Lower Floor Stiffness Reduces Peak Spine Forces in Falls
Peak spine forces decrease cranially, with lower forces at L3/L4 than at L5/S1
THURSDAY, Nov. 17 (HealthDay News) -- Peak spine force in backward falls is affected by the floor stiffness, according to a study published online Nov. 8 in Spine.
Carolyn Van Toen, from the University of British Columbia in Vancouver, Canada, and colleagues developed a lumped-parameter mathematical model to predict spine forces during backward falls, to evaluate the effect of floor stiffness on these forces. Data were collected from 10 individuals falling from standing height onto three types of compliant floors, and were used to develop and verify a six degree-of-freedom model of the body. The simulated ground forces and those measured experimentally were compared. The effect of floor stiffness on spine forces at various intervertebral levels was assessed.
The investigators found that model predictions and experimentally measured peak ground reaction forces differed by less than 14 percent, when averaged over all floor conditions. The average peak spine forces were reduced by 46, 43, and 41 percent for soft, medium, and firm floors, respectively, when compared to rigid floor. The forces on the spine were lower than those at the ground, and reduced cranially; and, on soft floor, measured 4.9, 3.9, 3.7, 3.5 kiloNewtons (kN) at the ground, L5/S1, L4/5, and L3/4, respectively.
"Lowering the floor stiffness (from 400 to 59 kN/m) can attenuate peak lumbosacral spine forces in a backward fall onto the buttocks from standing by 46 percent (average peak from 6.9 to 3.7 kN at L4/5) to values closer to the average tolerance of the spine to fracture (3.4 kN)," the authors write.