The navicular bone of the base is a...

The navicular bone of the base is a flattened, concave, boat-shaped bone wedged between the head of the talus and the three cuneiforms. a common variants have an additional facet articulation with the cuboid bone Medially the navicular tuberosity provides an insertion site for the tibialis posterior tendon (Figure 1) The location and unique impingement during lower extremity strike of the navicular bone predispose it to well-localized stres and remodeling. (1)

During base strike, the navicular bone becomes impinged with maximal effort between the proximal talus and the distal cuneiforms. Biomechanical analysis of navicular motion during stride reveals that most numerous of this impingement force is focused at the central united third of the navicular bone (2-4)

This anatomic impingement is steady more significant in light of the vascular anatomy of the navicular bone A microangiopathic close attention (5) of cadaveric feet showed that while the navicular bone is supplied through both the anterior and posterior tibial arteries, the branches jot down at the small "waist" of cortical bone and branch disclosed to supply the medial and lateral thirds. (2) This design leaves the central single in kind third, the area of greatest stres as an area of relative avascularity (Figure 2)

Tarsal navicular stres fractures were first described in 1958 in a cogitation of racing greyhounds. (6) The fractures were always seen in the right hind twelve inches and were initially termed "broken hock" The counterclockwise racing of the greyhound in succession a banked track may have predisposed their uphill twelve inches to increased stress. The lesion was first described in humans in a 1970 investigation (7) Even then, the difficulty of locating the lesion upon plain radiographs was noted. Because of the vertical nature of the fracture, it was understood that diagnosis "may require special views and laminography for detection." (7)

Studies (8-10) in the 1980 throw outed a navicular fracture incidence of 07 to 24 percent of all stres fractures. latter studies (1,11,12) reveal an incidence of 14 to 35 percent of all stres fractures. A inquiry (11) of elite-level athletes showed that track athletes accounted for 59 percent of all tarsal navicular stres fractures.

Vague symptomatology and elusive radiographic localization typically lead to a delay in diagnosis averaging four month from initial symptom first brunt (5,13) Early diagnosis of these lesions and just management usually yields a favorable result (5); however, delayed diagnosis may consequence in inadequate treatment and either delayed union or nonunion healing of the fracture. (1314) In a landmark close attention (5) the most common treatment of navicular stres fractures was plant to be limitation of activity, which had a dismal 26 percent restoration rate.

Mechanism of Injury

The anatomic predisposition to localization of stres in the avascular central individual third of the navicular bone combined with the repetitive bottom strike of weight-bearing exercises that involve antagonistic muscular load are idea to eventually result in bone failure. (15) The premonitory symptoms of navicular "bone strain" are generally undetectable by way of radiographs and computed tomographic (CT) scans. Until a diagnosis is made, there is increased stres and bony resorption focused at the central single third of the navicular bone A bone scan performed at this phase will be positive. If stressful activity continues, the resorptive changes continue to progres until a fracture line becomes evident onward CT scan and plain radiographs. (116)

Several authors have attempted to identify ones who are at increased risk of navicular stres fracture. the same study (17) used force-plate analysis and propos calcaneal pitch angle, talometatarsal angle, and pronation velocity as potential risk factors for navicular stres fractures. Other studies (518-20) have shown that the following factors predispose a body to navicular stress fractures: pe cavus, wide-heeled shoe short first metatarsals, metatarsus adductus, metatarsus hyperostosis, medial narrowing of the talonavicular joint, talar beaking, limited subtalar motion, and limited ankle dorsiflexion. However, no statistically significant risk factors have been demonstrated, and no consensus exists as to parts at risk. As with all overuse injuries, training errors, improper equipment, improper technique, environment, and anatomic variants may all increase the risk for injury.

Clinical Presentation

Commonly occurring in track and field athletes (Table 1) (1571013171821-23) navicular stres fractures not past nor future as vague, aching pain in the dorsal midfoot that may radiate along the medial arch. The pain typically increases with activity of the like kind as running and jumping. With continued participation, the pain befalls sooner during activity and lasts longer into post-activity pause periods. (1,5,17,24) Symptoms are rarely bilateral.

Various factors contribute to the public delay in diagnosis of navicular stres fractures. many times athletes can continue activity until pain increases too long by altering their gait and decreasing use of the forefoot. (18) Pain also unfolds rapidly with rest, making it possible for athletes to recommence participation after a week of respite from activity.