Marlene Jbara, MD discusses normal anatomy and mechanisms of injury for calcaneal, talar, and midfoot fractures. Dr Jbara also discusses methods to radiographically assess these fractures as well as developing sound treatments options for management.
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TAPE STARTS – [00:00]
Marlena Jbara: Hi, my name is Marlena Jbara and I will begin a focused session on calcaneal, talar and midfoot trauma. I or related party have no financial relationship to disclose. Objectives: Develop an approach to diagnosing calcaneal fractures based on understanding normal anatomy and mechanism of injury. Review of mechanism of tala fractures and Hawkins CT classification, review of mechanism of mid foot fractures and x-ray evaluation. We will begin with calcaneal fractures and this is an example of Mondor sign, which is hematoma and ecchymosis from the plantar aspect of the calcaneus, which dissects distally through the subcutaneous soft tissues. And let's not forget the associated thoracolumbar compression fractures in approximately 10% of these patients. The anatomy of the calcaneus is interesting and unique. There are three facets; anterior and middle facet and posterior facet is seen here on the left. There are a variety of variations in this that the anterior medial facet can be one continuous slap of cartilage. It could be two separate slaps. There can be coalitions where the middle facet is not just a cartilaginous coalition. So there is a lot of variable anatomy. Let's not forget the posterior tibial artery and nerve running medially along a groove posterior to the talar tubercles.
And within the center of the talus and calcaneus, we have the sinus tarsi, which has the cervical ligaments and talocalcaneal intraosseous ligaments. The assessment of the calcaneal fractures begin with Bohler's angle. Bohler's angle represents a line drawn tangential to the anterior calcaneal process and the most superior aspect of the posterior calcaneal process and then a second line drawn down to the aspect of the posterior calcaneal tuberosity. And when this angle measures less than 20 degrees, we can suspect calcaneal fractures. And here we can see these examples on the right where you have a comminuted depressed calcaneal fracture with Bohler's angle clearly decreased beyond its normal confines, which would be like so. Just to note on CT technique, when we performed CT of the calcaneus ideally, we would like to perform our ankle planes relative to the posterior subtalar joint and that's going to become important when we look at classifications schemes and the most common being Sanders. Soft tissues at risk for injury include the Achilles tendon as seen here on the example on the left where one can see the Achilles tendon inserting along the posterior calcaneal tuberosity and broad attachment. We can also see of course the plantar fascia here. In addition, we can see this tendon, which runs underneath the sustentaculum talus and that's a constant anatomic relationship. You can see that also over here and this is posterior tibial, the flexor digitorum, and of course the flexor hallucis longus as this tendon that runs underneath the sustentaculum talus.
And this is the view that we would ideally like to come to when we were doing [indecipherable] [04:05] reconstructions perpendicular to the posterior subtalar joint. The basic fracture mechanism includes developing an increased axial load, which drives inferiorly through the angle of Gissane. The primary fracture line being number one, which flaps just like a door step, which creates the #2 to ascend vertically. And then the fracture line can continue other inferiorly exiting at 3 or posteriorly exiting through the dash line of #4. And this is what we mean when we were talking about primary and secondary fractures. The primary fractures being that which is the direct blow #1 and the secondary fractures being whether it extends inferiorly or posteriorly to exit and drive the force out of the bone. Essex-Lopresti was the classification that had been used in the past that really showed this depression type of fracture where you had that primary axial loading through the angle of Gissane, which you could see her. In addition, there is a lateral taloprocess fracture and that fracture line extends inferiorly versus a fracture line extending to a tongue depression where there is a split reverse Y-shaped fracture ending posteriorly through the posterior calcaneal tuberosity. The Sanders classification is one of the most common applications for calcaneal fractures. And essentially we perform a coronal oblique view through the calcaneus in the talocalcaneal articulation and at the level of the sustentaculum talus as seen here. We are going to divide the portions of the calcaneus into the sustentacular fragment and medial, central and lateral fragment arbitrarily chosen.
And this will denote whether we are going to have fracture patterns that go with that. This is an axial image, a little harder to interpret, so for the most part you will be looking at these fracture patterns here and let's take a look at some examples. In a Sanders type 2A fracture, we have fractures through the central and lateral facet dividing that where one big fragment that can be placed together again. Generally speaking, we can see here in this comminuted calcaneal fracture and the main fracture line is this reverse Y-shaped fracture at Sanders 2A fracture. And in this example, Sanders 2B fracture where the fracture line is between the medial and central fragment and you have that nice large sustentacular fragment retained to the medial fragment and you can see that here in both the axial and coronal plane. Sanders 2B. You can have isolated sustentacular fractures as seen here where the sustentacular fragment has about 2 mm of displacement seen both axially and coronally. And of course there can be increase in comminution in Sanders 3AB where you have fractures through the medial, central and lateral facet as seen here with depression of the articular surface. Type 3AC with fractures through the medial and lateral segments here seen in this degree of comminution. Sanders 4, examples here comminuted fragments of depression through the posterior subtalar joint and of course there are extra-articular fractures. They can be through the anterior and posterior processes and you can see here A and C referred to the same portions of bones in both in the axial plane from above and the sagittal plane both medially and laterally. There are different apophysis applied laterally to where the peroneal tubercle lies.
Here is a type A extra-articular anterior process fracture. This can be more extensive and extend to the anterior process or here seen at the lateral corner close to the calcaneal cuboid articulation. And seen here is another version of type A extra-articular anterior process fracture, a common fracture in car accidents where your foot is essentially jammed into the brake as you are trying to stop the car. You can have type B body fractures here. This is a curvilinear fracture likely a stress fracture through the body. Of course, posterior calcaneal tuberosity fractures, you can have avulsion injuries of not only the Achilles or the plantar fascia. Here is an example of a medial calcaneal process fracture. Of course, a nice example of Achilles avulsion. Note these sclerotic edges along the fracture line denoting there was a stress fracture. The Achilles has probably had a chronic traction injury. The Achilles tendon itself looks fine. The piece of bone does not obviously displace superiorly. And of course these defects with perimeter plates. As seen here, complex shape and there are variety of these perimeter plates that can be applied to try to create the structure of the calcaneus. And complications are many.
Operative complications include malunion, stiffness, subtalar arthritis. The peroneal tendons can sublux. You can have sural nerve pain and heel pad problems. Non-operative complications also include malunion, the tendency for varus hind foot. You can have a shortened foot so that creates a short lever arm with effects on the gait. Peroneal impingement and dislocation and of course shoewear problems, stiffness and arthritis and pain. Moving on to one of my favorite bones, the talus. It's the second largest bone in the foot and it provides that crucial length between the tibia and navicula and calcaneus. It can be divided into the head, neck and body as seen here. And the talar neck has the smallest surface area, the place where anterior and posterior tibial arteries are anatomosing in addition to the peroneal artery. The talus is supplied again by the posterior tibial, the anterior tibial and the peroneal artery as seen here. The posterior tibial artery is the largest sort of coming in on the medial side and then percolating through the neck and anastomosis. This is an anastomotic ring that surrounds the head and neck and this provides that retrograde flow to the body and therefore disruption of the arterial flow after a talar neck fracture compromised the flow to the talar body and can create situations of osteonecrosis. Talar neck fractures are 3% to 6% of all fractures. Neck fractures are categorized by the fracture line located anterior or inferior to the lateral talar process and the talar dome cartilage. These are generally high energy, impact injuries. The mechanism is considered to be forced dorsiflexion of the talus against the anterior tibia. Isolated neck fractures do not extend into the subtalar, talonavicular and tibiotalar articulations.
And there is most commonly association with calcaneal and spine fractures. Hawkins and Canale have the most common classification type 1 through 4 and this applies when the vertical component of the fracture is through the talar neck. It's based on joint misalignment associated with that talar neck fracture. And here, we are going to look through examples of type 1, type 2, type 3 and type 4 injuries with increasing displacement and intra-articular involvement moving up to type 4. The complication of course includes talar osteonecrosis and the risk increases with Hawkins greater fracture. Of course, posttraumatic arthritis is one of the most common complications. There could be a tendency to malunion and non-union. A Hawkins and Canale type 1 is a vertical nondisplaced talar neck fracture without subluxation or dislocation. The talus remains in its anatomical position and only one of the three supplying blood vessels are generally disrupted. There is the lowest incident of AVN 0% to 15%. And on the left upper corner, we can see this lateral view of the ankle demonstrating a vertical fracture line through the talar neck without significant displacement. And here we can see the tibiotalar and talonavicular joints are preserved and this example on the right notices oblique view of the ankle demonstrating an intact ankle mortis in this Hawkins and Canale type 1 fracture.
This animation demonstrates a fracture line, which you can see with the orange arrow pointed through the talar neck without significant dislocation. Tibiotalar, talonavicular and subtalar articulations are maintained. In the Hawkins and Canale type 2 fractures, this is a vertical displaced fracture of the talar neck. The ankle mortis is preserved. Commonly, there is extension into the body and posterior facet of the talus and up to two or three supplying blood vessels are disrupted. The risk of AVN runs 20% to 50% and here we can see this illustration on the bottom right of Hawkins and Canale type 2 talar neck fracture. On the right lateral view, we demonstrated talar neck fracture. Again, the talonavicular and talotibial articulations are preserved and below we can see the ankle mortis is preserved. Additionally, there is a medial talar process fracture. Note the comminuted talar neck fracture with posterior subtalar subluxation. Note that the talotibial and talonavicular articulations are preserved. In a Hawkins and Canale type 3, it's a Hawkins and Canale type 2 essentially plus disarticulation of the tibiotalar joint. The ankle mortis is not preserved and the talonavicular articulation is preserved. Up to all three supplying blood vessels are disrupted and the risk of AVN is 90% to 100%.
Here in this example on the bottom right, this illustration showing a Hawkins and Canale fracture with displacement and disarticulation of these posterior subtalar and tibiotalar. Note in this example above the tibiotalar disruption with medial dislocation of the talar dome and noted above the disrupted tibiotalar articulation with anterior displacement of the tibial dome. Here on this animation, we demonstrated a talar neck fracture line and disarticulation of the talotibial joint with posterior dislocation of the talar body fragment. In a Hawkins and Canale type 4, this is a talar neck fracture with dislocation of the body from the ankle or subtalar joint plus dislocation or subluxation of the talar head from the talonavicular joint and up to all three supplying blood vessels are disrupted. The risk of AVN is between 90% and 100% for the talar dome. Notice here the talonavicular joint is disrupted. There is posterior subtalar and tibiotalar dislocation and I unfortunately do not have an example of that, but that brings to my next talar neck summary of fractures. In type 1, Hawkins fractures, these are non-displaced fracture of the talar neck with the articulations preserved and the risk of AVN is low.
In type 2, displaced fractures of the talar neck, the tibiotalar and talonavicular articulations are preserved and the risk of AVN is between 20 and 50%. There is disruption of the artery of the tarsal canal and generally this requires surgical reduction. In type 3, Hawkins and Canale fracture, the talar neck fracture with disarticulation of the talonavicular joint and tibiotalar articulations are preserved. A 100% of those cases generally result in AVN and the arteries of the tarsal canal deltoid and calcaneal branches of the posterior tibial artery are disrupted. There generally requires open reduction and internal fixation. In type 4, talar neck fractures with disarticulation of the talus from its navicular, subtalar and tibial articulations. Again, the risk of AVN being 100%. All three vessels are compromised and generally open reduction and internal fixation is the mechanism of choice for the repair. Moving onto midfoot trauma, the objectives of this sector of the lecture will include midfoot anatomy, mechanisms of injury. We will review foot function and shape, review treatment principles, Lisfranc joint injuries, midfoot crush, navicular injuries, cuboid injuries, cuneiform injuries and forefoot crush injuries. Associated anatomical structures of importance include the dorsalis pedis artery, which is extending anteriorly through the interspace between the first and second metatarsal bases. Adjacent to that you can have deep peroneal nerve, which runs alongside the artery. Reviewing the anatomy, the osseous stability of the midfoot is based on Roman arch configuration of the midfoot.
And also the recession of the second metatarsal base into this recessed keystone configuration. The anatomy of Lisfranc ligament in this schematic includes the dorsal intraosseous and planar ligaments as seen here on this short axis image of this MRI. You can see the dorsal and intraosseous component and the plantar component less well seen. The anatomy of Lisfranc ligament as seen here you can see the intraosseous component between the medial cuneiform and base of second metatarsal as a low signal normal ligament. And seen here on this long axis T1 weighted image, you can see the plantar component, a thinner portion of that ligament. Lisfranc joint injuries require a high degree of critical suspicion. Approximately 20% are misdiagnosed and 40% receive no treatment in the first week. In terms of the diagnosis when you first encountered the patient you want to check the neurovascular status. Possible compromise of the dorsalis pedis artery of the deep peroneal nerve and of course checking for compartment syndrome. Lisfranc joint injury evaluation requires AP, lateral and oblique views. At times, stress views may be called into play. And we are looking for two planes of instability and the standing views provide us sufficient stress and demonstrate the subtle diastasis as seen here in this example on the right where you have on a non-weight-bearing x-ray, minimal diastasis and no significant malalignment between the middle cuneiform and base of second metatarsal.
And of course in the standing x-ray, clearly you can see the widening of Lisfranc interval indicating a Lisfranc ligament tear. On this example at the upper right, this is a stress view, note the hand pulling the midfoot distracting the midfoot and opening up the medial Lisfranc joint. And of course, when in doubt you can obtain comparison views to see generally people are pretty symmetric bilaterally, so if there is an asymmetry and there is pain, generally there may be an injury. Oblique radiograph is necessary so that you can see that the medial base of the fourth metatarsal lines up with the cuboid and the fifth metatarsal base of portion of the epiphysis obviously is uncovered. In Lisfranc joint injuries, we can see the flex sign where you can barely see a sliver of bone. Clearly, I would be using a magnifying glass on my PAC system to see the small bone fragment but I wouldn't miss the malalignment between the middle cuneiform and the base of the second metatarsal. Here in the CT scan example on the right, it's easier to see when we use cross-sectional imaging, this fleck of bone located between the attachment of Lisfranc ligament. We can classify these into homolateral, isolated and divergent patterns as seen here where all the metatarsals either move towards the fibula or maybe it's only the first metatarsal and moves away being isolated or divergent where the first metatarsal dislocates medially and the remaining metatarsal sublux laterally giving you this diverging pattern from [indecipherable] [23:49]. Lisfranc joint injuries generally can require operative treatment and of course surgical emergencies would include open fractures, vascular comprise including the dorsalis pedis and compartment syndrome.
Moving on to midfoot crush injuries. As seen here, these are usually high velocity traumas, usually a motor vehicle accident or motor cycle accident, and essentially you have the midfoot driven into the hind foot and multiple fractures in comminution of the midfoot. The goal here is to restore length and you are going to look towards internal fixation, restoring medial and lateral columns and restoration of key anatomic joints, spanning the joint generally with 2.7 reconstruction plates and generally a staged removal at around six months. This is an example of forefoot crush injury where you can see multiple comminuted fractures of the metatarsal. The large soft tissue swelling on the lateral x-ray and the purpose of alignment would be to have the metatarsal heads contact to the ground evenly and we restore the length here, note the metatarsal plate in the fourth metatarsal plate with the second and third fixation wires. A note on navicular fractures, the blood supply because of its large articular surface, the vessels can only enter dorsally and plantarly, enter the tuberosity. So the medial and lateral thirds have a good blood supply but the central third is largely avascular and the number of vessels of course decreases with age. And here you can see this India Ink injection of the navicula demonstrating the small fine network of vessels making into dorsally and plantarly anastomosing greatest medially.
Navicular fractures, avulsion fractures are usually a dorsal lip fracture and essentially represents a severe sprain. The treatment generally requires the mobilization and then progressive weight bearing with possible excision of fragment only if it's painful. Navicular fractures generally body fractures are high energy fractures with trauma to axial loading. They are frequently associated with talonavicular subluxation and CAT scans are often helpful for preoperative planning. And here we can see this example of this dorsally subluxed navicular fracture later reduced with two fixation screws in this x-shaped pattern through the navicula reestablishing the dorsal column of Meary's line. Navicular stress factors, these are uncommon and delay in diagnosis is common. These are usually due to repetitive stress and poor blood supply and running is the most common etiology. The diagnosis includes vague arch pain with midfoot tenderness to have index of suspicion. Of course, x-rays are usually obtained, which are normal. You can of course obtain the AP, lateral and oblique but it will be very hard to see and of course you can obtain the CT bone scan or MRI if the diagnosis remains uncertain. Cuboid fractures, isolated fractures are rare. Most often they are associated with other fractures and of course you are looking for this avulsion or nutcracker type of fracture with axial loading and plantar flexion and forefoot abduction. Here you can see in this example on the right with external fixator pins.
A note on cuneiform fractures, isolated fractures are quite rare. Displacement is unusual. Mechanisms of injury include direct trauma and indirect trauma with direct being more common. Indirect trauma may occur in any direction including axial shortening and instability may require ORIF. In summary, we have reviewed intra and extra-articular calcaneal fractures based on understanding normal anatomy and mechanism of injury. We reviewed the Sander's CT classification of calcaneal fractures. We reviewed mechanisms of talar fractures and Hawkins and Canale CT classification. We reviewed mechanism of midfoot fractures and x-ray evaluation. References are available. Thank you for your time and attention.
TAPE ENDS - [28:57]