Metatarsal Fractures





KEY FACTS





  • Toe and metatarsal fractures are the most common fractures of the foot with an incidence of 140 per 100,000 per year.



  • The 5th metatarsal is the most frequently fractured metatarsal (23%).



  • The metatarsals are affected by stress fractures more commonly than all other sites in the body.



  • A majority of metatarsal fractures are low-energy injuries suitable for closed treatment.




    • The intact soft tissues splint the fracture.




  • A low-energy metatarsal shaft fracture typically does not disrupt proximal or distal stabilizing soft tissue structures.




    • The metatarsal head remains in the appropriate location for weight bearing.




  • A high-energy injury, with disruption of the stabilizing soft tissues proximally or distally, will elevate or depress the metatarsal head.




    • Thus, this may disrupt the normal distribution of weight in the forefoot.



    • Altered weight distribution may lead to metatarsalgia and painful plantar keratosis.




  • Displacement, shortening, or angulation of the 1st metatarsal in any plane anywhere along the bone can significantly alter the weight-bearing distribution of the foot and is therefore an indication for operative management.



  • An isolated, nondisplaced metatarsal base fracture may be stable, but if any uncertainty exists, further evaluation of the midfoot with stress x-rays is necessary.



  • High-energy injuries, even when closed, have extensive soft tissue disruption and may require operative treatment.



  • Lawn mower injuries are common with an incidence of between 50,000-160,000 each year.




    • They can cause significant morbidity and, rarely, even death.








This young man’s foot was crushed by a large garage door. The 1st metatarsal (MT) shaft is widely displaced.








There is not much vertical displacement of the MT head, suggesting that some of the soft tissue connections were intact between the 1st and 2nd MT heads.








Open reduction was performed through a medial incision with a lag screw and neutralization plate.








After 6 weeks of non-weight bearing, he went on to a full recovery.






Forefoot Structure





  • The metatarsals are the major weight-bearing structure of the forefoot.



  • The 1st metatarsal head and its 2 associated sesamoids bear ~ 1/3 of the body weight.




    • The remainder is distributed among the lesser 4 metatarsals.



    • The 2nd and 3rd frequently bear more than the 4th and 5th.




  • The metatarsal bases are rigidly stabilized to the cuneiforms and cuboid in the midfoot.



  • The proximal transverse metatarsal ligament runs from the 5th metatarsal base to the 4th, to the 3rd, then the 2nd, and then to the medial cuneiform.



  • The distal transverse intermetatarsal ligament runs from the 5th metatarsal head to the 4th, then the 3rd, then 2nd, and then finally to the lateral sesamoid.



  • There are no ligaments connecting the 1st metatarsal to the others.



  • A low-energy metatarsal shaft fracture does not disrupt these proximal or distal stabilizers, so the metatarsal head remains in the appropriate location for weight bearing.



  • A higher energy injury, with disruption of the stabilizing soft tissues proximally or distally, will elevate or depress the metatarsal head.




    • Thus, this may disrupt the normal distribution of weight in the forefoot.



    • Altered weight distribution may lead to metatarsalgia and painful plantar keratosis.




  • The 1st metatarsal is intimately associated with the sesamoids, which are held fixed in relation to the lesser metatarsals by attachments to the intermetatarsal ligaments and the 2 heads of the adductor hallucis.




    • Displacement of the 1st metatarsal head in any direction can alter the balance of the entire forefoot.




  • The tibialis anterior works to elevate the 1st metatarsal, while the peroneus longus plantar flexes.




    • Either of these muscles may act to deform a 1st metatarsal fracture.




  • The flexor digitorum longus, flexor hallucis longus, and intrinsic muscles place plantar flexion stress on the metatarsal heads in distal fractures and can cause plantar flexion deformities.



  • The 5th metatarsal, like the 1st, has less soft tissue coverage than the middle metatarsals and has extrinsic muscle attachments, the peroneus brevis and tertius, which attach at its base.




    • It also has a strong attachment to the lateral band of the plantar fascia.



    • It is the most mobile of the metatarsals.






Metatarsal Fractures


Mechanism





  • Metatarsal fractures result from a wide variety of mechanisms and may range from an isolated single bone fracture to multiple fractures with severe soft tissue compromise.



  • Direct trauma with a heavy falling object is common in industrial workers.



  • Many low-energy injuries arise from indirect trauma, a twisting force with a fixed forefoot.



  • Fractures of the 5th metatarsal base result from avulsion by the lateral band of the plantar aponeurosis.



  • Stress fractures occur as a result of repetitive force on the metatarsals and occur frequently in athletes, soldiers, and dancers.



Physical Examination





  • Patients with metatarsal fractures present with pain on ambulation or difficulty with weight bearing on the affected foot, swelling, deformity, and ecchymosis.



  • Dorsal swelling is typical, because the plantar skin allows little swelling due to the thick fibrous septa within the skin pad.



  • Each metatarsal and toe should be carefully and sequentially evaluated.



  • Palpation of each digit and each metatarsal shaft usually will elicit point tenderness at the fracture site.



  • Subungual hematoma is a hallmark of distal phalangeal fractures and may be associated with open fractures of the distal phalanx.



Imaging





  • Radiographs should include anteroposterior, lateral, and oblique views of the foot.



  • Metatarsal head alignment can be evaluated further with anteroposterior and lateral weight-bearing views of the whole foot and a tangential view of the metatarsal heads.




    • Unfortunately, these views are difficult to obtain in a patient with a new injury.




  • Stress fractures frequently do not appear initially on plain x-ray.




    • Follow-up films 3-4 weeks later will usually demonstrate periosteal reaction or, in the 5th metatarsal, a resorption gap, that confirms the diagnosis.




  • Magnetic resonance imaging can identify a stress fracture immediately but is not often needed, because the diagnosis can be made clinically.



  • Bone scans also will detect a stress fracture after a few days of symptoms.



Classification





  • Metatarsal fractures can be classified according to the location, and thus include head, neck, shaft, and base fractures.



  • It is useful to classify 1st and 5th metatarsal fractures separately from the rest, because the treatment options differ widely for these types.



  • Second, third, and fourth metatarsal fractures can be grouped together, as the treatment options are similar.



  • Proximal 5th metatarsal fractures can be categorized by zone.



  • Metatarsal base fractures can occur in isolation.




    • However, it is important to recognize that many, perhaps all, such fractures represent an injury to the midfoot.




  • An isolated, nondisplaced metatarsal base fracture may be stable, but if any uncertainty exists, then further evaluation of the midfoot with stress x-rays is necessary.



1st Metatarsal Fractures





  • Nondisplaced or minimally displaced fractures of the 1st metatarsal shaft or neck are generally stable and can be treated nonoperatively.




    • Nonoperative options range from a short leg cast with progressive weight bearing over 4-6 weeks to a CAM walker boot to a wooden rocker shoe for very stable fractures.




  • Displacement, shortening, or angulation of the 1st metatarsal in any plane anywhere along the bone can significantly alter the weight-bearing distribution of the foot and is therefore an indication for operative management.



  • It is important to restore the length and the alignment of the bone anatomically in both the sagittal and transverse planes in order to maintain normal weight bearing through the 1st ray.



  • For shaft fractures, the types of fixation are limited due to the thin layer of soft tissue surrounding the bone, necessitating the use of a low-profile device.




    • There is more room for plates on the plantar-medial side of the bone.




  • Long oblique fractures may be well treated with multiple lag screws, but most displaced shaft fractures will require a plate.




    • 3.5-, 2.7-, or 2.4-mm implants can be used.




  • Common approaches include a longitudinal approach between the 1st and 2nd metatarsals and the medial approach.




    • The superficial peroneal nerve, deep peroneal nerve, and dorsalis pedis artery are at risk with the former approach.



    • The terminal branches of the saphenous vein and nerve are at risk with the latter.




  • Comminuted base fractures may occasionally require bridging across the 1st tarsometatarsal joint to maintain proper alignment.




    • Occasionally, fusion of the 1st tarsometatarsal joint may be necessary.



    • So long as the fusion is performed with anatomical alignment of the metatarsal, no long-term consequences should be expected.




2nd, 3rd, and 4th Metatarsal Fractures





  • Most low-energy fractures of the middle metatarsals are minimally displaced due to the soft tissue restraints previously described.



  • 3-4 mm of displacement in the sagittal plane (elevation or depression of the metatarsal head) can significantly affect the distribution of weight in the forefoot.




    • This results in transfer of load to adjacent metatarsals (if the affected metatarsal is elevated) or overload of the fractured metatarsal (if it is plantar flexed).




  • Similarly, shortening of a metatarsal can lead to adjacent metatarsal overload (transfer lesions or intractable plantar keratoses).



  • Deformity in the transverse plane (medial or lateral angulation) does not have a large impact on weight-bearing distribution.




    • Thus, a higher degree of deformity, perhaps 4 mm of displacement and 10° of angulation, can be accepted in this plane.




  • Nonoperative treatment can be considered for shaft fractures with < 2 mm of shortening, elevation, or depression of the metatarsal head in the sagittal plane.




    • This will be the vast majority of lesser metatarsal fractures.




  • Such fractures in the lesser rays can be treated with cast immobilization, a wooden sole shoe, or a CAM walker with progressive weight bearing over 4-6 weeks.



  • Fractures that result in significant elevation or depression of the metatarsal head and alteration of the weight-bearing distribution should be treated surgically.



  • Closed reduction and percutaneous pin fixation is possible.




    • Pins enter from the metatarsal head.



    • The pins force the metatarsophalangeal (MTP) joints to remain extended while they are in place.



    • This can result in extension contractures at the MTP joints with claw toe deformity.



    • To avoid clawing, the surgeon can place the pins more medially or laterally in the metatarsal head.




      • This is technically more difficult.



      • The pins could enter through the toe and pass across the MTP joint and then across the fracture.




        • This is also difficult.






  • Shaft and neck fractures can also be treated with open reduction and internal fixation using mini implants (2.7, 2.4, or 2.0 mm).



  • The rare displaced metatarsal head fracture should probably be treated with open reduction and internal fixation.



Multiple Metatarsal Fractures





  • It is possible to fracture multiple metatarsals.



  • In some cases, the proximal and distal soft tissues will remain intact, so metatarsal head alignment will not be affected.




    • These injuries can be treated closed.




  • However, some injuries with multiple shaft fractures may represent a variant of a midfoot (Lisfranc) injury.



  • In all cases of metatarsal fracture, especially when there are multiple fractures, midfoot stability should be assessed carefully.



5th Metatarsal Fractures





  • There are 4 major types of fractures of the 5th metatarsal.




    • Proximal base (vast majority)



    • Acute proximal metaphysis



    • Distal shaft



    • Stress fractures




  • Fractures can be grouped by geographic zone.




    • Zone 2 includes both acute an chronic injuries.




Tuberosity Avulsion Fracture





  • Although it was once believed that the avulsion was due to the pull of the peroneus brevis during foot inversion, more recent studies implicate the lateral band of the plantar fascia.



  • Almost all tuberosity avulsions can be treated nonoperatively with a walking cast, boot, or hard-soled shoe and weight bearing as tolerated.




    • The majority will heal within 8 weeks, but symptoms may persist for several months.




  • Radiographic nonunion is not uncommon, but painful nonunion is rare.



  • Some of these injuries will have a larger proximal fragment and may extend into the articulation between the 4th-5th metatarsal bases.




    • Others may be displaced into the articulation with the cuboid.



    • Despite some displacement, all of these acute injuries tend to heal well without surgery.




  • The rare, painful nonunion can be treated with excision of the fragment and peroneus brevis repair or bone grafting and intramedullary screw fixation for larger fragments.



“Jones” Fractures





  • Jones fractures occur at the metaphyseal-diaphyseal junction, an area of poor vascularity and, therefore, reduced healing potential.



  • The textbooks describe the Jones fracture as exiting into the intermetatarsal region between the 4th-5th metatarsal bases.



  • It may be more useful to separate these “Jones fractures” into acute fractures of the proximal shaft and chronic stress fractures.



  • The literature on these injuries is confusing, mostly because authors have pooled acute and chronic injuries together.



  • The acute proximal shaft fracture appears transverse on x-ray with no cortical hypertrophy or periosteal reaction.




    • Although delayed union or nonunion is a concern, this injury can be treated successfully with protected weight bearing in a boot.



    • At least 1 study has shown that immediate weight bearing can result in a good outcome.




  • Because of concerns for delayed union or nonunion, some surgeons recommend early surgery for high-level athletes.




    • This allows for more aggressive and confident recovery with possibly less down time.




Stress Fractures





  • The chronic metadiaphyseal fracture is very different.



  • The patient may present with the same history as for acute fracture: New pain in the foot after an injury.




    • Others may have pain for weeks to months.




  • Radiographs show sclerosis, medullary canal narrowing, or periosteal reaction at the fracture site at the time of first presentation.




    • These imaging findings suggest a longstanding bone injury.




  • They are most frequently seen in young athletes who have a sudden increase in demand on the foot or who have mild genu varum or heel varus deformities that overload the 5th metatarsal.



  • Nonoperative treatment with a short leg walking cast can take from 6-20 weeks and requires a long period of rehabilitation.




    • Refracture and nonunion occur relatively frequently with nonoperative treatment when activity is resumed.




  • Most surgeons now advocate operative management for these fractures, especially in athletes.




    • Benefits of operative management are a lower refracture rate and a much quicker return to activity




  • Operative treatment consists of intramedullary screw fixation.




    • The drilling for screw insertion is thought to increase healing potential, just as with reaming for intramedullary nailing in the tibia.




  • A lot of research has studied fixation for these fractures.




    • In the lab, a plate may provide stronger fixation than a screw under cyclic loading.



    • But an intramedullary screw may be stronger in bending.



    • However, more important than simple strength of fixation is augmenting the healing.




      • It is important to stimulate the biology of fracture healing.




    • Some surgeons add bone graft as well.




  • In cases of chronic injury, alignment of the foot must be assessed.




    • Patients with a varus hindfoot will overload the 5th ray, leading to stress injury.



    • This can also be seen after varus tibial malunion.



    • If the deformity causing 5th metatarsal overload is not corrected, the fracture may recur.




“Dancer’s” Fractures





  • Fractures of the 5th metatarsal shaft have been referred to as dancer’s fractures, as they occur by “rolling over” the lateral forefoot while up on the toes.



  • The fracture is a long spiral fracture, sometimes with comminution.



  • The treatment of shaft fractures in the 5th metatarsal differs slightly from that of the medial 4 metatarsals because of the increased mobility of this bone.




    • Thus, a larger degree of displacement and angulation of shaft fractures can be accepted.




  • These fractures often appear to have significant displacement.




    • This is especially true on the oblique view.




  • Fortunately, most heal quite well.



  • Patients can be treated nonoperatively with a walking cast or boot.



  • Surgery is indicated for the rare, highly displaced injuries.



Other Metatarsal Stress Fractures





  • Stress fractures of the medial 4 metatarsals occur frequently.



  • They are commonly referred to as “march fractures” because of their occurrence in new military recruits going for long marches.



  • Treatment of these fractures is usually nonoperative and focuses on unloading the affected metatarsal with altered shoewear, orthotics, or a short leg cast for complete fractures.



  • It is important to look for underlying causes for the stress injury.




    • Often, none will be found.




  • Stress injuries can result from imbalance in the foot (osseous alignment).



  • Metabolic causes are also common, such as in the amenorrheic female athlete.


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Oct 29, 2019 | Posted by in ORTHOPEDIC | Comments Off on Metatarsal Fractures
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