Introduction:
Stress fractures of the navicular are one of the most frequently overlooked or delayed diagnoses in the foot due to the lack of acute trauma, pain, and edema, as well as the difficulty in spotting these fractures on standard radiographs, which increases the risk of non-union. The tarsal navicular bone, located in the foot's medial column, carries most of the stress while walking, making it prone to fractures. Hence, it is prone to a stress fracture. Stress fractures of the tarsal navicular are common among athletes who participate in cutting, pivoting, and particularly running sports, and can cause significant midfoot discomfort.
What Is the Tarsal Navicular Bone?
The navicular bone of the foot is a flattened, concave, boat-shaped bone, which predisposes it to localized stress and remodeling. The impingement force is focused on the complex central one-third of the navicular bone, which has a decreased blood supply. They can cause significant midfoot discomfort and were initially termed "broken hocks" due to increased stress. The fractures are difficult to identify on standard radiographs. Due to the fracture's complexity, the diagnosis “may require specialized imaging techniques for diagnosis."
The fractures of the navicular bone are classified into three types:
-
Type I: Less than 50 % of bone involvement with no significant deformity.
-
Type II: Oblique fracture of the bone with forefoot adduction deformity (tarsal bones turned towards the middle of the body), a Z-shaped foot, and residual clubfoot.
-
Type III: Central or lateral comminution with abduction deformity (tarsal bones turned away from the midline of the body; external lower limb rotation results in wide open feet while walking).
What Are the Causes of Tarsal Navicular Bone Fractures?
The most common causes of navicular bone fractures are sudden trauma and chronic overuse injuries, training errors, improper sports equipment, technique, environment, and anatomic variants, which may increase the risk for injury. These are often seen in athletes running on hard surfaces and also in baseball players. Mueller-Weiss syndrome is a rare condition that can cause navicular bone necrosis, and it is commonly seen in middle-aged adults with chronic midfoot pain. Patients with poor nutrition and low bone density have an increased risk of navicular bone fractures.
What Are the Symptoms of Tarsal Navicular Bone Fractures?
The common symptoms of tarsal navicular bone fractures are:
-
Significant or ambiguous foot pain and discomfort while running and leaping. Initially, patients experience pain only during high-intensity activities like running and jumping. Gradually, they can progress to pain with low-intensity activities, such as walking, and eventual steady pain, even at rest."
-
Bruising (internal bleeding).
-
Midfoot swelling.
-
Tenderness on compressing the navicular bone or midfoot.
How to Diagnose Navicular Bone Fractures?
The diagnosis of navicular fractures is based on a physical examination followed by radiological evaluation and imaging.
-
Examination: The examination of navicular stress fractures often reveals a normal range of motion and muscular strength with no evidence of edema, petechiae, or deformity. The pain is increased with hopping, toe hopping, and standing on their toes in the equinus position. By inverting-everting the forefoot, one may pinpoint the location of the talonavicular joint with tenderness. It is also referred to as the "N spot".
-
X-rays: It is difficult to evaluate the tarsal navicular fracture with plain X-rays because of its complexity. Most fractures must be completed and are frequently missed on the first images because of bone resorption. However, plain radiographs are used to evaluate the causes.
-
Bone Scan: The triple-phase bone scan is recommended if the X-ray results in negative or inconclusive remarks. In contrast to standard radiography, bone scanning detects early navicular stress fractures. Positive bone scans must always be correlated with further imaging like CT scans and MRIs due to their lack of specificity, clarity, and poor demonstration of comminution and displacement of the fractures.
-
CT (Computed Tomography) Scan: CT is the gold standard for evaluating bone fractures and has excellent clarity and specificity for navicular fractures. Based on CT, the navicular fracture is divided into three types:
-
Type I: Fracture extending into the navicular body.
-
Type II: The fracture extends into another cortex.
-
Type III: Complex fractures.
-
MRI (Magnetic Resonance Imaging): MRI is an alternative imaging technique for bone scanning with excellent resolution of fracture sites. It is widely used in the evaluation of edematous bone.
What Is the Treatment of Tarsal Navicular Fracture?
The severity and location of the injury determine the treatment of tarsal navicular stress fractures. Most of these fractures are initially treated with a cast and non-weight bearing for six weeks.
-
Non-Operative or Conservative Treatment Phase: The cast immobilization with no weight bearing for 6 to 8 weeks is indicated in mild to moderate fractures, followed by functional rehabilitation.
-
Operative or Surgical Phase: The fractures that fail to improve with the non-operative phase are converted to surgical intervention. Type III navicular body fractures, non-union, and displaced fractures are treated with surgery due to delayed healing and poor blood supply.
-
Rehabilitation Phase: Functional rehabilitation promotes regular day-to-day activity and gradually improves sports performance like running or jogging with no symptoms of tenderness in the affected area.
-
Week one to two: Normal essential activity.
-
Week three to four: Minor exercise on alternative days, like jogging on a smooth surface.
-
Week four to six: Gradually increase the speed of running and walking.
-
After week six, athletes can return to sports training if there are no symptoms.
How to Prevent Tarsal Navicular Injuries?
General bone health and nutrition play a vital role in preventing fractures. For example, adequate consumption of calcium and vitamin D has been shown to decrease the risk of stress fractures. In addition, stress fracture risk is reduced by equipping the trainer with the proper shoe and playing surface.
Conclusion:
Tarsal navicular stress fractures are considered high-risk because non-healing stress fractures are familiar with either conservative or surgical treatments due to the poor blood supply to the bone. Return to play can take several weeks or even months with either treatment. Usually, tarsal navicular stress fractures heal within a minimum of 12 weeks or even longer, depending on the degree of injury. These injuries require a slow and gradual return to sports based on the tenderness of the N spot.
