Stress Fractures

Edited Kenneth Hunt, MD 

Summary

Stress Fractures occur when excessive repetitive force is applied to a localized area of bone.  Activities such as walking, running, and repeated jumping can subject the bones of the foot to large forces, often leading to microscopic cracks in the bone, called “microfractures”.  Normally, the body is able to sufficiently heal these microfractures, leading to a stronger bone able to accommodate these higher forces in the future.  However, when the rate of loading on the foot is such that the body’s healing response can not keep up, a stress reaction can develop. Eventually, if the forces continue, the bone structure can fail and a stress fracture will occur. An individual’s lack of sufficient biology to heal microfractures (i.e., low calcium, vitamin D, or thyroid hormone) can also contribute or lead to stress fractures.

Indication

Stress fractures occur in the same manner that you would break a paper clip – excessive wiggling back and force will lead to breakage. Stress fractures can occur in:
  1. Normal bone that is subject to abnormally excessive repetitive loading. An example of this would be a new army recruit going on a long march as part of basic training who, as a result of this dramatic increase in repetitive loading, develops a stress fracture (often called a “March” fracture).
  2. Weakened bone that is subject to seemingly normal repetitive forces. For example, a person with thin bone (ex. osteoporosis) who walks much more than they are used to.

Stress fractures do not occur in random locations. They occur in certain bones, and locations within those bones, that are absorbing excessive repetitive force. Each person’s foot absorbs force in a slightly different manner, which is dictated by that person’s  foot shape, alignment, foot stiffness, and gait pattern. Common sites of stress fractures in the foot include:

Clinical Presentation

Diagnosis of a stress fracture requires a high degree of suspicion as the fracture often does not show up on the initial x-ray.  Patients will usually report localized aching pain in the effected area.  They will give a history of some increase in their normal activity level (ex. went for a long hike this weekend).  They usually do not report a specific injury when the pain began. They may have a history of a condition that predisposes them to weaker bones such as:  Osteoporosis (weak thin bone); Amenorrhea (loss of normal menstrual cycle); or a history of smoking.

Imaging Studies

X-rays may initially be negative, as it often takes 10 days or more for a callus (new bone) to form and be visualized on x-rays.  Bone scans and MRIs are more likely to be positive in stress fractures.  It is possible, and in fact common, to see fluid or “edema” in bones on an MRI without having an obvious stress fracture.  This represents a “stress reaction”, and is equivalent to microscopic bone fracturing without a complete stress fracture. The fracture, if present, is usually visible on an MRI. If there is concern, a CT scan can usually confirm the diagnosis of stress fracture, as well as clearly define the location and size of the fracture.

Treatment

Most stress fractures do not require surgery. Treatment generally involves:
  • Resting the effected area until the bone adequately heals, often 6-8 weeks or more. This can be accomplished with crutches and a CAM walker boot.
  • Avoiding any activities that caused the injury or exacerbate the symptoms.
  • Correcting any risk factor that may predispose to further stress fractures, including training issues, footwear, and nutritional or hormonal deficiencies.  Certain stress fractures may require surgery in order to aid in healing or prevent non-healing (i.e., non-union) or refracture. These “high risk” stress fractures include the Jones fracture, a displaced navicular stress fracture, and other stress fractures that may not heal adequately with non-surgical treatment. The decision for surgery should be made by an orthopaedic surgeon with experience treating these types of injuries.


Edited on November 2, 2016

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