Prediction model for stress fracture in young female recruits during basic training.

PURPOSE: To develop a new prediction model for stress fractures (SF) in female recruits during basic training (BT) to identify risk factors and to try to prevent orthopedic injuries.

METHODS: Measurements and data collection were taken from three companies of gender-integrated recruited units before the BT program (a total of 227 females and 83 males). Measurements included anthropometric variables, blood samples for hematology profile and markers for bone metabolism, fitness tests, bone quality (peripheral quantitative computed tomography), nutritional and activity habits, psychological assessment, and medical evaluation. SF were diagnosed during BT by bone scintigraphy and/or magnetic resonance imaging.

RESULTS: All collected measurements were used to construct a new prediction model for the 27 and 192 female soldiers found with and without stress fracture, respectively. There were no SF in the male soldiers. The model successfully predicts 76.5% of the female soldiers with and without stress fractures (SF) as follows:PSF = -13.98 + 0.079 Ht - 0.014 Fe + 0.464 BUR - 0.105 BMI + 0.035 Ferritin,where PSF is the SF prediction according to the log odds(SF); odds(SF) is the ratio between probability of SF existence and nonexistence; Ht is the height (cm); BUR is a subjective assessment of burnout on a scale of 1 to 7; Fe is the iron blood level (microg x dL); ferritin is the iron storage level (ng x mL); and BMI is the body mass index (kg x m).

CONCLUSION: A young female recruited to an integrated light combat unit is at risk for stress fracture if she is tall, lean, feels "burnout," has iron deficiency, and is at the high end of the normal ferritin range. However, further evaluation is required in different populations, conditions, and training programs to evaluate these results.