Hindfoot fractures include fractures to the calcaneus and talus. They are typically caused by high-impact forces like falls or motor vehicle accidents and commonly affect adult men. Hindfoot fractures present with pain, swelling, and bruising near the heel, as well as an inability to bear weight. Calcaneus fractures are the most common major fracture in the foot and make up the majority of hindfoot fractures. Talus fractures are less common; however, due to the complex anatomy, important function, and unique blood supply of the talus, these fractures are challenging to treat and can have devastating complications. Treatment of hindfoot fractures can be non-operative or operative depending on the severity and type of injury. Even with optimal management, hindfoot fractures are associated with a long recovery time and a high rate of complications.
Structure and function
The hindfoot begins at the talocrural (ankle) joint and ends at the calcaneocuboid joint. The bones of the hindfoot are the talus (lower bone of the ankle) and the calcaneus (heel bone). These are two of the seven bones that make up the tarsus along with the navicular, cuboid, and three cuneiform bones. The calcaneus and talus are the largest bones of the tarsus and also the most commonly fractured. The articulation between the talus and calcaneus is called the subtalar joint. The talus does not actually sit on top of the calcaneus, but rather toward the lateral-superior edge of the calcaneus.
Figure: Bony anatomy of the hindfoot and subtalar joint. Credit: http://en.wikipedia.org/wiki/Talus_bone#mediaviewer/File:Subtalar_Joint.PNG
The hindfoot functions to (1) bear and distribute weight to the foot while standing, and (2) permit complex foot movements in coordination with the ankle joint, especially inversion/eversion and axial rotation.
The talus has a complex architecture and blood supply. It serves to connect the bones of the lower leg to the bones of the foot functioning somewhat akin to a "ball-joint." The talus can be divided into three anatomical regions: the head, neck, and body. The head articulates with the navicular anteriorly (talonavicular joint) to permit abduction/adduction. The neck connects the body and head and is the most commonly fractured part of the talus. The vascular supply to the body is at the neck, so talar neck fractures increase the risk of avascular necrosis of the talar body. The talar body articulates with the calcaneus inferiorly (subtalar joint) at three articular surfaces. The space between these three articulations is known as the tarsal sinus. The talar dome lies on the superior aspect of the body and fits within the mortise formed by the tibia and fibula (ankle joint). These numerous articulations give the foot significant mobility across multiple planes of movement: plantarflexion/dorsiflexion at the talocrural joint, pronation/supination at the subtalar joint, and rotation and translation at the talonavicular joint.
Figure: Anatomical regions of the talus (body, neck, and head). Credit: http://www.footeducation.com/wp-content/uploads/2014/06/Figure-1-Talar-Anatomy-300x158.png
Given the number of articulations between the talus and surrounding bones, it is not surprising that 70% of the talus is covered by articular cartilage. Unlike the calcaneus which has many insertions and origins of muscles, the talus does not attach to any muscles.
The os trigonum is an accessory bone that develops posterior to the talus. It is present in 2.5-14% of people and is bilateral in 60% of these people. It can be mistaken on x-ray as a fractured bone.
Figure: Os trigonum (circled in red) on plain ankle x-ray. Credit: http://en.wikipedia.org/wiki/Talus_bone#mediaviewer/File:Os_trigonum_1.jpg
Despite its important position and function, the talus lacks a good vascular supply which makes it prone to delayed healing and avascular necrosis. Anastomoses between the posterior tibial artery, anterior tibial artery, and peroneal artery vascularize the talus. The posterior tibial gives off the artery of the tarsal canal that supplies the body, while the anterior tibial and peroneal give off the artery of the tarsal sinus to supply the head and neck. The posterior tibial also gives off a deltoid branch to the deltoid ligament that helps to supply the body. Anastomoses between the artery of the tarsal sinus and artery of the tarsal canal pass under the talar neck, forming the main “vascular sling” of the talus. Displaced fractures can disrupt the vascular sling, predisposing the talus to avascular necrosis.
The calcaneus articulates with the cuboid anteriorly but its major articulation is with the talus at three superior articular surfaces (anterior, middle, and posterior). The calcaneus can be anatomically divided into the anterior process, body, and the posterior calcaneal tuberosity. The Achilles tendon inserts at the calcaneal tuberosity on the posterior side of the calcaneus. The calcaneal tuberosity also has lateral and medial processes on its inferior side that are the origins of the abductor hallucis, abductor digiti minimi, and quadratus plantae. Near the medial talar articulation is the sustentaculum tali, the site of attachment for several ligamentous structures. The calcaneus is likened to a “hard-boiled egg” because its outer cortex is thin and surrounds the softer inner cancellous bone. If damaged, the outer cortex can collapse leading to severe comminution of the underlying cancellous bone.
Figure: Superior aspect of the left calcaneus. Credit: http://en.wikipedia.org/wiki/Calcaneus#mediaviewer/File:Gray264.png
Figure: Medial aspect of the left calcaneus. Credit: http://en.wikipedia.org/wiki/Calcaneus#mediaviewer/File:Gray267.png
Figure: Lateral aspect of the left calcaneus. Credit: http://en.wikipedia.org/wiki/Calcaneus#mediaviewer/File:Gray266.png
Talus fractures are rare but when they do occur they can be quite serious. The talus can be fractured at many different sites depending on the mechanism of injury. These sites include the talar head, talar neck, talar body, posterior process, and lateral process.
Fractures of the talar neck comprise half of all talus fractures. Talar neck fractures are caused by hyperdorsiflexion of the foot against the distal tibia and may also present with dislocation. Talar neck fractures are classified according to the Hawkins classification:
- Hawkins Type I: Nondisplaced fracture of the neck
- Hawkins Type II: Displaced fracture with subluxation/dislocation of the subtalar joint
- Hawkins Type III: Displaced fracture with subluxation/dislocation of the subtalar joint and talocrural joint
- Canale and Kelly Type IV: Displaced fracture with subluxation/dislocation of the subtalar joint, talocrural joint, and talonavicular joint
As talar neck fractures increase in severity from Type I to Type IV, the blood supply to the talus is increasingly compromised and the incidence of avascular necrosis, osteoarthritis, and other complications increases.
The second most common site of talus fracture is the lateral process – approximately one-quarter of talus fractures occur here. These often occur following axial compression, dorsiflexion, and eversion. They are common in snowboarders.
Figure: Fracture of the lateral process of the talus. Credit: http://www.footeducation.com/wp-content/uploads/2013/08/lateral-process-of-talus-11-287x300.jpg
Fractures of the talar head, body, and posterior process are less common. It would be helpful to understand the following points about these fractures:
- Talus head fx: involve the talonavicular joint
- Talus body fx: displacement is best visualized using CT imaging
- Posterior process fx: can be hard to distinguish from a normal os trigonum on x-ray
Figure: Radiographic images of a normal talus (top) and displaced talar body fracture (bottom). Credit: http://www.footeducation.com/wp-content/uploads/2014/06/Figure-2-X-rays-Normal-vs-Displaced-Talar-Body-fracture.png
Calcaneus fractures are more common than talus fractures. They are broadly classified according to whether they involve the subtalar articular surface (intra-articular) or not (extra-articular).
Extra-articular fractures are less common (25% of calcanear fractures) than intra-articular fractures. By definition, they do not involve the subtalar joint or its articular surfaces. Extra-articular fractures typically affect the anterior process, calcanear tuberosity, calcaneal body, and sustentaculum. Avulsion fractures can occur at the calcaneal tuberosity and sustentaculum due to the relative strengths of the attached Achilles tendon and deltoid ligament, respectively.
Intra-articular fractures comprise 75% of calcaneal fractures and are more clinically challenging than extra-articular fractures. There are four types of intra-articular fractures according to the Sanders classification system. This system uses coronal CT scans of the posterior articular facet and classifies fractures according to the number of fractures and location of the fracture lines:
- Type I: non-displaced intra-articular fracture
- Type II: displaced intra-articular fracture that splits the calcaneus into two pieces
- Type III: displaced intra-articular fracture that splits the calcaneus into three pieces
- Type IV: displaced intra-articular fracture that splits the calcaneus into more than three pieces
Figure: Sanders classification system of intra-articular calcaneus fractures. Credit: http://www.orthopaedicsone.com/download/attachments/27099874/4.JPG?version=2&modificationDate=1287444363000
Intra-articular calcaneus fractures can also be classified as either joint depression or tongue type fractures based on the location of the secondary fracture line. In these fractures, the primary fracture line passes anterior-posteriorly through the posterior facet at the crucial angle. In the joint depression fractures, the secondary fracture line exits dorsally on the posterior calcaneus. In tongue type fractures, the secondary fracture line extends through the tuberosity and exits posteriorly on the posterior calcaneus with the Achilles tendon attached to the displaced fragment.
Figure: Joint depression type calcaneus fracture. Note the secondary fracture line exits dorsally on the calcaneus. Credit: http://www.orthopaedicsone.com/download/thumbnails/27099874/3a_joint_depression_type.jpg?version=2&modificationDate=1287444447000
Figure: Tongue type calcaneus fracture. Note the secondary fracture line exits posteriorly on the calcaneus. Credit: http://www.orthopaedicsone.com/download/thumbnails/27099874/3b_tongue_type.jpg?version=2&modificationDate=1287444447000
Patients will present with significant swelling and pain. The heel will be shortened and widened with a possible varus deformity if the calcaneus is affected. The area of maximal tenderness will be localized around the heel but will vary slightly depending on the part of the calcaneus or talus that is fractured. It may be difficult to distinguish a fracture from a sprain with an acutely swollen ankle, so re-examination may be necessary after the swelling has subsided. Laceration, blood, or puncture wound, often on the medial aspect of the foot, will indicate an open fracture.
Figure: Gross appearance of a closed calcaneal fracture. Note swelling, bruising, and blister formation along the lateral hindfoot. Credit: http://www.orthopaedicsone.com/download/thumbnails/27099874/1.JPG?version=3&modificationDate=1287444363000
Inability to bear weight is a common sign of hindfoot fractures. Redness, hematoma, and fracture blisters may be present near the heel. “Mondor sign” is a hematoma extending distally along the sole of the foot – it is pathognomic for a calcaneus fracture.
Most patients will present with a history of acute trauma. Falls from height and motor vehicle accidents are the two most common causes of hindfoot fractures. It is helpful to elicit the mechanism of injury (position of the foot and force applied) as this will help determine the type of fracture that has occurred.
Hindfoot fractures are often accompanied by other injuries because the extent of axial loading necessary to cause a hindfoot fracture is likely to cause other problems too. Fractures and dislocations of the ankle joint may occur in these settings. Additionally, lumbar spine fractures are seen in 10% of patients with calcaneus fractures.
It is important to assess soft tissue damage in addition to the fracture, as the extent of soft tissue damage will dictate the prognosis and when to start definitive treatment. A comprehensive neurological exam should be performed to look for motor or sensory nerve injury. Anterior and posterior tibial pulses and distal capillary refill should be examined via palpation and or Doppler to assess for any vascular deficits.
Most hindfoot fractures can be diagnosed with plain radiographs. Non-displaced fractures may be harder to detect than displaced fractures. Talus fractures may be harder to detect than calcaneus fractures due to the fact that the view of the talus is obscured by the ankle mortise, calcaneus, and midfoot.
Anterior-posterior, lateral, and oblique/mortise X-rays should be taken of the ankle and foot. The Canale-Kennedy view (a superior view of the plantarflexed prontated foot) will allow for visualization of the talar arch to look for talar neck fractures. The Harris view (an axial end-on view of the heel) will allow for visualization of the anterior process of the calcaneus and the subtalar joint. The Broden view of the posterior facet can be used intraoperatively during calcaneus repair.
Two angles on the lateral x-ray can be helpful in assessing calcaneus fractures. Bohler’s angle is formed from two lines: (1) a line drawn from the superior point of the posterior calcaneal tuberosity to the highest midpoint of the posterior articular facet, and (2) the highest midpoint of the posterior articular facet to the anterior process. This angle should be 20-40 degrees – a decrease in Bohler’s angle suggests a depressed fracture of the posterior facet. The Angle of Gissane is formed from the downward slope of the posterior facet and the upward slope directed anteriorly. This angle should be 100-130 degrees – an increase suggests a fracture of the posterior subtalar articular surface.
Figure: Bohler’s angle as seen on lateral x-ray
When assessing a hindfoot fracture on x-ray, it is important to differentiate the presence of a normal os trigonum from a fracture of the lateral tubercle, medial tubercle, or posterior process. Unlike fractured bones, the os trigonum will have smooth bony margins and a relatively consistent location.
Figure: x-ray of a depressed calcaneus fracture
“Hawkins sign” is a highly sensitive radiographic indicator of revascularization and absence of avascular necrosis. It consists of a radiolucent line in the subchondral talus (patchy subchondral osteopenia) several weeks following injury on the AP or mortise views of the ankle. The radiolucency is the result of bone resorption and is a good sign – it indicates that the bone retained its blood supply. The absence of this sign may indicate impending avascular necrosis.
CT imaging is routinely performed to assess the fracture pattern, degree of displacement, and involvement of articular surfaces since radiographic imaging does not provide sufficient resolution to visualize the articular fragments. Sagittal, coronal, and transverse CT scans are helpful for (1) treatment planning, including the decisions to perform surgery and the type of operation, (2) pre-operative patient discussion about outcomes, and (3) intra-operative decision-making about type of reduction and ideal hardware.
MRI is mostly used to detect and quantify the degree of avascular necrosis of talar fractures. It is also used to diagnose osteochondral lesions of the talus.
Figure: CT scan of calcaneus fracture
Calcaneus fractures comprise 2% of all fractures and 60% of tarsal fractures. The annual incidence is approximately 12 per 100,000 per year, significantly less than ankle fractures (187 per 100,000) which may present similarly. According to Mitchell et al (PMID: 20307476), calcaneus fractures occur 2.4 times more often in males and most often affect men in their 20’s. 72% of calcaneal fractures are due to falls from a height and 19% occur in the workplace. A small minority of calcaneus fractures may be non-traumatic stress fractures due to repetitive axial loading, as seen in military personnel or long-distance runners. Ten percent of calcaneus fractures are bilateral. Ten percent will have associated thoracolumbar spine injuries and another 10% will have a hip fracture.
According to Fortin et al (PMID: 11281635), talus fractures are the second most common fractured bone in the foot but are rarer than calcaneus fractures, comprising only 0.1-0.9% of all fractures. The most common site of talus fractures is at the talar neck followed by the lateral process. Talus fractures are significant because of their potential for long-term morbidity and complications.
Shibuya et al (PMID: 24785202) found that open fractures occur in approximately 20% of calcaneus and talus fractures.
Because a high-energy impact is necessary to cause hindfoot fractures, it is possible that the same mechanism will cause cause other injuries to the lower limb. These include ankle sprains, ankle fractures, talus dislocations, tibial and fibular fractures, pilon fractures, hip fractures, and injuries to the other tarsal and metatarsal bones. In fact, one-quarter of calcaneal fractures are accompanied by other lower limb injuries. A high-energy axial load can also cause injuries outside the lower limb. One of the most common injuries is thoracolumbar spine fractures, occurring in 10% of patients with calcaneal fractures.
Effective history taking, thorough physical examination, and radiographic imaging can help discern the exact structures affected.
Assessment for numbness, tingling, pallor, or pulselessness can help to identify neurovascular compromise in the affected foot. Compartment syndrome should also be kept in mind during your assessment.
Do not forget to consider the possibility of life-threatening injuries associated with falling, collisions and rapid deceleration like pulmonary contusion, aortic transection, and brain injury.
Hindfoot fractures can be missed in patients who have sustained polytraumatic injuries. According to Berkowitz et al (PMID: 16330511), a missed diagnosis will lead to increased risk of non-union and post-traumatic osteoarthritis. It is important to assess foot injuries in the setting of polytrauma to avoid these complications.
The index of suspicion for a missed hindfoot fracture should be increased if a suspected ankle sprain does not improve with routine treatment. Subtle hindfoot fractures can be caused by the same type of mechanism (inversion injury) and are frequently misdiagnosed as ankle sprains according to Judd et al (PMID: 12322769).
Open fractures should be considered an orthopedic emergency and should be referred to an orthopedic specialist for immediate treatment to reduce the risk of infection and long-term complications.
Tenting of the skin is a worrisome sign indicative of potential skin necrosis.
Look out for pathognomonic symptoms of compartment syndrome or compartment pressures within 30mmHg of diastolic pressure. If compartment syndrome is diagnosed, urgent fasciotomy is needed.
Avascular necrosis (AVN) is a severe complication of talus fractures. It results from disruption of the tenuous blood supply to the talus that can lead to talar degeneration and collapse with subsequent damage to the talocrural and subtalar joints. Tamar AVN can take up to the 3 years to revascularize, during which time the bones and joints may collapse. Talus fractures, especially severe fractures and fractures to the talus neck, should be followed up for avascular necrosis. MRI is normally used to diagnose and quantify the degree of avascular necrosis following bone healing. The Hawkins sign is a radiographic indication of revascularization that is highly sensitive at 6-7 weeks post-injury.
Treatment options and outcomes
Initial treatment of hindfoot fractures should focus on reducing swelling and addressing any open wounds. After the fracture pattern has been identified, definitive treatment can begin.
Definitive treatment for hindfoot fractures can be operative or non-operative depending on the part of the bone fractured, the severity of the fracture, and the patient's risk factors. Non-operative treatment generally involves immobilization and no weight bearing for 6-12 weeks followed by progressive weight bearing and ROM exercises. Operative treatment generally involves open reduction and internal fixation (ORIF) followed by immobilization, no weight bearing and ROM exercises. It is important to maintain initial non-weight bearing in all cases, as premature weight bearing can lead to loss of reduction and malunion. According to Swanson et al (PMID: 19013401), timing of operative fixation is essential: there is a window of opportunity after resolution of swelling and before a soft callus has formed during which an open reduction should occur.
Regardless of the chosen treatment, recovery can be prolonged and complications like subtalar arthritis are common. Long-term outcomes can range from full recovery to residual pain and stiffness, to lifelong disability, depending on the degree of joint injury, accuracy of reduction, patient comorbidities, and complications.
In general, non-displaced or minimally displaced talus fractures are treated non-operatively while displaced fractures or very severe comminuted non-displaced fractures are treated with surgical fixation.
Fractures to the talar neck are the most common talus fractures. Hawkins Type I fractures (nondisplaced) are treated non-operatively and have good results 90% of the time. Healing time is approximately 6-8 weeks. If Hawkins Type II fractures are not displaced and have only mild subluxation, closed reduction can be attempted. Otherwise, Hawkins Type II-IV fractures will require ORIF to correct any displacement and restore the bony anatomy. Healing time takes 12+ weeks for Type II-IV talar neck fractures.
Fractures to the taller head and body are less common and may require longer healing times.
Treatment for lateral process fractures, like that for talar neck fractures, is determined by displacement. If the fractures are non-displaced or minimally displaced (<2 mm), they are treated non-operatively. Otherwise ORIF is required.
Figure: Surgical fixation of a lateral process fracture
Fractures to the talar head and talar body are uncommon. Non-displaced talar head and talar body fractures can be treated non-operatively. Displaced talar head and talar body fractures necessitate ORIF to re-establish the shape of the joints and minimize the risk of arthritis.
The risk of complications of talus fractures is related to the extent of the displacement, degree of damage to the blood supply, and damage to the articular surfaces. A common complication is avascular necrosis due to injury to the vascular sling supplying the talus. The risk of avascular necrosis is stratified according to Hawkins classification, with Type I having 0-15% risk of developing AVN compared to a 100% risk in Type IV fractures.
Elgafy et al (PMID: 11139032) reported on other complications of talus fractures aside from avascular necrosis. These include skin necrosis/infection, tibiocalcaneal fusion, foot compartment syndrome, delayed union, non-union, and malunion. These increase in frequency as the degree of displacement increases. Ankle and sub-talar osteoarthritis is another complication that is extremely common and can occur in >50% of cases.
Extra-articular calcaneus fractures can generally be treated non-operatively unless the fragments are large. In the case of fractures of the calcaneal tuberosity caused by Achilles tendon avulsion, screw fixation may be required to reduce the fracture and offset the force of the Achilles.
Treatment of intra-articular calcaneal fractures varies. Non-displaced fractures (Sanders Type I) are treated non-operatively. Either non-operative or surgical fixation may be indicated for displaced fractures (Sanders Type II-IV). Surgical fixation involves reconstructing the shattered calcaneus. This is a technically challenging procedure that needs to be individualized for each patient. Open fixation of calcaneus fractures has a high complication rate, with some studies finding wound complication rates >40%. Moreover, surgical fixation has been shown to be only marginally better than non-operative treatment in terms of functional results. In an analysis by Buckley et al (PMID: 12377902), it was shown that surgical fixation has optimal results in “low-risk” patients, including young patients, women, and those not receiving worker’s compensation. Otherwise, it may be prudent to avoid surgery in high-risk patients (smokers, diabetics, older patients, patients with vascular disease, and those receiving worker’s compensation) as surgical treatment can carry significant risk of wound healing problems and infection in these patients.
Figure: x-ray of calcaneus fracture following anatomic reduction and fixation with plate and screws. Credit: http://www.footeducation.com/wp-content/uploads/2010/08/Calcaneus-X-ray-Post-Fixation-277x300.jpg
Calcaneus fractures are fraught with complications. Major complications include:
- Wound dehiscence, infection, and osteomyelitis, especially after premature operative intervention on an edematous ankle
- Iatrogenic injury to the sural nerve or posterior neurovascular bundle
- Non-union or malunion
- Decreased ROM
- Heel deformity
- Residual pain
- Subtalar or ankle arthritis
- Foot compartment syndrome which can lead to claw toe deformities
- Complex regional pain syndrome around the heel
Risk factors and prevention
Because most hindfoot fractures occur in the setting of acute injury, such as falls or motor vehicle accidents, prevention mostly centers on avoiding such accidents. However, certain health conditions can also predispose people to hindfoot fractures. For example, Kathol et al (PMID: 1871285) and Cheng et al (PMID: 9200007) found that diabetes mellitus and low bone mineral density are major risk factors for hindfoot fractures.
Hindfoot fractures can also be sports-related. Chan et al (PMID: 12764342) found that snowboarders are 17 times more likely to sustain fractures to the lateral process of the talus compared to the general population. Additionally, Salzler et al (PMID: 22735197) found that running with minimalist footwear has been implicated in calcaneal stress fractures.
Calcaneus fractures are called “lover’s fractures” or “Don Juan fractures” because they are the injury a cheating wife’s lover would sustain if he jumped from an upstairs bedroom window to escape from the wife’s enraged husband. “Don Juan fractures” refer to both calcaneal fractures and burst fractures in the thoraco-lumbar spine, which occur in 10% of calcaneus fractures.
Talus fractures were historically referred to as “Aviator’s astralgus.” In the early 20th century, plane crashes at sub-lethal speeds were common, resulting in high-impact injuries to the foot including talus fractures. Nowadays talus fractures are mostly caused by falls and motor vehicle accidents, so this term is mostly obsolete.
Imaging the contralateral foot can help detect other injuries since one-tenth of hindfoot fractures are bilateral. Additionally, it may be useful to recognize the unique anatomical features of the patient.
Calcaneal Avulsion fracture
Angle of Gissane
Develop a differential diagnosis of possible foot injuries resulting from high-energy axial loading such as a fall or motor vehicle accident
Recognize the classic signs, symptoms, and history of hindfoot fractures
Identify and differentiate between calcaneus and talus fractures on plain radiographs
Use radiography and CT imaging to calculate Bohler’s and Gissane’s angles
Classify calcaneus fractures according to Sanders Classification using coronal CT images
Determine the appropriateness of operative vs. non-operative management depending on whether fractures are displaced