eMedicine Specialties > Radiology > Musculoskeletal
Calcaneus, Fractures: Imaging
Updated: Jul 22, 2008
Radiography
Findings
Calcaneus, fractures. Axial (Harris) views of both calcanei show a left calcaneal fracture. Bilateral calcaneal fractures are seen in 5-9%.
Calcaneus, fractures. Avulsion fracture. Rowe type II beak/avulsion fracture of the Achilles tendon. Rowe classifies fractures into 5 groups. Groups I–III do not involve the subtalar joint. Groups IV and V involve the subtalar joint and represented almost 60% of the originally described series.
Calcaneus, fractures. Rowe type IV calcaneal fracture. This type represents almost a quarter of the fractures in the original series.
Calcaneus, fractures. Essex-Lopresti depression-type calcaneal fracture.
Calcaneus, fractures. Normal variants, complications, and differential diagnosis. Old calcaneal fracture. Dorsoposterior (DP) and lateral views of the foot demonstrate an old Essex-Lopresti depressed-type calcaneal fracture. The patient now has degenerative change at the subtalar joint. Essex-Lopresti describes 2 fracture types involving the subtalar joint. The depression type and the tongue type. Note flattening of the Bohler angle.
Calcaneus, fractures. Normal variants, complications, and differential diagnosis. This normal variant—an unfused secondary ossification center—must not be mistaken for a calcaneal fracture.
Calcaneus, fractures. Normal variants, complications, and differential diagnosis. Calcaneal cysts are normal variants and should not be confused with pathology.
Conventional radiography
Conventional radiographic examination consists of axial and lateral views of the calcaneus and an anteroposterior (AP) view of the foot. However, because of the complexity of the anatomy, multiple radiographic views are often necessary. Giannestras and Sammarco suggested that multiple views be used, including the oblique view.11 Radiographs of the dorsal and lumbar spine are also often indicated, because an associated fracture is seen in a vertebral body in 10% of all patients. Further fractures of the tibia and fibula are seen in 9% of patients. Calcaneus fractures are bilateral in 5% of patients (see Images above and Images 9-24, 73, 76-84 in Multimedia).
Lateral view and the Bohler angle
The lateral view is the primary projection on which a diagnosis of a fracture is made, although some subtle fractures may be missed when reliance is placed on a lateral view only. Lateral views show the Bohler tuber angle and the crucial angle of Gissane clearly.
Lorenz Bohler described the tuber-joint angle (the so-called Bohler angle). In determining the Bohler angle, a line is drawn between the posterior superior aspect of the calcaneus and the highest point of the posterior subtalar articular surface; a second line, which intersects the first, is drawn from the highest point of the anterior process to the posterior margin of the subtalar surface. The angle that results from their intersection measures 20-40° (see Image below and Image 8 in Multimedia).
Calcaneus, fractures. The Bohler angle. In determining the Bohler angle, a line is drawn between the posterior superior aspect of the calcaneus and the highest point of the posterior subtalar articular surface; a second line, which intersects the first, is drawn from the highest point of the anterior process to the posterior margin of the subtalar surface. The angle that results from their intersection measures 20-40°. If the angle is reduced, a calcaneal fracture is present; however, a normal angle does not exclude a calcaneal fracture.
In intra-articular fractures of the calcaneus, the subtalar joint is depressed, causing a decrease in the Bohler angle. The Bohler angle may also be decreased in some calcaneus fractures that do not involve the subtalar joint. A flat Bohler angle is associated with intra-articular fractures; in such cases, the prognosis is poorer than it is in cases in which the angle is maintained.
Axial view
The axial view is used to evaluate the subtalar joint and the width of the calcaneus. Normally, in an adult, the calcaneus measures 30-35 mm in width. A fracture may cause the calcaneus to increase in width; the expanded, fractured calcaneus may then impinge upon the fibula, causing entrapment of the peroneal tendons.
AP view
The AP view is essential for evaluating the calcaneocuboid joint. This view also demonstrates avulsion fractures of the anterior lateral aspect of the calcaneus.
Oblique views
Various oblique views have been advocated. These are valuable in demonstrating fracture extending into the joint and loss of parallelism of articular surfaces.
Oblique views (ie, the Broden view) can define incongruity of the subtalar joint. These images are obtained by internally rotating the foot 45°, with the heel resting on the radiographic plate; the beam is directed cephalad in angles varying from 10° to 40°.
Peroneal tenography
Peroneal tenography involves injecting iodinated contrast material into the peroneal tendon sheaths under fluoroscopic guidance. The contrast material then descends behind the lateral malleolus.
Peroneal tenography helps in diagnosing abnormal conditions after calcaneus fractures or other trauma, such as peroneal tendon dislocation resulting from skiing accidents. Compression of the tendon sheath associated with partial or complete obstruction of the flow of contrast and tendon displacement may be depicted. Aspiration of the injected contrast material following use of a local anesthetic may relieve pain and help determine the source of the pain.
Degree of Confidence
Conventional radiography is the primary imaging modality in cases of suspected ankle fractures. Radiography may be the only modality required, though it is not always capable of depicting the relationship of bone fragments to the joint and to each other.
In complex fractures, CT scanning is used in addition to conventional radiography.
Conventional radiography is inexpensive and is universally available. It exposes the patient to a modest radiation dose. Study results are reproducible, and the images are easy to interpret.
Measuring the various angles not only enables reliable diagnosis but also helps in determining the ultimate prognosis.
False Positives/Negatives
Various anatomic variants in the calcaneus may mimic fractures.
Os subcalcis is a calcaneal apophysis seen in the adolescent on the posteroinferior plantar surface of the calcaneus, which is normally not visible on lateral radiographs.
The unfused secondary ossification center for calcaneal tuberosity may produce a simulated fracture.
Failed union of a portion of calcaneal apophysis in an adult may superficially mimic a fracture.
Calcaneus secundarius is an accessory ossicle attached to the posterosuperior aspect of the calcaneus.
The sustentaculum tali can produce a simulated fracture on the superior margin on lateral views.
Prominent trabeculation can simulate a fracture on plain radiographs and CT scans.
False-negative radiographic findings may occur when images show subtle fracture lines. These fractures may be confirmed with scintigraphy and/or MRI.
Computed Tomography
Findings
Calcaneus, fractures. Axial, coronal, and sagittal CT images in Images 19-28 in Multimedia demonstrate a comminuted, Saunders type IV calcaneal fracture.
Calcaneus, fractures. Saunders type IV calcaneal fracture.
Calcaneus, fractures. Saunders type IV calcaneal fracture.
Calcaneus, fractures. CT scan.
Calcaneus, fractures. CT scan.
Calcaneus, fractures. CT scan.
Calcaneus, fractures. CT scan.
CT is the modality of choice for calcaneus fractures. Coronal and axial views are generally obtained. Involvement of the subtalar joint can be clearly appreciated, and CT enables optimal evaluation of calcaneal widening (see Images above and Images 25-72 in Multimedia).12
Classification system
In 1992, Sanders developed a classification system based on coronal and axial CT scans of the calcaneus. This classification is the one used most frequently today in treatment decision making and reporting of results. This system defines 4 types of calcaneus fractures:
- Type 1 consists of nondisplaced fractures.
- Type 2 consists of fractures that are split into 2 parts.
- Type 3 are depressed fractures and/or fractures that are split into 3 parts.
- Type 4 fractures are comminuted fractures.
Patients with type 1 injuries do well with nonoperative treatment; patients with injuries of types 2 and 3 may be treated effectively with open reduction and internal fixation; and type 4 injuries defy operative reduction.13
Stress fractures
CT is occasionally performed to diagnose stress fractures. CT is capable of demonstrating disruption of the bony cortex and periostitis in most individuals. Its sensitivity is higher than that of plain radiography. However, compared with MRI or bone scanning, CT has low sensitivity for stress reactions and fractures; this leads to a high rate of false-negative results.
Soft tissue abnormalities
Bradley and Davies studied soft tissue abnormalities occurring after calcaneus fractures.14 CT scans of 50 acute calcaneus fractures were compared with scans of 77 fractures in which the date of injury preceded the CT study by 6 months or more. The investigators found that 42 of the fractures (84%) in the acute group and 55 in the chronic group (71%) were classified as intra-articular; these fractures formed the basis of the study.
The alterations in the position of the peroneal tendons in the 2 groups were similar, with a 5% or smaller difference in each category. In the acute group, the peroneal tendons were of normal location in 40.4% of cases; in 11.9% of cases, the peroneal tendons were entrapped by bone; subluxation was evident in 33.3% of cases; and dislocations were present in 14.2% of cases. Structural abnormalities of the peroneal tendons and surrounding soft tissues were identified in 52.4% of patients in the acute group and in 61.1% of patients in the chronic group.
The incidence of partial rupture of the peroneal tendons in the chronic group was approximately one third that in the acute group, but the low incidence of complete tendon rupture remained unchanged.
The inference from these observations is that, in most cases, partial peroneal tendon rupture is reversible, whereas complete rupture is not. Seven fractures were common to both series; from this limited group, the identification of hemorrhage around the peroneal tendons in the acute phase was shown not to be related to the subsequent development of chronic stenosing tenosynovitis. Various abnormalities of the medial tendons of the hindfoot were identified in 17% of patients in the acute group and in 18% of patients in the chronic group.
The authors found that, after calcaneus fractures, CT in both the immediate postfracture period and in the late phase may be used to detect and classify soft tissue changes.
Degree of Confidence
CT is the modality of choice for calcaneus fractures. Confidence in the diagnosis made on the basis of a positive CT scan of the affected area is high.
Furey evaluated 30 calcaneus fractures to assess the degree of interobserver variability by using the Sanders classification system.15 Thirty CT scans of calcaneus fractures taken over a 5-year period in 2 tertiary care centers were chosen randomly. Three orthopedic surgeons and 1 senior orthopedic resident reviewed the scans and classified the fractures.
The results were analyzed by using a weighted kappa test that included the subcategories. The weighted kappa value was 0.56, with a 95% confidence interval (CI) of 0.45-0.67. The subcategories of the classification were further combined, and a second analysis was performed to assess agreement between general classes. The weighted kappa value was 0.48, with a 95% CI of 0.37-0.59. The authors concluded that the Sanders classification system achieved moderate agreement among users and was thus useful.
False Positives/Negatives
In cases of stress fractures, a well-defined cortical discontinuity is suggestive of a fracture. However, the rate of false-negative results is high. Therefore, in the appropriate clinical setting, CT may be skipped, and either MRI or bone scanning may be performed.
Repeat CT scanning is not an attractive alternative, though it may result in the correct diagnosis because of interval development of necrosis. Prominent trabeculation can simulate a fracture on CT.
Magnetic Resonance Imaging
Findings
MRI is generally not used in the diagnosis of calcaneus fractures. However, MRI is often useful in patients with suspected stress fractures, particularly those with severe osteoporosis in whom skeletal scintigraphy may produce false-negative findings as a result of generalized poor uptake of tracer (see Images below and Images 74, 85 in Multimedia).
Calcaneus, fractures. Short-tau inversion recovery (STIR) sagittal MRI demonstrates high signal intensity at the anterior and middle processes. This represents bony edema secondary to a fracture, which is not appreciated on the plain radiographs.
Calcaneus, fractures. Normal variants, complications, and differential diagnosis. T2-weighted sagittal MRIs demonstrate fibrosis of the peroneal tendon sheath following a past calcaneus fracture, which is a recognized complication of calcaneal fractures.
MRI is highly sensitive for the detection of bone marrow changes. Anatomic resolution is better with MRI than with radionuclide imaging. Bone contusions are also well depicted on MRI.
On MRI, stress fractures typically appear as areas of low signal intensity on T1- and T2-weighted images. They often appear as a band of low signal intensity that arises from the cortex of the bone and extends perpendicular to the surface of the bone. If imaging is performed within 4 weeks of the injury, an area of high signal intensity often can be observed on T2-weighted images; this represents associated edema or hemorrhage.
Fat-suppressed sequences are sensitive to bone marrow edema, which accompanies bone bruises and stress fractures.
MRI also has a place in the investigation of ligamentous and tendon injury in association with calcaneus fractures.
Degree of Confidence
Confidence in the imaging findings is usually high in a patient who is believed on clinical grounds to have a stress fracture. MRI findings may be positive within 24 hours of the onset of symptoms. Stress fractures may take longer to become evident on radionuclide bone scans, particularly in patients with osteoporosis. MRI may be used to evaluate tendon and ligamentous injuries noninvasively.
False Positives/Negatives
Many pathologies can cause bone marrow edema; in patients with a history of trauma, the presence of edema may lead to an incorrect diagnosis of fracture. Pathologies associated with edema include osteomyelitis and neoplasm. The linear hypointensity is usually helpful in identifying stress fractures.
Ultrasonography
Findings
Ultrasonography of the foot region is indicated for the evaluation of the presence of foreign bodies. It is also indicated for the evaluation of dislocation of the peroneal tendons; lesions in the flexor and extensor tendons; and osseous capsular and ligamentous avulsions.
Signs of pathology that are apparent on sonograms of soft tissue include articular effusion, fluid conglomeration, ossification, and the development of vascular lesions.
Ultrasonography is useful for detecting all types of peroneal lesions. In particular, real-time ultrasonography may be performed to assess dynamic stability.16,17,18
Degree of Confidence
Ultrasonography is operator and institution dependent. Musculoskeletal ultrasonography is not universally available.
False Positives/Negatives
Sonograms of the hindfoot and ankle commonly depict articular, bursal, and tendon-sheath fluid in asymptomatic volunteers. The presence of fluid in these locations, even when unilateral or asymmetric, does not necessarily imply underlying abnormality.
Nuclear Imaging
Findings
Bone scintigraphy is typically utilized in cases in which radiographic and CT findings are negative for suspected fractures (see Image below and Image 75 in Multimedia).
Calcaneus, fractures. Technetium-99m diphosphonate bone scan depicts a stress fracture of the calcaneus, which was not apparent on plain radiographs.
Stress fractures are associated with hyperemia in the first 2 phases of the 3-phase bone scan. The injury is manifested by increased radionuclide uptake at the fracture site. In adults, detection of hyperemia is straightforward, but problems may arise in children, because in children, the uptake of radionuclide is often increased around the epiphyses; contralateral images are often needed for comparison.
The first phase demonstrates increased flow of blood in the arterial phase, and the second phase demonstrates tissue hyperemia. The third phase demonstrates increased osteoblastic activity in response to the stress fracture.19
Degree of Confidence
Stress fractures are relatively easily diagnosed with skeletal scintigraphy. The degree of confidence is high, because the diagnosis of stress fracture may be reliably excluded when bone scans are normal.
False Positives/Negatives
Osteomyelitis, calcaneonavicular bars, osteoarthritis, erosive arthritis, tumors, and pathologic fractures may have an appearance similar to that of fractures on scintigraphy.
In patients with multiple stress fractures, an accurate determination of the age of the fracture is not always possible.
In children, epiphyseal uptake may mask increased radionuclide uptake caused by osteoblastic activity.
In patients with severe osteoporosis, the level of tracer uptake by the bone may be too low, and false-negative results may be produced.
More on Calcaneus, Fractures |
| Overview: Calcaneus, Fractures |
 Imaging: Calcaneus, Fractures |
| Follow-up: Calcaneus, Fractures |
| Multimedia: Calcaneus, Fractures |
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Further Reading
Keywords
calcaneus fracture, calcaneal fracture, tarsal fracture, foot fracture, heel fracture, talus fracture, calcaneum fracture, os-calcis fracture, os calcis fracture, Lover fracture, Lover's fracture
