Force reduction by an external hip protector on the human hip after falls.

This is the first quantitative study of the impact force over the hips of volunteers who fell laterally from standing to a hard surface while wearing a hip protector. Protector pads were first tested with a drop weigh machine. Piezoelectric sensors were placed on the impact surface to record force-time curves with and without a pad covering the surface. Two types of pads transmitted only 9% of the force at a drop weight impact force of 13,372 N. Sensors were placed over the hip under a protective hip pad worn by 10 volunteers who deliberately fell from standing, to a concrete surface. Only 5% or less impact force was transmitted to the skin sensors, and no hip injuries occurred after 85 falls, providing evidence for the safety of such falls. Only transient skin pain and tenderness occurred in three volunteers. Force transmission through the pads was well below that required to fracture hips from cadavers with osteoporosis in vitro. There was variability in the reduction of force transmission among the volunteer subjects. A 1-month compliance study with 106 elderly subjects showed protector use for 70% to 95% of their hours out of bed.