that there is a dorsal subluxation at the proximal interferogen joint so as I told you that subluxations and dislocations are common with Volare plate injuries this is a Volare plate nauseous evulsion is another patient and again nauseous evulsions are better visualized on natural radiographs and sagittal CT views and in this patient you can see that there is a high grade or a near full signal stare at the distal attachment of the Volare plate even the proximal attachment is not looking good and if you see the Volare plate itself is bulky with a lot of hyper intense signal with it there is a Volare plate injury without any nauseous evulsion so now the question that you need to answer is which joint Volare plate is involved whether it is the distal or the proximal attachment in case of nauseous evulsion you need to mention the size and the percentage of the particular surface involved this is important because whenever there is a fracture involving more than 30-40% of the particular surface and when the collateral ligaments are attached to the broken nauseous piece or the broken bone piece it is called as an unstable injury now why do you need to differentiate between stable and unstable because stable injuries usually patients undergo a conservative management whereas unstable injuries usually require a surgical management so the surgeon needs to know if the injury is unstable similarly as I told you that the dislocation and subluxation are common if there is a dislocation you need to mention if the Volare plate is entrapped in the joint space because if there is any soft tissue within the joint space you cannot relocate the joint by just conservative management because the soft tissue will be a hindrance and hence these dislocations also called as complex dislocations require surgical management and lastly you need to mention the other soft tissue injuries mainly the collateral ligament injuries collateral ligament injuries happen with valgus or varus loading forces again you can grade them into different depending upon the grade of injury and you also in this case need to look for if there is any interposition of the ligament within the joint so the mechanism is a varus or a valgus loading force so if the force is directed on this side there is increased tension on these ligaments and if the force is directed on this side there is increased tension on these ligaments so whenever there is an increased valgus or a varus force it will result into tear of the collateral ligament now here this is a patient who had a high grade proximal collateral ligament attachment injury so there are some fibres which are attaching to the bone so it is not a complete tear but it is a high grade injury and also there is underlying bone against this patient you can see that there is a full thickness tear at the distal attachment of the collateral ligament so you can see that this is as much like a fluid signal so you can compare the fluid with the joint and if you see a fluid signal you know that it is a complete tear so it is always important to know the mechanism of injury for any structure and you can even classify the finger injury based on the mechanism of injury this particular indication is critically more important because if you know what was the mechanism of injury or what sport the patient was playing you know which structures to look at so hyper flexion injuries result into extensor tendon and surgical band injuries hyper extension injuries involve more the volar compartment which is the flexor injuries the pulley injury and the volar plate injury the varus and valgus loading injuries will affect the collateral ligament transaction injuries are nothing but open wound injuries and in that multiple structures can be involved depending upon the site of injury and the last thing is the axial loading injuries which result into dislocations whenever there is an added rotatory force or an x-axis force to it and for those which have a pure y-axis force it will result into something called a spelon fracture which is a split fracture that happens at the base of the phallus usually the middle phallus because the underlying bone is trying to insert into the phallus so what are the key take away points how can you add value to your report by mentioning which soft tissue structures are injured and by helping the orthopedic deciding what should be the further line of management that is conservative or surgical and for this few important points which will help you routinely but they are not a rule it is not applicable in all conditions but on an average whenever you see a large articular surface or shear evolution retracted tendon tears chronic injuries where the tissue has been scarred there is a lot of degeneration and for dislocations where there is soft tissue interposition in the joint space which is nothing but a complex dislocation these injuries will usually require a surgical management so it is very important to mention these points in your reports but again this is not a rule if you have any queries you can ask your questions in the comment section below or you can also mail me your queries this is my email id thank you so much