Marlena Jbara, MD discusses the osseous and ligamentous anatomy essential in the stabilization of the lisfranc joint, imaging sequences used to assess pathologies of the midfoot, as well as a checklist approach to evaluate midfoot anatomy on MRI.
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TAPE STARTS – [00:00]
Marlena Jbara: Hi. My name is Marlena Jbara and I'm an MSK radiologist with Northwell Health. In this segment, we'll review MRI of the Midfoot, review of normal anatomy. Disclosures, I, or related party, have no financial relationship to disclose. The objectives of this lecture will be to review the osseous and ligamentous anatomy essential in the stabilization of Lisfranc joint. I'll provide an overview of the imaging sequences used to assess pathologies of the midfoot and we will review the MRI evaluation of the midfoot anatomy using a checklist approach in the coronal, sagittal and axial imaging planes.
To begin with the osseous anatomy of the midfoot includes five bony structures, the navicular and the cuboid and the medial, middle and lateral cuneiforms. These are the bones of the midfoot seen in the frontal projection and in the sagittal projection. The osseous anatomy of the foot is divided into four major units. The first metatarsal unit with the middle cuneiform provides approximately six degrees of mobility. The second metatarsal with the middle cuneiform is a firmly fixed structure as is the third metatarsal with the lateral cuneiform. The fourth and fifth metatarsal articulations with the cuboid can by – be mobile.
In looking at the midfoot in the superficial dissection at the plantar aspect, we can appreciate that at about the level of the midfoot, we have the major portion of the plantar aponeurosis. We're beginning to decussate the plantar fascia bundles and they will eventually sweep off into their own digital slip so the plantar aponeurosis. But at the midfoot level, the plantar aponeurosis is still the majority structure. And removing the fascia, we come to the first layer and we expose the flexor digitorum brevis at the level of the midfoot. A portion of the abductor hallucis can be seen in abductor digiti minimi.
Moving deeper into the second and third layers at the level of the midfoot, we can appreciate the porta pedis now, which is the decussation of the tarsal tunnel at the level of the midfoot and you can see along medial to the first ray, we can see branches of the nerve artery and vein bundle as they course over the quadratus plantae, which is the deeper muscle deep to the flexor digitorum brevis muscle. Further deeper, we get to see the origin of the oblique head of the abductor hallucis muscle and we can see that at the level of the midfoot. We can also appreciate the deep structure of the peroneus or in this case which is written as the fibularis longus tendon.
And it's basically coming down from the distal fibula, the lateral malleolus to ascend in a cuboid tunnel underneath the cuboid towards it's attachment on the base of the helix metatarsal. So that's another thing that we're going to be appreciating in the short access plane of the midfoot, the attachment of the peroneus longus tendon. Furthermore, we can see the branching of the medial and lateral plantar nerves and the nerve artery and vein bundles as they dissect medial and laterally at the level of the midfoot.
Midfoot ligamentous anatomy, we can see on the example to our right, we can see the dorsal ligament, the intercuneiform, important ligament between the second metatarsal and medial cuneiform, that's the Lisfranc ligament. We can see the dorsal intermetatarsal ligaments also while seen in this dorsal rendition. Plantarly, there is a good degree of reinforcement of these intermetatarsal ligaments and tarsal, metatarsal ligaments. We can also see the reflected plantar cuneocuboid ligaments and the short plantar cuneocuboid ligament. Also, portions of the spring ligament can be seen supporting the talar head, the branches seen here at the medial and lateral and plantar oblique bands.
Of course, a quick note about the dorsalis pedis that is extending down the dorsum of the ankle and towards the first interspace between the first and second metatarsal bases, the deep peroneal nerve also runs alongside this artery. And we can see that's implicated in the deep peroneal nerve compression syndromes that can occur with pain and numbness. Furthermore, no discussion of the midfoot is complete without discussing the Roman Arch, which provides the Osseo stability of the metatarsals and also the recess keystone appearance of the second metatarsal base. Furthermore, midfoot anatomy will further be seen between the medial cuneiform and the base of the second metatarsal through its Lisfranc ligament, which has three bands taken at a transaxial slice as seen here on the left.
And we can see the dorsal, the interosseous and the plantar oblique bands as you can see here and we're going to see them further on MRI imaging. Here is a lovely example of a digitized rendition of the dorsal blue, interosseous red and green plantar bands of Lisfranc ligament. And here just to isolate, what we're looking at is a transaxial T1 weighted image demonstrating the dorsal attachment of Lisfranc ligament, the interosseous attachment and the plantar bands that attach to both the base of M2 and M3. And beginning our perusal of the midfoot, we begin at the plantar aspects and we can see on the left is coronal T1 weight image demonstrating the subcutaneous fats surrounded by the collagen vesicular network. We're volume averaging portions of the intrinsic muscles of the heel, here the abductor digiti minimi and the flexor digitorum brevis muscles.
Here is the T2 plantar corresponding image at the same level demonstrating the numerous blood vessels that normally exist within the plantar foot. Moving up through the midfoot, we've come into the slips of the plantar fascia and volume averaging through the plantar aspects of the flexor tendons and this is better seen in the transaxial and sagittal imaging, which we'll go through in the next sequences. But for now, we're moving up through the foot through the muscles of the intrinsic muscles of the foot to get into the bony structures and ligament structures, which are the work course of these sequences.
And now, we get into some of the flexor tendons. We can see the flexor tendons coming in towards the forefoot. We appreciate the sesamoids that flank either side of the flexor hallucis tendon. We're just beginning to see the base of the fifth metatarsal and we will take a look at the next image. Now, you can really see the base of the fifth metatarsal. We're still coming in through the intrinsic muscles of the foot. We can appreciate that on the long axis T1 weighted image that the fatty marrow signal is bright and on T2 weighted image, its normal signal intensity. There're no fractures or edema that can be seen here. Further moving into the plantar aspect of the midfoot, we can appreciate the base fifth metatarsal and the cuboid articulation. Of course, now we can really appreciate what was not well seen in the coronal plane, which was the peroneal tendon as it courses under the cuboid tunnel towards the base of the helix metatarsal and we can see it here attaching on the base of the first metatarsal. We can appreciate the congruency that's existing between the base of fourth metatarsal and the cuboid and even the small osteophytes that are occurring here. Furthermore, we can now see portions of the medial cuneiform and base of helix metatarsal and its congruency. We can appreciate the plantar bands of Lisfranc ligament coming through here from the base of the third towards the medial cuneiform.
We have yet to see the base of the second metatarsal and we'll complete our inspection of Lisfranc ligament when we see that. Again, noticing small osteophytes, joint congruency, lack of joint effusion as seen here. Further evaluation demonstrates the helix metatarsal base and the medial cuneiform where volume averaging a portion of the middle cuneiform and the lateral cuneiform as well as the cuboid. We can see the congruency between the third metatarsal base and the lateral cuneiform here. And now, we can really appreciate the interosseous attachment of Lisfranc ligament seen here between the medial cuneiform and the base of second metatarsal.
Notice the congruency that's existing better seen on the coronal T1 weighted images of the medial base of second metatarsal and middle cuneiform and lateral base of lateral cuneiform – I'm sorry, medial base of lateral cuneiform and base of third metatarsal well seen here. We're also volume averaging a portion of tibialis anterior, which will come to attach not only into the medial cuneiform, but also spend a gap attach at the base of the first metatarsal. We can further demonstrate the dorsal and attachment of Lisfranc ligament volume average tier. We can appreciate the congruency of the bony structures in their normal respective anatomic relationships.
We also note that there's no bone marrow edema, no elevated T2 signal within the bony structures. We can even see the cortical bone here. We're seeing some of the subcutaneous soft tissues and we can use the T1 weighted image to get a sense of how patchy or heterogeneous it is noticing that this is not homogeneous elevated T2 signal. There're certain areas of fat that are seen within that retain the normal signal. So you would not want to drain something that look like this.
And further evaluation of the midfoot demonstrates the medial cuneiform with the base of second metatarsal and you can appreciate the close proximity and lack of intervening – interval widening that can be seen with tears. We're appreciating the congruency of the joint articulations, the lack of bone marrow edema, the lack of fracture, the cortical and cancellous bone. And further completing our inspection of the congruency between the medial cuneiform and base of second metatarsal seen here. Congruency again, addressed and established between the cuneiforms and the metatarsal basis and lack of bone marrow edema here on T2 weighted images, lack of fracture and stress related changes.
Now, we can move on to midfoot anatomy seen in the transaxial plane, which is really the work course in this region. We're going to take transaxial slices through the midfoot and we can appreciate the dorsal interosseous implant, our ligamentous anatomy. So the transaxial anatomy of the midfoot is the definitive way to assess whether or not the ligaments are intact. The anatomy of Lisfranc ligament can be seen here in this illustrated example of the dorsal blue component, the red interosseous component and the green plantar component. And we can see this very nicely in the transaxial midfoot image. This is an axial T1 weighted image, the blue arrow denoting the dorsal component of Lisfranc ligament between the medial cuneiform and base of second metatarsal.
You're seeing some of the strands of the interosseous in red ligament and the green plantar band seen here on this transaxial T1 weighted image. And then further imaging in the transaxial plane in the midfoot reveals the first slices that we usually come into, would be slices that show the tibialis anterior tendon here, beginning to attach at the base of the medial cuneiform, but not yet and the base of the helix metatarsal, also not seen yet. We're seeing the extensor digitorum brevis musculature, the abductor hallucis, the flexor digitorum brevis and the quadratus plantae with its tendons. You get a great look at the abductor digiti minimi and some of the crossing peroneal tendon as it's headed towards the base of the helix metatarsal.
Seen here, transaxial T1, transaxial T2 imaging noticing that there's some elevated signal here in the subcutaneous soft tissues. And further, we see the tibialis anterior beginning to come in and you begin to see some of the intermetatarsal ligaments seen here rather thicken. You see some of the degenerative changes, see this osteophyte formation between the base of the second and the third metatarsal and here, we're still in the level of the medial cuneiform. We're beginning to come in to the attachment of tibialis anterior, the Roman Arch configuration noting the T1 axial imaging with normal fatty marrow, no bone marrow edema, notice you still see the muscles with its central tendon units, the extensor digitorum musculature beginning to thin and end at this level.
You are not yet seeing all of the extensor tendons and the flexor tendons free yet, and we're keeping our eye in the region of Lisfranc joint where the dorsal attachment here enter osseous and plantar bands will come in. And here, you can appreciate the dorsal band still you can see a portion of them, the portion of the interosseous. And of course, much better seen here, this interosseous ligament between the medial cuneiform and the base of second metatarsal. And of course, no interval separation, no evidence of increased signal and the tears that do occur, generally, predictably occur from a dorsal force that tear the dorsal component, the interosseous and then eventually the plantar.
We can see the subcutaneous soft tissues and the extensor tendons beginning to poke their heads through the muscle. We see the Roman Arch anatomy, the interosseous ligaments between the metatarsal bases and of course the intrinsic muscles of the foot seen very well on T1 weighted image and assessed again on T2 weighted images for signal abnormalities, elevated signals and what have you to see whether there's a strain or a neuritis pattern. And of course, further seeing the attachments of the dorsal Lisfranc ligament, the interosseous bands and not seeing the plantar bands, seeing the Roman Arch configuration again.
Of course, assessing the transaxial T1 weighted images for bone marrow edema, we can see the extensor digitorum tendons, the muscle's tendon units of the sole of the foot. We're appreciating the lack of separation between the base of the helix metatarsal seen here, no bone marrow edema. We're able to assess the Roman Arch, the presence for fractures of edema, we can see the extensor tendons and of course, the intrinsic muscle of the foot.
And of course, more involvement of seeing just the bony structures, the cortical bone and then cancellous bone, the presence of extensor tendons picking through here with subcutaneous soft tissue swelling. The intrinsic muscles of the foot seen here with flexor tendons not yet free of the muscles. And now, we're beginning to see some of the extensor tendons. We can appreciate the intrinsic muscles of the foot for signal intensities that are normal on T2 so that we may be able to pick up whether or not there's an intramuscular hematoma or trauma. We're seeing small normal blood vessels of the foot and a little subcutaneous edema at the lateral aspect of the midfoot.
The same, we're beginning to see more of the same. We're beginning to see the dorsal interosseous musculature and the plantar interosseous musculature, the intrinsic muscles of the foot. We can still see that the bony structures, the cortical bone and cancellous bone, and comparing that to T2 weighted images, and assessing whether or not there's any kind of fracture, bone marrow edema or periosteal reaction. And more extensor tendon anatomy, the interosseous muscular anatomy, in these cases, we can see whether or not there's a neuritis pattern, which would be demonstrated by elevated T2 and T1 weighted signal and the flexor tendons of the foot with the distal plantar fascia seen here beginning to serve and invest the flexor tendon bundles.
Moving on to sagittal anatomy of the midfoot. Again, looking at the bony structures in the midfoot, what we are looking at are the cuboid navicular and medial, middle and lateral cuneiform articulations. The boundaries of the midfoot are two, the Chopart articulation is between the talocalcaneo and navicular cuboid articulations. And of course, we have Lisfranc joint between the cuneiforms and the metatarsal bases as well as cuboid. And moving sagittally through the foot, the first articulation we encounter is the helix MTP joint where obviously the forefoot can usually be wider than the midfoot. So the first slices that you will see when you're imaging skin to skin may be boundaries of the forefoot seen here at the plantar plate complex of the first MTP joint.
And of course, moving further in we begin to see the investment of the sesamoids with the deeper flexor brevis tendon and of course, portions of the abductor hallucis and the congruency of the articulation. Notice, you can see a portion of the flexor hallucis tendon at its distal aspect in the forefoot. Similar perusal of the myotendon junction, the bony structures noting the T1 normal fatty marrow and the low T2 signal denoting no bone marrow edema or fracture or periosteal reaction.
And we're beginning to move in towards regions of the midfoot that we can see. This is where we can see the tibialis anterior beginning to attach on the base of the helix metatarsal and the medial cuneiform. And moving further from medial to lateral, we can appreciate the helix metatarsal base and the medial cuneiform. The tibialis anterior beginning to attach the dorsal ligamentous anatomy and some of the intrinsic muscles of the foot, we can appreciate mostly the congruency. And again, we see the congruency between the medial cuneiform and the base of the helix metatarsal. On this image, you're also volume averaging a portion of the sesamoid complex and the sesamoid hallucal articulation seen here.
Moving further in, we have the medial cuneiform, a base of helix metatarsal with small osteophyte identified here, the congruency of the joint, the intervening cartilage and lack of surrounding edema. Similarly, we can see the joint articulation seen here with a small osteophyte and small osteophyte seen here. Joint alignment is maintained, interosseous muscles normal in signal intensity, still volume averaging a portion of the MTP joint here. This band represents the distal deep portions of the superficial and deep subcutaneous soft tissues and portions of the plantar fascia. Here, we can appreciate further bones of the midfoot seen in the sagittal plane and volume averaging a piece of the joint space and the bony structures and lack of edema.
More of the same of the congruency degenerative change that we can appreciate comparing T1 and T2 weighted images. Similarly here, we can see the medial cuneiform and actually, this is the middle cuneiform with the second metatarsal base and the dorsal osteophytic ridge seen here. We can see a portion of the muscles and the signal intensity being normal on T2 weighted images. Appreciating more of the degenerative change, the joint congruency and the lack of inflammatory change seen in sagittal imaging. Similar sagittal congruency of articulations, we can appreciate the intrinsic muscles, the interosseous tendon -- I'm sorry, the intrinsic tendon and the further plantar plate complex just included here in sagittal imaging of the midfoot will always include sagittal imaging of the forefoot.
And again, appreciating the midfoot structures, we can see portions of the cuneiform, metatarsal, dorsal ligaments and we're really beginning to appreciate the extensor tendons seems so beautifully here through the musculature and mild surrounding inflammatory change within the subcutaneous soft tissues denoted here with changes of the signal intensity down to one, decreasing the normal fat signal intensities that you can see here. Extensor tendons, joint congruency, those are the features that you look for in sagittal MRI imaging of the midfoot.
Further seen extensor tendon petering out, we're seeing some of the articulations, no bone marrow edema or fracture, no subcutaneous plantar swelling or evidence of a fibroma. Coming further into the metatarsal cuneiform or cuboid articulation seen here at the base of the fourth metatarsal with the cuboid and you can appreciate the surrounding, lack of two signals. Here seen really coming into its own, the base of the fifth metatarsal with the cuboid. Notice the joint congruency, the normal signal intensity within the bony structures and the lack of STIR elevated signal. Of course, coming to the lateral aspect of the base fifth metatarsal, we can see the bony structures, we see the lack of bone marrow edema denoting there's no fracture, a little dorsal subcutaneous soft tissue swelling seen there.
And further coming into the fifth metatarsal base, a portion of the muscle is seen here, some of the subcutaneous soft tissue swelling. And again, scanning from skin to skin that we're out of the midfoot at this point, we still see a portion of the metatarsal and we'll evaluate everything on every image that we see. And lastly, the last slice is through the fifth MTP joint seen here, you can, you can actually see a portion of the cartilage and a piece of the muscle, the abductor digiti minimi.
So in summary, this tutorial has reviewed the osseous and ligamentous anatomy essential in the stabilization of Lisfranc joint. We provided an overview of the imaging sequences used to assess pathologies in the midfoot. And lastly, we reviewed MRI evaluation of midfoot anatomy using a checklist approach in the coronal, sagittal and axial imaging planes. I thank you for your generous time and attention and hope this lecture has been a value for you.
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