A 12-MONTH PROSPECTIVE-STUDY OF THE RELATIONSHIP BETWEEN STRESS-FRACTURES AND BONE TURNOVER IN ATHLETES

Bone remodeling may be involved in the pathogenesis of stress fracture s in athletes. We conducted a 12-month prospective study to evaluate b one turnover in 46 female and 49 male track and field athletes aged 17 -26 years (mean age 20.3; SD 2.0) 20 of whom developed a stress fractu re. Baseline levels of bone turnover were evaluated in all athletes an d monthly bone turnover levels were evaluated in a subset consisting o f the 20 athletes who sustained a stress fracture and a matched compar ison group who did not sustain a stress fracture. Bone formation was a ssessed using serum osteocalcin (OC) measured by human immunoradiometr ic assay and bone resorption by urinary excretion of pyridinium cross- links (Pyr and D-Pyr); high performance liquid chromatography and N-te lopeptides of type 1 collagen (NTx) using ELISA assay. Athletes who de veloped stress fractures had similar baseline levels of bone turnover compared with their nonstress fracture counterparts (P > 0.10). Result s of serial measurements showed no differences in average levels of Py r, D-Pyr, or OC in those who developed stress fractures (P = 0.10) com pared with the control group. In the athletes with stress fractures, t here was also no difference in bone turnover levels prior to or follow ing the onset of bony pain. Our results show that single and multiple measurements of bone turnover are not clinically useful in predicting the likelihood of stress fractures in athletes. Furthermore, there wer e no consistent temporal changes in bone turnover associated with stre ss fracture development. However, our results do not negate the possib le pathogenetic role of local changes in bone remodeling at stress fra cture sites, given the high biological variability of bone turnover ma rkers and the fact that levels of bone turnover reflect the integratio n of all bone remodeling throughout the skeleton.