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Marlena Jbara: My name is Marlena Jbara and in this tutorial we'll review pathology, MRI of the ankle. I, or related party, have no financial relationship to disclose. The objectives of this lecture will be to recognize MRI pathology of the ankle, including tendon, ligaments, inflammatory condition and nerve pathology. We'll gain an understanding of the best imaging strategies utilizing MRI to assess ankle pathology, and we'll develop a checklist approach to evaluation of MRI ankle pathology.
We'll begin with the posterior tendons, the normal Achilles tendon, generally about seven millimeters thick. Notice the plantaris on the medial aspect. And on this example, see, we see the slight increase signal within the distal Achilles tendon, representing a small interstitial tear on the order of tendinosis. In general, when we discuss tendon pathology, all tendons basically will run through this essential classification where grade A or a grade 1 tendon pathology, or tendinosis, is viewed, a form of swelling of a tendon or enlargement.
In time, some of those fibers may tear and retract, and we'll have thinning of the tendon, or type B tendinosis. In grade 3 or C type of tendon tears, we have a complete transaction. And then, in the example shown in D in the schematic, we can have interstitial tearing. A note about the posterior tendons, the normal plantaris, this is seen anteromedial in the Achilles in approximately 90% of people.
And we can see it here. It's a tendon that crosses two articulations that begins at the superolateral condylar bridge of the knee and extends distally to the middle aspect of the calcaneus. Posterior tibial tendons, the normal plantaris again, see immediately. And in this example, we can see on the right the Achilles being completely raptured with the plantaris remains intact and simulates an intact Achilles tendon.
The Achilles can exhibit a series of inflammatory conditions known as paratenonitis since the Achilles just not have an actual tendon sheath. And of course we can see the thickening on the example on the right of Achilles tendinosis diffusely with low signal. The Achilles has risk of partial tendon tears as seen here, and then the transaxial image we would see the degree of percentage of cross-sectional involvement.
And of course, this example on the right, a complete Achilles tendon tear with an intratendinous gap, which we would measure and provide that information in the report. Also notice the edges of the tendon are frayed and expanded, a finding consistent with map head appearance of the tendon edges and may need debridement before repair. So in this example when the gap of the Achilles is greater than five centimeters, generally, we'll be using some type of graft to establish length of the Achilles tendon.
Of course, Achilles full thickness tears have a variety of appearances. Some of them are completely retracted. Some of them are partially retracted. Here in this example, in this transaxial T1 weighted image, we're seeing amorphous signal in the Achilles tendon. And here in the fluid sensitive sequence on the right, we can see the complete gap as identified by the tendon. We only can see one clear edge of the tendon. Definitely, that much gap is present with surrounding inflammatory change in paratenonitis.
In tendons that have been primarily repaired, we can use MRI to evaluate for partial re-tears, noticing the elevated signal within this tendon. We can see on cross section the percentage of a fiber involvement, and assess the risk to re-tear or go on to full thickness tears. A related entity of Achilles partial tears occur at the insertion, the well-known Haglund deformity, where a prominent posterior superior calcaneal tuberosity is felt to be implicated in diseases of the Achilles insertion, creating retrocalcaneal and retro tendon bursitis associated with insertional Achilles tendonitis.
Of course, clinically, retrocalcaneal bursitis can be obtained or ascertained by palpating for tendons in front of the Achilles tendon, the retrocalcaneal bursa being implicated in this disease. And here in this example on the right, we can see the retro calcaneal bursa distended in the retro tendon bursa, and this patient with an intact Achilles tendon insertion.
More about Haglund deformity, these are felt to be pump bumps where perhaps if you're in the plantar flexed state in a pair of high heels, you can have pump bumps created and pressure between the posterior process, and where the Achilles inserts, and the triad of retrocalcaneal bursitis and Achilles retrotendon bursitis, and a partial tear of the Achilles represents Haglund deformity.
Moving on to the medial tendons, we discussed this earlier. We have the posterior tibial inserting on the medial aspect of navicula, also the medial cuneiform, and the bases of the second through fourth metatarsals. We have the flexor digitorum and the flexor hallucis longus tendon, as well as the posterior tibial artery nerve and vein, all moving through the tarsal tunnel.
Of course, the posterior tibial tendon, as seen here, the insertions of the navicular cuneiforms in second through fourth metatarsals, the risk of pathology occurs in middle-aged women, patients with rheumatoid arthritis, of course athletes, and those patients with an accessory, os navicularis. We can assess spring ligament tears, sinus tarsi syndrome, as well as primary posterior tibial tendon dysfunction.
Looking at posterior tibial tendon partial tears, we'll first orient ourselves with the location of the tendon. So here we're seeing the posterior tibial tendon just coming in front of the flexor digitorum and the flexor hallucis longus tendons at the distal tibia. As we move down towards the ankle, we see the posterior tibial tendon and at least three pieces here, consistent with a tear of the posterior tibial tendon. We have the flexor digitorum and the flexor hallucis longus tendons, and of course the tarsal tunnel with its nerve, artery and vein.
Moving further distally, we can see the blown out appearance of the toe and posterior tibial tendon, and this patient that has a small sub-Tenon remaining at the medial retromalleolar groove. We can still see the flexor digitorum and the flexor hallucis, as well as the nerve, artery, vein bundle in the tarsal tunnel.
And in this example to the right here, we can see the torn posterior tibial tendon coursing to its attachment on the middle navicula. Flexor digitorum and flexor hallucis longus tendon is going under the sustentaculum talus in this patient with a partial tear of the posterior tibial tendon. Posterior tibial tendon dislocations, essentially we're looking here at the blown up view of the middle retromalleolar groove, and we're seeing these enthesophytes on either side of what represents an empty groove. And the groove is empty because the posterior tibial tendon can be seen here anteromedially. It has subluxed out of that groove, and what we have is realty the flexor digitorum and the flexor hallucis longus tendons, remaining as seen here.
Other tendons, the flexor digitorum longus tendon, is rarely abnormal and it inserts on the second through fifth distal phalanges. The medial flexor tendons, namely the flexor hallucis longus tendon, of course is underneath the sustentaculum between the hallux sesamoids to insert at the base of the great toe distal phalanx. The sheath communicates with the joint and approximately 20%. Therefore, fluid within the flexor hallucis longus tendon sheath is not necessarily primary disease but may represent communication with the joint effusion, and the location of pathology varies.
We can have pathology of the FHL at the posterior talus with the stenosing tenosynovitis and os trigonum syndrome. Repeated bouts of plantar flexion as seen in ballet and basketball players can cause this entity.
And of course patients who have a good deal of toe off namely in running or ballet, can run the risk of having tendon pathology at the level of the forefoot. The medial tendons of the FHL again communicate between the ankle and the tendon sheath as seen here, where we can see the FHL coming through the fibro-osseous tunnel of the posterior talus, and this is a midline structure, a midline image. So we can't really appreciate that but we can see the tenosynovitis related to the joint effusion without primary tendon pathology, and that communicates in approximately 20% of patients.
The medial ankle tendons, namely the flexor hallucis longus tendon with stenosing tenosynovitis and os trigonum syndrome, we can see the FHL coming through its fibro-osseous tunnel with the lateral talar process not communicating with the talus. And there's a situation of synovitis and ganglion cyst noted at the posterior joint line. This is an entity that can result in difficulty or painful walking, where the tendon does not glide normally through this area.
Medial tendons include pathology of the FHL, again at the distal aspect between the sesamoid complex. This transaxial grade and eco image demonstrating the sesamoids, the intersesamoidal ligaments, and the flexor hallucis longus tendon, which is in the weight bearing portion with distal tenosynovitis. The lateral tendons can be seen here again with a schematic. We're seeing the peroneus longus and brevis, secured to the lateral malleolus and calcaneus by way of the superior peroneal retinaculum. We can see the inferior peroneal retinaculum and of course the peroneus brevis insertion.
The peroneal tendons are evertors. The brevis is located anterior or medial to the longus, and flattened oval is a good shape but boomerang is bad, and it may mean that the central fibers are torn out. In the presence of a calcaneal fracture, there can be entrapment and the risk for peroneus brevis tears include entrapment by the longus and fibula with dorsiflexion We can have tearing of the superior peroneal retinaculum.
The shape of the lateral malleolus can add pressure to the peroneus brevis. Of course, the presence of accessory muscles within the canal include low lying peroneus brevis or peroneus quartus, and this can result in compression. And pitfalls include either a bifurcate peroneus brevis or an accessory peroneus quartus, and a split tear by conventional only have one muscle belly where the others, the bifurcate or the peroneus quartus, will have two muscle bellies.
Again, just a quick review of the normal peroneal tendons, we can see the peroneus brevis is eyebrow-shaped on this transaxial image in front of the peroneus longus, and it has a muscle belly here. Now, we'll have to see further whether this is going to join the peroneus brevis or its own tendon and it will be a peroneus quartus.
In this example of a peroneus brevis splits here, we're seeing three tendons, so at the level of the lateral malleolus. You're seeing a nice example of the fibrous ridge of the superior peroneal retinaculum. We're seeing the peroneal retinaculum band and we're seeing the two portions of the peroneus brevis with the peroneus longus, so that build up to the front of the groove and the split tear. In here, you can see on this example to right, you see the peroneus brevis with the peroneus longus in its position but a good deal of synovitis in this patient who has peroneus brevis pathology.
An accessory peroneus quartus can be seen here as a separate tendon structure. Here's your peroneus longus and here's your peroneus brevis and your peroneus quartus. Again, here, you can see your peroneus brevis, trying to come in front of the longus with an accessory peroneus quartus. A nice example of dislocated peroneals in this common pathologic state for peroneals, we see the peroneus longus and brevis are no longer restrained by the superior peroneal retinaculum and the fibrous ridge.
And moving towards the joint line, we can see that the peroneus longus, the peroneal tendon has dislocated lateral to the tip of the lateral malleolus. And we can see a pouch has been formed, which allows egress of the tendons into the space through the torn superior peroneal retinaculum.
Again, looking at the intra tendons from medial to lateral, we're looking at the tibialis anterior, which can be judged for tendinosis based on its size related to the posterior tibial tendon. It's about 1.5 times the size of the flexor digitorum or the extensor hallucis longus. And of course the extensor digitorum longus and the peroneus tertius is poorly seen here, the action of the extensor tendon cyst to dorsiflex and they're rarely injured.
Sometimes I've seen injuries where we can drop a structure, direct force on a tendon and that can cause a tendon to snap like a rope. Intratibial tendons, we can have a tibialis anterior tear as seen in this enlarged example of the tibialis anterior, where you can see multiple discontinuities between the low signal fibers.
Of course, more than two to three times the size of the normal posterior tibial tendon. Moving on to ligament pathology in our discussion, the lateral ligaments, we can talk about the level of the syndesmosis at the tibia and fibula here seen in this schematic, and we can see those in transaxial image. And of course at the level of the tibia and fibula, you have the anterior and posterior syndesmosis. By convention on MRI, we generally combine these ligaments so they can be distinguished with careful inspection.
Again, normal examples of the tibia and fibula, these are best seen on axial images to the level of the talar dome. And really the anterior talar fibular, the posterior -- I'm sorry, the anterior tibia fibula, the posterior tibia fibula, and intraosseous membrane altogether represent the syndesmosis.
The lateral ligaments include the normal tibia fibular posterior syndesmotic ligaments where we're seeing that at the level of the posterior ankle joint, and contrasting that to the torn anterior tibia fibular ligament as seen here in the syndesmotic injury. We see disruption of the anterior syndesmotic ligaments and inflammatory change along the ankle joint line.
The lateral ligaments more inferiorly, we'll be looking at the anterior talofibular, the posterior talofibular and the calcaneal fibular ligaments as seen here. The anterior talofibular ligament, seen with the talus and the fibula anteriorly, is one complete band, as opposed to what the poster talofibular ligament looks like, which is more of a broad shape band like ligament with fibrils.
And here just to give you an example before we look at abnormal, we can look at the normal talofibular ligament, seen here as one thick band, and the strayed appearance of the posterior talofibular ligament. Lateral ligaments, namely the calcaneal fibular ligament, we can see here as coursing between the calcaneus and the fibula deep to the peroneal tendons, and you can see that nicely on this axial image here where you're seeing the calcaneal fibular ligament deep to the peroneus brevis and longus.
Of course, notice the FHL with fluid and its constant relationship to the sustentaculum talus. Note this example of this torn ATFL, complete discontinuity, and infects small enthesophytes coming from the talar side of the anterior talofibular ligament. Lateral ligaments, more about the torn anterior talofibular ligament, notice fluid egressing through the joint space out to the anterior lateral joint line, indicative of the anterior talofibular ligament tear.
Lateral ligaments here, including tears of the anterior talofibular ligament and the posterior talofibular ligament. And when you have this situation by definition, the calcaneal fibular ligament must be torn, that they usually go in succession with anterior talofibular to calcaneal fibular ligament tears, and then lastly, with posterior talofibular ligament tear.
In terms of the anterior talofibular ligament, we can see evidence of a chronic tear with a formation of a small neoligament bridging towards the talus here in this thickened anterior talofibular ligament with reapproximated fibers.
Moving on to the medial ligaments, looking at the straight appearance of the deltoid, we can see the deep and superficial bands, and even the flexor retinaculum seen most superficially between the medial malleolus, and the muscles of the medial aspect of plantar foot, the abductor hallucis. A torn deltoid is representative of seeing incomplete fibers or fluid gap between the fibers, and we have lost striations, and the tibial calcaneal ligament can become discontinuous or thick.
Moving on to the spring ligament, the normal spring ligament is that sheath that really holds the talar head like a mother's arm with her baby. And you can see here the superomedial band is really an important part of the structure, providing a whole sheath of ligament to support to the medial talar, as seen here with some bone marrow edema.
In the coronal image, we can see the superomedial band of the spring ligament hugging the talar head and more of the inferior fibers. Spring ligament tears are generally difficult on MRI but there's a surgically proven tears denoted by Toye et al. in HAR in 2005. And here you can see some waviness of the spring ligament in this patient with a spring ligament tear.
Moving on to inflammatory conditions, and here you can see on this example of a chronic sprain of the anterior talofibular ligament with synovitis, possibly representing anterior lateral gutter syndrome in the appropriate clinical setting. This can present with pain, swelling and limited dorsiflexion, mostly result of inversion injuries. It can create a situation of synovitis and fibrosis in the anterolateral gutter, essentially identified by a low signal mass deep to the anterior talofibular ligament and ligaments.
Moving on to the sinus tarsi, by definition when the sinus tarsi interosseous ligaments become sprained, there's a degree of synovitis that occurs and that would be the definition on MRI of having sinus tarsi syndrome. Generally speaking, this is the clinical syndrome of a patient experiencing a wobbliness or an instability when they heel strike not knowing how to position their foot towards the unlocking of the midtarsal joints in the phases of gait.
Essentially, you can see on these images that the schematic that the ligaments are in a crisscrossing orientation, providing support during the locking and unlocking phase as we move from the hind to midfoot stance of gait. So a normal sinus tarsi should have preservation of the fat as you can see here. We're in the sinus tarsi and you can see the interosseous ligaments. This is the lateral talar process. This represents the roof and the floor of the sinus tarsi and you can see here on the coronal image, both the roof and the floor with the interosseous ligaments.
Moving on to sinus tarsi syndrome, this is lateral foot pain relieved by anesthetic injection. This is subjective feeling of hindfoot instability. The etiology includes an inversion injury or multiple inversion injuries in approximately 70% of patients. We can have tears of the lateral and subtalar ligaments, and injury to the proprioceptive nerves coursing through the tunnel. Inflammatory arthritis has been implicated in this entity in approximately 30%. And we would want to assess the ATFO calcaneal fibular ligament, the posterior tibial tendon, and the spring ligament as many of these cases go on to have overpronation and hindfoot impingement.
In this example of sinus tarsi syndrome, notice the obliteration of the fat on the sagittal T1 weighted image and the elevated signal denoting synovitis on this fluid sensitive image. Sinus tarsi obliteration can also occur unrelated to other areas of soft tissue swelling. We can have fluid or hemorrhage in acute ankle sprains so it's not something that we would be diagnosing in the acute setting.
Moving on to the normal plantar fascia, the normal plantar fascia is approximately 4.5 millimeters thick or about four millimeters. We're going to be looking for things like preaponeurotic edema in focal areas of discontinuity.
These patients present with excessive heel pain. They maybe obese, runners, zero negative inflammatory arthritis with chronic repetitive stress and inflammation. The MRI is going to show a stick with elevated signal at the calcaneal attachment. Perifasciitis or preaponeurotic edema I like to call it, end marrow edema of the calcaneus. Raptures would be involved in forced dorsiflexion with a thickened disrupted ligament distal to the calcaneal attachment.
Plantar fasciitis seen here as a thickened plantar fascial central cord with elevated increased signal, a large degree of preaponeurotic edema, and even partially seen stress factor in the calcaneus by this low signal wavy line identified here. Plantar fascial rapture as in this example here with retraction of the central cord lobbing up with surrounding preaponeurotic edema.
Moving on to nerve pathology. We can assess nerves within the normal tarsal tunnel. The posterior tibial nerve can be seen either branching at the level of the angle or distally into branches of the medial and lateral plantar, and calcaneal nerves. The tarsal tunnel syndrome is reserved for this burning paresthesia and the swollen toes, the compression of the posterior tibial nerve and branches is implicated. And etiologies are many, though many are not usually found, including ganglion cyst, nerve sheath tumors, varices, pannus formation, hemangiomas, fibrous coalitions and fibrosis.
And MRI, if we find the mass, that usually it's going result in some surgical implication for the patient. In tarsal tunnel syndrome, we can see here schwannomas that surround the posterior tibial nerve and its branches on this post contrast exam. Notice there is enhancement of this lesion. Ganglion cyst of course can occupy the tarsal tunnel, creating a mass effect on branches of the posterior tibial nerve.
Of course, hemangiomas can occur in this region and compressed branches of the nerve, creating a tarsal tunnel-like syndrome. So an overview of what we've just discussed includes an anatomy and search pattern in our first lecture, and soft tissue pathology review including tendons, ligaments, inflammatory conditions and nerves.
In summary, this has been a review of soft tissue pathology of the ankle. We've developed an imaging strategy utilizing MRI to assess a variety of ankle pathologies and we've reviewed this checklist to approach to evaluate MRI pathology. Thank you for your time and attention.
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