Bone stress injury: EPIDEMIOLOGY

As BSIs develop in response to repetitive mechanical loading, it is not surprising that they occur frequently in athletes. BSI's cause a considerable loss of participation time and are a significant source of frustration, especially if they occur in the lead-up to an important event or competition.

Between one- and two-thirds of runners have a history of BSIs and the one-year cumulative incidence of BSIs in cross-country and track and field athletes ranges from 5% to 21%. Half of track and field athletes report a history of BSIs on more than one occasion and 10 to 13% of XC/T+F athletes with a history of a BSI sustain a subsequent BSI when followed for 1 -2 years. This highlights the high recurrence rate of BSIs.

BSIs are site-specific, occurring at sites exposed to repetitive mechanical loading. BSIs usually occur at weight-bearing sites, with the most common sites being the tibia, fibula and metatarsals. The exact location depends on how the skeleton is loaded, as different activities result in different loading patterns within different bones. For example, long-distance runners typically use a rearfoot strike pattern to preferentially load long bones (tibia, fibula, femur), whereas sprinters use a forefoot strike pattern to introduce relatively greater loads to the bones of the feet. As a result of differential bone loading, distance runners are at a greater risk of developing long BSIs and sprinters are more prone to BSIs of the tarsals and metatarsals.

BSIs can also occur in response to repetitive loading at non weight-bearing sites. For instance, rowers repeatedly load their rib cage during the drive phase of the rowing stroke and so are at a higher risk of developing BSIs in their ribs. Similarly, throwing athletes are prone to developing humeral diaphysis BSIs as they repetitively expose their humerus to significant loads during the motion of throwing. BSIs can occur in virtually any bone and so must be considered in the differential diagnosis of all presenting injuries.

REFERENCES

Brukner, P., 2012. Brukner & Khan's clinical sports medicine. North Ryde: McGraw-Hill.