Navicular Stress Fractures
The navicular bone is one of the seven bones of the rear foot. It is a small boat-shaped bone (hence the name navicular), located just in front of the anklebone on its inner side, right above the arch of the foot.
Excessive repeated stress on the bone that exceeds its normal remodelling capacity leads to the formation of micro fractures known as stress fractures. In the case of the navicular bone, the incidence of stress fractures has increased over the past few decades. In 1980, navicular stress fractures accounted for 1–2 percent of total stress fractures, while in studies conducted in the late 90s, the ratio increased to 14-35 percent.
More than half of these fractures are seen in track and field athletes. Football players, basketball players and persons involved in vigorous physical activities (jumping, sprinting etc.) are also at higher risk of developing navicular stress fractures.
The tibialis posterior muscle is attached to the navicular bone and exerts a pulling force on the bone every time it contracts. Along with this, the anatomical location of the navicular bone predisposes it to increased stress. As we walk or run, the navicular bone gets compressed between the talus bone at its back and the other tarsal bones located in front. The central portion of the bone takes the greatest stress and, because of the relatively limited blood supply to this area, its remodelling or healing capacity is also limited. For this reason, an undue stress or excessive strain leads to the formation of stress fractures (micro fractures) in the bone structure.
- The onset of pain is always gradual. It starts as a diffuse dull pain on the upper surface of the mid foot, which may spread to the inner side of the food along the arch.
- Pain initiates with activity and diminishes at rest
- Over time, pain sets in early with activity (even walking may initiate pain) and lasts longer (even at rest)
- The area over the navicular bone (N spot) becomes tender to the touch, there may also be a mild swelling
- Usually, only one foot is involved.
The main hurdle in navicular stress fracture management is that these are hard to diagnose early on. X-rays are no help in the initial stages. A bone scan is useful in detecting the early changes, however, a CT scan or MRI is required to get accurate details and establish a treatment plan.
Early treatment gives best results. The more delayed the treatment is, the more time will be required for the fracture to heal properly.
For non-displaced stress fractures, use of non-weight-bearing casts is a very effective treatment that works in about 86% of cases. The cast is applied for a 6 week-period and the area is examined for tenderness afterwards. If the N spot is still tender, the cast is reapplied for a further two weeks.
Once the cast is removed, it is imperative to check the N spot for any tenderness or pain every two weeks for about two months. If there is no tenderness the person can start with physiotherapy and gradually return to normal activity levels.
If the immobilization treatment does not work, or if the fracture is diagnosed late and/or is displaced, surgery is required.
Surgery involves fixing the fractured bone using bone screws and/or placing bone grafts. It provides quick healing and may also be performed if an athlete requires quick healing to return to sports activities.
Strengthening exercises, using proper techniques and equipment, sports massage and correcting lower limb biomechanics are all important factors in preventing navicular stress fractures.
Innersoles are used to correct any biomechanical abnormalities in the feet.