To start us off into the world of rare pathologies, we will be covering navicular fractures this week. A navicular fracture is rare but can be seen, especially in athletes. First, lets talk about what and where the navicular bone is.
The navicular is a bone in the foot also known as the scaphoid bone. It is located towards the inside of the foot (medially) between the heel and the metatarsals. It can be found by running your fingers along the inside of the foot starting at the heel and moving towards the toes. As you slide your fingers along your foot, the first small bump/bulge you feel indicates the location of the navicular. The bone extends from the medial side of the foot, half way across the top over to the outside (lateral side) of the foot. Picture a sideways teardrop-shaped piece of bone that serves as a stabilizer of the foot, particularly the arch.
The best way to discuss navicular fractures is to break them down by the type of fracture suffered. Navicular fractures come in 4 types, as classified by the Watson and Jones Classification System (here we go again: we Podiatrists classifying and naming everything)! Each type of fracture results from a slightly different mechanism of injury and, thus are treated according to that mechanism.
- Avulsion fracture of the most medial side (fracture of the palpable bump along the inside of the foot). At this area of the bone a large tendon, known as the Posterior Tibial Tendon, responsible for supporting the arch of the foot, attaches. An avulsion injury occurs when increased tension is placed on the tendon while the foot is moving away from the body, whereby the strength of the tendon pulls off (avulses) the most prominent piece of the navicular bone. Most of these fracture fragments remain in close proximity to the main portion of the navicular and will heal properly with immediate immobilization via casting and non-weight bearing for at least 4 to 6 weeks.
- Chip fracture off of the top surface of the bone. This type of navicular fracture is the most common of the 4 types (although still a rare injury) and can also be referred to as an avulsion injury. Although this time it is not a tendon that is pulling off a piece of bone, but rather a ligament on the top of the foot that becomes tensioned while the foot is moving downward and inward at the same time. If the avulsed fragment is small, casting with non-weight bearing for 4 to 6 weeks is indicated, but if the fragment is much larger surgery may be required to accurately reposition the fragments.
- Fracture of the body. This type of navicular injury is the least common fracture type and typically results from direct injury, such as a can of soup tumbling out of the pantry and falling onto the foot! The fracture line usually extends from the top to the bottom of the foot, splitting the bone in half. If the two pieces remain close in proximity, casting with non-weight bearing for 4 to 6 weeks is adequate treatment. However, if the pieces become separated or if there are more than two pieces created with injury, surgery may be indicated to re-approximate the fragments and encourage a greater chance for healing.
- Stress fracture of the body of the navicular. This diagnosis is commonly overlooked because the injury is very difficult to evaluate on standard x-ray therefore, diagnosis comes with a high index of suspicion on the part of your Podiatrist. Sufferers of navicular stress fractures are commonly track and field athletes who describe vague and diffuse pain in the midfoot region. If not recognized and treated with immobilization immediately, a stress fracture can lead to complete fracture.
Navicular fractures can be treated in a fairly straightforward fashion, by recognition and casting with non-weight bearing until healing has been achieved. Unless the fracture fragments are displaced (separated from one another), surgery can typically be avoided. Navicular fracture may not be the first injury to come to mind in foot and ankle injuries, as it is fairly uncommon, but it can be seen!