How Do You Know if You Have a Navicular Fracture?
Tarsal Navicular Stress Fractures
Am Fam Physician. 2003 Jan ane;67(i):85-91.
Article Sections
- Abstract
- Mechanism of Injury
- Clinical Presentation
- Physical Examination
- Radiologic Tests
- Handling and Return to Action
- References
Stress fractures of the tarsal navicular bone are being recognized with increasing frequency in physically active persons. Diagnosis is commonly delayed, and issue often suffers because physicians lack familiarity with the condition. Navicular stress fractures typically present in a running athlete who has gradually increasing pain in the dorsal midfoot with occasional radiation of pain downwards the medial arch. Because initial plain films are often normal, the side by side diagnostic exam of choice is triple-phase bone scan, which is positive early on in the process and localizes the lesion well. After a positive bone scan, a computed tomographic scan should be obtained to provide anatomic detail and guide therapy. Nondisplaced, noncomminuted fractures respond well to six weeks of not–weight-bearing cast immobilization. Displacement, comminution, and delayed or nonunion fractures are indications for surgical open reduction internal fixation.
The navicular bone of the foot is a flattened, concave, boat-shaped os wedged between the head of the talus and the three cuneiforms. Some 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 foot strike of the navicular os predispose information technology to well-localized stress and remodeling.1 During pes 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 about of this impingement strength is focused at the central one third of the navicular bone.2–4
Figure 1.
Radiograph of the foot, anteroposterior view, showing the calcaneus (blackness arrow), talus (white arrow), and navicular bone (arrowhead).
This anatomic impingement is even more than significant in light of the vascular beefcake of the navicular bone. A microangiopathic study5 of cadaveric feet showed that while the navicular bone is supplied by both the anterior and posterior tibial arteries, the branches enter at the small-scale "waist" of cortical bone and branch out to supply the medial and lateral thirds.2 This blueprint leaves the fundamental 1 third, the expanse of greatest stress, equally an area of relative avascularity (Figure 2).
FIGURE 2.
Dorsal view of the tarsal navicular bone. The avascular primal 1-third is also the fulcrum of the impingement forces from the starting time and third metacarpal bones, equally well as the talus.
Tarsal navicular stress fractures were starting time described in 1958 in a study of racing grey-hounds.half-dozen The fractures were always seen in the right hind foot and were initially termed "broken hock." The counterclockwise racing of the greyhounds on a banked track may have predisposed their uphill foot to increased stress. The lesion was offset described in humans in a 1970 study.seven Fifty-fifty then, the difficulty of locating the lesion on evidently radiographs was noted. Because of the vertical nature of the fracture, information technology was understood that diagnosis "may require special views and laminography for detection."7
Studies8–ten in the 1980s projected a navicular fracture incidence of 0.7 to 2.4 percent of all stress fractures. Recent studies1,xi,12 reveal an incidence of xiv to 35 percent of all stress fractures. A study11 of elite-level athletes showed that rails athletes accounted for 59 percent of all tarsal navicular stress fractures.
Vague symptomatology and elusive radiographic localization typically lead to a delay in diagnosis averaging 4 months from initial symptom onset.v,13 Early diagnosis of these lesions and proper management ordinarily yields a favorable outcome5; nonetheless, delayed diagnosis may result in inadequate treatment and either delayed union or nonunion healing of the fracture.xiii,14 In a landmark report,5 the most common treatment of navicular stress fractures was found to exist limitation of activity, which had a dismal 26 percent cure rate.
Mechanism of Injury
- Abstract
- Mechanism of Injury
- Clinical Presentation
- Concrete Exam
- Radiologic Tests
- Treatment and Render to Activity
- References
The anatomic predisposition to localization of stress in the avascular central one third of the navicular bone combined with the repetitive human foot strike of weight-begetting exercises that involve antagonistic muscular load are thought to somewhen issue in bone failure.15 The premonitory symptoms of navicular "os strain" are generally undetectable by radiographs and computed tomographic (CT) scans. Until a diagnosis is made, in that location is increased stress and bony resorption focused at the primal i 3rd of the navicular bone. A os scan performed at this stage volition exist positive. If stressful activeness continues, the resorptive changes continue to progress until a fracture line becomes axiomatic on CT browse and plainly radiographs.1,16
Several authors have attempted to identify persons who are at increased risk of navicular stress fracture. One study17 used force-plate analysis and proposed calcaneal pitch angle, talometatarsal angle, and pronation velocity as potential risk factors for navicular stress fractures. Other studies5,xviii–xx have shown that the following factors predispose a person to navicular stress fractures: human foot cavus, wide-heeled shoes, short first metatarsals, metatarsus adductus, metatarsus hyperostosis, medial narrowing of the talonavicular articulation, talar beaking, limited subtalar motility, and express ankle dorsiflexion. Notwithstanding, no statistically significant risk factors have been demonstrated, and no consensus exists every bit to persons at risk. As with all overuse injuries, training errors, improper equipment, improper technique, environment, and anatomic variants may all increment the adventure for injury.
Clinical Presentation
- Abstract
- Mechanism of Injury
- Clinical Presentation
- Physical Examination
- Radiologic Tests
- Treatment and Return to Action
- References
Normally occurring in rail and field athletes (Table 1),1,5,seven,10,13,17,18,21–23 navicular stress fractures present as vague, aching hurting in the dorsal midfoot that may radiate along the medial arch. The pain typically increases with action such as running and jumping. With continued participation, the hurting occurs sooner during activity and lasts longer into postactivity balance periods.i,v,17,24 Symptoms are rarely bilateral.
Table 1
Action-Specific Incidence of Navicular Stress Fractures
| Activity | Incidence (%) | |
|---|---|---|
| Track and field | 59 | |
| Football | ||
| Australian | nineteen | |
| American | 3 | |
| Soccer | 1 | |
| Basketball | ten | |
| Field hockey | 2 | |
| Racquet sports | 2 | |
| Ballet | 1 | |
| Gymnastics | ane | |
| Cricket | one | |
Various factors contribute to the common delay in diagnosis of navicular stress fractures. Oftentimes, athletes tin can continue activity until pain increases besides much by altering their gait and decreasing use of the forefoot.eighteen Pain also resolves rapidly with rest, making information technology possible for athletes to resume participation after a calendar week of respite from activeness.
Physical Examination
- Abstract
- Machinery of Injury
- Clinical Presentation
- Physical Exam
- Radiologic Tests
- Treatment and Return to Activity
- References
Patients who present with navicular stress fractures typically have a normal range of motion and strength to manual muscle testing, and the neurovascular examination is normal. There is no ecchymosis or deformity and usually no swelling. The talonavicular joint can exist localized by inverting-everting the forefoot. The nickel-sized area at the central region of the proximal dorsal navicular bone, referred to as the "N" spot, is tender in 81 percent of patients with navicular stress fractures.five Patients generally showroom increased pain with hopping, toe hopping, and standing on their toes in the equinus position.18
Radiologic Tests
- Abstract
- Machinery of Injury
- Clinical Presentation
- Concrete Test
- Radiologic Tests
- Treatment and Return to Activity
- References
Evidently RADIOGRAPHS
When suspicion justifies diagnostic studies, the initial footstep is typically patently radiographs. Unfortunately, only 33 per centum of plain radiographs accept sensitivity for navicular stress fractures,ane,25 because the majority of fractures are incomplete.1 In improver, because bony resorption requires 10 days to three weeks to allow visualization of these fractures on plain radiographs, even consummate fractures are oft not seen on initial films.26 However, patently films are useful if positive, and they also assist in ruling out other etiologies.27
BONE SCAN
If plain films are negative or inconclusive, triple-phase bone scan is the next recommended diagnostic process. Bone browse, unlike plain radiography, is positive at an early on stage and is almost 100 percentage sensitive for navicular stress fracture.one The entire navicular bone demonstrates uptake in all phases in a positive test24 (Figure three); delayed-phase images may take up to two years after spousal relationship to render to normal.15 The high negative predictive value of os scanning essentially excludes the diagnosis with a negative test; however,the positive predictive value is lower. A bone browse may exist positive with negative follow-up studies (e.k., CT scan, magnetic resonance imaging [MRI]). This phenomenon is thought to stand for "bone strain" or subclinical stress reaction, and it inevitably proceeds to actual fracture if concrete activeness is continued at the aforementioned intensity level.28 Positive bone scans must e'er be correlated with further imaging (i.e., CT scan) because of lack of specificity, poor sit-in of comminution and deportation, and lack of resolution of the anatomic characteristics of these fractures.24
Figure 3.
Triple-phase os scan of the lower extremities revealing intense uptake in the entire left navicular bone (arrow), the classic sign of a navicular stress fracture.
CT SCANNING
CT scanning is the gilded standard for optimal evaluation of a fracture one time bone scan has demonstrated increased uptake in the navicular bone.24 Unlike bone scanning, the anatomic resolution of CT scans is splendid. The best images are obtained with 1.v-mm slices using a os algorithm through the plane of the talonavicular articulation.29 Fake-negative CT reports, estimated at 7 percent, are typically caused past defoliation of an actual fracture with nutrient arteries.xiii
CT scans about commonly demonstrate a partial fracture coursing from the proximal dorsal primal ane third of the navicular os and extending toward the distal plantar pole of the bone1 (Effigy four). Fragmentation is seen in approximately 14 percent of navicular fractures.xiii Sclerosis is typically seen at the proximal articular rim; this finding is believed to correspond the normal stress of weight bearing, not early bear witness of nonunion.29
FIGURE 4.
Computed tomographic scan of the left human foot. This axial view reveals consummate fracture of the navicular bone (pointer), located more laterally than is typical. Incidentally noted is a calcaneonavicular tarsal coalition (double arrow).
A proposed CT-based classification system separates fractures into three groups: dorsal cortical pause (blazon I), fracture propagation into the navicular body (type II), and fracture propagation into some other cortex (type 3). Type III lesions take the longest average healing time with conservative care. These lesions may warrant more aggressive treatment and orthopedic referral for possible open reduction internal fixation.30
MRI
MRI is a reasonable choice for imaging navicular stress fractures, particularly if bone scanning is non available, because it is extremely sensitive and provides good spatial resolution.31 Because of its toll and limited availability, MRI is frequently overlooked equally a modality; however, in cases of high pre-exam probability, MRI offers the bonny profile of nigh 100 percent sensitivity also equally practiced anatomic resolution of the fracture. Bony edema on Ttwo-weighted images, an early finding, can add useful data regarding the acuity of the injury and delineate associated injury32 (Effigy 5). MRI does not add together significant information if bone scan and CT scan are available. If cost is non an upshot, and time is of the essence, an MRI can give information similar to that of bone scan plus CT scan.
Effigy 5.
Magnetic resonance image of the foot, revealing a sagittally oriented fracture through the central region of the navicular (arrow). Note all-encompassing surrounding edema.
Treatment and Return to Activity
- Abstract
- Mechanism of Injury
- Clinical Presentation
- Concrete Examination
- Radiologic Tests
- Treatment and Return to Action
- References
Therapeutic intervention in navicular stress fractures has been clearly defined1,13,eighteen,19 (Tabular array 2).xiii In 86 pct of cases of nondisplaced navicular stress fracture, six weeks in a well-molded non–weight-bearing cast results in healing.one If clinical healing has occurred and in that location is no tenderness at the "North" spot afterward six weeks in the cast, functional rehabilitation may begin1 (Table 31). The patient should be reassessed every two weeks and, if there is no increase in tenderness at the "North" spot, can typically return to full action six weeks after removal of the cast. If the navicular os remains tender, the patient should exist kept in the non–weight-bearing cast for two more than weeks and clinically reexamined after that fourth dimension.1,5,thirteen,nineteen,24
Table 2
Outcomes of Various Treatments for Tarsal Navicular Stress Fracture
| Treatment | Number of cases | Success rate (%) | Return to activity (months) |
|---|---|---|---|
| Non–weight-begetting bandage (≥six weeks) | 22 | 86 | five.six |
| Non–weight-bearing cast (2 to v weeks) | 13 | 69 | three.7 |
| Limitation of activeness (≥half dozen weeks) | 34 | 26 | 5.8 |
| Limitation of activity (3 to 5 weeks) | 6 | 50 | iii.vii |
| All conservative, excluding non–weight-begetting bandage | 58 | 38 | nine.3 |
| Surgery | half dozen | 83 | iii.viii |
| Continued sporting action | 5 | 20 | 0.0 |
One time rehabilitation has begun, whatever foot hurting must be reevaluated advisedly. General discomfort caused past immobilization, forth with stiffness of the talocrural, subtalar, and midtarsal joints, is to be expected and responds to physical therapy.1 However, if the discomfort localizes over the navicular bone, further immobilization or surgical intervention may be indicated.
TABLE 3
Functional Rehabilitation of Tarsal Navicular Stress Fracture
| Weeks one to ii: | Normal activities of daily living, swimming, and water running are permitted. |
| Weeks 3 to 4: | If in that location is no increase in tenderness at the "Northward" spot, jogging on grass for v minutes on alternating days is permitted. Subsequently i week, increment to 10 minutes on alternate days. |
| Weeks v to 6: | If "N" spot is not tender, running at l pct of maximum speed with walk recovery on alternate days is permitted. This speed can be increased to 75 percentage over some other two weeks. |
| Later 6 weeks: | If "Northward" spot is not tender, patient can gradually return to full grooming activeness, as tolerated. |
Radiologic follow-up is non useful in about circumstances. Patently films are not sensitive plenty to detect subtle changes in almost cases and filibuster the clinical moving-picture show significantly.ane,25 Os scans tin can remain abnormal for up to two years after clinical healing.15 CT scanning can reveal pregnant loss of bony mineralization, sclerosis, notching of the proximal articular surface, and subchondral cysts even in a normal healing fracture; it is, therefore, unreliable as a guide to follow-up.1,five,13,xv,24,25
Analysis of the patient'south gait with orthotic evaluation is prudent to assistance compensate for any underlying biomechanical abnormality and forbid recurrence.1,15,nineteen,25 Information technology is important to address whatever grooming abnormalities, nutritional concerns, flexibility issues, or other factors that may place the athlete at risk of recurrence.
OPERATIVE Handling
Indications for operative intervention include the rare displaced fracture, fragmentation, and failure of conservative therapy leading to delayed union or nonunion.xiv,xviii,24 Some physicians advocate more aggressive surgical handling for blazon III complete fractures.30 Surgical intervention also may be indicated in athletes who need quick healing to allow them to render to play. The boilerplate time for athletes to return to play after surgical intervention compared with conservative management using a non–weight-bearing cast is three.eight months and v.half-dozen months, respectively.1 Typically, surgical intervention consists of screw fixation, with possible os graft inlay.
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Figure 1 provided by Gail Wadley, the Ohio State University Sports Medicine Heart.
REFERENCES
bear witness all references
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Coordinators of this serial are Mark Meyer, M.D., University of Kansas School of Medicine, Kansas City, Kan., and Walter Forred, Thou.D., Academy of Missouri–Kansas Metropolis Schoolhouse of Medicine, Kansas Urban center, Mo.
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