Bone stress in runners with tibial stress fracture.
BACKGROUND
Combinations of smaller bone geometry and greater applied loads may contribute to tibial stress fracture. We examined tibial bone stress, accounting for geometry and applied loads, in runners with stress fracture.


METHODS
23 runners with a history of tibial stress fracture & 23 matched controls ran over a force platform while 3-D kinematic and kinetic data were collected. An elliptical model of the distal 1/3 tibia cross section was used to estimate stress at 4 locations (anterior, posterior, medial and lateral). Inner and outer radii for the model were obtained from 2 planar x-ray images. Bone stress differences were assessed using two-factor ANOVA (α=0.05). Key contributors to observed stress differences between groups were examined using stepwise regression.


RESULTS
Runners with tibial stress fracture experienced greater anterior tension and posterior compression at the distal tibia. Location, but not group, differences in shear stress were observed. Stepwise regression revealed that anterior-posterior outer diameter of the tibia and the sagittal plane bending moment explained >80% of the variance in anterior and posterior bone stress.


CONCLUSIONS
Runners with tibial stress fracture displayed greater stress anteriorly and posteriorly at the distal tibia. Elevated tibial stress was associated with smaller bone geometry and greater bending moments about the medial-lateral axis of the tibia. Future research needs to identify key running mechanics associated with the sagittal plane bending moment at the distal tibia as well as to identify ways to improve bone geometry in runners in order to better guide preventative and rehabilitative efforts.
2410 Health Sciences Building, Department of Physical Therapy, East Carolina University, Greenville, NC 27834, United States. Electronic address: meardons@ecu.edu.
Stacey A
SA
Meardon
2410 Health Sciences Building, Department of Physical Therapy, East Carolina University, Greenville, NC 27834, United States.
John D
JD
Willson
1300 Badger Street, Health Professions Department, Physical Therapy Program, University of Wisconsin-La Crosse, La Crosse, WI 54601, United States.
Samantha R
SR
Gries
1300 Badger Street, Health Professions Department, Physical Therapy Program, University of Wisconsin-La Crosse, La Crosse, WI 54601, United States.
Thomas W
TW
Kernozek
249 Barbara E. Forker Building, Department of Kinesiology, Iowa State University, Ames, IA 50011, United States.
Timothy R
TR
Derrick
D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D015775:Fractures, Stress / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D008297:Male; D011859:Radiography; D012420:Running / Q000293:injuries*; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013978:Tibial Fractures / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055815:Young Adult
Biomechanics; Bone parameters; Injury; Running