Chapter 23 – Fractures and Dislocations of the Forefoot




Chapter 23 Fractures and Dislocations of the Forefoot


Timothy A. Coughlin and Ben J. Ollivere



Introduction


Forefoot trauma ranges in severity from the seemingly trivial “turf toe” to significant fracture dislocations of the tarsal bones and complex multicolumn injuries. Both ends of the spectrum provide their own unique challenges in treatment and diagnosis, but the main challenge is knowing when to operate and how to optimize the outcome. Even the most insignificant appearing fracture can result in significant long-term disability.


High-energy forefoot and midfoot trauma is a significant cause of long-term morbidity. The lifelong impact of a poorly functioning forefoot should not be underestimated. These patients often present with open injuries with soft tissue loss, and associated muscle and tendon damage. Patients presenting with ankle, pilon, and tibial plateau fractures should all be carefully examined and investigated to ensure that they do not have associated mid- and forefoot fractures. Long periods of non-weightbearing are often necessary, which coupled with the associated soft tissue damage results in a poorly functioning, stiff foot.


Lower energy trauma presents its own difficulties, with isolated Lisfranc and cuneiform fractures often being misdiagnosed in the Accident and Emergency department as sprains. Careful investigation of all persistently swollen midfeet following trauma is essential to reach the correct diagnosis early and improve the long-term outcome.


There is an increasing burden of fragility fractures in the elderly who present with complex metatarsal base fractures on a background of poorly controlled diabetes or osteoporosis. These patients present their own challenges with a “less is more” approach often being appropriate. Judicious use of internal fixation can, however, prevent long-term deformity and ulceration, and so should be considered in selected cases. In many ways older fragility fractures present a more difficult decision-making process than the high-energy fractures seen in younger patients. It is clearly in the patient’s interest to have treatment decisions made by a senior foot and ankle or trauma surgeon.


The main principles of treatment in the forefoot include restoration of the stability of the medial column, allowing soft tissue healing, and ensuring that the foot continues to function as a stable tripod without loss of length or overload of the lesser rays. A stepwise approach to reconstruction with medial bridge plating of the first ray to maintain length, and reconstruction of the lesser rays, is usually appropriate. In many cases, metalwork should be removed after a suitable interval. Management of expectations can be difficult and treatment should be undertaken bearing in mind that a proportion of patients will require secondary fusion surgery. In summary, reconstruction of complex forefoot fractures is among the most challenging surgery.



Pathogenesis


The three parts of the foot have very different functions. The hindfoot is used for propulsion, deceleration, and as a shock absorber. The midfoot controls the relationship between the hindfoot and the forefoot. Fixing the midfoot and forefoot is key in locking the metatarsals to provide a sound platform through the third rocker to toe-off. The locked forefoot provides a platform for standing and a lever for push-off. During gait, load is distributed unevenly with the first metatarsal bearing one-third of the body’s weight and the second to the fifth sharing the other two-thirds. The metatarsal heads and the toes are in contact with the floor for around 75% of the stance phase. A supple and functioning forefoot is required to maintain stability with the assistance of the windlass mechanism, allowing function of the major muscles and tendons crossing the ankle and ensuring the body’s weight is correctly distributed under the metatarsal heads to prevent transfer metatarsalgia.



Lisfranc Injuries


The Lisfranc “joint” is usually used eponymously to mean the tarsometatarsal joint, although Lisfranc injuries often involve the tarsometatarsal, intermetatarsal, and intertarsal joints. The central stabilizing structure is the Y-shaped Lisfranc ligament, which runs from the medial cuneiform to the base of the second metatarsal; the ligament stabilizes the second metatarsal and is central to maintenance of the midfoot arch. The second metatarsal is the keystone of the transverse arch, and thus rupture of the Lisfranc ligament tends to be the key to Lisfranc injuries. Although initially described as a specific injury, Lisfranc injuries are now taken to refer to any injury defunctioning the Lisfranc joint. These injuries are usually caused by axial loading or indirect rotational forces through the Lisfranc joint in a plantar flexed foot. The plantar directed “V” shape of the second metatarsal makes it susceptible to dorsal dislocation. This family of injuries can also be caused by direct crush injuries when a heavy load lands on the foot, usually resulting in a plantarly displaced fracture.



First Metatarsal Fractures


The first ray is relatively rigid, providing a stable lever arm around which the windlass mechanism functions during the third rocker of gait. Shortening of as little as 7 mm from malunion of a first metatarsal fracture can lead to transfer of load to the lateral side of the foot. This can often result in pain, with transfer lesions of the lesser rays.


The first metatarsal is wider, shorter, and stronger than the lesser metatarsals. As a result of its relative size and strength, when fractures do occur in the first metatarsal they are often resultant on a high-energy injury, with more comminution and a higher incidence of being open.



Fifth Metatarsal Fractures


Injuries to the fifth metatarsal are common, comprising 25% of all metatarsal fractures. They are a significant burden for surgeons and patients alike, with a surprising number of unsatisfactory results and dissatisfied patients. The three common fractures of the base of the fifth metatarsal all occur by different mechanisms.




  1. 1. Avulsion fractures are caused by the pull of peroneus brevis and are classically seen in dancers. Affecting the proximal 1.5 cm of the fifth metatarsal these injuries do not place the blood supply at risk.



  2. 2. Jones’ fractures are more distal and are caused by inversion injuries. They involve the intermetatarsal facet between the fourth and fifth metatarsals, usually 1.5 to 3 cm from the styloid process.



  3. 3. Stress fractures are the least common fracture and are seen in the diaphysis, distal to Jones’ fractures.


The fifth metatarsal has a relatively poor blood supply and therefore all three types of fracture risk non-union1. The diaphyseal blood supply primarily comes from a single vessel entering the diaphysis at the junction of the proximal and middle thirds. Secondary arteries supply the tuberosity and base. This leaves a relatively avascular area in zone 2, where Jones’ fractures occur, and accounts for the high rates of non-union with these fractures. The only level 1 evidence available shows a non-union rate of 33% for those treated in cast, falling to 6% for those who have open reduction and internal fixation2.



Second to Fourth Metatarsal Fractures


Acute fractures of the middle metatarsals are rarely isolated and often occur as a result of a high-energy injury, usually either as an extension of a Lisfranc injury, or as a result of the metatarsal bases being forced plantarward. Stress fractures are usually isolated and found in the second and third metatarsals, which are relatively fixed in comparison to the first, fourth, and fifth rays. In stress fractures low bone mineral density is a risk factor for occurrence and also an independent risk factor for non-union.


Together the metatarsal heads form a curved cascade when looked at from above (Lelièvre’s parabola). In the horizontal plane the plantar aspect of the second to the fourth metatarsal heads should all be on the same level. The first metatarsal head lies higher than the other four as the sesamoids are the weightbearing point.



Hallux Fractures and Dislocations


Intra-articular “corner” fractures of the proximal phalanx usually occur with a “stubbed toe” when the great toe is caught while walking barefoot or in sandals. Diaphyseal injuries are usually the result of direct trauma such as kicking a wall, and very high-energy axial loads can result in a pilon type fracture of the base of the toe. Patients commonly present late after the simpler great toe fractures.



Sesamoid Fractures


The two sesamoid bones of the hallux, which lie within the tendon of flexor hallucis brevis, and fibers of the abductor hallucis and adductor hallucis, also attach, respectively, to the tibial and fibular sesamoids. The two sesamoids are connected to each other by the intersesamoidal ligament. As a result of the lever arm of the first metatarsal head the sesamoids bear up to three times the body weight in the normal gait cycle, with the tibial sesamoid bearing a greater proportion of this due to its size and position.


The sesamoids are commonly injured during sport, usually as a result of either a direct axial loading force resulting in a comminuted fracture, or forced hyperextension of the first MTPJ. Stress fractures are seen three times more commonly than acute fractures, often in long-distance runners. The risk of a sesamoid fracture is increased by cavus deformity of the foot and hallux valgus deformity of the great toe.


Misdiagnosis is common, as bipartite or multipartite sesamoids are present in 20%3 of the population as a result of the ossification centers failing to fuse. A bipartite or multipartite sesamoid is only bilateral in 25% of patients and so unilaterality is not a useful sign for assessing a fracture. To compound matters, when a bipartite sesamoid is fractured, it often does so through the fibrocartilagenous junctional zone making detection very difficult. It should therefore be more accurately termed a “diastasis” injury. Diagnosis may be aided by either MRI scanning or more traditionally bone scanning with areas of high signal or tracer uptake indicative of fracture.



Turf Toe


The term “turf toe” was coined in 1976 to describe a plantar capsulo-ligamentous injury of the hallux MTPJ4. The condition commonly affects athletes and ballet dancers, and is caused by hyperdorsiflexion of the first MTPJ, usually with an axial load applied with the foot in fixed equinus (such as when a ballerina attempts to land “en pointe”). This results in tearing of the plantar plate and the surrounding structures. Injuries have become commoner in sports people as the use of hard synthetic sports surfaces and soft-soled shoes has become commoner. Astroturf has a higher coefficient of friction than living grass and loses some of its shock absorbency over time. This results in the forefoot being “fixed” to the playing surface, making hyperdorsiflexion injury more likely.


Turf toe is associated with significant morbidity with as many as 50% of athletes complaining of persisting symptoms five years following injury5. Once torn, unrestricted motion of the proximal phalanx causes significant compression of the dorsal articular surface of the metatarsal head. Turf toe may be associated with a sesamoid fracture.



Phalangeal Dislocations and Fractures


Fractures of the lesser toe phalanges are seen four times as frequently as those of the hallux6. Fractures of the proximal phalanx and dislocations of the proximal interphalangeal joint are usually sustained when barefoot, as the toe can easily catch and be forced into abduction. Distal phalangeal fractures are usually caused by a direct crushing injury or an axial loading force (a “stubbed” toe). Great care must be made not to miss a nailbed injury or open fracture as these injuries need thorough washout and repair of the nail bed.



Classification


There are many classification systems that have been proposed over the years for the various injuries of the forefoot – far too many to be considered in their entirety in this chapter. Many are just descriptive, but some guide treatment or deepen understanding of the pathophysiology and are worth consideration.



Lisfranc Injuries


Sprains of the Lisfranc joint are relatively common and have been classified by the grade of injury to the Lisfranc ligament7. Differentiation of the grades is aided by weightbearing AP films, to demonstrate instability.




  • Grade 1: Pain at the site of the Lisfranc ligament with minimal swelling and no instability.



  • Grade 2: Pain and swelling with associated laxity, but no instability. Diastasis present between the first and second metatarsals, but no collapse of the medial arch.



  • Grade 3: Complete ligamentous disruption with diastasis and loss of the longitudinal arch.


Grade 3 injuries are usually a fracture dislocation, which can also be classified as below.


Complete injuries of the Lisfranc joint, with ligament rupture and defunctioning of the base of the second metatarsal, were originally classified by Quénu and Küss in 19098, a classification that was subsequently modified in 1982 by Hardcastle9 and finally updated in 1986 by Myerson10. The Myerson classification is in common use as it guides treatment and also indicates prognosis (Figure 23.1).




  • A: Homolateral




    • A1: total incongruity medial displacement



    • A2: total incongruity lateral displacement.



  • B: Isolated




    • B1: partial incongruity medial displacement



    • B2: partial incongruity lateral displacement.



  • C: Divergent




    • C1: partial divergent displacement



    • C2: total divergent displacement.


It is important to bear in mind that in the normal foot radiograph:




  • The lateral border of the medial cuneiform should align with the lateral aspect of the first metatarsal.



  • The medial aspect of the second metatarsal should align with the medial cortex of the middle cuneiform.



  • The medial aspect of the third metatarsal should align with the medial edge of the lateral cuneiform.



  • The medial aspect of the fourth metatarsal should align with the medial edge of the cuboid.





Figure 23.1 Myerson classification of Lisfranc injuries.



Fractures of the Base of the Fifth Metatarsal


Fractures of the base of the fifth metatarsal are most commonly classified using the Dameron–Lawrence–Botte zonal classification1112. The classification (Figure 23.2) divides injuries into three zones: avulsion fractures of the tubercle (zone 1); Jones’ fractures at the metadiaphyseal junction (zone 2); and diaphyseal stress fractures (zone 3). While this classification is useful, in that it does predict the likelihood of fracture union, it does suffer from the problem that in vivo many injuries cross more than one zone.





Figure 23.2 Dameron–Lawrence–Botte zonal classification of fractures of the base of fifth metatarsal.


Jones’ fractures and stress fractures within 1.5 cm of the tuberosity are also subclassified by the Torg classification13:



Type I: Acute fracture with sharp margins and no widening


Type II: Delayed union with some periosteal reaction, widened fracture site and intramedullary sclerosis


Type III: Non-union with intramedullary sclerosis.



Presentation


Clinical assessment can be difficult at the time of initial examination. A number of different forefoot injuries present with a painful, swollen, and contused foot. Initial evaluation of the patient should include a careful history including the mechanism and position of the foot at the time of injury. At least three radiographic views (AP, lateral, and oblique) of the foot should be obtained.


There is a surprisingly high incidence of vascular compromise and compartment syndrome associated with metatarsal fractures and careful examination of the vascularity of the foot, and in particular the toes distal to the fracture, should be undertaken. Any significant swelling with pain out of proportion to the injury and pain on passive motion of the toes should alert the clinician to the possibility of compartment syndrome. Although there is no universal agreement on the precise indications for fasciotomy in the foot, establishing the diagnosis is important. The presence, or absence, of pulses should always be documented.


All patients should be assessed for diabetes mellitus and, in particular, the presence of a peripheral neuropathy. This is easily assessed with a Semmes–Weinstein 10 gram monofilament. In those patients with diabetes, management should be as part of a multidisciplinary team, as tight control of the blood glucose will help optimize outcome. Patients who smoke tobacco should be advised to cease usage, as it is associated with higher overall complication rates, not just non-union.


Patients presenting with severe open injuries should be managed in a multidisciplinary team, with plastic and, if required, vascular surgical input. A staged approach to skeletal and soft tissue reconstruction is used. While clean grade I and II injuries can always be treated in a planned manner, severe grade III injuries, or those with contamination, should be treated as an emergency. Careful documentation of the neurovascular status, in particular plantar sensation, and operative findings at the initial debridement should be used to guide subsequent decision making. Limb salvage is not always the best option, but for the majority of isolated severe open foot fractures it should be the goal.


In many of the less severe fractures and soft tissue injuries of the forefoot diagnosis can be difficult. It is worth maintaining a high level of clinical suspicion and if doubt persists then a CT scan should be arranged to rule out fractures or dislocations. Patients presenting with severe swelling should be admitted for elevation and treatment with a pneumatic foot pump. Outcomes are generally better if prolonged periods of immobilization can be avoided.



Investigations


The majority of forefoot injuries can be adequately imaged with standard series x-rays, nevertheless specialist radiological views and more complex imaging modalities are frequently helpful.



X-Ray


X-ray is the standard investigation for the forefoot with anteroposterior, oblique, and lateral views (Figure 23.3). These will adequately show most injuries. Acutely radiographs are normally taken with the patient non-weightbearing as a result of pain or for fear of causing further damage. Nevertheless significantly more information, particularly in defining Lisfranc instability and collapse, can be garnered from weightbearing films and stress views. It is essential to correlate radiological and clinical findings. X-rays are often normal in stress fractures from two to six weeks of symptom onset, though they usually progress to show either the stress fracture itself or evidence of healing.





Figure 23.3 A standard radiological trauma series. (a) AP, (b) oblique, and (c) lateral. If the series can be obtained weight bearing this is ideal.



Special Views


Weightbearing Views. AP and lateral x-rays with the patient weight bearing can be useful to show displacement of the Lisfranc joint where there has been complete ligament rupture. This is often missed on standard non-weightbearing films. Where there remains any doubt weightbearing films of the uninjured side may be useful.


Stress Views of the Lisfranc Joint. Stress views can be used to ascertain the extent of the injury if this remains unclear after weightbearing x-rays. They are rarely performed in the emergency department in the acute setting, as to do so would usually require an anesthetic and interpretation can be difficult. They can, however, be very informative at the start of an operation if for no other reason than to document the degree of instability. The widespread availability of preoperative CT and MRI scanning has rendered these views obsolete in many centers.


Sesamoid Views. When assessing the sesamoids two sets of views are useful:




  • – The medial oblique view, to assess the tibial sesamoid, and the lateral oblique view, to assess the fibular sesamoid, show each sesamoid in a near AP or PA view (depending on technique) and clear the metatarsal head from the projection. The two views are taken with the foot in the AP position and the x-ray beam directed 15° cephalad with the MTPJ extended to 50°.



  • – Axial views, with the hallux held dorsiflexed, and a radiograph taken along the longitudinal axis of the sole of the foot to profile the two sesamoids, can also be helpful.


Contralateral x-rays should not be used for interpretation due to the significant variation in bipartite and multipartite sesamoids between sides.



CT Scan


A CT scan is commonly used to assess the extent of injury, especially of the Lisfranc joint. The complex overlapping geometry of the forefoot and midfoot can be clearly viewed with cross-sectional imaging and 3D reconstructions assisting in the assessment of the metatarsal arcade and other fracture patterns. CT is particularly useful in assessing the degree of plantar comminution, which may not be appreciated on plain radiographs. The use of volume rendered images (Figure 23.4) is particularly helpful in understanding fracture patterns, and hence in surgical planning. When assessing fractures using 3D-rendered views there is a risk of missing fractures, or oversimplification of fracture configurations, as these are inherently lower resolution images and should be carefully compared to plain slices.





Figure 23.4 (a) An AP x-ray and (b) a 3D volume-rendered image of the same injury looking at the plantar aspect. While some comminution can be appreciated on the AP x-ray the comminution of the bases of the second to fourth metatarsals can be fully appreciated on the CT scan.



MRI Scan


An MRI scan can aid in the diagnosis of metatarsal stress fractures, as x-rays can remain normal for up to six weeks. MRI may also show a stress reaction within the metatarsal, showing low signal on the T1 and high signal intensity on T2 and STIR sequences, but with no evidence of extension into the cortices. A stress reaction should be treated in the same way as a stress fracture. The diagnosis of a stress reaction is never made on x-ray.


Sesamoid fractures can also be diagnosed on MRI, and the technique is particularly useful in identifying those patients with a diastasis injury of a bipartite or multipartite sesamoid. It may also reveal avascular necrosis of the sesamoid14.

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Sep 15, 2020 | Posted by in ORTHOPEDIC | Comments Off on Chapter 23 – Fractures and Dislocations of the Forefoot
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