Biomechanical Factors Associated with Tibial Stress Fracture in Female Runners

MILNER, CLARE E.1; FERBER, REED2; POLLARD, CHRISTINE D.3; HAMILL, JOSEPH4; DAVIS, IRENE S.1

Medicine & Science in Sports & Exercise: February 2006 - Volume 38 - Issue 2 - pp 323-328
doi: 10.1249/01.mss.0000183477.75808.92
APPLIED SCIENCES: Biodynamics

Purpose: Tibial stress fractures (TSF) are among the most serious running injuries, typically requiring 6-8 wk for recovery. This cross-sectional study was conducted to determine whether differences in structure and running mechanics exist between trained distance runners with a history of prior TSF and those who have never sustained a fracture.

Methods: Female runners with a rearfoot strike pattern, aged between 18 and 45 yr and running at least 32 km·wk−1, were recruited for this study. Participants in the study were 20 subjects with a history of TSF and 20 age- and mileage-matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected during overground running at 3.7 m·s−1 using a six-camera motion capture system, force platform, and accelerometer. Variables of interest were vertical impact peak, instantaneous and average vertical loading rates, instantaneous and average loading rates during braking, knee flexion excursion, ankle and knee stiffness, and peak tibial shock. Tibial varum was measured in standing. Tibial area moment of inertia was calculated from tibial x-ray studies for a subset of runners.

Results: The TSF group had significantly greater instantaneous and average vertical loading rates and tibial shock than the control group. The magnitude of tibial shock predicted group membership successfully in 70% of cases.

Conclusion: These data indicate that a history of TSF in runners is associated with increases in dynamic loading-related variables.

1Department of Physical Therapy, University of Delaware, Newark, DE; 2Faculty of Kinesiology, University of Calgary, Calgary, Alberta, CANADA; 3Department of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA; and 4Department of Exercise Science, University of Massachusetts, Amherst, MA

Address for correspondence: Clare Milner, Department of Physical Therapy, 301 McKinly Lab, University of Delaware, Newark, DE 19716; E-mail: milner@udel.edu.

Submitted for publication February 2005.

Accepted for publication August 2005.

©2006The American College of Sports Medicine