EFFECT ON THE FEMUR OF A NEW HIP FRACTURE PREVENTIVE SYSTEM USING DROPPED-WEIGHT IMPACT TESTING

To reduce hip fractures during falls, we devised a new hip fracture pr eventive system to attenuate impact on the greater trochanteric region and studied the effects of the system on the femur. Twelve coupled, e mbalmed, cadaveric femora were used. Right femora were fractured witho ut protection as a control and compared with left femora covered by th e protection system, which consisted of a silicone gel pad or the sili cone gel pad combined with a resin cover. The impact of a fall was sim ulated by mounting a femur in the horizontal plane and dropping an 8.4 kg mass on its greater trochanteric region. The impact load and Lime were measured using a load cell within the mass. The maximum strain du ring impact at the inferior side of the femoral neck was determined fr om an attached strain gauge. Trochanteric fractures were produced in 1 8 of the 24 femora (75%). The mean impact load for a drop height of 25 cm was reduced from 3117 N to 2176 N by silicone gel (p < 0.01) and t o 1681 N by the addition of the resin cover (p < 0.01). The mean maxim um strain was similarly reduced from 2276 mu epsilon to 1872 mu epsilo n (p = 0.15) and to a mean 1559 mu epsilon (p < 0.05), The mean impact time was prolonged from 13 ms to 20 ms (p < 0.01) and 22 ms (p < 0.01 ), respectively. The effect of the cover became more conspicuous as he ight increased. We concluded that the silicone gel pad provided effect ive impact attenuation, and the addition of the rigid cover was even m ore effective for impact reduction. This system was thought to be clin ically useful in preventing hip fractures.