QUS measurements were made on 4139 female Army recruits at the beginning of basic training (BT). QUS predicted stress fracture in female recruits as well as it predicts hip fracture in elderly women. Recruits with low QUS values and a history of smoking and not exercising had an extremely high risk of stress fracture.
Introduction: Stress fractures during basic military training (BT) cause morbidity for the recruits and expense for the Military Services. Females have a higher incidence than males. If recruits at high risk for stress fracture could be accurately identified before they began BT, the military might find it advantageous to provide adaptive training programs for them. Currently no accurate methods of risk identification are available. We measured quantitative ultrasound (QUS) in a population sample of female Army recruits to determine if QUS is a useful tool for determining soldiers at high risk of stress fracture during BT.
Materials and methods: We recruited 93% of the population of female recruits entering BT at Fort Leonard Wood, MO, during a 10-month period. We measured calcaneal QUS and administered a risk factor questionnaire at baseline and ascertained stress fractures during the 8 weeks of BT. Logistic regression was used to calculate relative risk (RR) of stress fracture. The area under the receiver-operating characteristic (ROC) curve was also analyzed to determine the sensitivity and specificity of speed of sound (SOS) in predicting stress fracture.
Results: The incidence of stress fracture was 4.7%. SOS was significantly related to the risk of stress fracture. (p < 0.000) The area under the ROC curve was 0.70. The relative risk (RR) of fracture of those in the lowest quintile (Q1) of SOS was 6.7. The highest risk of stress fracture was found in the subgroup of white women in Q1 of SOS who smoked and didn't exercise (RR, 14.4). Over 16% of the fractures occurred in this subgroup, which indicates that about six of these women would need to be assigned to an alternate BT regimen to prevent one stress fracture.
Conclusions: The combination of QUS measurements with evaluation of individual risk factors can identify recruits who are at the very highest risk of stress fracture. The military may find these data helpful to determine the cost-effectiveness of alternate BT regimens.