It is suggested that 30 percent of vertebral compression fractures in persons with osteoporosis is due to falling.
Compliant flooring may be a promising way to reduce impact force during a fall and reduce vertebral fracture risk during a fall.
Previous studies have shown that peak impact backward forces are 6.4 to 9.0 times body weight in a fall onto a bare floor. Elderly male lower thoracic and upper lumbar spines have been shown to fracture at loads of 3009 to 4150 Newtons at 6.5 milimeters per second.
The authors of the study evaluated forces generated in staged falls of 11 healthy young males onto various surfaces. The falls were considered worst case. This means that they were not allowed to absorb the impact of the fall by using their arms, or by rolling. The subjects were trained to fall from a vertical position directly onto their buttocks. A force plate on the floor where the buttocks landed was used to measure the force of the fall.
The authors compared the force plate measurements when the subjects fell onto a foam surface of three different thicknesses. The foam flooring had layers of closed cell cross linked ethylene vinyl acetate, EVA. The depth of the foam used was 4.5 cm, 7.5 cm, and 10.5cm thickness.
Unlike some of the previous studies, this study measured force at the buttocks rather than the spine. Mean peak vertical force at the buttocks when landing on 4.5 cm foam flooring was 5.7 to 7.5 times body weight. This was 15 percent less than the proposed forces generated from falling on a hard surface.
This may be enough of a reduction in force to be under the threshold for fracture. The force attenuation from the 7.5cm foam flooring was 20 percent. The force attenuation from the 10.5 cm flooring was 24 percent. These findings were similar to reduction in forces at the femoral neck in other studies.
The authors are aware that while closed cell foam my reduce the risk of compression fractures from falls among the elderly, it may not be feasible to use it in a facility. Balance, rolling wheelchairs and furniture may be more difficult with this surface type. The authors feel that testing other materials such as viscoelastic flooring would be worthwhile. This would be a surface that may be viable in hospitals and nursing homes to reduce risk of compression fractures from falls.