BOSTON, Massachusetts—Hip protectors are not effective for preventing hip fractures in nursing home residents, according to a new study in the July 25th issue of the Journal of the American Medical Association.¹ The study was terminated early because of the hip protector's lack of effectiveness.

"This large multicenter clinical trial failed to demonstrate a protective effect of a hip protector on hip fracture incidence in nursing home residents despite high adherence, confirming the growing body of evidence that hip protectors are not effective in nursing home populations," conclude researchers led by Douglas P. Kiel, MD, MPH, the director of medical research at the Institute for Aging Research of Hebrew SeniorLife, in Boston. "With the development of better pad materials and more thorough testing, future studies should examine new hip protectors using nonclustered randomized designs like ours to avoid many methodological biases."

The randomized trial included 37 nursing homes in which 1042 residents with an average age of 85 wore a hip protector on only one hip, so that each participant served as their own control. Overall adherence of the participants was 73.8%,  and mean participation time in the trial was 7.8 months. The hip protector is built up of a hard high-density polyethylene vinyl acetate foam shield sandwiched between two layers of ethylene vinyl acetate foam.

Lack of adherence not factor in lack of efficacy

The 3.1% incidence rate of hip fracture on protected hips was the same as the 2.5% incidence rate on unprotected hips. In a separate analysis of the 334 residents with greater than 80% adherence, the 5.3% incidence of hip fracture on protected hips did not differ from the 3.5% incidence of hip fracture on unprotected hips.

Calling the new study "interesting," Stephen Honig, MD, director of the osteoporosis center at New York University Hospital for Joint Diseases, in New York City, said that "the data suggest that the hip protector used in this study did not protect the hip…from sustaining a hip fracture when compared to the hip that was uncovered."

Still some questions remain, he said. "We don't know if the fracture rate was different than the rate seen among ‘matched' residents of nursing homes because no comparison with that type of ‘control' population was done; [that is], did the hip protector change the way residents walked that either positively or negatively affected the rate of falls?"

Fall-induced fractures occur when the force of the blow (the fall) is greater than the combined resistance of the bone and the surrounding soft tissue. Hip protectors are designed to augment the soft tissue surrounding the hip and reduce the force generated to the bone, thereby cushioning the blow to the femur. "It appears logical that the more effective the hip protector is at force absorption, the more likely it will be to reduce the rate of hip fractures," Dr. Honig speculated. Unfortunately, many nursing home residents are at increased risk for hip fractures because they have osteoporosis and they fall frequently. "Additionally, the neuromuscular reaction to falling changes with age so that the very elderly tend to fall in the direction of their body lean and do not have the muscular coordination to change the direction of the fall," Dr. Honig said. "Because of this, the types of falls that the elderly have are often of very high impact, and when they are imposed on thin and weakened bones, fractures are all too common."

Building a better hip protector

"Theoretically, it seems likely that a more effective protector should be able to impact the rate of fractures, but such a protector has to be strong enough to significantly reduce the effect of the fall while still being light and comfortable enough for an elderly person to wear."

As it stands, "we do not routinely recommend such devices for community-dwelling people," Dr. Honig continued. "We recommend a balance assessment to help identify causes of poor balance and falling after which a program of remedial exercises is recommended for those who can benefit from such an intervention."

Reference

1. Kiel DP, Magaziner J, Zimmerman S, et al. Efficacy of a hip protector to prevent hip fracture in nursing home residents. The HIP PRO randomized controlled trial. JAMA. 2007;298:413-422.