➢ The navicular is the keystone of the medial column of the foot and is an integral component of the transverse tarsal locking mechanism.
➢ With fusion of the talonavicular joint, all subtalar joint motion is eliminated.
➢ Avulsion fractures constitute 50% of all acute navicular fractures.
➢ Radiographs usually are sufficient for the diagnosis and treatment of tarsal navicular fractures.
➢ Nonoperative treatment is reserved for small avulsion fractures, nondisplaced body fractures, and minimally displaced tuberosity fractures.
➢ When operative intervention is indicated, open reduction and internal fixation is the preferred approach.
➢ The long-term sequelae of both operatively and nonoperatively treated navicular fractures include persistent pain, stiffness, loss of hindfoot motion, posttraumatic arthritis, and osteonecrosis.
Tarsal bone injuries are most often incurred during motor-vehicle collisions and other high-energy trauma1. Although uncommon, they are being seen with increasing frequency. This trend is attributed to enhancements in automobile safety that have improved the protection of the abdomen, head, and neck but have left the feet unprotected in the pedal box area2,3. Despite the adverse impact of foot injuries on overall outcome and long-term function in patients with polytrauma, the diagnosis sometimes is not made or is made on a delayed basis as treating physicians focus on more obvious or life-threatening injuries1,4,5.
The navicular is the most frequently injured tarsal bone3. In the acute setting, avulsion, tuberosity and body fractures, and comminuted fracture-dislocations can occur. Stress fractures of the navicular represent more chronic, low-energy injuries. They often present with an insidious onset of midfoot pain after an increase in the duration or intensity of exercise or other activity. It is important for orthopaedic surgeons to consider this injury when patients present with vague symptoms in the midfoot as complications such as arthritis and osteonecrosis can occur6,7.
The navicular plays a crucial role in foot function and forms part of the medial column of the foot. Despite the importance of the navicular, the literature pertaining to acute fractures of this bone is limited, predominantly consisting of case series and reports3,8-14. This article reviews the relevant anatomy and biomechanics of the navicular bone, the classification and presentation of tarsal navicular fractures, and the indications for and outcomes following both conservative and operative interventions for tarsal navicular fractures.
The navicular is a saucer-shaped bone that is surrounded on three sides by cartilage. It articulates distally with the three cuneiforms, proximally with the talar head, and laterally with the cuboid. Its distal articulation with the cuneiforms is via three facets that share a common synovial cavity. Plantar and dorsal ligaments, the inferior calcaneonavicular ligament, the anterior fibers of the deltoid ligament, and the broad insertion of the tibialis posterior tendon reinforce each articulation and are vital to the integrity of the medial longitudinal column of the foot, of which the navicular is the keystone15.
The tibialis posterior tendon has three major insertions, all of which provide dynamic support to the medial column. The largest portion inserts on the navicular tuberosity; the middle portion inserts on the cuneiforms, cuboid, and medial three metatarsal bases; and the posterior portion inserts as a band on the anterior aspect of the sustentaculum tali16.
The extensive articular cartilage surrounding the navicular limits blood vessels to dorsal and plantar entry into the bone. Branches of the dorsalis pedis artery enter the dorsal surface of the bone, whereas the medial plantar branch of the posterior tibial artery enters the plantar surface. The navicular tuberosity receives its blood supply from an anastomosis between these vessels17. This perfusion pattern, which recedes with age, renders the central one-third of the bone largely avascular, making this area the most vulnerable to nonunion if fractured acutely or with repetitive stress.
The transverse tarsal joint complex (including the talonavicular and calcaneocuboid articulations) facilitates the transition of the foot from a flexible structure at heel strike to a more rigid construct at toe-off. As the calcaneus begins to evert at heel strike, the talonavicular and calcaneocuboid articulations are parallel and unlocked, making the foot more flexible and cushioning heel strike. At toe-off, the calcaneus inverts and the articulations become divergent and locked. This creates the rigid lever necessary for effective propulsion during gait. The talonavicular joint also works together with the subtalar joint to allow hindfoot inversion and eversion, which are vital for locomotion on uneven surfaces.
Talonavicular joint motion is tightly coupled with subtalar motion, as evidenced by fusion of the talonavicular joint, which eliminates all subtalar motion18. With fusion of the subtalar joint, only 26% of normal talonavicular motion remains18. Isolated fusion of the calcaneocuboid joint has less of an impact on subtalar motion and hindfoot stiffness as 67% of talonavicular motion and 92% of subtalar motion remain intact following fusion18.
The midfoot comprises medial and lateral columns. The medial column, which includes the navicular, the cuneiforms, and the medial three metatarsals, is a rigid construct. Conversely, the lateral column, which comprises the cuboid and the fourth and fifth metatarsals, is more mobile. As described by DiGiovanni, the relationship between the columns is like that of the pelvic ring as the forces required to damage the navicular and/or its surrounding soft tissues must also damage adjacent medial or lateral column structures15. This concept has important diagnostic and treatment implications.
Acute navicular fractures are broadly classified into three types: avulsion fractures, tuberosity fractures, and body fractures5. Sangeorzan et al. stratified body fractures into three types on the basis of the direction of the fracture line, the direction of displacement of the forefoot and midfoot, and the pattern of joint disruption14.
A type-1 body injury (Fig. 1, A and B) is characterized by a transverse fracture line in the coronal plane, with the dorsal fragment consisting of <50% of the body. Comminution is minimal. There is no angulation of the forefoot and no disruption of the alignment of the medial border of the foot14.
A type-2 fracture (Fig. 2, A, B, and C), the most common type, is characterized by a primary fracture line extending dorsal-lateral to plantar-medial, with the major fragment and forefoot displaced medially. Although the naviculocuneiform joint usually remains intact, the talonavicular joint is frequently subluxated or dislocated, with dorsomedial displacement of the dorsomedial navicular fragment. In type-2 fractures, the forefoot appears adducted or medially translated, with a large and medially displaced navicular fragment evident on anteroposterior radiographs14.
A type-3 injury (Fig. 3, A, B, and C) involves a comminuted fracture in the sagittal plane of the navicular body. The medial border of the foot is usually disrupted at the naviculocuneiform joint, and there is lateral displacement of the forefoot, with some involvement of the calcaneocuboid joint as well10. Radiographs typically reveal loss of height of the medial longitudinal arch or shortening of the medial column due to the impaction, comminution, and joint incongruity seen in association with these fractures14.
Mechanism of Injury
Avulsion fractures, which constitute approximately 50% of all acute navicular fractures, can be seen on the dorsal lip or medial surface of the bone or can present as larger fragments involving the navicular tuberosity. Dorsal avulsions are low-energy injuries resulting from disruption of the dorsal talonavicular ligament, which occurs following extreme inversion and plantar flexion15. Medial avulsion injuries result from traction of the anterior division of the deltoid ligament following a substantial eversion stress15. Tuberosity fractures result from traction of the posterior tibial tendon or spring ligament complex following an acute eversion or valgus injury to the hindfoot5,19. Tuberosity fractures can appear similar to type-2 body fractures on radiographs. However, the primary fracture fragment in true tuberosity injuries is smaller.
Acute navicular body fractures are caused by both direct and indirect forces. There are several different theories regarding the indirect mechanisms. Sangeorzan et al. described forces traveling along the central axis of the foot as the cause of type-1 fractures, axial compression and dorsomedial forces exerted on the forefoot as the cause of type-2 fractures, and axial and laterally directed forces as the cause of type-3 fractures14. Main and Jowett described a shearing mechanism in which longitudinal compression of the plantar-flexed foot causes impaction of the cuneiforms into the navicular20. Nyska et al. hypothesized that the navicular body is crushed by the talar head with the ankle in plantar flexion as the cuneiforms are compressed backward and medially21. Both Eftekhar et al.22 and Nadeau and Templeton8 theorized that navicular fractures occur through a combination of plantar flexion and abduction at the midtarsus. Although each of the aforementioned theories have distinguishing features, they all involve axial loading of a plantar-flexed foot.
A different mechanism was proposed by Rockett and Brage, who suggested that the medial aspect of the forefoot or midfoot is subjected to a strong dorsiflexion force in the setting of hindfoot eversion23. In this position, plantar flexion and adduction of the talar head occurs as the subtalar and transverse tarsal joints are unlocked. Forceful contact ensues between the head of the talus and the articular surface of the navicular body, leading to fracture.
In the setting of avulsion fractures, patients typically complain of pain in the midfoot that is most severe with push-off. Conversely, patients with navicular body fractures are unable to bear any weight and have substantial swelling of the dorsal and medial aspects of the midfoot as these injuries occur via high-energy axial loading mechanisms. A detailed neurovascular and skin assessment always must be performed, with consideration given to the presence of an associated compartment syndrome and any open wounds.
Evans et al. reported that navicular fractures were associated with other injuries in the foot in 63% (fifteen) of twenty-four patients3. This association should be investigated as other components of the medial or lateral column may no longer be intact. Concomitant navicular dislocation or subluxation is often associated with gross deformity, skin tenting, ecchymosis, or instability.
Navicular stress fractures typically present with indolent and vague midfoot discomfort of prolonged duration. However, an acute, exacerbating injury is at times the impetus for a patient to seek care. In such instances, examination may reveal focal pain localized over the dorsal aspect of the midportion of the navicular, which in the absence of high-energy trauma is most consistent with a navicular stress fracture.
Non-weight-bearing anteroposterior, lateral, and oblique radiographs of the foot are usually sufficient to identify a navicular fracture. For patients with minor injuries and some avulsions, weight-bearing and/or stress radiographs can also be used to demonstrate ligamentous injury. An external oblique radiograph of the foot (opposite to the oblique radiograph of the foot that is usually made) is indicated when there is concern about a tuberosity fracture as it provides the best visualization of this injury. Because of their small size, avulsion fractures may only present on one radiograph, appearing as a fleck of cortical bone. An accessory navicular must be distinguished from a tuberosity fracture, with the former being a well corticated and smooth structure on radiographs. Comparison radiographs of the contralateral foot can be helpful for identifying an accessory navicular as this structure can be observed bilaterally24.
Computed tomography (CT) can provide additional information with regard to midfoot anatomy and the geometry of the talonavicular joint. CT also can better delineate high-energy fracture patterns, identify intra-articular involvement, and assist the orthopaedic surgeon in operative planning. In addition to recommending the traditional coronal, sagittal, and transverse images, Cronier et al. recommended the use of three-dimensional CT reconstructions with suppression of the talus and calcaneus12. Magnetic resonance imaging has a limited role in the setting of acute navicular fractures and is used more often in the setting of a suspected stress fracture, in the presence of an accessory navicular, or when there is concern about an injury to the posterior tibial tendon25.
The treatment of acute navicular fractures is dependent on several factors, including individual fracture characteristics (size, comminution, location, displacement), the soft-tissue integrity of the foot, the presence of concomitant injuries involving the ipsilateral foot, the presence of additional axial and appendicular skeletal trauma, the presence of extraskeletal injuries, comorbidities, and overall functional status (Table I)18.
Nonoperative treatment is reserved for small avulsion fractures, nondisplaced body fractures, and tuberosity fractures with <2 to 3 mm of displacement. The use of a weight-bearing short leg cast for six weeks followed by the use of a walking boot for an additional four to six weeks will assist in preventing further displacement. Serial radiographs should be made to identify any displacement that may occur during the course of treatment. Stress fractures are also treated nonoperatively. Patients are managed with non-weight-bearing in a short leg cast for six to eight weeks, with progressive weight-bearing in a walking cast or boot thereafter.
Operative intervention is indicated for displaced body fractures; intra-articular fractures with >1 mm of joint incongruity; medial column shortening of >2 to 3 mm; instability, subluxation, or dislocation of the talonavicular or naviculocuneiform joints; lateral column involvement (e.g., shortening, displacement) that by itself requires operative fixation; open wounds; compartment syndrome; skin compromise; and irreducible dislocations26. Surgery is contraindicated for low-demand, elderly patients; patients with compromised soft tissues; heavy smokers; patients with poorly controlled diabetes; patients with vascular compromise; and noncompliant patients.
Open reduction and internal fixation is the preferred surgical intervention. The goals of open reduction and internal fixation include anatomic fracture reduction, the restoration of medial column length, and the creation of a rigid osseous construct allowing for early range of motion. Complications and poorer outcomes occur in association with failure to adhere to these treatment principles. External fixation also can be used with limited internal fixation or percutaneous fixation for the treatment of comminuted fractures in patients with a poor soft-tissue envelope. It can also be used to lengthen the medial column during surgery, and the fixator can be left on after the reduction if the construct is not inherently stable27.
Avulsion and tuberosity fractures rarely require operative intervention. However, when a large, displaced avulsion fracture is present, the fragment with its capsule or the posterior tibial tendon may be reattached to the navicular. This reattachment can be achieved with a mini-fragment or small-fragment interfragmentary compression screw and washer or with an approach similar to that used for some greater tuberosity fractures of the proximal part of the humerus, with drill holes through bone and fixation with use of nonabsorbable suture28. A longitudinal dorsomedial incision between the insertions of the anterior and posterior tibial tendons is used to approach the navicular tuberosity.
Type-1 body fractures are typically easier to reduce and fix in comparison with type-2 and 3 fractures. The surgical approach is the same as that used to access the tuberosity. Exposure of the talonavicular and naviculocuneiform joints is performed via capsulotomies. The optimal fixation of these injuries is with use of two 3.5-mm interfragmentary screws placed in a dorsal-to-plantar trajectory.
The longitudinal dorsomedial incision is used for many type-2 and 3 injuries. Although simple fractures can be fixed with 2.4, 2.7, or 3.5-mm lag screws, most fractures are too complex and comminuted. In these instances, additional incisions may be required, and plate-and-screw constructs must be used. A second, dorsolateral incision can be made between the extensor hallucis and extensor digitorum brevis muscles. The superficial peroneal nerve and the motor branch of the deep peroneal nerve need to be protected with this approach. The plates available for body fractures include small washer plates, one-quarter tubular plates with 2.7-mm screws, 2.4-mm mini-plates with 2.4-mm screws, and 2.0-mm mini-plates and T-plates with 2.0-mm screws. Selection is dependent on the size of the navicular and its fracture fragments. Another approach to the more comminuted type-2 and 3 fractures involves screw constructs, with placement across the lateral cuneiforms or cuboid to maintain reduction and appropriate medial column length, in addition to external fixation27. Navicular locking plates are another option in this setting and can help to stabilize and bridge comminuted fractures with less periosteal disruption than that occurring in association with the use of conventional plates. Bone graft is sometimes needed and can help to buttress the articular joint surface.
When there is substantial comminution, isolated open reduction and internal fixation may be suboptimal and insufficient to maintain reduction and medial column length and alignment. In this setting, the surgeon has several options, including primary arthrodesis of the naviculocuneiform joints or the entire medial column, delayed reconstruction, and temporary medial column bridge-plating27. Primary fusion of the navicular to the first and second cuneiforms restores the medial column while preserving the talonavicular joint. The temporary bridging technique described by Schildhauer et al. involves navicular open reduction and internal fixation and the application of a spanning plate that traverses the entire medial column, extending from the talar neck to either the first cuneiform or metatarsal29. The talonavicular joint is never violated, with motion restored at the joint once the bridge plate is removed after healing of the navicular.
Several types of enhanced fixation also have been described for the treatment of both osteoporotic and severely comminuted fractures, including screw fixation extending into the second and third cuneiforms or cuboid; standard open reduction and internal fixation with additional fixation across the calcaneonavicular, naviculocuneiform, or talonavicular joints; spanning external fixation; and supplemental transverse Kirschner wire fixation through the cuneiforms and cuboid27,30-32.
The operative treatment of navicular stress fractures is limited to patients for whom nonoperative treatment has failed and to elite athletes, who may elect to undergo percutaneous screw fixation at the time of diagnosis. Aggressive intervention in the latter group is thought to facilitate an earlier return to competition and to decrease the risk of recurrent stress fracture.
Suboptimal outcomes following the operative treatment of navicular fractures are often due to malreduction. In order to prevent talonavicular subluxation after healing, at least 60% of the proximal articular surface of the navicular must be restored20. In addition, medial column stability is compromised with malreduction, which reduces push-off strength and hindfoot motion18.
Patients must be counseled on the possibility of persistent stiffness, pain, and loss of hindfoot motion following open reduction and internal fixation. Posttraumatic arthritis may be the underlying cause of these symptoms and can result from the chondral damage sustained at the time of injury, malreduction, or osteonecrosis. The tenuous blood supply of the navicular and the soft-tissue stripping that is performed during surgery are factors that contribute to the development of osteonecrosis. In the setting of symptomatic posttraumatic arthritis, arthrodesis can be performed and reliably relieves pain. However, isolated talonavicular fusion achieves this pain relief at the expense of hindfoot motion. Nonunion, another possible complication, is usually related to comorbidities and the limited vascularity of the navicular. As such, rigid fixation with autologous bone-grafting is often effective. An additional complication is the progressive and late development of hindfoot varus, which occurs secondary to progressive collapse of the navicular and resultant medial column shortening. This deformity should be treated with a corrective procedure and concurrent talonavicular or triple arthrodesis.
The literature pertaining to navicular fracture fixation is limited. In the studies that are available, the fracture pattern and the quality of reduction have been shown to most strongly correlate with outcomes3,14. Sangeorzan et al., in a retrospective case series of twenty-one patients who were followed for an average of forty-four weeks after the fixation of a navicular fracture with a single screw, reported good results for four (100%) of four patients with a type-1 fracture, nine (75%) of twelve patients with a type-2 fracture, and one (25%) of four patients with a type-3 fracture14. Satisfactory reduction was obtained in all four patients with a type-1 fracture, eight (67%) of the twelve patients with a type-2 fracture, and two (50%) of the four patients with a type-3 fracture. Of the patients with a satisfactory reduction, 93% had a good result. No patient with an unsatisfactory reduction had a good result (50% had a fair result and 50% had a poor result), emphasizing the importance of fracture reduction.
Cronier et al. specifically evaluated the role of preoperative CT with three-dimensional reconstruction and subsequent locking plate fixation in a prospective case series of ten patients with comminuted fractures12. Incisions were made on the basis of the delineation of fracture morphology provided by the three-dimensional reconstructions. All patients had radiographic evidence of union at a mean of 20.5 months, with a mean American Orthopaedic Foot & Ankle Society (AOFAS) score of 90.6 of 100. There were also no instances of secondary bone collapse due to osteonecrosis. Although the authors acknowledged that locking plates are more invasive than simple screw fixation, they suggested that the enhanced preoperative imaging enables such constructs to be optimally placed with minimal periosteal stripping.
Evans et al. found no instances of nonunion, loss of reduction, or deep infection in a retrospective review of twenty-four patients who were managed with mini-plate fixation3. Although the authors reported isolated cases of broken screws, painful and prominent hardware necessitating removal, posttraumatic arthritis, and avascular collapse, mini-fragment fixation was determined to be a good fixation option for rigid stabilization of navicular body fractures.
It is only with tremendous force that acute navicular fractures occur, as the stout ligamentous network surrounding the navicular and its various articulations provide structural support and protection. Avulsion, tuberosity, and body fractures can pose diagnostic and treatment challenges as the literature is sparse on optimal interventions. As the navicular is the central support of the medial longitudinal arch of the foot and is an important player in hindfoot motion as part of the talonavicular joint, only nondisplaced fractures should be treated nonoperatively. When displaced and/or intra-articular fractures are present, surgical intervention is warranted. All patients must be advised on potential complications following surgery, which include pain, loss of motion, osteonecrosis, and nonunion. When painful, posttraumatic degenerative changes occur, arthrodesis may be necessary.
Source of Funding: No external funds were received in support of this work.
Investigation performed at Albany Medical College, Division of Orthopaedic Surgery, Albany, New York
Disclosure: None of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of any aspect of this work. None of the authors, or their institution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.
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