Radiography
Talar body fracture, anteroposterior radiograph. There is a sagittally oriented fracture through the body of the talus and disruption of the tibiotalar and subtalar joints. The injury was from a motor vehicle accident.
Talar body fracture, lateral radiograph (same patient as in Images above and below). There is a significant degree of comminution of the talar fracture, with comminuted fracture lines extending into the posterior and lateral processes of the talus.
Talar body fracture (same patient as in Images above). Coronal computed tomography (CT) scan through the posterior subtalar joint. There is wide separation of the talar fragments. The degree of the subtalar joint dislocation and the marked comminution of the medial portion of the talus are evident.
Talar body fracture, anteroposterior radiograph. This patient had a fall resulting in a pilon fracture of the tibia, a sagittally oriented fracture of the body of the talus, and a central compressive fracture of the calcaneus.
Talar body fracture, lateral radiograph (same patient as in Image above). The fracture of the talus, existing purely in the sagittal plane, is not visible on the lateral radiograph. However, the central compressive calcaneal fracture is well visualized.
Findings
Talar Body Fractures
- Mechanism of injury - Axial load or shear
- Associated injuries - Calcaneus, tibia, talar neck
- Radiographic assessment - AP, mortise (15° internal oblique), lateral, and Broden views (It is important to quantify the degree of articular involvement and displacement.)
- Displacement of articular facet of posterior subtalar joint - Broden view, CT scan
- Advanced imaging - CT scan in coronal plane (defined as coronal relative to the tibia) to assess comminution, articular disruption, and associated fractures
- Treatment - Open reduction and internal fixation (ORIF)7
- Complication - High incidence of subtalar arthritis
Osteochondral fractures of the talar dome
The terms osteochondral fracture, transchondral fracture, and osteochondritis dissecans (OCD) are used interchangeably in the region. However, the first 2 terms are preferable because the fracture is caused by a single episode of trauma. These fractures are most commonly classified by the system devised by Berndt and Harty, which has been modified to include MRI findings.
Table 1. Classification of Osteochondral Fractures of the Talar Dome
Open table in new window
Table
| Stage | Radiographs | MRI T2WI * | Arthroscopy |
| 1 | Normal | Diffuse, high-signal intensity | Normal, or softening of cartilage |
| 2 | Semicircular lucent line | Semicircular, low-signal line | Break in cartilage; fragment, no displacement |
| 2a** | Subcortical round lucency | High-signal fluid within fragment | |
| 3 | Same as 2 | High-signal fluid surrounds fragment | Displaceable fragment |
| 4 | Loose body | Defect talar dome, possibly loose body | Defect plus loose body |
| Stage | Radiographs | MRI T2WI * | Arthroscopy |
| 1 | Normal | Diffuse, high-signal intensity | Normal, or softening of cartilage |
| 2 | Semicircular lucent line | Semicircular, low-signal line | Break in cartilage; fragment, no displacement |
| 2a** | Subcortical round lucency | High-signal fluid within fragment | |
| 3 | Same as 2 | High-signal fluid surrounds fragment | Displaceable fragment |
| 4 | Loose body | Defect talar dome, possibly loose body | Defect plus loose body |
*T2WI= T2-weighted imaging
**Stage 2a is a variant in which a cyst forms in the subcortical bone
- Mechanism of injury - Inversion injury of the ankle. A lateral osteochondral fracture results from shearing of a small fragment of cartilage and bone; compression of the talar dome causes medial fracture.
- Associated injuries - These include tears of the lateral collateral ligament of the ankle.
- Location - Injury occurs in the lateral or medial aspect of the talar dome.
- Radiographic assessment - AP and mortise views. Sensitivity is increased if the mortise view is performed in plantarflexion and dorsiflexion.
- Advanced imaging - MRI to evaluate cartilage and the presence of a loose fragment. CT arthrography also can be used.8,9
- Classification - The most commonly used classification is the Berndt and Harty system (containing later modifications to incorporate MRI findings).
- Treatment - Drilling may be performed in the early stages to promote healing.9,10 Large fragments may be reattached or removed.
- Complications - Injury may lead to ankle arthritis and loose bodies.
Posterior process fractures
- Terminology - Occasionally known as Shepherd's fracture
- Mechanism of injury - Hyperplantarflexion or avulsion of the posterior talofibular ligament; also, stress fracture in athletes and (especially) ballet dancers
- Associated injuries - Talar body fracture, injury of FHL tendon (see Anatomy)
- Radiographic assessment - Seen on lateral radiograph; must differentiate this injury from an os trigonum (a nonunited, accessory center of ossification of the posterior process)
- Advanced imaging - Not needed (although posterior process fractures are readily seen on axial CT scans)
- Treatment - Conservative; removal of fragment if there is painful nonunion
- Complications - May result in chronic pain and nonunion
Lateral process fractures
- Terminology - Also known as snowboarder's fracture11
- Mechanism of injury - Eversion injury. The lateral process is caught between the lateral malleolus of the fibula above it and the calcaneus below it. The injury may also be caused by inversion and dorsiflexion. It is increasing in incidence.
- Radiographic assessment - Mortise or Broden view. The fracture is vertically oriented, and the fragment varies in composition from a small flake of cortical bone to most of the lateral process. The degree of involvement of the subtalar joint should be assessed. The fracture may be radiographically occult.
- Advanced imaging - MRI or CT scanning are useful for occult fractures. These modalities can be used to assess the subtalar joint and evaluate for nonunion.12
- Treatment - Nonarticular chip fractures are treated conservatively. Articular fragments may be excised or treated with ORIF. There is a high incidence of nonunion and osteoarthritis of the subtalar joint.
Talar Neck Fractures
The classification system created by Hawkins, as modified by Canale and Kelly, should be used.1
Table 2. Hawkins Classification of Talar Neck Fractures
Open table in new window
Table
| Radiographic findings | Risk of AVN | |
| Type I | Nondisplaced fracture line | 0-13% |
| Type II | Displaced fracture, subluxation or dislocation of subtalar joint | 20-50% |
| Type III | Displaced fracture, dislocation of subtalar and tibiotalar joints | 69-100% |
| Type IV | Displaced fracture, disruption of talonavicular joint | High |
| Radiographic findings | Risk of AVN | |
| Type I | Nondisplaced fracture line | 0-13% |
| Type II | Displaced fracture, subluxation or dislocation of subtalar joint | 20-50% |
| Type III | Displaced fracture, dislocation of subtalar and tibiotalar joints | 69-100% |
| Type IV | Displaced fracture, disruption of talonavicular joint | High |
- Three mechanisms of injury
- The most common mechanism is a dorsally directed force on a braced foot, such as that encountered in head-on motor vehicle accidents. Talar neck fractures were once known as "aviator's astragalus," because World War I pilots suffered the fracture during plane crashes in which their foot was dorsiflexed on the floorboard of the plane.
- Another mechanism is inversion of the ankle, with impingement of the talar neck against the medial malleolus.
- A third mechanism is a direct blow to the dorsum of the foot.
- Radiographic assessment
- A lateral radiograph of the foot should be employed. The injury is difficult to see on AP of the foot unless displacement has occurred. An angled view was described by Canale and Kelly but is difficult to perform.
- Follow-up radiographs should be evaluated for the presence of a Hawkins sign, a subcortical lucency that is caused by hyperemia and consequent bone resorption. If a Hawkins sign appears, this indicates that AVN will not develop.
- Advanced imaging - CT scanning can be used to confirm presence of a subtle fracture and to evaluate reduction.
- Complications - Since most of the blood supply to the talar body comes by way of the talar neck, fractures of the neck place the patient at risk of developing AVN.
- Treatment - ORIF is employed, with attention to precise anatomic reduction, especially of the articular surfaces.13
- Complications - AVN and subtalar arthritis can occur.
Talar Head Fractures
- Mechanism of injury - Axial compression; can also occur secondary to talonavicular joint dislocation
- Associated injuries - Other foot fractures, dislocation of the talonavicular joint
- Radiographic assessment - AP and lateral radiographs of the foot (The fractures are usually obliquely oriented.)
- Advanced imaging - Not routinely indicated; may be useful to assess the talonavicular joint
- Treatment - Reduction of joint, occasionally ORIF
Degree of Confidence
Several fractures of the talus can be difficult to detect radiographically, including osteochondral fracture, lateral process fracture, and nondisplaced talar neck fracture. Whenever trauma radiographs of the foot or ankle are obtained, a high degree of attention should be paid to the areas where these subtle fractures occur. If doubt exists as to the presence of a fracture, MRI is the test of choice. CT scanning also shows occult fractures, but unlike MRI, it cannot differentiate between stage II and stage III osteochondral fractures.
False Positives/Negatives
The os trigonum, an accessory center of ossification for the posterior process of the talus, must be differentiated from a posterior process fracture. The following criteria are used:
- A fracture line is sharply angled relative to the remainder of the bone, while an accessory center of ossification tends to be shaped like a smooth pebble.
- The pieces of a fractured bone fit together precisely, like 2 pieces of a jigsaw puzzle, while an accessory ossicle usually does not fit tightly with the parent bone. CT scanning may occasionally be necessary to make this differentiation.
- An acute fracture line will not have a sclerotic margin, while an accessory ossicle is surrounded by dense, cortical bone.
Computed Tomography
Fractures of the lateral and posterior processes of the talus, axial computed tomography (CT) scan. These fractures were associated with a talar body fracture.
Axial computed tomography (CT) scan showing an osteochondral fracture lesion. On an axial image, the area of the osteochondral fracture is circular, and the density within it is heterogeneous.
Findings
CT scan findings are integrated with plain radiographic findings for each type of fracture (see Radiograph/Findings).14,15
Magnetic Resonance Imaging
Patient OA. Lateral process fracture; sagittal, fast spin-echo, inversion recovery magnetic resonance image. The tip of the lateral process shows high signal intensity consistent with edema. The magnetic resonance imaging (MRI) scan was performed several months after the fracture, and the fracture line has partially healed.
Patient BM. Coronal, T1-weighted magnetic resonance image of a stage 3 osteochondral fracture. A thin cortical fragment is seen; it is separated from the concave bony defect beneath it by intermediate–signal-intensity material. A stage 3 lesion is confirmed on T2-weighted and fast spin-echo, inversion recovery images.
Patient BM. Coronal, fast spin-echo, T2-weighted magnetic resonance image with fat saturation, showing a stage 3 osteochondral fracture of the talar dome. A tiny cartilage defect is seen in the talar dome, showing the higher signal intensity of fluid compared to the intermediate signal intensity of cartilage. Fluid is also seen between the osteochondral fragment and adjacent bone, indicating that the fragment is detached but nondisplaced.
Patient BM. Sagittal, fast spin-echo, inversion recovery magnetic resonance image showing a stage 3 osteochondral fracture. On a fast spin-echo, inversion recovery image, the high–signal-intensity line around the osteochondral fragment is better seen.
Findings
MRI findings are discussed above with plain radiographic findings (see Radiograph/Findings).16
Nuclear Imaging
Patient OA. Lateral process of the talus fracture. Lateral view of technetium-99m (99mTc) bone scan at 5 hours following injection. The fracture site shows a markedly increased uptake of radionuclide.
Findings
Nuclear medicine currently has little role in the evaluation of talus fractures. MRI has equal sensitivity to nuclear medicine imaging techniques but with much greater specificity. However, a bone scan performed to evaluate chronic pain will show uptake corresponding to the fracture site.
More on Talus, Fractures |
| Overview: Talus, Fractures |
 Imaging: Talus, Fractures |
| Follow-up: Talus, Fractures |
| Multimedia: Talus, Fractures |
| References |
| Further Reading |
| « Previous Page | Next Page » |
References
Hawkins LG. Fractures of the neck of the talus. J Bone Joint Surg Am. Jul 1970;52(5):991-1002. [Medline].
Hawkins LG. Fracture of the lateral process of the talus. J Bone Joint Surg Am. Sep 1965;47:1170-5. [Medline].
Tezval M, Dumont C, Stürmer KM. Prognostic reliability of the Hawkins sign in fractures of the talus. J Orthop Trauma. Sep 2007;21(8):538-43. [Medline].
Chan G, Sanders DW, Yuan X, Jenkinson RJ, Willits K. Clinical accuracy of imaging techniques for talar neck malunion. J Orthop Trauma. Jul 2008;22(6):415-8. [Medline].
Haverstock BD. Foot and ankle imaging in the athlete. Clin Podiatr Med Surg. Apr 2008;25(2):249-62, vi-vii. [Medline].
McCarthy CL, Wilson DJ, Coltman TP. Anterolateral ankle impingement: findings and diagnostic accuracy with ultrasound imaging. Skeletal Radiol. Mar 2008;37(3):209-16. [Medline].
Thordarson DB, Kaku SK. Results of step-cut medial malleolar osteotomy. Foot Ankle Int. Dec 2006;27(12):1020-3. [Medline].
De Smet AA, Fisher DR, Burnstein MI, et al. Value of MR imaging in staging osteochondral lesions of the talus (osteochondritis dissecans): results in 14 patients. AJR Am J Roentgenol. Mar 1990;154(3):555-8. [Medline]. [Full Text].
Yulish BS, Mulopulos GP, Goodfellow DB. MR imaging of osteochondral lesions of talus. J Comput Assist Tomogr. Mar-Apr 1987;11(2):296-301. [Medline].
Loomer R, Fisher C, Lloyd-Smith R. Osteochondral lesions of the talus. Am J Sports Med. Jan-Feb 1993;21(1):13-9. [Medline].
von Knoch F, Reckord U, von Knoch M, et al. Fracture of the lateral process of the talus in snowboarders. J Bone Joint Surg Br. Jun 2007;89(6):772-7. [Medline].
Sanders TG, Ptaszek AJ, Morrison WB. Fracture of the lateral process of the talus: appearance at MR imaging and clinical significance. Skeletal Radiol. Apr 1999;28(4):236-9. [Medline].
Daniels TR, Smith JW. Talar neck fractures. Foot Ankle. May 1993;14(4):225-34. [Medline].
Ebraheim NA, Karkare N, Gehling DJ, et al. Use of a 30-degree external rotation view for posteromedial tubercle fractures of the talus. J Orthop Trauma. Sep 2007;21(8):579-82. [Medline].
He F, Huang H, Deng YM, Wang B, Zhang CQ, Zhao Z, et al. Application of spiral CT image 3D reconstruction in severe talar neck fracture. Chin J Traumatol. Feb 2007;10(1):18-22. [Medline].
Elias I, Zoga AC, Raikin SM, Peterson JR, Besser MP, Morrison WB, et al. Bone stress injury of the ankle in professional ballet dancers seen on MRI. BMC Musculoskelet Disord. Mar 28 2008;9:39. [Medline].
Berndt AL, Harty M. Transchondral fractures (osteochondritis dissecans) of the talus. J Bone Joint Surg Am. Sep 1959;41-A:988-1020. [Medline].
Cantrell MW, Tarquinio TA. Fracture of the lateral process of the talus. Orthopedics. Jan 2000;23(1):55-8. [Medline].
Crim JR, Cracchiolo A, Hall RL. Injuries of the foot. Imaging Foot Ankle. 1996;54-64.
Dipaola JD, Nelson DW, Colville MR. Characterizing osteochondral lesions by magnetic resonance imaging. Arthroscopy. 1991;7(1):101-4. [Medline].
Higgins TF, Baumgaertner MR. Diagnosis and treatment of fractures of the talus: a comprehensive review of the literature. Foot Ankle Int. Sep 1999;20(9):595-605. [Medline].
Further Reading
Related eMedicine topics
Osteochondral Lesions of the Talus
Congenital Vertical Talus
Ankle Fracture
Fracture, Foot
Dislocation, Ankle
Ankle Taping and Bracing
Ankle Arthroscopy
Clinical guidelines
Suspected Ankle Fractures
Chronic Ankle Pain
Keywords
talus fracture, astragalus fracture, talar neck fracture, talar body fracture, talar head fracture, osteochondral fracture of the talar dome, transchondral fracture of the talar dome, osteochondritis dissecans
