The calcaneus is the most commonly fractured tarsal bone, with over 75% of lesions involving the joint space.
These injuries are generally the result of a high-energy mechanism, such as a fall from height or motor vehicle collision, and present as a shortened, widened ecchymotic heel with varus deformity.
Structure and function
Os calcis, also called calcaneus, is the foundation of the foot and is integral to normal human mobility. The talus and calcaneus collectively make up the "hindfoot." Some characterize the calcaneus as a "hard-boiled egg," in that its outer cortex is thin and if sufficiently damaged, gives way to severe collapsing comminution of the underlying cancellous bone. It articulates with both the talus and cuboid, but its major articulation is the the subtalar joint.
The subtalar joint, in which the talus articulates with calcaneus, is responsible for 20 degrees of pronation and supination, as well as axial rotation of the leg over a fixed foot. The articular surface of the calcaneus consists of three facets (anterior, middle, & posterior). The middle facet is the superior surface of the sustentaculum tali and supports the neck of the talus. The tendon of flexor hallucis longus passes beneath the sustentaculum. The posterior facet bears the majority of force transmitted axially to the calcaneus.
Fractures of the calcaneus are significant, especially when intra-articular, because the calcaneus supports 3 times the weight of the body during normal gait and makes direct contact with the ground. This relationship predisposes fracture fragments to loss of reduction and malunion if the patient bears weight prematurely.
Due to the complexity of the ankle joint and surrounding anatomy, calcaneal fractures have a high rate of complications. The sustentaculum tali is a common site of avulsion due to the strength of the attached deltoid ligament. A malaligned or damaged articular surface causes chronic pain, a loss of range of motion and resultant difficulty with intense activity such as running, jumping, and changing directions, which is given the general term "post-traumatic osteoarthritis".
Tarsal fractures represent only 2% of all adult fractures, however 60% of these involve the calcaneus primarily. One British study recorded a rate of 11.5 cases/100,000 and males were twice as likely to be injured as females (2). American researchers report that 90% of these fractures are found in middle aged men, especially those employed in construction and industrial occupations. The calcaneus is also important for its associated injuries. Seven percent of cases are open fractures.
Ten percent of patients will have bilateral lesions, another 10% will have a lumbar spinal compression fracture, and 10% will have a hip fracture. Twenty-five percent of cases will have an associated extremity fracture.
It is important to note that some calcaneal fractures are non-traumatic stress fractures due to a repetitive axial-loading mechanism seen in patients such as military personnel and long-distance runners.
Calcaneal fractures present as a shortened-widened heel with varus deformity. Mondor's sign or ecchymosis of the foot extending distally onto the heel is a hallmark of this injury. Fracture blisters may appear within 36 hours of injury. Open fractures will most likely present with a laceration or puncture wound on the medial aspect of the foot.
Figure 1: Axial loading mechanism with focus at the crucial angle
A high-energy axial loading injury mechanism (see Fig. 1) typically results from a fall greater than 10 feet in height directly onto the heel, although falls as short as 6 feet can cause a fracture (2). In vehicular collisions, the calcaneus is injured from below as the floor or gas/brake pedal is compressed upward. These mechanisms typically involve sufficient force to injure adjacent joints.
It is of primary importance to consider soft tissue injuries such as pulmonary contusion and aortic transection when the injury mechanism involves abrupt deceleration. The patient will typically refuse to bear weight on the affected heel, but usually in a trauma setting the patient is not ambulatory. This requires a high level of suspicion and attention to the details of the injury mechanism.
Numbness, tingling, severe pain, pallor, and/or pulselessness of the posterior tibial artery may signify impending neurovascular compromise. It is not uncommon to find an acute compartment syndrome occurring in these cases, especially in comminuted fractures.
It is important to consider the impact of comorbidities such as diabetes or peripheral vascular disease which may complicate surgery, healing, and full recovery, especially in open fractures. Tobacco use is also a source of complication for these patients and may prolong healing time. Advanced age may lead the surgeon to opt for nonoperative forms of treatment.
High index of suspicion for compartment syndrome is necessary, and urgent fasciotomy is indicated for pathognomonic symptoms or compartment pressures within 30mmHg of diastolic pressure. Ten percent of cases will require a fasciotomy and may result in hammer toe or "clawing". Early surgery has also been implicated as a source of complication as fixation prior to resolution of swelling can cause difficulty in approximation of the skin edges and resulting compartment syndrome, dehiscence, and/or infection.
Again, don't forget to rule out the common injuries associated with falling, collisions, and rapid deceleration (i.e, spinal burst fracture, femoral fracture, hip fracture, aortic transection, brain injury).
The differential diagnosis for cases that present in this manner includes any fracture within the foot, however the calcaneus is unique in that if you have a foot fracture, probability favors the calcaneus.
Important structures to check for coexisting injury include all joint surfaces in the foot, especially the tarsometatarsal joint, the talus, the midfoot, the tibia, the fibula, and their syndesmosis. Phalanx fractures are typically more visually evident and their pain distribution should differ as well.
The tibiotalar, knee, and hip joints are of particular concern in falls because if the calcaneus is injured, it implies that the lower limb and trunk were in a sufficient degree of extension when contact was made. Pilon fractures are also of significant concern as the distal tibia bears the majority of compressive force transmitted in a fall mechanism and is at risk for comminution.
Considering injuries to the axial skeleton from head to toe is essential when a patient has fallen from great height, however the most common location of vertebral injury is the lumbar spine.
Due to nature of the mechanism of injury, some cases will require an extensive radiographic workup. AP & lateral images of the foot are needed as well as a Harris axial view (see Miscellany), and an ankle series. Bohler's and Gissane's angles can be calculated from the lateral image of the foot (See Fig. 2). These parameters give the surgeon an idea of how depressed the articular surface or bone fragment is and how difficult reduction, fixation, and recovery of function may be. Always consider imaging of the contralateral foot, as bilateral injuries are found in roughly one-tenth of cases.
Figure 2: Bohler's angle: normally between 25-40 degrees, decreased with facet depression
Generally speaking, radiographic parameters such as displacement, depression, and angulation guide the surgeon in determining a method of treatment. All imaging, but especially the foot films, should be thoroughly evaluated for displacement and intra-articular extension of the fracture. A Harris view of the foot will allow evaluation of the subtalar joint and positioning/orientation of the tuberosity fragment .
CT is the gold-standard for evaluation of the joint space and is required for proper utilization of the Sanders classification system. Tomography is requisite to the proper evaluation and reduction of intra-articular fractures as plain films do not provide sufficient resolution to ensure proper approximation of the articular fragments.
Extra-articular calcaneal fractures circumvent the posterior facet and are found in 25% of cases.
Sites of injury include:
- anterior process
- medial process
- sustentaculum tali
Intra-articular fractures disrupt the posterior facet and represent 75% of cases.
Based on Sanders Classification of intra-articular fractures (coronal CT of posterior facet):
There are 4 specific fragments recognized as a result of a given fracture line. (lateral, A; central, B; medial, C)
- sustentaculum tali
Type I or nondisplaced (<2mm), extra-articular fractures with intact Achilles tendon can be treated with 10-12 weeks of cast immobilization without weight bearing.
Type II (two-part fractures), Type III (three-part fractures with centrally depressed fragment), and Type IV (comminuted fractures) are treated operatively.
These types are given an A,B, or C designation based on a lateral, central, medial, or combination of fracture lines. (e.g. Sanders Type III BC)
Following the Essex-Lopresti classification of intra-articular fractures, the primary fracture line proceeds anteroposteriorly through the posterior facet at the crucial angle. Types A-C represent joint depression fractures, in which the secondary fracture line extends from below the crucial angle to a point just posterior to the posterior facet. Types D-F are tongue-type fractures and the secondary line extends through the tuberosity.
Risk factors and prevention
Risk factors for calcaneal fracture include the use of ATVs, motorcycles, and high speed watercraft. In addition, people who work on roofs, ladders, and scaffolding are predisposed to a fall from sufficient height to cause this injury. Military personnel are at risk for blast injuries to the hindfoot by mines and IEDs. Osteopenic patients are at significant risk for injury and malunion resulting from poor bone quality and insufficient fixation.
Prevention consists of proper harnessing and suspension equipment, as well as avoidance of dangerous speeds/maneuvers when riding recreational vehicles. Osteopenic and osteoporotic patients should optimize their nutritional and exercise regimens for better bone health. Smoking and alcohol cessation are also beneficial to bone remodeling and recovery.
Treatment options can be categorized as non-operative and surgical. It is been shown that surgery decreases the probability of the patient undergoing subsequent talar fusion (3). However, surgical treatment of the hindfoot is a very complex undertaking, as timing is essential to the proper management of these fractures. Studies describe a "window" of opportunity within which surgeons are able to plan fixation. The basis for this approach is the necessity of 1-2 weeks delay pending resolution of edema (skin wrinkles return). In addition, at 3 weeks, soft callus has begun to form and may complicate the surgery, thus any reduction should take place prior to that time (4).
Non-operative or percutaneous pinning cases include:
- non-displaced or minimal displacement (extra-articular/intra-articular)
- anterior process fracture (<25% articular involvement)
- red flag patients (vasculopath, diabetic, elderly, surgical risk)
- protracted edema, blistering, or co-morbidity
- open wounds
- life-threatening illness or injury
Their treatment consists of dressing, reduction, splinting, and placement in a boot with non-weight-bearing restrictions for at least 10 weeks. Range of motion therapy should be initiated as soon as possible.
Open reduction and internal fixation is required for:
- displaced intra-articular fractures
- anterior process fractures (>25% involvement)
- displaced tuberosity fractures
- certain open fractures
In reinforcing the gravity of the operating "window," it is important to note that studies have shown complications such as infection, flap necrosis, and multiple revisions in patients who received surgery prior to resolution of edema (4).
The WITHDRAWN systematic review of displaced intra-articular fractures, showed that operative intervention significantly increased the chance of a patient returning to the same type of work, although residual pain was similar for operative and non-operative groups. Patients who had surgery were also more likely to wear the same shoes as before (5).
A study from the Canadian Orthopaedic Trauma Society found that non-operative treatment increased the probability of a patient requiring subtalar fusion by a factor of 5.5.
Risk of fusion was found to be greatest in a specific sub-population (11):
- Male patient
- Heavy labor occupation
- Workers' compensation board patient
- Displaced intra-articular fracture*
- Bohler's angle < 0 degrees
*Initial non-operative treatment increased risk of fusion
Severe traumatic fractures such as those experienced by military personnel and victims of under-vehicle explosions are particularly complicated by infection and amputation (8).
Possible complications include:
- Wound dehiscence: usually results from premature operative intervention
- Infection: risk increased by surgical manipulation of edematous ankle
- Post-traumatic osteoarthritis: results from initial damage to articular surface, may occur in spite of anatomic reduction
- Heel deformity: possibly an inevitable consequence of fracture, may impinge on lateral structures of ankle (tendons, fibula)
- Decreased ROM: results from disruption of the articular surface
- Peroneal tendonitis: consequence of lateral impingement of calcaneus onto peroneal tendons
- Sural neuropathy: a negotiated risk of utilizing a lateral L-incision (10% of ORIF cases)
- Residual pain: consequence of the complex anatomy and biomechanical demand placed on the hindfoot and subtalar joint
- Malunion: high risk in both operative and nonoperative cases, compliance with weight-bearing restrictions must be encouraged and reinforced
Calcaneal fractures are severe injuries and potentially very debilitating, depending on the general health and nutritional status of the patient. Elderly, osteoporotic, and diabetic patients are at increased risk for complications such as infection and malunion. Diabetic patients have been found to exhibit increased rates of Achilles tendon avulsion. Workers' compensation has been shown to complicate the prognosis. For patients hoping to return to work or an active lifestyle, operative treatment is recommended.
- Normal Bohler's angle: 20-40 degrees
- Normal Gissane's angle: 105-135 degrees
- Harris axial view = foot in dorsiflexion + beam at 45 degrees cephalad
The Broden view of the foot was formerly used to visualize reduction intra-operatively, but has fallen out of practice with most surgeons opting for postoperative CT scanning.
The most common site of compartment syndrome in tarsal fractures is the central superficial compartment, which contains flexor digitorum brevis, adductor hallucis, and the lumbricals.
- Axial load
- Crucial angle
- Mondor's sign
- Sustentaculum tali
- Be able to develop a differential diagnosis of associated lesions resulting from traumatic fall/rapid deceleration/high-energy axial loading injury
- Be able to recognize impending neurovascular comprimise
- Be able to evaluate lower limb neurovascular status, strength, and tone
- Be able to evaluate chest radiograph for common trauma pathology
- Be able to recognize calcaneal fractures on xray/CT and calculate Bohler's and Gissane's angles on lateral foot film
- Be able to determine Sanders Classification using coronal CT image of calcaneus
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