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Abstract & Commentary
Synopsis: Anatomic variables that put athletes at risk for multiple stress factors included high foot arch, leg length inequality, and excessive forefoot varus.
Source: Korpelainen R, et al. Risk factors for recurrent stress fractures in athletes. Am J Sports Med. 2001;29(3):304-310.
Although stress fractures are common in athletics, our understanding of which risk factors are important and how to prevent them is not altogether clear. Korpelainen and colleagues from Finland used an extensive database at a sports medicine clinic, with a series of more than 12,000 athletes treated more than 23 years, to identify 34 athletes who had at least 3 separate stress fractures in the lower extremity. Amazingly, 31 were available to complete an extensive questionnaire that detailed their training history, menstrual history, height, weight, dietary history, and use of tobacco and alcohol. Half of the subjects were available for a body biomechanical analysis to include radiographic determination of leg length, femoral anteversion, and bone mineral density. Additional measurements included a pedogram to determine foot shape, forefoot varus, pronation of the ankle, and range of motion at the ankle and hip. Motor performance testing measured reaction times, balance, speed, and accuracy of movement. A group of patients treated for other lower extremity problems and matched for body mass index, demographics, and sports event served as the controls.
Their hypothesis was that certain anatomic variables associated with the ankle and lower extremity would put the athlete at risk for stress fractures. After statistical analysis of all of these variables, a high longitudinal foot arch, leg length inequality, and forefoot varus greater than 10° had the strongest correlation with multiple stress fractures. Not surprisingly, distance runners were the largest subgroup (61%); yet, weekly mileage did not correlate directly with frequency of fracture. In fact, some athletes developed stress fractures with only moderate training activity. This supported Korpelainen et al’s premise that anatomic variables influenced risk of fracture more than training alone.
Almost half of the female athletes reported menstrual irregularities. Two athletes with primary amenorrhea were osteoporotic by bone densitometry (> 2.5 standard deviations from the mean). Because of variability among subjects and sample size, differences between the 2 groups were not statistically significant.
Comment by David R. Diduch, MS, MD
Stress fractures hurt in more ways than one, frequently preventing an athlete from competing in events for which they trained so hard that they developed the problem. Yet, our understanding of what risk factors are most important, and how to prevent stress fractures, is limited. Korpelainen et al have enhanced our understanding with an extensive study from a database spanning 12,000 athletes and 23 years. By analyzing a selected group of 31 athletes with multiple stress fractures and comparing them to a carefully matched control group, they tried to determine what anatomic risk factors were important. The methodology and the statistics were valid and the conclusions sound.
While type of training (ie, distance running) was important, a direct correlation with extent of training (ie, weekly mileage) was not. This supports Korpelainen et al’s hypothesis that anatomic variables play a key part in determining who gets stress fractures. Forefoot varus, leg length difference (shorter leg most often involved), and pes cavus were most frequently associated with multiple stress fractures.
It would seem that the logical next step is to screen the athletic population and correct these anatomic problems where possible with orthotics and proper shoewear. Such prospective data are critical to support this hypothesis. It is also essential for sports medicine providers to be able to affect this problem in a preventive way.
Dr. Diduch, Editor of Sports Medicine Reports, is Associate Professor in the Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville.