Strategies for avoiding hip impact during sideways falls.
During a fall, hip fracture risk increases 30-fold if there is direct impact to the hip. We conducted sideways falling experiments and found that subjects were able to avoid hip impact by rotating forward or by rotating backward during descent. These simple safe-landing strategies should be considered in designing hip fracture prevention programs.


BACKGROUND
Ninety percent of hip fractures in the elderly are caused by falls. During a fall, hip fracture risk is increased 6-fold by falling sideways (instead of backward or forward) and 30-fold if direct impact occurs to the hip. Previous studies suggest that impact to the hip during a sideways fall can be avoided by rotating forward during descent to land on the outstretched hands. Presumably, an alternative strategy for avoiding hip impact is to rotate backward to land on the buttocks. We conducted sideways falling experiments to test the hypothesis that each of these falling strategies is equally effective in allowing one to avoid hip impact.


METHODS
Twenty-two young adult women participated in trials where they were released from an inclined standing position into a sideways fall onto a foam mattress. Subjects were instructed to "land as softly as possible" and to "avoid impacting the hip" by either rotating forward or rotating backward during descent.


RESULTS
We found that absolute values of the hip proximity angle, which described how close the impact site was to the lateral aspect of the pelvis, were not different in forward rotation and backward rotation trials (mean = 55.9 +/- 22.4 degrees versus 61.5 +/- 15.8 degrees, respectively). However, compared with forward rotation trials, backward rotation trials involved greater pelvis impact velocity (2.95 +/- 0.25 versus 2.45 +/- 0.77 m/s; p = 0.001) and greater whole-body kinetic energy at impact (238 +/- 70 versus 156 +/- 90 J; p = 0.001).


CONCLUSIONS
These results suggest that, during a sideways fall, individuals can avoid impact to the hip and thereby lower the risk for hip fracture by rotating forward or by rotating backward during descent. These simple yet effective safe-landing strategies should be considered in designing exercise-based hip fracture prevention programs.
Robinovitch
Stephen N
SN
Injury Prevention and Mobility Laboratory, School of Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada. stever@sfu.ca
Inkster
Lisa
L
Maurer
Jessica
J
Warnick
Brady
B
D000058:Accidental Falls; D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006615:Hip / Q000033:anatomy & histology; D006620:Hip Fractures / Q000517:prevention & control*; D006801:Humans; D011315:Preventive Medicine / Q000379:methods*; D012399:Rotation