A new US study shows that using an energy-absorbing hip protector does not help to reduce risk of hip fracture in elderly nursing home residents.

The study is published in the July 25th issue of the Journal of the American Medical Association and according to the authors adds support to a body of evidence that comes to the same conclusion.

However, critics say, even with this study, there is still not enough evidence to recommend for or against the use of hip protectors by the elderly.

Dr Douglas P. Kiel of the Hebrew SeniorLife and Harvard Medical School in Boston, Massachusetts, US, and colleagues carried out a randomized controlled trial among over 1,000 residents in 37 nursing homes between October 2002 and October 2004.

The participants who were of average age 85 and comprised 79 per cent women, each wore a hip protector on only one hip for an average duration of 7.8 months. This meant they did not need a separate control group as the participants' experience of not having a hip protector on the other hip effectively meant they were their own controls.

The energy-absorbing hip protector has an outer layer made of polyethylene backed by a hard high-density polyethylene shield lined by ethylene vinyl acetate foam. It is designed to cushion the hip from the impact of a fall and thereby reduce the risk of fracture.

There are nearly 340,000 hip fractures a year in the US, over 90 per cent of them linked to falls, and the number is set to double or even triple by the year 2050. Half of hip fractures take place in nursing homes said the researchers, and studies done on the effectiveness of hip protectors show conflicting results.

This study was stopped early, after 20 months of follow up, because the hip protectors were not shown to be effective. Kiel and colleagues found that the incidence of fracture on protected hips (3.1 per cent) was not significantly different from that on non protected hips (2.5 per cent).

Even when they only included residents who adhered more closely to the protocol (the average adherence was 73.8 per cent, and they did a further analysis on 334 residents with an adherence of 80 per cent and over) the incidence of fracture for protected versus non protected hips did not differ significantly (5.3 per cent versus 3.5 per cent).

Kiel and colleagues concluded that:

"In this clinical trial of an energy-absorbing/shunting hip protector conducted in US nursing homes, we were unable to detect a protective effect on the risk of hip fracture, despite good adherence to protocol. These results add to the increasing body of evidence that hip protectors, as currently designed, are not effective for preventing hip fracture among nursing home residents."

In an accompanying editorial, Drs Pekka Kannus and Jari Parkkari of the UKK Institute for Health Promotion Research, Tampere, Finland said that although Kiel and colleagues had carried out an important trial that yielded useful data, these findings, together with those from other studies conducted so far, are not enough to justify recommending or not recommending hip protectors for the frail and elderly residents of nursing homes.

They said the diversity of models is too wide to make a general recommendation one way or another, and further detailed investigations into the specific biophysical and patient usage characteristics of each device should be done to determine their individual effectiveness. The main variables of such an investigation would be the biomechanical force attenuation capacity of the different models (basically their ability to absorb the shock of a fall) and the extent to which patients adhere correctly to instructions for their use.

They recommend a two stage process, first in simulated falls in the lab (or "in vitro" as they call it), and then in actual falls (with real patients), where the position of the protector should also be taken into account.

"Efficacy of a Hip Protector to Prevent Hip Fracture in Nursing Home Residents: The HIP PRO Randomized Controlled Trial."
Douglas P. Kiel, Jay Magaziner, Sheryl Zimmerman, Linda Ball, Bruce A. Barton, Kathleen M. Brown, Judith P. Stone, Dawn Dewkett, Stanley J. Birge.
JAMA. 2007;298:413-422.
Vol. 298 No. 4, July 25, 2007

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: Catharine Paddock