Marlena Jbara, MD discusses normal midfoot anatomy, the pathomechanics of the common injuries, and reviews the trauma pathologies associated with the midfoot. Dr Jbara also composes a method to assist with evaluating midfoot pathologies on radiograph.
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TAPE STARTS – [00:00]
Marlena Jbara: My name is Marlena Jbara and this lecture is entitled Midfoot Trauma. I, or a related party, have no financial relationships to disclose. The objectives of the lecture are to review midfoot anatomy, mechanisms of injury. We'll review foot function and shape, imaging evaluation of Lisfranc joint injuries. We'll go over midfoot and forefoot crush injuries, navicular, cuboid and cuneiform injuries.
The anatomy of the midfoot is divided into four major units. The first metatarsal with the middle cuneiform has about six degrees of mobility. The second unit is the second metatarsal with the middle cuneiform and it's a firmly fixed articulation. The third metatarsal, articulating with the lateral cuneiform, also firmly fixed. And the fourth and fifth metatarsals, as it articulates with the cuboid, our mobile portions of this articulation.
The anatomy of the midfoot stability is provided by the arrangement of the bones in a Roman arch with the metatarsals, and the additional recession of the base of the second metatarsal as seen here on the left relative to the first and third metatarsals.
Reviewing anatomy-associated structures of importance would be the dorsalis pedis artery, which is located between the first and second metatarsal bases, and a deep peroneal nerve, which runs alongside that artery, and often that cause pain and numbness in the region of the midfoot.
Columnar anatomy as related with the schematics can be demonstrated with the medial column, including articulation of the talonavicular joint, cuneiforms, and medial three rays of the forefoot. The lateral column, as demonstrated on the right, includes the calcaneocuboid and the fourth and fifth metatarsals.
Moving on to pathologic anatomy, you can see in the midfoot here the bases of the second metatarsal recessed with the middle cuneiform, and notice all of the intercuneiform and naviculocuneiform ligaments dorsally. And of course, plantarly, you can see these ligaments as well. The first metatarsal has been cut out on the right picture and you get to see some of the intraosseous and plantar oblique ligaments of Lisfranc.
Moving on to functional anatomy again, the medial column joints, the tarsometatarsals first through third, are qualitatively different from the lateral column joints. The medial column joints are more similar to intertarsal joints with less mobility. The medial column joints need to be aligned and stiff as treatment measures, and lateral column joints would like to be mobile and flexible. The anatomy of Lisfranc can be seen here in this schematic on the left where you're seeing the dorsal, the intraosseous in red, and the plantar ligament in green.
And here on this image on the right, you can see on this short axis T1-weighted image, you can see the dorsal low signal ligament of Lisfranc joint, the more bend-like membranous portion of the intraosseous, and the plantar ligament less well-defined here in this example.
The anatomy of Lisfranc ligament can further be seen here on these long axis images. This one on the left being fluid sensitive and this one on the right being a T1-weighted image, and you can see that because of the fat within the marrow and the bones is bright. And on the left, this is a fat-suppressed image, bringing out the fluid signal background. And we can see the intraosseous component of Lisfranc ligament here on your example on the left and the plantar component of Lisfranc ligament on the right.
Again, the anatomy of the intraosseous ligament is connecting the metatarsal bases, not only two to five, but also one to two. You can see these dorsal, tarsometatarsal ligaments. They're of course both dorsal and plantar, and the plantar ligaments are stronger and larger. This is reinforced by secondary stabilizers such as the plantar fascia, the peroneus longus, which is swinging along the lateral foot down the lateral malleolus, to cross through the cuboid tunnel to the base of the first metatarsal. And of course your intrinsic muscular attachments to the bones forming stability in dynamic motion.
Mechanisms of injury. Motor vehicle accidents account for one to two-third of cases. The incidents of lower extremity foot trauma has increased with the use of airbags. There are increased crush injuries and sports-related injuries are occurring with the increasing frequency.
In terms of mechanisms of injury, we can describe indirect, which is the more common typical athletic injury. It's rarely associated with an open injury of vascular compromise and you can see here as this football player falls into another football player, and this person who's in plantar flexion as an indirect injury, as opposed to a direct injury which is less common. This is something falling from a direct force or some inferior force loading from the inferior direction like similar to plafond type injuries. And the direct injury compartment syndrome is more common than with an indirect injury.
Mechanisms of injuries in associated fractures for the foot in forceful abduction, you may result in a second metatarsal base fracture as part of a Lisfranc injury, and you can also withstand the compression fracture of the cuboid, also known as the nutcracker injury. Continuing with mechanisms of injury, forceful abduction of the forefoot may result in avulsion of the navicular as seen here with this triangular fragment. And also it can relate much less commonly in isolated medial cuneiform fractures.
Treatment principles, the goals are to restore alignment, protect talonavicular motion, and protect fourth and fifth tarsometatarsal motion. Motion of the other joints is not as important and arthrodesis is probably okay for most small joints. In terms of the hindfoot, we want to protect ankles, subtalar and talonavicular joint motion. For the midfoot, it's important to establish length and alignment of the medial and lateral columns. And in the forefoot, we'd like to have an even weight distribution at the metatarsal heads.
In terms of midfoot crush injuries, you can see here in this example at this overlap of the second, third and fourth metatarsal bases with fractures of the middle and lateral cuneiforms, and the cuboid is medially subluxed. And you can see here on this rotated lateral, we can see the intact subtalar joints posteriorly and anteriorly, and then we have essentially a comminuted dorsally subluxed navicular fracture with multiple metatarsal base and cuneiform fractures here with multiple overlapping structures.
The goal in that case would be to establish length. So external fixators would be applied, four millimeters Shantz pins in the hindfoot, 2.5 millimeter terminally threaded Shantz pins in the forefoot. We can maintain length and alignment until that swelling resolves. Internal fixation will include bridging plates, restoring medial and lateral columns, restoring the anatomy of the key articulations. And in this case, we can span the joints with 2.7 centimeter reconstruction plates and plan of stage removal at six months.
More examples of midfoot crush injuries after the -- this is an internal fixation. It's used as a temporary fixation as in the previous slide. When mobile joints are involved, we can place multiple of these internal fixators to keep everything in alignment. Midfoot crush injuries, we can have a staged implant removal of those plates at six months postoperative, and these are examples of a few remaining lag screws at the medial midfoot.
Outcomes of midfoot crush injuries, 25% of polytrauma patients do not return to work at one year. Lower extremity fractures of course can cause significantly more disability than upper, and foot injury scores worse in physical function, social function, pain, and physical and emotional roles.
Moving on to examples of forefoot crush injuries. Here, you can see these transverse mid metatarsal fractures with subluxations fibularly of the distal relative to proximal fragments. Notice on this lateral, besides the high degree of soft tissue swelling and increased density, we have dorsal subluxation and apical dorsal angulation of the fracture site with regards to these forefoot crush injuries.
In these examples, we can look to plate and establish length. For the smaller bones, we can establish digital wiring from the second and third with plate fixation of the first and fourth. In here, a lateral example of that.
Moving on to Lisfranc joint injuries, we can have bony or ligamentous injuries involving the tarsometatarsal complex. This is named after the Napoleonic era surgeon who described amputations at this level without ever specifying or defining a specific injury. This requires a high degree of clinical suspicion and approximately 20% of them are misdiagnosed, with about 40% of them receiving no treatment within the first week.
The evaluation of Lisfranc joint injuries requires AP lateral and oblique stress views. We're looking for two-plane instability and standing views provide stress, and may demonstrate subtle diastasis between the medial cuneiform and base of second metatarsal. And if there's any question, don't forget the importance of obtaining comparison views. This can be powerful in determining injury. And here in this example, we can clearly see on the original film where there was a slight diastasis, which is brought out more and stress X-rays on the right.
Injury and evaluation of Lisfranc joint injuries include the oblique radiograph. We're looking for the medial base of the fourth metatarsal to line up with the medial margin of the cuboid as seen here. A graded radiographic sign includes the fleck sign, which is a fleck of sliver bone, which you can barely see on this example on the left with a CT long access reconstruction demonstrating a cortical bone fragments with the donor site from the base of the second metatarsal, the fleck sign indicating Lisfranc injury. We can use MILS line as a radiographic correlate when the medial column no longer intersects the first metatarsal. There is generally a midfoot displaced injury and you can see from these cadaveric examples with abduction stress at the ligaments intact.
We have alignment between the base of the second metatarsal and the medial cuneiform. And here with abduction stress, we can see the widening, not only of Lisfranc interval between the medial cuneiform and base of second metatarsal, but also between the cuneiforms and metatarsal bases.
Lisfranc injuries can be classified according to homolateral, isolated and divergent patterns, and we can see these three patterns of injury here on this example from Quenu and Kuss, essentially looking at the homolateral where the first through fifth metatarsals move in a fibula direction all in the same direction. We can have an isolated Lisfranc middle injury with just medial divergence of the -- I'm sorry, medial subluxation of the first metatarsal base. And we can have a divergent injury where force drives between the first and second metatarsal, splitting this region and displacing the second through fourth metatarsals laterally and the first metatarsal medially.
Lisfranc joint injuries with regards to treatment. Early recognition is key to preventing long term disability. Anatomic reduction is necessary for the best results and displacement greater than one millimeter or gross instability of the tarsometatarsal, intercuneiform, or naviculocuneiform joints needs reduction.
Principles of treatment for Lisfranc joint injuries include that the first, second and third tarsometatarsal joints have limited motion with rigid fixation, and the fourth and fifth metatarsal joints require mobility so they require flexible or temporary fixations.
The metatarsal has need to meet the floor evenly and the plantar tarsometatarsal ligaments intact with a short leg walking cast. If it's unstable in two planes due to fracture at the base, generally K-wire fixation is a useful tool. If it's unstable in two planes due to ligament rupture, rigid fixation or arthrodesis maybe a more stable construct. And here, we can see examples of Lisfranc joint injuries with treatment pins to naviculocuneiform is not a mobile joint and can be fixed with multiple pins -- I'm sorry, screws. They're going to look to watch the rotation of the naviculocuneiform and with possible primary fusion of immobile joints.
Lisfranc joint injuries for non-operative treatment, for non-displaced injuries with normal weight bearing or stress X-rays. That patient can be placed in a short leg cast with four to six weeks of non-weight bearing, and we can repeat the X-rays due to rule out displacement as swelling decreases. And the total treatment time for this may require two to three months. In terms of assessing Lisfranc joint injuries for operative treatment, surgical emergencies include open fractures. Vascular compromises, we're always checking the pulse of the dorsalis pedis and we're checking for compartment syndrome routinely.
Lisfranc joint treatment. Screws are generally positional, not lag, and three and a half to four millimeter screws are generally used. Here, you can see in this example on the left, this X-ray demonstrates displacement of the base of second metatarsal and the fibula direction relative to the medial cuneiform.
And we can see the screws requiring fixation across the base of second metatarsal to middle cuneiform, and between the first and third metatarsals.
Lisfranc joint injuries in terms of operative treatment, we can see in this example of the left, there has been a midfoot injury with multiple fractures of the middle lateral cuneiform and bases of the second through fifth metatarsals. In addition, there's a fleck sign. There's an obvious diastasis between the medial cuneiform and base of second metatarsal. And the flexible joints like we talked about before, we could fix those fractures with K-wires. And for the stiff joints, we can fix with screws as we saw before, three and a half to four millimeter fully threaded without a lag technique. And if intercuneiform instability exists, there's an intercuneiform screw placed in the transverse plane here. And here's a lateral X-ray demonstrating restoration of alignment in the sagittal plane.
Moving on to navicular fractures, the navicula is a horseshoe-shaped bone between the talus and cuneiforms. There are numerous short ligaments which are attached dorsally, plantarly and laterally. And the posterior tibial tendon attaches medially to its undersurface primarily. And here, you can see on this anatomic drawing depicting the portion of the talus cut away.
And you could see the talar had articulating with the navicula which has put out for the medial, middle and lateral cuneiforms, as well as articulating with the cuboid and a portion of the anterior subtalar joint. Navicular fractures, what's important to know is the blood supply. Because of the large articular surfaces, vessels can only enter dorsally, plantarly, and through the tuberosity. And the medial and lateral thirds have an adequate blood supply but the central third is largely a vascular and a number of vessels decreases with age.
Navicular fractures can be seen here. These are avulsion fractures at the dorsal lip. Usually, it's essentially this is a result of severe sprain. Treatment includes immobilization and then progressive weight bearing is tolerated. And in frequently, we can excise the fragment if it's painful. Navicular fractures come in different flavors. We can have a tuberosity fracture, which is avulsion by the posterior tibial tendon and spring ligament complex. These are usually minimally displaced. Also can associate -- can have an associated calcaneocuboid impaction and may require ORIF depending on the degree of displacement if it's greater than five millimeters, as in this example here where you can see this dorsal subluxation of the fractured navicula with a process, you can see overlying the cuboid. That would be the lateral process still articulating and there's the medial process likely with the tuberosity segment dorsally subluxed.
Navicular body fractures can occur with high energy trauma with axial foot loading. They're frequently associated with talonavicular subluxation and CT scans can be helpful for preoperative planning. Anatomic reduction would be essential in these displaced cases.
Navicular body fracture treatment. Of course again we're going to establish ORIF if there's any degree of displacement greater than five millimeters. This will be performed by placing an anteromedial incision along the medial aspect of tibialis interior and a second incision along the anterolateral aspect as help needed to reduce the lateral fragment. And here, we can see on this oblique X-ray a comminuted displaced fracture of the navicula. And on the lateral X-ray, you can see the comminution and minimal displacement.
And in that example of the minimally displaced navicular fracture, we can see the stage treatments. First, fixating with wires and pins to establish position. Later, adding plate with removal of some of the pins. And then finally, moving to a dorsal fixation plate.
Navicular body fractures again may require stabilization or fusion to the cuneiforms, and if at all possible, fusion of the talonavicular joint is avoided and sometimes of course this cannot be avoided. There's a comminuted fracture of the talus and arthrodesis essentially is performed as in this example in the right.
Other types of fractures maybe radiographically occult including navicular stress fractures. They are uncommon and a delay in diagnosis is common. It's usually secondary to repetitive stress and poor blood supply, and running is implicated as the most common ideology. The diagnosis includes vague arch pain with midfoot tenderness and X-rays can be obtained, which are generally normal. Of course if pain persists and there's no X-ray finding correlate, the recommendation is always to get CT or an MRI. Bone scan is going to be less utilized these days given the anatomic advantage of MRI and its lack of ionizing radiation.
Moving on to cuboid fractures, isolated fractures are rare. They're most often associated with other fractures and two types of fractures can be seen with cuboid fractures. Usually avulsion injuries can occur or a nutcracker axial loading with plantar flexion and forefoot abduction. In this example on the right, you can see these two external fixator pins maintaining length for this comminuted cuboid fracture.
Cuneiform fractures, these are isolated quite rare fractures. Displacement is unusual. The mechanism of injury includes direct trauma which is most common. It heals rapidly with non-operative treatment. Of course, indirect trauma, Lisfranc variance, this may occur in any direction including axial shortening and instability requires ORIF.
So in summary, what we've done in this past segment is to review midfoot anatomy in terms of Lisfranc ligament, the Roman arch, and the recession of the base of the second metatarsal. We've reviewed mechanisms of injury, including direct and indirect forms of injury, and noting how the direct form of injury has a higher incidence of compartment syndrome. In terms of foot function and shape, we've reviewed imaging evaluation of a Lisfranc joint injury, looking at its different components from dorsal to interosseous, to plantar. We have reviewed midfoot and forefoot crush injuries, reviewed the importance of maintaining flexibility along the fourth and fifth metatarsal complex, with alignment and stiffness restored to the medial midfoot.
Forefoot crush injuries, what's most important, we want to allow those metatarsal heads to meet the ground evenly following treatment. In terms of navicular injuries, we have looked at dorsal chip fractures, essentially sprains, and more severe displaced injuries greater than five millimeters, possibly requiring ORIF. We took a quick look at cuboid injuries, avulsions, and nutcracker types with comminution of the cuboid and of course rare cuneiform injuries, rarely injured in isolation, though it's possible in the form of a direct injury.
Bibliography and reference is available. Thank you for your time and attention.
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