Regional bone geometry of the tibia in triathletes and stress reactions—An observational study

ObjectivesThe association between tibial morphology and tibial stress fractures or tibial stress syndrome was examined in triathletes with an unusually high incidence of these injuries.DesignA cross-sectional study design examined associations between tibial geometry from MRI images and training and injury data between male and female triathletes and between stress fracture (SF) and non-stress fracture (NSF) groups.MethodsFifteen athletes (7 females, 8 males) aged 17–23 years who were currently able to train and race were recruited from the New Zealand Triathlete Elite Development Squad. Geometric measurements were taken at 5 zones along the tibia using MRI and compared between symptomatic and asymptomatic tibiae subjects.ResultsSF tibiae displayed either oedema within the cancellous bone and/or stress fracture on MRI. When collapsed across levels, symptomatic tibiae had thicker medial cortices (F1,140 = 9.285, p = 0.003), thicker lateral cortices (F1,140 = 10.129, p = 0.002) and thinner anterior cortices (F1,140 = 14.517, p = 0.000) than NSF tibiae. Only medial cortex thickness in SF tibia was significantly different (F4,140 = 3.358, p = 0.012) at different levels. Follow-up analysis showed that athletes showing oedema within the cancellous bone and/or stress fracture on MRI had, within 2 years of analysis, subsequently taken time off training and racing due a tibial stress fracture.ConclusionsThe thinner anterior cortex in SF tibiae is associated with a stress reaction in these triathletes.