Edited by Anthony Van Bergeyk, MD
Navicular stress fractures (NSF) are uncommon but serious injuries, characterized by a chronic midfoot ache at the top of the arch of the foot in front of the ankle. The cause is a repetitive chronic load to the midfoot, often from dynamic sporting-type activities. NSF is difficult to diagnose as it may not be seen on regular x-rays. Treatment involves a period of prolonged non-weight-bearing. Navicular stress fractures that are not healing may require surgery to stabilize the fracture with one or more screws.
Patients who develop navicular stress fractures will present with a chronic mid-foot ache. Although anyone can get NSF, the most common presentation is in the athlete. However, unlike a typical stress fracture of the metatarsals (which are much more common), these loading episodes tend to be more dynamic. Some examples include the lead foot of an active golfer, a middle distance runner, or any college or professional athlete performing dynamic repetitive activities.
The symptoms are often generalized to the mid-foot. The relatively vague location of the symptoms makes NSF difficult to diagnose. Pain may be with athletic activities only; however, some patients might even have a limp while walking.
Physical examination will demonstrate a generalized tenderness around the top of the mid-foot. An astute physician may be able to localize the tenderness to the top of the navicular bone. Certainly, attempts to hop or rise up on the toes of the affected foot will be painful. There is some suggestion that patients with slightly higher arch feet, as well as patients with an unusually long second toe (the second toe is usually the longest toe anyway), may have an increased risk of developing navicular stress fractures. These two situations may increase the force transmitted into the navicular, particularly in patients doing activities that involve them getting up on their toes such as sprinting and jumping. But most commonly, the person with a Navicular Stress Fracture has a normally-aligned foot.
X-rays are often read as normal. Sometimes a subtle fracture line can be identified. In more advanced cases, or in cases where there is degeneration of the talonavicular joint, x-rays will be abnormal.
Diagnosis can be made with an MRI, a CT scan, or a bone scan. An MRI or a CT scan will allow the fracture orientation to be identified. In addition, those studies will allow determination of whether the fracture is complete or incomplete through the bone. MRI can also be helpful in determining the presence or absence of blood flow to the bone but costs more.
Navicular stress fractures can be difficult to treat due to the poor blood supply to the navicular (a good blood supply is needed for healing of any bone injury), and the fairly extensive force that this bone absorbs in both normal walking and in sporting type activities. Good results have been reported when treating undisplaced navicular stress fractures with treatment involving casting, and a period of non-weight-bearing of 6 weeks. Success rates of 85-90% have been reported with this treatment method. Doctors may also recommend the use of a bone stimulator, which is designed to encourage bone healing. However, there is no clear evidence that the stimulator shortens the time to healing.
Surprisingly, if the patient walks on the cast, the rate of healing may fall as low as 25%. It is common to require three, four, or more months to make a full recovery from an undisplaced navicular stress fracture, and it may be a season-ending injury for an athlete. Unfortunately, patients who have developed a navicular stress fracture are at risk for having a recurrent fracture, because the original reasons for the NSF are usually unchanged even after the fracture has healed.
Surgery may be recommended for some patients, especially if an initial period of non-operative treatment is not successful. Surgery may include drilling across the fracture, placement of one or more screws, and possibly the addition of a bone graft to improve healing. Surgery usually results in successful healing, but a period of rest and non-weight bearing is required after surgery, and overall recovery time is still prolonged.
Displaced Navicular Stress Fractures
In rare cases, a navicular fracture may go on to displace. Non-operative treatment is no longer appropriate; surgery is needed to reduce the fracture (set it in exact position), hold it in place with screws, and possibly add a bone graft.
Potential Complications of Navicular Stress Fractures
The most obvious and concerning potential problem with non-operative treatment is persistence of the fracture and the accompanying pain. If the fracture is not showing signs of healing, then surgery should be considered.
In rare cases, the navicular bone can collapse. This may be part of a more complex and rare disease. Collapse compromises the function of the hindfoot joints and is difficult to manage.
If a navicular fracture heals in poor alignment, arthritis of the associated joint (the talonavicular joint) will set in, with resulting pain and stiffness. Surgery to fuse the talonavicular joint can alleviate much of the midfoot pain associated with talonavicular arthritis. However, it has a fairly prolonged recovery time of six or more weeks of non-weight bearing. In addition, it greatly increases the stiffness of the midfoot.
Edited on August 14, 2017
Previously edited by Mark Perry, MD and Justin Greisberg, MD