Marlena Jbara, MD discussed normal foot anatomy as well as the normal foot X-rayviews. Dr Jbara also discusses the mechanism of injury as well as the classification systems and X-ray evaluation of adult talar, calcaneal, midfoot, base of 5th, stress, and sesamoid fractures.
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TAPE STARTS – [00:00]
Marlena Jbara: Hi everyone. Again it's Marlena Jbara and this is the second of two lectures regarding podiatric emergency radiology. This is foot trauma. I or related party have no financial relationship to disclose. Learning objectives for this will include reviewing foot anatomy, x-ray evaluation, mechanisms of injury. We will review talar fractures, calcaneal, midfoot fractures. We will spend a time to discuss base of fifth fractures, stress fractures and sesamoid pathology. The foot. This is my daughter in Snug Harbor in Staten Island as she is learning her cart wheels about 10 years ago. The foot is complicated. It's comprised of 28 bones or 26 plus two sesamoids and it comprises 57 articulations. It's subdivided into three segments or movements including the hind foot, which results in inversion and eversion movement, the midfoot abduction and adduction occurs their forefoot with flexion and extension. The joints include the talocrural responsible for inversion and eversion, the hind foot to midfoot or Chopart resulting in inversion and eversion maneuvers, and the mid foot and fore foot and Lisfranc joint responsible for abduction and adduction and of course the flexion and extension at the MTP and IP joints.
The bones of the hind foot and forefoot and the medial midfoot segments here are seen from dorsal to plantar noticed the calcaneus and talus overriding each other with a more spread out arrangement on the Roman arch of the navicular cuboid and cuneiforms. Moving on to the struts of the metatarsal and the articulating phalanges and sesamoids. No evaluation is complete without the lateral x-ray evaluation and it's important to note that the weightbearing bones would include the calcaneus above the talus joint through the subtalar joints, C referring to navicula, D referring to the all important cuboid, which though this patient has pes cavus and it's quite elevated from the ground at this point. Later on diabetic neuropathy, you can see that the cuboid will move into a weightbearing Charcot plantar position. And the cuneiforms overlying the letter E. F denoting the base of the fifth metatarsal, which should be something you visualized on all lateral x-rays. In terms of the x-rays, the evaluation again will include an AP, lateral and oblique x-ray and 45 degrees of internal rotation, the AP and oblique is the best image for evaluation of the forefoot and the midfoot and the lateral x-ray is the best for evaluating the hind foot and soft tissue such as ankle effusion. Assessment of the talus as the second most common fractured tarsal is extremely important. There are three parts to the talus including the head, the neck and the body and it's prone to dislocation when the foot is in plantar flexion. And here is a bony rendition of the talus where you can see that the blue articulating surfaces include the head, the body and the posterior subtalar joint and then seen from superior to inferior, you can see the broad based body and the thin head of articular cartilage.
And looking at the actual bony structure noting the perforation along the neck where you have the confluence of the anterior and posterior tibial arteries and the trochlea for the tibia and the depression for the medial malleolus can be seen here. Fractures of the talus include minor fractures like chip fractures, which could be treated like sprains or major fractures, which include the head. A 5% to 10% of all talar fractures involve the head. The neck is involved in 50% of all major fractures and the body is involved to 23% of all talar fractures and it's usually a high energy mechanism. The treatment for minor fractures would be the same as a sprain fragments. Greater than 5 mm mainly may need excision. The arterial supply of the talus includes branches of the posterior and anterior tibial and the peroneal artery providing an anastomotic ring of vessels to produce retrograde flow, which percolates to the body. Disruption of arterial flow after a talar neck fracture can result in avascular necrosis given this retrograde recurrent flow. The Hawkins classification is a useful classification for evaluating the commonly associated talar neck fractures in high speed motor vehicle collisions. And essentially type 1 is a non-displaced talar neck fracture, type 2 is involved in subtalar subluxation associated with the fracture, type 3 is dislocation of talar body and 50% of these are open fractures, type 4 is dislocation of talar body and destruction of talar navicular joint.
And the fracture type influences management and prognosis. Examples of Hawkins Canale type 1 fracture in this example here demonstrates this vertical essentially non-displaced talar neck fracture without subluxation or dislocation from the subtalar position. The talus remains in its anatomic position and generally only one of the three supplying blood vessels will be routinely disrupted in this injury. This is the lowest incidence of AVN, 0% to 15%. Here is your illustration to the left and to the right you can see the talar neck fracture. An example of a Hawkins Canale type 2 where you have a vertical displaced fracture of the talar neck. The ankle mortis in this case is preserved and it's commonly extension into the body and posterior facet of the talus. Up to two of three supplying blood vessels are disrupted and the risk of AVN is 20% to 50%. Here in this example, you can see the subtalar subluxation here. You noticed the fracture line image on the middle with the blue arrows pointing it out and you could see that's the blow up of this image to the right where you can see there is an ankle effusion, soft tissue swelling and intraarticular extension into the posterior subtalar joint. This is an example of a Hawkins Canale type 3 injury. In this injury, the talonavicular articulation is preserved with the talar neck fracture resulting in a subtalar and tibiotalar dislocation. In this injury, up to all three supplying blood vessels are disrupted and the risk of AVN goes up with that fact going up to 90% and 100%.
Here, you can see in this illustrative example on the left, the talar neck fracture with subtalar and posterior tibiotalar dislocation and preservation of the talonavicular joint. Here, in a real example, you can see the ortho-splint artifact overlying the dorsal soft tissues and calcaneus with a displaced talar neck fracture remaining articulated to the navicula with tibiotalar and subtalar dislocations. This animation demonstrates the talar neck fracture line, which is seen here and note the tibiotalar dislocation here. That's a Hawkins Canale type 3. A Hawkins Canale type 4 represents a talar neck fracture where there is dislocation of the talar body from the ankle or subtalar joint plus dislocation or subluxation of the talar head from the talonavicular joint. And in this type of injury, up to all three supplying blood vessels are disrupted and the risk of AVN is also 90% to 100%. And what I have here is an illustrated rendition of a Hawkins Canale type 4. Note the talonavicular subluxation with the fracture through the talar neck, disruption of the subtalar articulation and tibiotalar articulation. Moving on to osteochondral injuries noting there is a classification referred to as Berndt and Hardy classification of osteochondral injuries of the talus and this refers to stage 1 injuries being an osteochondral contusion resulting in degenerative change perhaps an articular fissure and some bone marrow edema followed by a stage 2A and 2B, which includes a partially but incomplete fracture line.
And stage 3 would be completion of that fracture line. Stage 4 includes completion of fracture line plus displacement of the fragment. And both stage 3s and 4s are considered unstable or potentially unstable and may be treated with surgical means whereas stages 1, 2A and 2B will be either followed or perhaps a chondroplasty with conservative intervention. In a calcaneal fracture, also known as a Lover's fracture, these are five times more common in men. The largest and most frequently fractured tarsal bone and this often is resulted in axial loads, falls and twisting mechanisms. Greater than 50% of cases have associated upper extremity or other spinal fractures, 7% of them are bilateral and 50% will have long-term disability and the point here would be to obtain a CAT scan early in the disease. The preoperative planning is based on the intra and extra articular fractures. X-ray evaluation of calcaneal fracture is best denoted with a depressed Bohler's angle. Bohler's angle is that point drawn when you draw line from the posterior calcaneal process to the posterior subtalar joint and then second line, which intersects this at the posterior subtalar joint to the anterior subtalar process. So if it's less than 20 degrees in a weightbearing x-ray, you are going to consider that there is a calcaneal fracture and perhaps get a CT.
And the treatment would be orthopedic consultation with perhaps a followup ORIF or conservative management. Example of calcaneal fracture here, notice the primary axial fracture line driven through the direct line of compression through the posterior subtalar joint and of course a calcaneal stress fracture is a fracture that is when the trabecular lines of stress are insufficient for the current weightbearing load either it's in abnormal stress on a normal bone or an abnormal stress on a normal bone. But either way which you are looking for is that there will be a condensation of sclerosis, which is perpendicular to the lines of trabecular stress. In this case, you can see more clearly in the follow-up x-rays the trabecular line of sclerotic stress denoting the calcaneal stress fracture. In terms of navicular fractures, the blood supply to the navicula can be tenuous and there is often the risk of AVN. And frankly, the most common fractures I see of navicula are related to a dorsal avulsion, 40% of navicular fractures are this type. A tuberosity fracture or body fracture and the mechanism is usually from an eversion injury. There is pain over the dorsal and medial aspect of the foot with swelling of course. Navicular fractures, the treatment includes walking cast for four to six weeks and orthopedic followup regarding avulsions. The tuberosity and body fractures, if they are not displaced, we can initially use nonweightbearing with close followup. And if they are displaced or they are greater than 20% of the articular surface area, we will often require ORIF.
Lisfranc injuries, these include either severe dorsal or plantar flexion at midfoot or the forefoot junction and they are usually very displaced and obvious, although they can be subtle and almost all will require surgery. A Lisfranc fracture dislocation can be classified and whether there is total incongruity, partial incongruity or divergent and we can further divide them in dislocations as homolateral or divergent types of type As, Bs and Cs. Lisfranc injuries can include ligamentous injury with usually a fracture at the base of the second metatarsal given its locking key anatomic configuration. A homolateral fracture dislocation will include lateral dislocation of all the metatarsal bases. You can have an isolated Lisfranc injury where you can have medial dislocation at the base of the first metatarsal. Or you can have the more common divergent dislocation where the base of the hallux metatarsal can divert medially and the remaining second to fifth metatarsal bases can dislocate laterally. And this example of Lisfranc fracture dislocation. What we are going to be looking at is evaluating the base of second metatarsal as it extends to the base of the second metatarsal at Lisfranc ligament noting the obvious dislocation in this example of a Lisfranc divergent fracture dislocation. Another example of a divergent dislocation where you can clearly see that there is complete uncovering of the medial cuneiform with the base of first metatarsal laterally displaced and the base of the second metatarsal completely displaced providing this opening.
Also note on the oblique view the dorsal subluxation of the base of the first metatarsal popping out of its articulation. Base of fifth metatarsal fractures are important and that there are different types and there are different treatments based on different types. So the most common is apophyseal or avulsion fractures at the base of fifth metatarsal because this is the location of the abducted digiti minimi, plantar aponeurosis attaching as well as the peroneus brevis attaching there and of course the peroneus tarsi is an extensor that attaches approximately 2 to 3 cm distal in the proximal diaphysis. So apophyseal or avulsion fractures occur on the proximal 1.5 cm of the fifth metatarsal. Jones fractures are transverse fractures at the base of the fifth metatarsal that include the metaphyseal or diaphyseal junction and in this illustration here, you can see that the navy blue fractures result in the apophyseal fractures. The Jones fractures are those denoted in green at the metaphysis and the red line should really be extended through the metatarsal as stress fractures. So these are fractures of stress that are abnormal stresses placed on a normal bone or abnormal bone with normal bony stresses. Here is an example of a single simple base of fifth metatarsal apophyseal avulsion fracture. See here with a red arrow and this is your avulsion fracture. Here is an example on your left of a Jones fracture with apophysis extending nearly to the metaphysis and examples of stress fractures on the bottom ray where you can see the sclerosis and partial healing of this metadiaphyseal fracture.
This example on the top right is really more of a Jones fracture or between Jones and stress, really almost nearly extending if you imagine next view would be extending right into the base of the fifth metatarsal. And of course, here a Jones fracture, transverse fracture into the metaphysis potentially [indecipherable] [18:46]. In terms of metatarsal fractures, we have two flavors, spiral and stress fractures and the treatment of second through fourth metatarsal fractures would mostly be conservative with a well-padded shoe, although the first metatarsal may require plating and ORIF. And the exception to this is when it's greater than 3 mm displaced or angulated in the plantar direction greater than 10 degrees. In that case, you may offer a close reduction and possible pinning if it's unstable and it may require nonweightbearing in a cast for four to six weeks. Here, in this example to the left, we are seeing the fifth metatarsal spiral fracture of the distal diaphysis with less than 1 mm of displacement and here in this example to the right, we are seeing the fluffy periosteal reaction along ill-defined zone band of sclerosis at the second metatarsal neck. In terms of toe fractures, I highly recommend that you obtain toe x-rays and this can be ordered in addition to foot x-rays so that you can order a foot x-ray and then in addition a dedicated to x-ray, which we will ask the technologist to isolate the digit off of the lateral film, which is often where you best see some of these fractures.
In terms of toe fractures, you can have stub fractures, which include the distal tuft. You can have crush injuries, which are axillary loads to the distal phalanges or any bone really. There is turf toe where you can have plantar plate rupture of the great toe or nail avulsions, which are considered open injuries and may require prophylactic antibiotics since the germinal matrix of the nail bed is contiguous with the periosteum at the base of the distal phalanx. It may be clinically necessary to distinguish a bipartite sesamoid versus a fracture. Sesamoid bones are frequently multiparte and it's difficult to distinguish fractures versus the normal anatomy and the ankle and MTP joints are hot spots for the presence of accessory ossicles. One must rely on the clinical presentation and knowledge of predictable anatomy. It's an extremely common entity so in runner with forefoot pain, think about possible sesamoid stress fracture or reaction. In the bipartite medial sesamoid with a transverse avulsion fracture as evidenced by this frontal x-ray here, note the presence of a bipartite medial sesamoid with an additional avulsion fracture, which is MR proven in this published example and radiographic pitfalls in lower extremity trauma published out of AJR in 2014.
Bipartite sesamoid versus fractures can be assessed from history and physical exam. Looking at the x-ray for a linear lucency with no sealing sclerosis. This may be a fracture. Bipartite, it may be curvilinear with sclerosis and sesamoiditis may adjust these sclerosis. Of course, AVN would have sclerosis, osteomyelitis and CPPD. These are all entities of pathology in the differential diagnosis of sesamoid pain. In terms of sesamoid anatomy, the two sesamoids form their own articulation with the hallux and hallucal articulation, which is supported by multiple attaching tendons including the abductor hallucis, longus, the flexor hallucis brevis and the adductor hallucis. In terms of what we can expect from sesamoid fractures and their evolution initially, you can have a transverse fracture through the sesamoid, which you can see here on next example to the left. And then in about six weeks, you can notice that there has actually been osteoclastic activity resorbing the edges of the fracture line. Chronic fractures often can be seen with increasing sclerosis where the patient returns with pain, you aren't sure if it's fracture, AVN and you may choose to go on to an MRI where you can see here this sagittal MR depiction of the hallux metatarsal head, the proximal phalangeal base, this sesamoid here seen with hyperintense T2 signal changes and a low signal divider, which is your bipartite or fracture line. There is stress response and bone marrow edema denoting this fracture line. Here you can also see how well-defined, you can see the sesamoid phalangeal ligament and that's thickening the proximal phalangeal ligament here.
In terms of sesamoid AVN, which you are encountering here on this special sesamoid x-ray where you see there has been not only subluxation of the sesamoid out of its tibial hallucal location, you are seeing increasing sclerosis, which can be seen here on the MRI with bone marrow edema and a subchondral patchy area of sclerosis. Of course, you are seeing joint effusion and rotation out of hallucal articulations. Of course, in addition to fractures, we can also have sesamoid osteomyelitis, which is where you can see the soft tissue ulceration at this plantar aspect and the invasion of the sesamoid bone on the geographic T1 marrow replacement in the sesamoid. Of course, a rare entity seeing sesamoid crystal deposition. In your routine x-ray evaluation, you may encounter a heterogeneous lucency and further evaluation of the remaining joints may reveal different chondrocalcinosis often with advanced degenerative change often implicating hydroxyapatite deposition and pyrophosphate arthropathy. In summary, what we have done over the past 25 minutes is essentially to review all of foot anatomy and develop an approach to x-ray evaluation. We looked at mechanism of injury. We reviewed Hawkins Canale, talar fracture classification of talar neck fractures, looking at how the propensity of the grading scale will increase the risk of AVN given that grade 1 is a non-displaced fracture moving up to grade 4 where you will have tibiotalar and subtalar dislocation.
We briefly touched on calcaneal fractures noting the two types of fractures would be the traumatic fractures occurring through different classification of Essex Lopresti and also the Lover's fracture or the stress fractures that occur. We looked at midfoot fractures, which is where you are going to see Lisfranc fracture dislocations through careful evaluation of the base of second metatarsal. We looked at base of fifth fractures assessing the apophyseal fractures occurring within 1.5 cm of apophysis. Moving on to the Jones fracture at the metatarsal base and the stress fractures occurring along the fifth metatarsal. We looked at stress fractures at the metatarsal themselves and looking at the hypertrophic periostitis as opposed to a spiral traumatic fracture. And we spent a good deal of time discussing sesamoid pathology looking at the multipartite sesamoid and contrasting that to evaluating a fracture looking at the normal fracture line widening that occurs with healing and then the complications including AVN and stress related change. I thank you for your generous time and attention and I hope this has been of value for you. Thanks again.
TAPE ENDS - [27:29]