Stress Fractures

By Jonathan Blood Smyth

Stress fractures are a common occurrence particularly in sporting endeavours and in recruits in the armed services, with overuse of the lower limbs a common theme. The lower leg is the most frequently affected area but other parts, even the arms, can be affected. The tibia, fibula and metatarsals are the most obvious areas to suffer, with further up the lower limbs much less commonly occurring. Repetitive stresses to the bones of a level not sufficient to cause direct fracture are the underlying cause of this injury.

During activity and exercise there may be an increased report of pain in the part, with patients typically noting they have recently made changes to their training regime's frequency or intensity. Treatment is typically without complication by reducing the person's activity or by immobilisation of the part. These fractures heal well in most cases although non-union is a possibility, in which case surgical fixation may be required. Once the fracture is surgically fixed the vast majority of cases heal well with suitable immobilisation.

These types of fractures occur because bone has been loaded again and again and there is rarely any specific traumatic event responsible for the fracture. Bones remodel to reinforce themselves when they are subjected to loads involving tension or compression, with minor damage of the bone occurring due to the stresses. If the remodelling process gets behind as the microscopic bone damage occurs then a fracture can result. The most common occurrence is for the person to have significantly increased their activities recently.

The risk factors include an increase in the frequency of the applied stresses, an increase in the intensity of those stresses or a change in the area to which the stresses are being applied. If the surface area of the bone to which the stress is applied is reduced then the absolute stresses through those bony areas increase, or the load may be absolutely increased. Running and jumping are examples of more high risk activities, as may be changes in performance technique or in the nature of the surface exercised upon.

Additional factors could be risk factors such as reduced bone density, dietary changes, weakness or other mechanical factors as the other factors are all mostly presumed to be the key ones. Scientific research has indicated being female, having a low body weight, poor diet and many other factors may be important. Female runners are particularly at risk, with reduced caloric intake, disturbances in menstrual cycle and lower bone density presenting in such athletes and others who require a low body weight such as ballet dancers.

A stress fracture typically comes on without much warning and often without severe symptoms, during an activity of repeated limb loading and without trauma. Resting will usually abolish the pain which will re-appear on performance of the weight bearing activity again. Tenderness and swelling may be apparent locally around the fracture site but it may be two to four weeks before a fracture can be discernible on x-ray. Bone scanning may detect fractures much earlier, within 72 hours of the incident, but are less clear as to the exact cause.

The usual management of stress fractures is conservative care, with the simplest and often the most effective method being a reduction in the responsible activity for 4 to 6 weeks. If there is a significant degree of pain on weight bearing then they can be placed in a brace, a rigid walking boot or a below knee cast, with crutch use as required. Orthoses in the shoes have been studied and found to allow a reduction in fracture incidence of a certain amount, with shock absorbing insoles having less clear benefits but potential.

Typical healing of stress fractures is uncomplicated but there is a risk of the fracture suffering from poor healing or non-union in particular bodily regions. The fifth and second metatarsals can suffer from delayed or lack of healing at their bases and as such should be reviewed in case more controlled immobilisation or surgical intervention is required. - 32188

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