Practice Essentials
The navicular plays an important role in maintaining the medial longitudinal arch of the foot. Commonly, fractures of the navicular are not evident on plain radiographs. This often leads to a delay in diagnosis, which may result in prolonged disabling foot pain in individuals, particularly young athletes. The 4 types of navicular fractures are (1) cortical avulsion, (2) tuberosity, (3) body, and (4) stress. [1, 2, 3, 4, 5]
Cortical and tuberosity avulsion fractures
Avulsion fracture, the most common fracture of the navicular, is often associated with ligamentous injuries and results from twisting forces on the mid foot. These fractures are commonly treated conservatively, except for avulsion of the posterior tibial tendon insertion (tuberosity fracture), which may be repaired operatively, especially if a proximal dislocation of 1 cm or more is present. An avulsion of the posterior tibial tendon insertion must be differentiated from an accessory navicular (see Other Problems to Be Considered).
Fractures of the navicular body
Fractures of the body are commonly associated with other injuries of the midtarsal joint. Sangeorzan et al categorized navicular body fractures into 3 types, as follows [6] :
-
Type 1 is a coronal fracture with no dislocation.
-
Type 2 is a dorsolateral to plantomedial fracture with medial forefoot displacement.
-
Type 3 is a comminuted fracture with lateral forefoot displacement and carries the worst prognosis.
All navicular body fractures with 1 mm or more of displacement require open reduction and internal fixation.
Stress fractures
The rest of this article primarily discusses the diagnosis and treatment of navicular stress fractures, which are usually sports-related injuries.
In 1855, Brehaulpt first described stress fractures in military recruits who were subjected to long marches. As more civilians took up physically demanding sports, the incidence of stress fractures has increased in the general population. Towne et al first described stress fracture of the tarsal navicular in 1970. [7]
In athletes, navicular stress fractures are of particular concern because they are underdiagnosed and can lead to significant disability if the diagnosis is delayed. [1, 2, 3, 4, 5, 8] In a study by Torg et al in 1982, the average time between the fracture and diagnosis was estimated to be 7 months. [9] Given the significant improvement in outcome with early diagnosis and proper treatment, navicular stress fractures should be considered in any athlete with midfoot pain. In a 2006 study by Saxena and Fullem, navicular stress fractures took up to 4 months to heal posttreatment. [10]
Fracture-dislocation of the navicular may occur in athletes. [11, 12, 13, 14, 15, 16, 17, 18] This uncommon injury generally requires reduction and examination for stability via fluoroscopy, with the patient under general anesthesia. If the postreduction examination findings confirm stability of the navicular, treatment with a non–weight-bearing cast may be sufficient; otherwise, internal fixation is required.
Epidemiology
United States statistics
Navicular stress fractures may account for up to 35% of stress fractures in athletes. Because navicular stress fractures are not easily observed on plain radiographs, the reported incidence rates vary widely. The overall incidence may appear to be increasing due to advances in imaging. [19, 20, 21, 22, 23, 24, 25]
Among track-and-field athletes, up to 21% may experience a stress fracture in the course of a year. [26, 27] In these athletes, up to 15% of stress fractures are of the navicular. [26] Other studies have demonstrated similar findings. [28, 29, 30, 31] The highest incidence of stress fractures is in jumping and sprinting events.
Among military recruits, the incidence is approaching that of athletes, as the training of military recruits closely mirrors the training of athletes. [28, 32, 33, 34]
International statistics
Worldwide, the incidence of navicular stress fracture is related to the sport of participation and to the training that is involved rather than to geographic location.
Functional Anatomy
The tarsal navicular is a disk-shaped bone that articulates distally with the 3 cuneiforms, proximally with the talar head, and, occasionally, laterally with the cuboid. The distal articulation with the 3 cuneiforms is by means of 3 facets that have a common synovial cavity. The plantar and dorsal cuneonavicular ligaments reinforce the distal articulation.
On the lateral side are the plantar, dorsal, and interosseous cuboideonavicular ligaments and, occasionally, a syndesmotic joint with the cuboid. Medially, the distal articulation serves as an attachment for the posterior tibial tendon and the spring, or plantar calcaneonavicular, ligament. On the proximal side, it envelops the talar head completely. The thickened talonavicular ligaments reinforce the talonavicular joint in a plantar and dorsal orientation. Medially, the anterior fibers of the deltoid ligament add support.
Along with the calcaneocuboid joint, the talonavicular joint forms the transverse tarsal joint, which allows motion of the forefoot on the hindfoot. The ligamentous structure is such that when the hind part of the foot is everted, the joint is mobile, and when the hind part of the foot is inverted, the joint is fixed.
The blood supply of the navicular comes from small branches of the posterior tibial and dorsalis pedis arteries. This supply leaves the medial and lateral areas of the navicular relatively well supplied compared with the central section of the navicular. This relative difference correlates with the common site of stress fractures.
Sport-Specific Biomechanics
The navicular is part of 2 important structures that are essential for normal gait: (1) the medial longitudinal arch and (2) the transverse tarsal joint (also called the midtarsal or Chopart joint).
The medial longitudinal arch is composed of the navicular, calcaneus, talus, 3 cuneiforms, and 3 medial metatarsals. This arch provides support for normal gait, in particular from mid stance until push-off.
The transverse tarsal joint is essential for normal gait and is composed of the talonavicular joint and the calcaneocuboid joint. At heel strike, this joint is flexible and plays an important role in absorbing ground impact and accommodating the foot to the ground. At push-off, the transverse tarsal joint is locked and is helpful in forward propulsion.
Etiology
The particular cause of stress fractures in athletes or military recruits is often elusive. Obviously, the repetitive stress of their chosen activity leads to the fracture, but identifying a defect in technique, equipment, or schedule of activity is often difficult.
-
Some factors that have been implicated as causes of stress fractures include the following:
Starting athletic activity at a high level without a gradual increase in activity over time
Starting a second sport and assuming that the body is conditioned to participate at that sport immediately and at a high level. The navicular is at particular risk when runners participate in sports that require jumping and do not take the time for proper conditioning in their new sport.
Ill-fitting and/or old, worn equipment
Change in running or field surfaces
Relative osteopenia
Biomechanical abnormality
-
Some risk factors for stress fracture include the following:
Female sex
Unequal leg length
Any medical condition or behavior that may result in relative osteopenia, including smoking, hypothyroidism, steroid use, and rheumatoid arthritis
Sudden, significant weight loss
Prognosis
Using the aforementioned stepwise regimen of 6 weeks of not bearing weight on the injured foot, followed by a gradual return to normal activity (see Physical therapy in the Recovery Phase, Rehabilitation Program section, above), one can expect 86% of patients who receive such treatment to return to normal activity.
Complications
The complications of a navicular stress fracture can include delayed union, nonunion, and progression to overt fracture-dislocation. [11, 12, 13, 14, 15, 16, 17, 18] Any of these complications can lead to prolonged disability and/or arthritis of the talonavicular joint. Up to 14% of patients treated correctly do not return to previous activities. Often, these complications require surgical intervention.
Patient Education
Importantly, recognize that navicular stress fractures can occur in a wide range of athletes in many different sports, and that the diagnosis is made based on clinical considerations, positive bone scan findings, and confirmatory CT scan findings. However, once the diagnosis is made, non–weight-bearing treatment often results in full recovery.
For excellent patient education resources, visit eMedicineHealth's First Aid and Injuries Center. Also, see eMedicineHealth's patient education articles Broken Foot and Cast Care.
-
Palpation of the N spot.
