TRAUMA 2023, Jan, 22 | 12:00 am

TALUS Fractures

  1. TALUS Fractures

     

     

     

     

    EPIDEMIOLOGY

  2. These are second in frequency among all tarsal fractures.

  3. The incidence of fractures of the talus ranges from 0.1% to 0.85% of all fractures and 5% to 7% of foot injuries.

  4. Approximately 14% to 26% of talar neck fractures have associated fracture of the medial malleolus.

  5. Lateral process of the talus fractures are frequently seen in snowboarding injuries and account for 15% of all ankle injuries.

  6. Fractures of the talar head are rare with an incidence of 3% to 5% of all fractures of the talus.

    ANATOMY

  7. The body of the talus is covered superiorly by the articular surface through which a person’s body weight is transmitted. The anterior aspect is wider than the posterior aspect, which confers intrinsic stability to the ankle (Fig. 40.1).

     

     

     

  8. Medially and laterally, the articular cartilage extends plantar to articulate with the medial and lateral malleoli, respectively. The inferior surface of the body forms the articulation with the posterior facet of the calcaneus.

  9. The neck of the talus is roughened by ligamentous attachments and vascular foramina. It deviates medially 15 to 25 degrees and is the most vulnerable to fracture.

  10. The talar head has continuous articular facets for the navicular anteriorly, the spring ligament inferiorly, the sustentaculum tali posteroinferiorly, and the deltoid ligament medially.

  11. There are two bony processes. The lateral process is wedge shaped and articulates with the posterior calcaneal facet inferomedially and the lateral malleolus superolaterally. The posterior process has a medial and lateral tubercle separated by a groove for the flexor hallucis longus tendon.

  12. An os trigonum is present in up to 50% of normal feet. It arises from a separate ossification center just posterior to the lateral tubercle of the posterior talar process.

  13. Sixty percent of the talus is covered by articular cartilage. No muscles originate from or insert onto the talus. The vascular supply is dependent on fascial structures to reach the talus; therefore, capsular disruptions may result in osteonecrosis.

  14. The vascular supply to the talus consists of:

    • Arteries to the sinus tarsi (peroneal and dorsalis pedis arteries)

    • An artery of the tarsal canal (posterior tibial artery)

    • The deltoid artery (posterior tibial artery), which supplies the medial body

    • Capsular and ligamentous vessels and intraosseous anastomoses

       

      MECHANISM OF INJURY

  15. Most commonly associated with a motor vehicle accident or a fall from a height with a component of hyperdorsiflexion of the ankle. The talar neck fractures as it impacts the anterior margin of the tibia.

  16. “Aviator’s astragalus”: This historical term refers to the rudder bar of a crashing airplane impacting the plantar aspect of the foot, resulting in a talar neck fracture.

    CLINICAL EVALUATION

  17. Patients typically present with ankle pain.

  18. Range of foot and ankle motion is typically painful and may elicit crepitus.

  19. Diffuse swelling of the hindfoot may be present, with tenderness to palpation of the talus and subtalar joint.

  20. Associated fractures of the foot and ankle are commonly seen with fractures of the talar neck and body.

    RADIOGRAPHIC EVALUATION

  21. Anteroposterior (AP), mortise, and lateral radiographs of the ankle, as well as AP, lateral, and oblique views of the foot are obtained.

  22. Canale view: This provides an optimum view of the talar neck. Taken with the ankle in maximum equinus, the foot is placed on a cassette, pronated 15 degrees, and the radiographic source is directed cephalad 15 degrees from the vertical (Fig. 40.2). This view was described for evaluation of posttraumatic deformity and is difficult to obtain in the acute setting.

     

     

     

  23. Computed tomography (CT) is helpful to characterize fracture pattern and displacement further and to assess articular involvement.

  24. Technetium bone scans or magnetic resonance imaging (MRI) may be useful in evaluating possible occult talar fractures.

    CLASSIFICATION

    Anatomic

  25. Lateral process fractures

  26. Posterior process fractures

  27. Talar head fractures

  28. Talar body fractures

  29. Talar neck fractures

    Hawkins Classification of Talar Neck Fractures (Fig. 40.3)

    Type I: Nondisplaced

    Type II: Associated subtalar subluxation or dislocation

    Type III: Associated subtalar and ankle dislocation

    Type IV: (Canale and Kelley): Type III with associated talonavicular subluxation or dislocation

     

     

     

    Orthopaedic Trauma Association Classification of Talar Fractures See Fracture and Dislocation Classification Compendium at http://www.ota.org/compendium/compendium.html.

    TREATMENT

    Fractures of the Talar Neck and Body

    These represent a continuum and are considered together.

    Nondisplaced Fractures (Hawkins Type I)

  30. Fractures that appear nondisplaced on plain radiographs may show unrecognized comminution or articular step-off on CT scan. Fractures must truly be nondisplaced with no evidence of subtalar incongruity to be considered a type I fracture.

  31. Treatment consists of a short leg cast or boot for 8 to 12 weeks. The patient should remain non–weight bearing for 6 weeks until clinical and radiographic evidence of fracture healing is present.

    Displaced Fractures (Hawkins Types II to IV)

  32. Immediate closed reduction (plantar flexion) is indicated, with open reduction and internal fixation (ORIF) for all open or irreducible fractures (Fig. 40.4).

     

     

     

  33. If anatomic reduction is obtained and confirmed by CT scan, the patient may be placed in a short

    leg splint and fracture fixation may be delayed.

  34. Surgical approaches include:

  1. Anteromedial: This approach may be extended from a limited capsulotomy to a wide exposure with malleolar osteotomy (as the fracture progresses toward the body). The internal is just medial to the anterior tibial tendon. This approach allows visualization of the talar neck and body. Care must be taken to preserve the saphenous vein and nerve and, more importantly, the deltoid artery.

  2. Posterolateral: This approach provides access to posterior process and talar body. The interval is between the peroneus brevis and the flexor hallucis longus. The sural nerve must be protected. It is usually necessary to displace the flexor hallucis longus from its groove in the posterior process to facilitate exposure.

  3. Anterolateral: This approach allows visualization of the sinus tarsi, lateral talar neck, and subtalar joint. Inadvertent damage to the artery of the tarsal sinus can occur through this approach.

  4. Combined anteromedial–anterolateral: This is often used to allow maximum visualization of the talar neck.

    • Internal fixation: Two interfragmentary lag screws or headless screws may be placed perpendicular to the fracture line. The screws can be inserted in antegrade or retrograde fashion. Posterior-to-anterior–directed screws have been demonstrated to be biomechanically stronger in a cadaver model, but clinically more difficult to place. Retrograde screw placement requires the use of headless screws or screws that are buried beneath the articular surface of the talar head. Areas of significant comminution and bone loss should be grafted.

    • Mini-fragment plates have been used laterally more recently in cases of significant comminution to avoid shortening of the neck (Fig. 40.5).

       

       

       

    • Use of titanium screws allows better visualization with MRI for evaluation of subsequent osteonecrosis.

    • A short leg cast or removable boot should be placed postoperatively for 8 to 12 weeks, and the

      patient should be kept non–weight bearing.

    • Hawkins sign: Subchondral osteopenia (seen on the Mortise ankle radiograph) in the talus at 6 to 8 weeks tends to indicate talar viability. However, the presence of this sign does not rule out osteonecrosis; its absence is also not diagnostic for osteonecrosis.

    • Open fracture: This complicates up to 15% to 25% of injuries and reflects the often high-energy mechanism that produces these fractures. Copious irrigation and meticulous debridement are necessary to prevent infectious complications. The reported infection rate for open talus fractures is 35% to 40%. The “extruded” talus is an extreme situation. Several reports have documented fair outcomes with replantation.

      TALAR BODY FRACTURES

      Classification

    • Shear type I (A, B) (Fig. 40.6)

       

       

       

    • Shear type II (C)

    • Crush (D)

      Treatment

    • Non/Minimally displaced—Nonoperative

    • Displaced-ORIF (may require medial malleolar osteotomy)

      Lateral Process Fractures

      These are intra-articular fractures of the subtalar or ankle joint that occur most frequently when the foot is dorsiflexed and inverted. There has been an increase in incidence with the rise in popularity of snowboarding.

    • Lateral process fractures are often missed on initial patient presentation. Fracture is misinterpreted as a severe ankle sprain.

    • Because of the difficulty in detecting and defining the extent of a lateral process fracture, a CT scan is often necessary to fully appreciate the extent of injury.

    • Less than 2-mm displacement: Patients should have a short leg cast or boot for 6 weeks and be non–weight bearing for at least 4 weeks.

    • More than 2-mm displacement: ORIF is performed using lag screws or wires through a lateral approach.

    • Comminuted fractures: Nonreconstructible fragments are excised.

      Posterior Process Fractures

      These involve the posterior 25% of the articular surface and include the medial and lateral tubercles. Fractures may occur in a severe ankle inversion injury whereby the posterior talofibular ligament avulses the lateral tubercle or by forced equinus and direct compression.

    • Diagnosis of fractures of the posterior process of the talus can be difficult, in part relating to the presence of an os trigonum.

    • Nondisplaced or minimally displaced: Patients should have a short leg cast for 6 weeks and be non–weight bearing for at least 4 weeks.

    • Displaced: ORIF is recommended if the fragment is large; primary excision is performed if the fragment is small; a posterolateral approach may be used.

      Talar Head Fractures

      These fractures result from plantarflexion and longitudinal compression along the axis of the forefoot. Comminution is common; one must also suspect navicular injury and talonavicular disruption.

    • Nondisplaced fractures: Patients should be placed in a short leg cast molded to preserve the longitudinal arch and should be partial weight bearing for 6 weeks. An arch support is worn in the shoe to splint the talonavicular articulation for 3 to 6 months.

    • Displaced fractures: ORIF is indicated, with primary excision of small fragments through an anterior or anteromedial approach. Headless screws or buried implants will be needed for this intra-articular fracture.

      COMPLICATIONS

    • Infection: This may be unavoidable because of the need to operate through a compromised soft tissue envelope.

    • Osteonecrosis: The rate of osteonecrosis is related to initial fracture displacement:

      Hawkins I: 0% to 50%

      Hawkins II: 20% to 50%

      Hawkins III: 50% to 100%

      Hawkins IV: Up to 100%

    • Posttraumatic arthritis: This occurs in 40% to 90% of cases, typically related to articular incongruity or chondral injury at the time of fracture. This may be evident in either the ankle or subtalar joints. The rates of arthritis in the subtalar joint, ankle joint, or both joints are 50%, 30%, and 25%, respectively.

    • Delayed union and nonunion: Delayed union (>6 months) may occur in up to 15% of cases. It may be treated by repeat fixation and bone grafting or placement of some type of osteoinductive material.

    • Malunion: Commonly varus (following talar neck fractures), this is related to initial fracture reduction associated with dorsomedial comminution. Malunion results in subtalar stiffness and

      excessive weight bearing on the lateral side of the foot; malunion is frequently painful.

    • Skin slough: This may occur secondary to prolonged dislocation, with pressure necrosis on the overlying soft tissues. When severe, it may result in pressure erosion, compromising soft tissue integrity and resulting in possible infection.

    • Interposition of long flexor tendons: This may prevent adequate closed reduction and necessitate ORIF.

    • Foot compartment syndrome: Rare. However, pain on passive extension of the toes must raise clinical suspicion of possible evolving or present compartment syndrome of the foot, particularly in a patient in whom symptoms are out of proportion to the apparent injury. Urgent fasciotomy is controversial. Some authors feel that the sequelae of foot compartment syndrome (claw toes) are less morbid than the fasciotomies required to release all foot compartments.

      Subtalar Dislocation

    • Subtalar dislocation, also known as peritalar dislocation, refers to the simultaneous dislocation of the distal articulations of the talus at the talocalcaneal and talonavicular joints.

    • It most commonly occurs in young men.

    • Inversion of the foot results in a medial subtalar dislocation, whereas eversion produces a lateral subtalar dislocation.

      • Up to 85% of dislocations are medial.

      • Lateral dislocations are often associated with a higher energy mechanism and a worse long-term prognosis compared with medial subtalar dislocations.

    • All subtalar dislocations require gentle and timely reduction.

    • Reduction involves sufficient analgesia with knee flexion and longitudinal foot traction. Accentuation of the deformity is often necessary to “unlock” the calcaneus. Once the calcaneus is unlocked, reversal of the deformity can be applied. Reduction is usually accompanied by a satisfying clunk.

    • In most cases, a subtalar dislocation is stable following closed reduction.

    • CT scan is useful after closed reduction to determine whether associated fractures are present and to detect possible talocalcaneal subluxation.

    • A variety of bone and soft tissue structures may become entrapped, resulting in a block to closed reduction. With medial dislocations, the talar head can become trapped by the capsule of the talonavicular joint, the extensor retinaculum or extensor tendons, or the extensor digitorum brevis muscle. With lateral dislocations, the posterior tibial tendon when entrapped may present a substantial barrier to open reduction (see Fig. 40.5).

    • Open reduction, when necessary, is usually performed through a longitudinal anteromedial incision for medial dislocations and through a sustentaculum tali approach for lateral dislocations.

    • Following a short period of immobilization, physical therapy is instituted to regain subtalar and midtarsal mobility.

      Total Dislocation of the Talus

    • Total dislocation of the talus is a rare injury, resulting from an extension of the forces causing a subtalar dislocation.

    • Most injuries are open (extrusion) (Fig.40.7).

       

       

       

    • Initial treatment is directed to the soft tissues.

    • In general, open reduction of the completely dislocated talus is recommended.

    • Results may be complicated by infection, osteonecrosis, and posttraumatic arthritis.