Hip protectors - Editorial

Age and Ageing, March, 1998 by Tim J. Wilkinson, Richard Sainsbury

Introduction

Hip fractures are worrying. Not only are they common in elderly people, but they are associated with an appreciable mortality and morbidity and are a serious threat to independence. Furthermore, the age-standardized incidence of femoral neck fractures is increasing in many countries [1].

Preventing fractured necks of femur

Femoral neck fractures do not occur in isolation. They are more common in the frail elderly person and in people who have thin bones and recurrent fails. Although the management of such fractures is ostensibly an orthopaedic problem, geriatricians become involved in treating people with fractured necks of femur in both the peri-operative and rehabilitation periods [2]. Management of people with femoral neck fractures has come a long way, and the value of early operation, early mobilization and prompt treatment of co-existent medical problems is generally accepted. Unfortunately, prevention has not enjoyed similar success.

Prevention of hip fractures requires effort both in avoiding, or modifying, the fall and in strengthening bone. There have been advances in osteoporosis treatment over the past decade. Many new drugs have been developed which increase bone density and prevent vertebral fractures. Their effect on preventing femoral neck fractures has been disappointing and mostly restricted to people living in institutional care [31. Similarly, although with some notable exceptions, it has been difficult to show benefits from fall prevention programmes [4, 5]. What has become clear from these studies is that complex problems rarely have simple solutions. Fall and fracture prevention require individualized and targeted interventions.

The hip protector concept

It is on this background that any novel method for preventing hip fractures will deservedly attract interest. External hip protectors first became known to the wider medical community in 1993, when Lauritzen and colleagues demonstrated an over 50% reduction in hip fractures in a group of nursing home residents assigned to wear hip protectors [6]. The same year also saw less positive results from a study using a different design of hip protector [7]. A hip protector is a plastic shield sewn into special underwear so that it lies over the greater trochanter. It is believed to be effective as it absorbs or diffuses energy rather than relying on bone strength to resist a fracture. As overweight women have a lower rate of hip fracture [8], it has been suggested that there may be benefit in extra soft tissue, which diffuses the energy from a tall [9]. The higher bone density found in overweight women may also be relevant [10].

Lauritzen's study was inevitably unblinded, although the study endpoints (fractures) are not liable to much bias. The intervention and control groups were allocated by nursing home ward rather than on the basis of individuals. This means that other environmental factors may have been important. Only 24% of the residents given hip protectors actually wore them regularly, yet this study showed a 53% reduction in fracture rate. This discrepancy has been explained by postulating that recurrent fallers may have been more likely to wear (or be encouraged to wear) the protectors. It would be difficult, in an unblinded study, not to alter behaviour in the intervention group where the garment itself would remind all involved in the study that falls and fractures are important hazards. This potential bias was controlled for as much as possible and the recorded fall rates in the intervention and control groups over the observation period were similar.

Encouraging concordance

Concordance with any prophylactic treatment is subject to a number of factors, including personal perception of risk and side-effects from the intervention. Compliance will be poorer if the participant does not perceive the risk or potential benefit to be sufficiently great. This is seen in such diverse issues as wearing a seat belt while travelling or taking antihypertensive drugs to prevent stroke. The patient whose necklace alarm hangs out of reach beside the bed or the bath after a fall is almost a cliche: possessing the alarm is of no benefit unless it is used. Hourly compliance is just as important as long-term compliance. Side-effects or discomfort from an intervention are poorly tolerated if people are asymptomatic.

It is therefore of interest to read a British study and a Finnish study in this issue of the Age and Ageing which have assessed the acceptability of external hip protectors for elderly people in institutional care [11, 12]. (Compliance with hip protectors has also become the target of an ongoing FICSIT study in the United States [13].) The authors of the British study persuaded 101 female residents in a rest home to wear external hip protectors for up to 12 weeks. These women came from an overall population of 626. Over one-third were excluded because of cognitive impairment--this was because of inability to obtain consent rather than because they were considered less likely to benefit from such protectors. Only 50% of eligible subjects were willing to be allocated to the intervention. Of this highly selected 16% of the original population, just over one-quarter managed to wear hip protectors for the full 12 weeks. The subjects in this study were within an at-risk group as 44% had reported a fall in the preceding year. Despite this motivation, discomfort and poor fit were the main reasons for poor compliance.