The term stress fracture describes a fracture that is the result
of repetitive load (stress) and the failure of the bone to manage and heal the
effects of that load. If a
bone is unable to manage and repair repetitive load (stress), the bone undergoes
fatigue and breaks (fractures). Stress fractures are not due to trauma but are
the result of biomechanical loads that are greater than the ability of the bone
to support that load over time.
How do we define the different types of load that are applied to
bone? Load may be defined as the duration of load, the frequency of load or the amount of load.
Other factors that play into the onset of stress fractures include the general
medical status of a patient. Malnutrition, age, osteoporosis, smoking and a host of
medical co-morbidities play a role in the ability of bone to repair itself, prior to and leading up to a stress fracture.
These co-morbidities make the bone less able to heal repetitive stress.
Therefore, the greater the number of co-morbidities, the less stress that is
needed to ultimately result in a stress fracture.
The most common stress fractures that occurs in the foot
are found in the metatarsal bones.
Metatarsal stress fractures are also referred to as march fractures. The
term march fracture came about as the result of forcing young, sedentary army recruits to march 20 miles with a full backpack. Their transition from civilian to soldier was too abrupt resulting in a load that was greater than what the metatarsal bone could tolerate.
Other stress fractures that occur in the foot include
calcaneal stress fractures (the heel), navicular stress fractures (medial arch) and cuboid stress fractures (the lateral arch). Essentially any bone, when put under too much stress, for too long a period of time can sustain a stress fracture.
Treatment of stress fractures
At the onset of symptoms, the diagnosis of a stress fracture may
be challenging to make. Stress fractures are a microscopic change in the
structure of the bone, therefore, x-ray findings of stress fractures are subtle
if present at all. Suspected stress fractures should be screened with an x-ray
at the onset of symptoms to rule out other bone pathology such as bone tumors or
arthritis.
Over the course of several weeks, the repair process of the bone
will become evident on x-ray leading to the confirmation of a stress fracture.
The fracture itself isn't actually visualized on x-ray, but rather the repair
process in response to the fracture is seen. This radiographic finding is
called bone callus. Bone callus helps to stabilize the stress fracture and
acts as the body's own internal cast. When visualized on x-ray, bone callus can
be identified 4 weeks following the onset of symptoms. If bone callus is
not seen and a stress fracture is still suspected, computerized tomography (CT Scan)
can be helpful in defining stress fractures. A stress fracture in some bones, particularly hard cortical bone, may create a fracture line that is sharp and clear on CT scanning. MRI's are also used to test for stress fractures. MRI's are particularly helpful in identifying areas a edema (swelling) within
soft, cancellous bone that may be associated with a stress fracture.
The technique of treating stress fractures varies in each case but the fundamental principles are the same. First, we need to confirmed that the fracture is stable, well aligned and that the ends of the fracture appose each other. Once we've confirmed alignment and apposition, treatment is simply variation of rest. Treatment may include bed rest, a
hard non-weight bearing cast, a
walking cast, a
fracture shoe,
bandaging or just decreasing activity. As you can see, each of these methods of treatment is a variation of rest. Most stress fractures of the foot will heal over time with just a little help. How long? Patients are usually surprised to find out that stress fractures take 8-12 weeks
(or more) to heal.
In a limited number of cases, stress fractures may require
surgical care. Surgical care focuses on stimulating the fracture repair
process. Treatment may include bone grafting, drilling of the bone or
stabilization with fixation.
