The calcaneus is the most frequently fractured tarsal bone. Calcaneus fractures account for 60% of all tarsal fractures but only about 2% of all fractures.
Calcaneus fractures may occur as a result of falls from heights or from twisting injuries or through a pathologic process such as osteoporosis, cysts, and tumors. About 60% of calcaneal fractures result from falling from a height. Os calcis fractures can be broadly classified into intra-articular and extra-articular types.
Calcaneus fractures resulting from falls onto the heels from heights are bilateral in 5-9% of patients; they are associated with compression fractures of the lumbar and/or dorsal spine in 10%. These fractures are complicated by a compartment syndrome in 10% of cases, with half of these involving development of clawing of the lesser toes or other chronic problems, such as stiffness and neurovascular dysfunction.
Calcaneus fractures are divided into intra-articular and extra-articular fractures based on involvement of the subtalar joint. In adults, about 75% of calcaneal fractures are intra-articular.
According to a study based on data from the American College of Surgeons National Trauma Data Bank (NTDB), of 14,516 patients with calcaneous fractures, concurrent injuries were present in 11,137, with associated lower extremity fractures being present in 61% (the most common of which were other foot and ankle fractures). There were spinal fractures (lumbar spine being the most common) in 23%. In addition, 18% had concurrent head injuries and 15% concurrent thoracic organ injuries.
Soft tissue injuries include subluxation or dislocation of the peroneal tendons from the fibular sulcus, entrapment of neurovascular bundle, and interposition of the flexure hallucis longus tendon between bone fragments from sustentaculum tali.
The calcaneus functions as a lever arm for the gastrocsoleus complex, providing a foundation or vertical support for one’s body weight and providing support for and maintaining the lateral column of the foot. Any fracture that impairs one of these functions substantially affects the person’s gait if not restored.
These fractures may remain undiagnosed clinically, as there may be no obvious deformity. Often, a history of the patient falling from a height and landing on his or her heels is helpful, but radiographic examination is essential to confirm fracture. Management of these fractures depends on the type of fracture. Therefore, imaging plays a primary role.
The Sanders classfiication system is the one most widely used. Other classifications exist, such as Essex-Lopresti, AO-ICI, Zwipp, and Crosby.
The management of calcaneus fractures and their associated soft tissue injuries are controversial. Open reduction and stable internal fixation with a lateral plate and without joint transfixation are established as standard therapy for displaced intra-articular fractures.
Good to excellent results are achieved in two thirds to three quarters of all cases, as shown in large clinical series. Anatomic reduction of joint congruity and the overall shape of the calcaneus are important prognostic factors. The quality of joint reduction should be proved intraoperatively with the acquisition of Broden views, high-resolution fluoroscopy, or open subtalar arthroscopy.
CT imaging is the investigation of choice in calcaneus fractures.
Coronal and axial views are generally taken. CT best defines the relationship of bone fragments.
MRI is increasingly being used to characterize ankle sprains, occult fractures, bone bruises, growth-plate injuries, and ligamentous/tendon injuries. MRI is the criterion standard for identifying peroneal tendon injury. This injury is identified by the high signal intensity in tendon on T2-weighted axial views.
Tenography is useful for assessing large lesions of the tendons.
Scintigraphy may be useful in occult fractures and in the differential diagnosis of pathologic fractures. Pathologic features may become apparent on scintigraphy a few weeks before they become apparent on plain radiographs because the increased osteoblastic activity associated with stress fractures is more easily detected with scintigraphy.
Physical examination usually is required to assess the integrity of tendons and ligaments. Approximately 75% of calcaneus fractures are intra-articular and involve the subtalar articular surface. Because these injuries are associated with a poor prognosis, it is important to identify patients with these fractures.
Conventional radiographs provide a benchmark for the diagnosis of fractures around the ankle in general, and they usually suffice for the diagnosis of the osseous component of the injury
; however, in most cases, supplemental imaging is needed to define characteristics fully, owing to the complex anatomy of this region. Comminuted fractures with fragment displacement of the calcaneus are common, and the relationship of the multiple fragments is difficult to appreciate on conventional radiographs. See Radiograph.
See the images of calcaneus fractures below.
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.
Calcaneus, fractures. CT scan.
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. Technetium-99m diphosphonate bone scan depicts a stress fracture of the calcaneus, which was not apparent on plain radiographs.
Limitations of techniques
Conventional radiographs may be negative in cases involving subtle fractures, particularly in cases involving stress fractures. Comminuted fractures and displacement are common in fractures of the calcaneus, and the relationship of the multiple fragments is difficult to appreciate on conventional radiographs.
CT is the modality of choice, especially in complex fracture patterns, although it is expensive and it imparts a relatively high dose of radiation; it should be used sparingly in young patients or in pregnant patients. It is noteworthy that CT tends to be somewhat overutilized in the United States; this tendency has increased in recent years.
MRI is expensive and may cause problems in patients with claustrophobia. MRI is sensitive in the immediate documentation of stress changes in osseous structures. MRI is well known to show even minor stress changes (eg, after a marathon) that occur before the actual stress fracture.
A severe bone contusion is associated with multiple microfractures, whereas a stress fracture involves a linear component; the distinction between the 2 diagnoses may seem arbitrary.
In the absence of a linear component, it may be difficult to distinguish an underlying severe stress reaction associated with a bone contusion from a stress fracture on MRI. Bone contusion associated with a stress fracture may be difficult to distinguish from red marrow. With MRI, it may be difficult to detect small intra-articular fragments—a fact that likely limits the use of MRI on a routine basis.
Scintigraphy is sensitive in imaging bone trauma but lacks the specificity and the spatial resolution that MRI provides. A physiologic periosteal reaction, bone tumor, avascular necrosis, plantar fasciitis, or bone spur can cause false-positive findings.