Calcif Tissue Int (2015) 97:1–11 DOI 10.1007/s00223-015-0002-9
REVIEW
Hip Protectors: Are They Worth it? Luisella Cianferotti1 • Caterina Fossi1 • Maria Luisa Brandi1
Received: 13 February 2015 / Accepted: 11 April 2015 / Published online: 30 April 2015 Ó Springer Science+Business Media New York 2015
Abstract Hip fractures are one of the most serious conditions in frail elderly subjects, greatly increasing morbidity and mortality, and decreasing healthy life years. Since their first introduction on the market, hip protectors have been revealed to be a potential preventive measure for hip fractures, in addition to other well-known recognized medical interventions and rehabilitation procedures. However, randomized controlled trials have given contradictory results regarding their efficacy. Moreover, little data are available on the cost effectiveness of hip protectors. Adherence is a major problem in assessing the effectiveness of hip protectors in preventing fractures. Indeed, there is a lack of general consensus on a standard definition and quantitative objective estimation of adherence to hip protectors, along with still scarce evidence on specific interventions on how to ameliorate it. From what is known so far, it seems reasonable to advise the use of hip protectors in aged care facilities, since recent pooled analyses have suggested their efficacy in this setting. The introduction of sensors combined with hip protectors will probably address this issue, both for monitoring and optimizing compliance, especially in elderly people. In the meantime, new, welldesigned studies following specific guidelines are strongly
& Maria Luisa Brandi [email protected] Luisella Cianferotti [email protected] Caterina Fossi [email protected] 1
Department of Surgery and Translational Medicine, Section of Endocrinology, Unit of Bone and Mineral Metabolism, University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
encouraged and needed. In particular, studies in community-dwelling elderly individuals at high risk of first or further fragility fractures are required. The optimization of the tested devices in a preclinical setting according to international standard biomechanical testing is necessary. Keywords Hip fracture Osteoporosis Frailty Falls Nursing homes Effectiveness
Introduction The worldwide burden of fragility fractures is responsible for major economic and social challenges for national health systems and the individual [1–3]. Among different types of fractures, hip fractures are considered one of the most serious complications of falling and osteoporosis, since they lead to increased morbidity (i.e. long-term functional impairment and loss of independence) and mortality, especially in the elderly, in both sexes [4, 5]. Although hip fractures are more common in women with a female to male ratio of 4:1, by the year 2050, figures in men are expected to rise and surpass those of women, at least in developed countries, along with an overall increase in the total number, due to the changes in demographics and an overall increase in population ageing [6]. It is estimated that 10 % of patients will die 1 month after a hip fracture, but this percentage can rise up to 65 % if the patient suffers another acute medical problem, such as pneumonia or heart failure, immediately following the fracture. Up to one-third will die after 1 year, although a decrease in overall mortality rates is expected, likely due to optimized and prompt orthopaedic procedures. Half of the surviving patients lose independence, and nearly 10 % are forced to be bedridden [7, 8]. Elderly people are at major
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risk of fall and fracture, due to an overall decline in musculoskeletal functions and competences. A broken bone is the result of poor skeletal resistance against mechanical forces applied. More than 90 % of hip fractures result from a fall. Elderly subjects are at major risk of hip fractures because of poor balance and weaker bones. A sideways fall produces a high-energy impact, which increases sixfold the risk of a hip fracture compared to a backward or a forward fall, even in young subjects [9] (Fig. 1). Indeed, the number of reported falls is more predictive of hip fractures than low BMD in women, and falling is now considered the strongest risk factor for hip fractures [10–12]. At the same time, treatment with antiosteoporotic medications has proven to be cost-effective, mainly in the secondary prevention of fragility fractures, while for a primary prevention strategy, cost effectiveness has not been demonstrated [13–15]. Vitamin D supplementation has failed to show efficacy in the prevention of falls and fractures in numerous clinical trials [16]. Conversely, exercise programmes improving muscular performance and balance may reduce the incidence of hip fractures by reducing falls [17]. Moreover, proper safelanding strategies and self-protective responses can reduce the impact on the hip [18, 19]. It is still a matter of debate whether currently marketed devices such as hip padding offering biomechanical protection during a fall, thus decreasing the force of the impact on the bone, could decrease the incidence of fractures of the proximal hip, at least in high-risk elderly
Fig. 1 Schematic representation of a sideways fall and consequent hip fracture (panel A) and potential preventive effect of a hip protector (panel B)
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institutionalized individuals [20, 21]. This review will give an overview of the latest advances in the use of hip protectors in hip fracture prevention, starting with a description of basic biomechanical properties, and then focusing on evidence coming from randomized clinical trials and meta-analyses.
Types of Hip Protectors and Their Mechanical Properties: Preclinical Studies Hip protectors are hard or soft plastic (polypropylene or polyethylene) shields properly embedded into pants or undergarments in proximity of the outside of the hip, just over the trochanter, i.e. the bony protuberance on the outer surface of the proximal hip. The particular design of hip protectors is aimed at decreasing and/or absorbing the impact of a sideways fall, ultimately preventing fractures of the proximal hip, encompassing intracapsular fractures (i.e. at the site of femoral neck) and extracapsular fractures involving the trochanter [22]. Commercial types of hip protectors can be either ‘‘crashhelmet like’’, i.e. rigid pads designed to spread the energy of the impact to the soft tissue of the thigh surrounding the hip, or ‘‘energy-absorbing’’. The latter are made of specific soft, shock-absorbing materials, which decrease the force of the impact ultimately transmitted to the bone [23] (Figure 2). The primary aim of hip protectors is to reduce the energy transmitted to the trochanter during a fall below
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Fig. 2 Photographs showing top and side views of different commercially available hip protectors tested (source Laing et al. [23])
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the force causing a fracture, also referred to as hip fracture threshold. In this respect, hip protectors incorporating hard materials seem superior [24], even if they are less comfortable to wear, thus potentially decreasing short- and long-term compliance [25]. The effectiveness of a hip protector in preventing fractures in preclinical studies is evaluated by in vitro biomechanical testing, which was not standardized until recently [26]. The first preliminary studies evaluated existing materials suitable for hip protectors, which are required to display basic properties, such as a good shock-absorbing competence against a reasonable impact of 3 m/s (likely to reproduce the velocity of a fall), elastic properties, toughness, reasonable weight, availability and modest price [27]. The authors concluded that hip pads made up of existing soft materials could not provide sufficient protection at an acceptable thickness. Indeed, hip pads conceived to spread the energy developed during a fall away from the great trochanter could decrease the force applied to the hip. These devices were developed later and yielded energyabsorbing and energy-shunting properties, thus providing a proper attenuation of the final impact on the hip after a sideways fall, as in vitro reproduced by means of the impact pendulum [28, 29]. It was clear from the beginning that the pads had to be sufficiently small, comfortable and resistant to increase compliance. Experiments with devices designed to be fixed directly on the skin without specific undergarments and worn permanently up to 1 week were carried out. These pads were tested by a drop rig, i.e. a mechanical device vertically reproducing the impact on the greater trochanter in a sideways fall. Unfortunately, the efficacy of these new hip pads has not been tested in randomized controlled trials [30]. Indeed, given the complexity of designing and conducting proper clinical trials in this field, it is necessary to perform accurate and standardized biomechanical laboratory testing in a preclinical setting in order to measure and optimize their biomechanical properties before studies in humans. For this reason, the International Hip Protectors Research Group (IHPRG) has developed evidence-based recommendations to properly test the biomechanical efficacy and performance of old and newly developed hip protectors [26] (Table 1). The primary objective of a hip protector should be the percentual reduction in the ‘‘peak axial compressive force’’ applied to the femoral neck below a certain threshold known to cause hip fracture in the reference population (estimated 3472 N by studies on cadavers), achieved by blunting the stiffness of the trochanter and/or deflecting the force towards the surrounding soft tissue, thereby better absorbing the applied energy. Secondary objectives of hip protectors would be to protect from falls in different directions in addition to the side, from diverse type of forces (torsional and/or bending vs axial), suitable aesthetic characteristics,
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L. Cianferotti et al.: Hip Protectors: Are They Worth it? Table 1 Recommended design parameters of biomechanical test systems for measuring the force attenuation provided by hip protectors (source Robinovitch et al. [26]) Parameter
Recommended value or type
Basic design
Impact pendulum or drop tower
Effective (drop) mass
28 kg (acceptable range, 22–33 kg)
Effective pelvic stiffness
47 kN/m (acceptable range, 39–55 kN/m)
Soft tissue covering
Polyethelene or polyurethane foam rubber
Minimal thickness of soft tissue covering over the greater trochanter
18 mm
Impact velocity
3.4 m/sb
Peak compressive force in unpadded case
3.5–4.5 kNc
Time to peak compressive force in unpadded case
30–50 ms
Filtering of force signals
Low pass recursive, cut off frequency = 50 Hz
durability, skin tolerability and capacity to stay in place once positioned. Biomechanical in vitro testing is obtained by means of a device (drop tower or pendulum-based system) simulating the force developed during a sideways fall of an old woman to the ground from standing height. Further advances in this field will come from basic biomechanical studies on the dynamics of falls which will help to better simulate and reproduce a fall by means of complex devices that have to take into account hip and pelvis geometry/stiffness, kinetic energy and the relative attenuation developed by a hip protector. For this reason, other attempts for standardization using mechanical testing methods validated for protective impact clothing have been criticized, given that the system is not suitable for properly studying the deflation of force during impact [31, 32]. To address the issue whether flooring properties could influence the force attenuation/deflection of hip protectors, the standardized pendulum technique mentioned above has recently been applied to testing different hip protectors against various flooring materials (i.e. concrete, wood and tatami flooring) using a simplified device. These Japanese authors concluded that soft protectors against tatami flooring offered the best force-attenuation effect [33]. It has also been suggested that the design and geometric parameters of the different hip pads could directly influence biomechanical effectiveness, depending on impact velocities [23]. These studies suggest that other parameters, other than force of impact and material, should be taken into consideration in the preclinical setting and in designing proper clinical trials.
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Soft hip protectors with air cushions seem to offer greater protection against a given impact by means of a better dual energy-absorbing and energy-shunting mechanism [34]. The next generation of hip protectors, still at the stage of prototypes, used only in the preclinical research setting and not yet commercialized, includes specific sensors able to monitor and record temperature, thereby indirectly measuring the amount of time the device is worn [35] and/or register the force of a given impact on the ground and monitor body sway/gait performance [36]. In general, combining electronic sensors in pre-existing hip pads offers the possibility to remotely monitor the patients for adherence, falls and muscular performance. Airbag inflation devices properly combined with fall-sensing mechanisms have also been patented, but not yet tested on a large scale in randomized trials [37].
Assessing Hip Protector Efficacy and Effectiveness in Reducing the Incidence of Hip Fractures in Clinical Studies Hip protectors were first developed in the late 1980s and have been tested in clinical trials since 1993. The first randomized controlled trials yielded promising results, since it was demonstrated that the use of hip protectors in nursing home residents could prevent hip fractures, consistently and similarly reducing the relative risk of hip fractures by nearly 50 % [38–41]. Notably, no fracture event was observed when a hip protector was worn. Conversely, fractures were observed in the intervention group when the pad was not in place. Nonetheless, all authors acknowledged that compliance to wear the device was crucial for hip fracture prevention, as shown by the fact that in less than 50 % of the people who fell, the hip protector was in a correct position. In addition, most of these initial studies could be biased by the fact that they were not individual but cluster randomized and small sized, since they included less than 200 participants [42, 43]. Nonetheless, an individual-randomized trial in female residents in Japanese nursing homes led to similar results, with a significant reduction in hip fracture events in the women who wore hip pads, independent of number of falls, anthropometric data and bone ultrasound parameters, as demonstrated by regression analysis [44]. Conversely, an Australian individual-randomized study carried out in a similar small-sized group of frail, higher-risk women admitted in aged care facilities (selected for having experienced two falls or one major fall requiring admission to hospital in the previous 3 months) failed to demonstrate a significant reduction of fall-related injuries in the group that was selected to receive the hip protector. This was probably also due to low compliance (57 %) in
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permanently wearing the hip protectors, as demonstrated by the percentage of falls (54 %) which occurred without hip protector in place in the women in the intervention group, despite having been appropriately encouraged to use it [45]. Similar negative results were obtained in a parallel study carried out in community-dwelling frail older women living in the community [46]. On the other hand, a randomized intervention trial carried out in 1725 frail community-dwelling elderly adults, including both sexes, demonstrated that the use of an external hip protector decreased the rate of hip fracture from 46/1000/year to 21.3/ 1000/year, although the reduction in the risk of pelvic fracture was not significant [47]. Since these first studies, a variety of clinical studies have further assessed the efficacy and effectiveness of hip protectors in reducing the risk of hip fractures, both in institutionalized subjects and in community-dwelling elderly, producing conflicting results [48–55]. This is mainly due to problems in the design of the trials and low adherence, i.e. scarce acceptance to wear the device permanently (as further addressed in this paper), together with a lack of a precise standardized validation of the device used by specific biomechanical characteristics and performance in preclinical testing, as previously described. A total of 16 individual or clustered randomized controlled trials on hip protectors have been considered eligible to be included in a recent Cochrane meta-analysis (totalling over 16,000 participants), 13 involving elderly living in aged care facilities (11,573 participants) and three including older adults living at home (5135 participants) [21, 38–41, 44–58]. These studies have been taken into account because their primary outcomes were the reduction of fractures and falls, with acceptance and adherence, side effects (e.g. skin irritation) and cost-effectiveness as secondary outcomes. The use of hip protectors was associated with a significant decrease in the incidence of hip fractures in six studies, including those previously described [38, 40, 41, 44, 47, 55] and with borderline significance in two [39, 50]. In eight studies, hip protectors failed to demonstrate a reduction in the risk of hip/pelvic fractures [45, 46, 48, 49, 51–54]. The conclusion of the meta-analysis by Gillespie et al. (with comment added in 2011, no change to conclusions), taken together with other systematic reviews of this kind, is that hip protectors are ineffective in decreasing the incidence of hip fractures in community-dwelling elderly subjects. Conversely, there is sufficient evidence of their efficacy in nursing homes or residential care settings in frail elderly at high risk for fractures. Nonetheless, the overall size of the reduction of hip fracture events in nursing home residents demonstrated by the systematic review by Gillespie et al. is smaller compared to the results of other meta-analyses, similar in the methods but with
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more stringent criteria for the inclusion of the trials for the pooled analysis [20, 21, 56–60]. After the first reports and initial enthusiasm about the use of hip pads to prevent fractures and their consequences, other well-designed, individually randomized large studies failed to confirm the positive results [48–52]. In the Amsterdam Hip Protector Project, an example of a well-designed study carried out in 561 subjects aged C70 years with low bone density (as assessed by calcaneous ultrasound) and/or at high risk for falling (excluding those who experienced previous hip fractures), the subjects included were residents in nursing homes or apartment houses/homes for the elderly who were randomized to receive and appropriately educated to wear a hard shell hip protector 24 h/day, or to a control group [49]. The adherence in the intervention group, which was supervised by nurses in nursing homes and in the houses for the elderly, decreased significantly to 37 % during the mean follow-up of 70 weeks (at least 1 year for each participant). Taking the measurement of the time to the first hip fracture as a primary outcome, there was no statistically significant difference between the two groups, both in the univariate and the multivariate analysis (HR 1.05; 95 % CI 0.55–2.03). Also, regarding the number of fractures, the number of events was comparable between the two groups (18 in the intervention group versus 20 in the control group). Even the per protocol analysis in the compliant subjects failed to show any statistical significance (HR, 0.77; 95 % CI 0.25–2.38) [49]. However, the results of this study are limited because of the small sample size, considering that hip fractures are a relatively rare event. For this reason, the observed 23 % reduction in fracture events in the group wearing the hip protectors did not reach statistical significance. In a subsequent cost-effectiveness analysis of this study, the use of hip protectors was not associated with lower costs compared to the cost of hip fracture and subsequent rehabilitation [61]. This was in contrast to a previous study, which demonstrated in a US setting the cost-effectiveness of an intervention with hip protectors when they achieved a risk of fracture less than 0.65 or adherence greater than 42 % [62]. A more recent study (Hip Impact Protection PROject, HIP PRO), adopting an innovative clustered match-pair design [63], has tested a biomechanically superior onesided hip protector harbouring energy-absorbing and energy-dispersing properties in 1042 subjects (mean age 85 years, 79 % women) in nursing homes in the US, which had been randomly selected to receive hip protectors for their residents, followed up for 20 months, with a mean adherence of 73.8 % [54]. The primary outcome was a reduction in the risk of hip fracture, with the main outcome measure being the number of fracture events on the padded
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hip versus fracture occurrence on non-padded hip. Since an interim analysis showed no statistical difference in terms of primary outcome, both in the whole group (3.1 %; 95 % CI 1.8–4.4 % vs. 2.5 %; 95 % CI 1.3–3.7 %; P = .70) and in the group of more compliant subjects (adherence C80 %), the study was discontinued due to the lack of efficacy [54]. This further demonstrated that, despite an overall mean adherence of 73.8 %, hip protectors as currently designed may not offer an advantage to nursing home residents in terms of protection from fractures. Because of the innovative design of this study with respect to other RCTs, no direct comparisons on the adherence results can be drawn at this stage. However, when both the professionals and the residents are trained by a dedicated, structured education programme regarding the meaning and usefulness of hip protectors, and provided with free devices, compliance can effectively increase, together with a significant rise in the protection against fractures, as demonstrated in a European individual-randomized trial in nursing home residents at high risk of falling [50]. Recently, a cluster randomized trial carried out in 76 Japanese nursing homes and aged care facilities, randomly allocated in a 3:1 ratio to intervention group or control group, has demonstrated that in institutionalized women at high risk of falls and hip fracture (low BMI), wearing hip protectors is significantly associated with a decrease in the incidence of fracture (HR of hip fracture in the intervention group 0.56; 95 % CI 0.31–1.03, P = 0.06) [55]. This latter study, appropriately included in the meta-analysis of Gillespie et al., has led to the concept that hip protectors may be effective when worn by frail institutionalized elderly subjects, while there is still no evidence that they could be of certain utility in older individuals living at home (Primary Care Hip Protector Trial) [51], even in the subgroup of frail people who had previously experienced a hip fracture [52]. Regarding this latter study, and as assessed in a retrospective observational study, the maximal preventive effect of a hip protector is around 50 %, since hip fractures often occur in people with low risk for hip fracture and in circumstances which prevent the use of hip protectors [64]. Two studies have recently addressed the prevention of hip fractures with hip protectors as secondary outcome, the first objective being the improvement of adherence. The intervention failed to increase adherence through specific educational programmes and by providing free devices, both in institutionalized subjects and older people living in the community, and no significant decrease in hip fracture was reported in the intervention groups [65, 66]. The latest update of the Cochrane meta-analysis on this matter included 19 studies, nine of which were cluster randomized, with a total of nearly 17,000 elderly subjects
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(mean age range of 78–86 years) [67]. Hip protectors were found to modestly decrease the risk of hip fractures in nursing homes or residential care settings, without affecting the rate of fracture in community dwellers. Wearing these devices did not influence the rate of falls, while there was an overall slight increase in the risk of pelvic fractures. Nonetheless, the evidence supporting this latter finding is still poor, given the small number of studies that included this information, and the small number of events [67].
Short- and Long-Term Adherence in Wearing Hip Protectors The clinical effectiveness of intervention studies employing hip protectors is clearly dampened by the lack of adherence, i.e. ‘‘the wearing of hip protectors in accordance with the recommendations of the study protocol, measured as the amount of time hip protectors are worn’’ [68], which has been proposed as a standard definition. Indeed, wearing time, which relies on user compliance, is crucial to obtain benefits from a hip protector in order to reduce the risk of fracture. According to the different types of measurements and definitions adopted and the different populations studied, the quantification of adherence to the wearing of hip pads varies greatly in the various trials [69]. This issue was addressed when intervention trials began to yield contradictory results. In a systematic review on this subject, which included early observational and intervention studies on this matter [70–72], primary acceptance with hip protectors was 68 % (ranging from 37 to 72 %), with a compliance of 56 % (ranging from 20 to 92 %) [69]. In the Amsterdam Hip Protector Project, compliance assessed by unannounced visits decreased steadily during the 12 months of observation (from 60.8 % at 1 month to 44.7 % at 6 months, and 37 % at 12 months). Among the compliant subjects, not all were wearing the device in a correct way, or during the night, despite the fact that they had been advised to use it 24 h/day at enrolment [73]. Several factors have been acknowledged as interfering with the compliance in wearing hip protecting pads. General discomfort, urinary incontinence, problems in correctly putting on and positioning the undergarment, along with poor health conditions and cognitive impairment, greatly decrease the overall time of using the devices [69, 74]. In addition, a general perception of low risk, in the absence of specific educational programmes, and coexistence of dementia may lead to non-acceptance and/or removal of the devices [69, 74]. Nonetheless, data on adherence to wear hip protectors in elders with cognitive impairment are contradictory. The largest study on this matter, in which an analysis of adherence by ‘‘intention to
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treat’’ has been performed, has indeed shown that institutionalized subjects with cognitive impairment at high risk for fall and fracture are more likely to not discontinue the use of hip protectors [75]. Initial acceptance to wear the device and subsequent compliance seem to strictly depend on the perceptiveness of the risk of hip fracture and/or the effectiveness of hip protectors in regard to reduction of fracture events, both from a patient and nurse viewpoint [76, 77]. With respect to the latter, staff could require further educational, financial and organizational support to increase adherence and appropriate training, in order to acquire the proper attitude in advising and supporting the use of hip protectors [78, 79]. Indeed, wearing hip protectors per se has been shown to increase fall self-efficacy, especially when specific educational programmes have been carried out [80, 81]. It has been postulated that wearing these devices can hamper the quality of life (QoL), thus decreasing compliance. A recent study has addressed this issue [82]. QoL, as assessed by specific questionnaires (i.e. EQ-5D questionnaire, developed by EuroQol Group-5 Dimension questionnaire, EQ-5D, encompassing self-care, mobility, usual activities, anxiety/depression and pain/discomfort), was not affected in patients adhering to wearing hip protectors. Although the lack of compliance is recognized as a major issue in intervention studies assessing effectiveness of hip protectors in preventing hip fractures, few randomized controlled trials have examined specific intervention to improve adherence as primary outcome. Two recent randomized trials, one cluster randomized performed in institutionalized elderly subjects and one individually randomized in older community-dwelling people, failed to show any benefit either in improving adherence or in reducing the incidence of hip fracture by means of appropriate educational programmes and/or providing hip protectors at no cost in the long term, although they can promote the initial acceptance [65, 66]. Monitoring compliance per se has been revealed to be a major issue in all the clinical studies testing the efficacy of hip protectors in preventing fractures. Adherence has been assessed mainly by self-reporting methods (e.g. by keeping a diary) or by indirect assessment by medical or paramedical personnel (e.g. by interviews, unannounced visits, assessment of hip pads wearing after a fall). With these methods, the quantification of adherence is frequently inaccurate and often overestimated. Moreover, it has been acknowledged that it is difficult to perform meta-analyses on adherence to hip protectors, since it is impossible to pool studies employing different assessment methods [69]. In this respect, the introduction of pads with sensors aimed to objectively monitor adherence and/or balance/falls is likely to increase compliance. As a matter of fact, a study in adolescents has shown that compliance to wear spinal
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Table 2 Key recommendations of the International Hip Protector Study Group for future clinical trials of hip protectors (source: Cameron et al. [85]) Further randomized trials should be conducted in nursing care facilities and possibly community settings for high-risk groups Participants in clinical trials of hip protectors should be at high risk (annual incidence [3 %) of proximal femoral fracture—suggested indicators are history of bone fragility fracture, low weight, functional impairment, increased fall risk and older age Hip protectors used in clinical trials should have been assessed using agreed international testing methods. ‘‘Sham’’ hip protectors should be used with intra-individual randomization (i.e. on random basis, the same person has an ‘‘active’’ protector on one hip and a ‘‘sham’’ protector on the other), and, in an ideal study design, a randomized comparison group without any protector should be used to clarify whether the use of hip protectors affects the general risk of hip fracture A ‘‘run-in’’ period prior to the clinical trial should occur with adequate adherence to be demonstrated Falls and, ideally, fall directionality should be monitored Adherence should be monitored by research staff across day- and night-time hours Economic analyses should be included in future clinical trials of hip protectors
orthoses equipped with sensors increased simply because of the awareness of being monitored [83]. Computer chips designed to be embedded in close proximity to the hip protector and able to detect and record temperature differentiate between environmental and skin surface temperature, thus giving a direct measurement of adherence (iButtonÒ Thermochron sensors) [35]. A recent study has shown a high compliance to custom-made monitors containing a combination of an accelerometer and a temperature sensor enclosed in a hard shell shield [36]. These devices have been tested in small groups of subjects wearing hip protectors and are likely to be tested in randomized controlled trials testing the overall effectiveness of hip protectors in preventing hip fractures in high-risk patients.
Evidence-Based Recommendations Given the absence of compelling evidence coming from the randomized controlled studies on the efficacy of hip protectors in preventing falls and fractures, definitive evidence-based recommendation on their use cannot be drawn. Heterogeneity in the studies, lack of compliance (also due to multimorbidities), different study populations and problems with the design of the trials (clustered versus individual), preventing an easy pooling of the results, prevent definitive conclusion about their use in clinical practice. Despite the fact that it has been demonstrated that hip protectors may be useful to the elderly living in aged care facilities, availability and use of these devices tend to be not homogeneous, and depend on sex (the likelihood of being offered a hip protector was lower for men), migration status, welfare aid and care needs (people with low and high care needs tended not to have hip protector offered) [84]. In this respect, specific instructions for nurses and frail individuals as to why the device must be worn, also during the night, are necessary in order to increase acceptance and overall compliance.
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It is likely that identifying and including in the intervention subjects at higher risk for fractures with objective measurements of muscular performance, muscle mass, gait analysis and bone density, in addition to qualitative or semi-quantitative measures, could increase the efficacy and the effectiveness of wearing hip protectors. However, few studies have been carried out in specific yet large subgroups of patients, such as those who have experienced a major osteoporotic fracture. Recently, recommendations as to how to optimize the devices in a preclinical setting from a biomechanical point of view according to agreed international testing methods [26] and how to correctly design and perform intervention trials [85] have been published (Tables 1, 2). These consensus statements acknowledge the opportunity to conduct further larger randomized trials in nursing care facilities, and possibly community settings, in high-risk individuals (estimated annual incidence of hip fracture [3 %). They advise to use ‘‘sham’’ hip protectors with intra-individual randomization, which could decrease the bias in cluster randomized trials which allow the inclusion of a larger number of subjects in institutionalized settings. An assessment of adherence with a given hip protector should precede the real intervention study in a ‘‘run in’’ period. Monitoring of falls and fall directionality, as well as monitoring of adherence throughout day- and night-time hours, is necessary. This could be more easily achieved by means of biosensors embedded in the device. Lastly, economic analysis on short- and long-term cost-effectiveness of hip protectors should always be included in future clinical trials.
Conclusions and Further Developments Despite current debate on the efficacy of hip protectors, mainly due to lack of adherence in the short and long term, they continue to demonstrate the potential of decreased hip fracture when correctly worn. In this regard, their use can
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be associated with a decrease in morbidity and mortality in elderly, especially in institutionalized individuals. Biosensors, by remotely tracking adherence to hip protectors in addition to monitoring gait, could represent a real turning point in this field. Inflatable airbag protection devices (patented), not yet tested in randomized trials, have the potential to significantly increase comfort, thus increasing overall compliance. Trials in particular settings, i.e. frail elderly at high risk of fall and fractures, are likely to achieve better statistical significance in demonstrating the usefulness of hip protectors. Optimizing adherence through specific educational programmes directed towards the elderly at higher risk of fracture and towards nursing staff, together with primary care physicians in community settings, could ultimately increase the effectiveness of intervention with hip protectors, making them a first-line intervention, in addition to rehabilitation procedures and medication, to reduce morbidity and mortality due to fragility fractures. Acknowledgments Luisella Cianferotti is the recipient of a grant on in vivo studies on bone and muscle crosstalk provided by the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS). This work was also supported by an unrestricted grant from Fondazione Italiana sulla Ricerca delle Malattie dell’Osso (F.I.R.M.O. Foundation) to Maria Luisa Brandi. Conflict of interest Luisella Cianferotti and Maria Luisa Brandi declare that they have no disclosures to make relevant to work in this paper.
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Human and Animal Rights and Informed Consent This article does not contain any studies with human participants or animals performed by any of the authors.
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Life (2012) A systematic review of hip fracture incidence and probability of fracture worldwide. Osteoporos Int 23:2239–2256 Bleibler F, Konnopka A, Benzinger P, Rapp K, Ko¨nig HH (2013) The health burden and costs of incident fractures attributable to osteoporosis from 2010 to 2050 in Germany—a demographic simulation model. Osteoporos Int 24:835–847 Cummings SR, Melton LJ (2002) Epidemiology and outcomes of osteoporotic fractures. Lancet 359:1761–1767 Bentler SE, Liu L, Obrizan M, Cook EA, Wright KB, Geweke JF, Chrischilles EA, Pavlik CE, Wallace RB, Ohsfeldt RL, Jones MP, Rosenthal GE, Wolinsky FD (2009) The aftermath of hip fracture: discharge placement, functional status change, and mortality. Am J Epidemiol 170:1290–1299 Kannus P, Leiponen P, Parkkari J, Palvanen M, Ja¨rvinen M (2006) A sideways fall and hip fracture. Bone 39:383–384 Kaptoge S, Benevolenskaya LI, Bhalla AK, Cannata JB, Boonen S, Falch JA, Felsenberg D, Finn JD, Nuti R, Hoszowski K, Lorenc R, Miazgowski T, Jajic I, Lyritis G, Masaryk P, Naves-Diaz M, Poor G, Reid DM, Scheidt-Nave C, Stepan JJ, Todd CJ, Weber K, Woolf AD, Roy DK, Lunt M, Pye SR, O’neill TW, Silman AJ, Reeve J (2005) Low BMD is less predictive than reported falls for future limb fractures in women across Europe: results from the European prospective Osteoporosis study. Bone 36:387–398 Ja¨rvinen TL, Sieva¨nen H, Khan KM, Heinonen A, Kannus P (2008) Shifting the focus in fracture prevention from osteoporosis to falls. BMJ 336:124–126 Ja¨rvinen TL, Sieva¨nen H, Kannus P, Jokihaara J, Khan KM (2011) The true cost of pharmacological disease prevention. BMJ 342:d2175 Eisman JA, Bogoch ER, Dell R, Harrington JT, McKinney RE Jr, McLellan A, Mitchell PJ, Silverman S, Singleton R, Siris E (2012) Making the first fracture the last fracture: a SBMR task force report on secondary fracture prevention. J Bone Miner Res 27:2039–2046 Kanis JA, McCloskey EV, Johansson H, Cooper C, Rizzoli R, Reginster JY, Scientific Advisory Board of the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) and the Committee of Scientific Advisors of the International Osteoporosis Foundation (IOF) (2013) European guidance for the diagnosis and management of osteoporosis in postmenopausal women. Osteoporos Int 24:23–57 Rizzoli R, Boonen S, Brandi ML, Bruye`re O, Cooper C, Kanis JA, Kaufman JM, Ringe JD, Weryha G, Reginster JY (2013) Vitamin D supplementation in elderly or postmenopausal women: a 2013 update of the 2008 recommendations from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO). Curr Med Res Opin 29:305–313 Reid IR, Bolland MJ (2014) Skeletal and nonskeletal effects of vitamin D: is vitamin D a tonic for bone and other tissues? Osteoporos Int 25:2347–2357 Kannus P, Sieva¨nen H, Palvanen M, Ja¨rvinen T, Parkkari J (2005) Prevention of falls and consequent injuries in elderly people. Lancet 366:1885–1893 Robinovitch SN, Inkster L, Maurer J, Warnick B (2003) Strategies for avoiding hip impact during sideways falls. J Bone Miner Res 18:1267–1273 Feldman F, Robinovitch SN (2007) Reducing hip fracture risk during sideways falls: evidence in young adults of the protective effects of impact to the hands and stepping. J Biomech 40:2612–2618 Parker MJ, Gillespie WJ, Gillespie LD (2006) Effectiveness of hip protectors for preventing hip fractures in elderly people: systematic review. BMJ 332:571–574 Gillespie WJ, Gillespie LD, Parker MJ (2010) Hip protectors for preventing hip fractures in older people. Cochrane Database Syst Rev 10:CD001255
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10 22. Parker M, Johansen A (2006) Hip fracture. BMJ 333:27–30 23. Laing AC, Feldman F, Jalili M, Tsai CM, Robinovitch SN (2011) The effects of pad geometry and material properties on the biomechanical effectiveness of 26 commercially available hip protectors. J Biomech 44:2627–2635 24. van Schoor NM, van der Veen AJ, Schaap LA, Smit TH, Lips P (2006) Biomechanical comparison of hard and soft hip protectors, and the influence of soft tissue. Bone 39:401–407 25. Bentzen H, Forse´n L, Becker C, Bergland A (2008) Uptake and adherence with soft- and hard-shelled hip protectors in Norwegian nursing homes: a cluster randomised trial. Osteoporos Int 19:101–111 26. Robinovitch SN, Evans SL, Minns J, Laing AC, Kannus P, Cripton PA, Derler S, Birge SJ, Plant D, Cameron ID, Kiel DP, Howland J, Khan K, Lauritzen JB (2009) Hip protectors: recommendations for biomechanical testing—an international consensus statement (part I). Osteoporos Int 20:1977–1988 27. Parkkari J, Kannus P, Poutala J, Vuori I (1994) Force attenuation properties of various trochanteric padding materials under typical falling conditions of the elderly. J Bone Miner Res 9:1391–1396 28. Parkkari J, Kannus P, Heikkila¨ J, Poutala J, Sieva¨nen H, Vuori I (1995) Energy-shunting external hip protector attenuates the peak femoral impact force below the theoretical fracture threshold: an in vitro biomechanical study under falling conditions of the elderly. J Bone Miner Res 10:1437–1442 29. Kannus P, Parkkari J, Poutala J (1999) Comparison of force attenuation properties of four different hip protectors under simulated falling conditions in the elderly: an in vitro biomechanical study. Bone 25:229–235 30. Nabhani F, Bamford J (2002) Mechanical testing of hip protectors. J Mat Proc Tech 124:311–318 31. Holzer LA, von Skrbensky G, Holzer G (2009) Mechanical testing of different hip protectors according to a European Standard. Injury 40:1172–1175 32. Kannus P, Parkkari J, Robinovitch S (2010) The European standard testing method for motorcyclists’ protective clothing (EN 1621-1) is unsuitable for hip protectors. Injury 41:430–431 33. Li N, Tsushima E, Tsushima H (2013) Comparison of impact force attenuation by various combinations of hip protector and flooring material using a simplified fall-impact simulation device. J Biomech 46:1140–1146 34. Tadano S, Nakatsuchi H, Goto N, Fujisaki K, Nakatsuchi Y (2011) Mechanical evaluation of hip pads to protect against fracture of elderly femurs in falls. Biomed Mater Eng 21:235–246 35. Cameron ID, Fisher W, Lockwood K, Cook B, Oen C, Stocks J, Quine S, Kurrle SE, Schaafsma FG (2011) Assessing adherence to use of hip protectors: automated monitoring is feasible. J Am Geriatr Soc 59:1766–1767 36. Evans KR, Lou E, Woloschuk C, Hill D, Li M, Wong MS (2014) Quantitative measurement of hip protector use and compliance. Med Biol Eng Comput 52:9–15 37. Wu G, Xue S (2008) Portable preimpact fall detector with inertial sensors. IEEE Trans Neural Syst Rehabil Eng 16:178–183 38. Lauritzen JB, Petersen MM, Lund B (1993) Effect of external hip protectors on hip fractures. Lancet 341:11–13 39. Ekman A, Mallmin H, Michae¨lsson K, Ljunghall S (1997) External hip protectors to prevent osteoporotic hip fractures. Lancet 350:563–564 40. Ja¨ntti PO, Aho HJ, Ma¨ki-Jokela PL, Heikinheimo RJ (1998) Hip protectors and hip fractures. Age Ageing 27:758–759 41. Chan DK, Hillier G, Coore M, Cooke R, Monk R, Mills J, Hung WT (2000) Effectiveness and acceptability of a newly designed hip protector: a pilot study. Arch Gerontol Geriatr 30:25–34 42. Hahn S, Puffer S, Torgerson DJ, Watson J (2005) Methodological bias in cluster randomised trials. BMC Med Res Methodol 5:10
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L. Cianferotti et al.: Hip Protectors: Are They Worth it? 59. Sawka AM, Ismaila N, Cranney A, Thabane L, Kastner M, Gafni A, Woodhouse LJ, Crilly R, Cheung AM, Adachi JD, Josse RG, Papaioannou A (2010) A scoping review of strategies for the prevention of hip fracture in elderly nursing home residents. PLoS ONE 5:e9515 60. Vestergaard P, Mosekilde L, Langdahl B (2011) Fracture prevention in postmenopausal women. Clin Evid (Online) 2011, pii: 1109. 61. van Schoor NM, de Bruyne MC, van der Roer N, Lommerse E, van Tulder MW, Bouter LM, Lips P (2004) Cost-effectiveness of hip protectors in frail institutionalized elderly. Osteoporos Int 15:964–969 62. Honkanen LA, Schackman BR, Mushlin AI, Lachs MS (2005) A cost-benefit analysis of external hip protectors in the nursing home setting. J Am Geriatr Soc 53:190–197 63. Barton BA, Birge SJ, Magaziner J, Zimmerman S, Ball L, Brown KM, Kiel DP (2008) The hip Impact protection project: design and methods. Clin Trials 5:347–355 64. van Schoor NM, Smit JH, Bouter LM, Veenings B, Asma GB, Lips P (2007) Maximum potential preventive effect of hip protectors. J Am Geriatr Soc 55:507–510 65. Cameron ID, Kurrle SE, Quine S, Sambrook PN, March L, Chan DK, Lockwood K, Cook B, Schaafsma FF (2011) Improving adherence with the use of hip protectors amongst older people living in nursing care facilities: cluster randomized trial. J Am Med Dir Assoc 12:50–57 66. Cameron ID, Kurrle S, Quine S, Sambrook P, March L, Chan D, Stocks J, Lockwood K, Cook B, Schaafsma FG (2011) Increasing adherence with the use of hip protectors for older people in the community. Osteoporosis Int 22:617–626 67. Santesso N, Carrasco-Labra A, Brignardello-Petersen R (2014) Hip protectors for preventing hip fractures in older people. Cochrane Database Syst Rev 3:CD001255 68. Kurrle SE, Cameron ID, Quine S, Cumming RG (2004) Adherence with hip protectors: a proposal for standardised definitions. Osteoporos Int 15:1–4 69. van Schoor NM, Deville´ WL, Bouter LM, Lips P (2002) Acceptance and compliance with external hip protectors: a systematic review of the literature. Osteoporos Int 13:917–924 70. Parkkari J, Heikkila¨ J, Kannus IP (1998) Acceptability and compliance with wearing energy-shunting hip protectors: a 6-month prospective follow-up in a Finnish nursing home. Age Ageing 27:225–229 71. Cryer C, Knox A, Martin D, Barlow J, Cantebury hip protector project team (2002) Hip protector compliance among older people living in residential care homes. Inj Prev 8:202–206
11 72. Thompson PW, Jones C, Villar T (2002) Hip protectors. Rate of adherence is 42 % at 3 months in residential homes. BMJ 324:1454 73. van Schoor NM, Asma G, Smit JH, Bouter LM, Lips P (2003) The Amsterdam Hip Protector Study: compliance and determinants of compliance. Osteoporos Int 14:353–359 74. Kurrle SE, Cameron ID, Quine S (2004) Predictors of adherence with the recommended use of hip protectors. J Gerontol A Biol Sci Med Sci 59:M958–M961 75. O’Halloran PD, Cran GW, Beringer TR, Kernohan G, Orr J, Dunlop L, Murray LJ (2007) Factors affecting adherence to use of hip protectors amongst residents of nursing homes—a correlation study. Int J Nurs Stud 44:672–686 76. Cryer C, Knox A, Stevenson E (2006) Factors associated with the initial acceptance of hip protectors amongst older people in residential care. Age Ageing 35:72–75 77. Cryer C, Knox A, Stevenson E (2008) Factors associated with hip protector adherence among older people in residential care. Inj Prev 14:24–29 78. Zimmerman S, Magaziner J, Birge SJ, Barton BA, Kronsberg SS, Kiel DP (2010) Adherence to hip protectors and implications for U.S. long-term care settings. J Am Med Dir Assoc 11:106–115 79. Milisen K, Coussement J, Boonen S, Geeraerts A, Druyts L, Van Wesenbeeck A, Abraham I, Dejaeger E (2011) Nursing staff attitudes of hip protector use in long-term care, and differences in characteristics between adherent and non-adherent residents: a survey and observational study. Int J Nurs Stud 48:193–203 80. Cameron ID, Stafford B, Cumming RG, Birks C, Kurrle SE, Lockwood K, Quine S, Finnegan T, Salkeld G (2000) Hip protectors improve falls self-efficacy. Age Ageing 29:57–62 81. Lach HW, Ball LJ, Birge SJ (2012) The nursing home falls selfefficacy scale: development and testing. Clin Nurs Res 21:79–91 82. Schaafsma FG, Kurrle SE, Quine S, Lockwood K, Cameron ID (2012) Wearing hip protectors does not reduce health-related quality of life in older people. Age Ageing 41:121–125 83. Miller DJ, Franzone JM, Matsumoto H, Gomez JA, Avendan˜o J, Hyman JE, Roye DP Jr, Vitale MG (2012) Electronic monitoring improves brace-wearing compliance in patients with adolescent idiopathic scoliosis: a randomized clinical trial. Spine 37:717–721 84. Klenk J, Kurrle S, Rissmann U, Kleiner A, Heinrich S, Ko¨nig HH, Becker C, Rapp K (2011) Availability and use of hip protectors in residents of nursing homes. Osteoporos Int 22:1593–1598 85. Cameron ID, Robinovitch S, Birge S, Kannus P, Khan K, Lauritzen J, Howland J, Evans S, Minns J, Laing A, Cripton P, Derler S, Plant D, Kiel DP (2010) Hip protectors: recommendations for conducting clinical trials–an international consensus statement (part II). Osteoporos Int 21:1–10
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REVIEW
Hip Protectors: Are They Worth it? Luisella Cianferotti1 • Caterina Fossi1 • Maria Luisa Brandi1
Received: 13 February 2015 / Accepted: 11 April 2015 / Published online: 30 April 2015 Ó Springer Science+Business Media New York 2015
Abstract Hip fractures are one of the most serious conditions in frail elderly subjects, greatly increasing morbidity and mortality, and decreasing healthy life years. Since their first introduction on the market, hip protectors have been revealed to be a potential preventive measure for hip fractures, in addition to other well-known recognized medical interventions and rehabilitation procedures. However, randomized controlled trials have given contradictory results regarding their efficacy. Moreover, little data are available on the cost effectiveness of hip protectors. Adherence is a major problem in assessing the effectiveness of hip protectors in preventing fractures. Indeed, there is a lack of general consensus on a standard definition and quantitative objective estimation of adherence to hip protectors, along with still scarce evidence on specific interventions on how to ameliorate it. From what is known so far, it seems reasonable to advise the use of hip protectors in aged care facilities, since recent pooled analyses have suggested their efficacy in this setting. The introduction of sensors combined with hip protectors will probably address this issue, both for monitoring and optimizing compliance, especially in elderly people. In the meantime, new, welldesigned studies following specific guidelines are strongly
& Maria Luisa Brandi [email protected] Luisella Cianferotti [email protected] Caterina Fossi [email protected] 1
Department of Surgery and Translational Medicine, Section of Endocrinology, Unit of Bone and Mineral Metabolism, University of Florence, Viale Pieraccini, 6, 50139 Florence, Italy
encouraged and needed. In particular, studies in community-dwelling elderly individuals at high risk of first or further fragility fractures are required. The optimization of the tested devices in a preclinical setting according to international standard biomechanical testing is necessary. Keywords Hip fracture Osteoporosis Frailty Falls Nursing homes Effectiveness
Introduction The worldwide burden of fragility fractures is responsible for major economic and social challenges for national health systems and the individual [1–3]. Among different types of fractures, hip fractures are considered one of the most serious complications of falling and osteoporosis, since they lead to increased morbidity (i.e. long-term functional impairment and loss of independence) and mortality, especially in the elderly, in both sexes [4, 5]. Although hip fractures are more common in women with a female to male ratio of 4:1, by the year 2050, figures in men are expected to rise and surpass those of women, at least in developed countries, along with an overall increase in the total number, due to the changes in demographics and an overall increase in population ageing [6]. It is estimated that 10 % of patients will die 1 month after a hip fracture, but this percentage can rise up to 65 % if the patient suffers another acute medical problem, such as pneumonia or heart failure, immediately following the fracture. Up to one-third will die after 1 year, although a decrease in overall mortality rates is expected, likely due to optimized and prompt orthopaedic procedures. Half of the surviving patients lose independence, and nearly 10 % are forced to be bedridden [7, 8]. Elderly people are at major
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risk of fall and fracture, due to an overall decline in musculoskeletal functions and competences. A broken bone is the result of poor skeletal resistance against mechanical forces applied. More than 90 % of hip fractures result from a fall. Elderly subjects are at major risk of hip fractures because of poor balance and weaker bones. A sideways fall produces a high-energy impact, which increases sixfold the risk of a hip fracture compared to a backward or a forward fall, even in young subjects [9] (Fig. 1). Indeed, the number of reported falls is more predictive of hip fractures than low BMD in women, and falling is now considered the strongest risk factor for hip fractures [10–12]. At the same time, treatment with antiosteoporotic medications has proven to be cost-effective, mainly in the secondary prevention of fragility fractures, while for a primary prevention strategy, cost effectiveness has not been demonstrated [13–15]. Vitamin D supplementation has failed to show efficacy in the prevention of falls and fractures in numerous clinical trials [16]. Conversely, exercise programmes improving muscular performance and balance may reduce the incidence of hip fractures by reducing falls [17]. Moreover, proper safelanding strategies and self-protective responses can reduce the impact on the hip [18, 19]. It is still a matter of debate whether currently marketed devices such as hip padding offering biomechanical protection during a fall, thus decreasing the force of the impact on the bone, could decrease the incidence of fractures of the proximal hip, at least in high-risk elderly
Fig. 1 Schematic representation of a sideways fall and consequent hip fracture (panel A) and potential preventive effect of a hip protector (panel B)
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institutionalized individuals [20, 21]. This review will give an overview of the latest advances in the use of hip protectors in hip fracture prevention, starting with a description of basic biomechanical properties, and then focusing on evidence coming from randomized clinical trials and meta-analyses.
Types of Hip Protectors and Their Mechanical Properties: Preclinical Studies Hip protectors are hard or soft plastic (polypropylene or polyethylene) shields properly embedded into pants or undergarments in proximity of the outside of the hip, just over the trochanter, i.e. the bony protuberance on the outer surface of the proximal hip. The particular design of hip protectors is aimed at decreasing and/or absorbing the impact of a sideways fall, ultimately preventing fractures of the proximal hip, encompassing intracapsular fractures (i.e. at the site of femoral neck) and extracapsular fractures involving the trochanter [22]. Commercial types of hip protectors can be either ‘‘crashhelmet like’’, i.e. rigid pads designed to spread the energy of the impact to the soft tissue of the thigh surrounding the hip, or ‘‘energy-absorbing’’. The latter are made of specific soft, shock-absorbing materials, which decrease the force of the impact ultimately transmitted to the bone [23] (Figure 2). The primary aim of hip protectors is to reduce the energy transmitted to the trochanter during a fall below
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Fig. 2 Photographs showing top and side views of different commercially available hip protectors tested (source Laing et al. [23])
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the force causing a fracture, also referred to as hip fracture threshold. In this respect, hip protectors incorporating hard materials seem superior [24], even if they are less comfortable to wear, thus potentially decreasing short- and long-term compliance [25]. The effectiveness of a hip protector in preventing fractures in preclinical studies is evaluated by in vitro biomechanical testing, which was not standardized until recently [26]. The first preliminary studies evaluated existing materials suitable for hip protectors, which are required to display basic properties, such as a good shock-absorbing competence against a reasonable impact of 3 m/s (likely to reproduce the velocity of a fall), elastic properties, toughness, reasonable weight, availability and modest price [27]. The authors concluded that hip pads made up of existing soft materials could not provide sufficient protection at an acceptable thickness. Indeed, hip pads conceived to spread the energy developed during a fall away from the great trochanter could decrease the force applied to the hip. These devices were developed later and yielded energyabsorbing and energy-shunting properties, thus providing a proper attenuation of the final impact on the hip after a sideways fall, as in vitro reproduced by means of the impact pendulum [28, 29]. It was clear from the beginning that the pads had to be sufficiently small, comfortable and resistant to increase compliance. Experiments with devices designed to be fixed directly on the skin without specific undergarments and worn permanently up to 1 week were carried out. These pads were tested by a drop rig, i.e. a mechanical device vertically reproducing the impact on the greater trochanter in a sideways fall. Unfortunately, the efficacy of these new hip pads has not been tested in randomized controlled trials [30]. Indeed, given the complexity of designing and conducting proper clinical trials in this field, it is necessary to perform accurate and standardized biomechanical laboratory testing in a preclinical setting in order to measure and optimize their biomechanical properties before studies in humans. For this reason, the International Hip Protectors Research Group (IHPRG) has developed evidence-based recommendations to properly test the biomechanical efficacy and performance of old and newly developed hip protectors [26] (Table 1). The primary objective of a hip protector should be the percentual reduction in the ‘‘peak axial compressive force’’ applied to the femoral neck below a certain threshold known to cause hip fracture in the reference population (estimated 3472 N by studies on cadavers), achieved by blunting the stiffness of the trochanter and/or deflecting the force towards the surrounding soft tissue, thereby better absorbing the applied energy. Secondary objectives of hip protectors would be to protect from falls in different directions in addition to the side, from diverse type of forces (torsional and/or bending vs axial), suitable aesthetic characteristics,
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L. Cianferotti et al.: Hip Protectors: Are They Worth it? Table 1 Recommended design parameters of biomechanical test systems for measuring the force attenuation provided by hip protectors (source Robinovitch et al. [26]) Parameter
Recommended value or type
Basic design
Impact pendulum or drop tower
Effective (drop) mass
28 kg (acceptable range, 22–33 kg)
Effective pelvic stiffness
47 kN/m (acceptable range, 39–55 kN/m)
Soft tissue covering
Polyethelene or polyurethane foam rubber
Minimal thickness of soft tissue covering over the greater trochanter
18 mm
Impact velocity
3.4 m/sb
Peak compressive force in unpadded case
3.5–4.5 kNc
Time to peak compressive force in unpadded case
30–50 ms
Filtering of force signals
Low pass recursive, cut off frequency = 50 Hz
durability, skin tolerability and capacity to stay in place once positioned. Biomechanical in vitro testing is obtained by means of a device (drop tower or pendulum-based system) simulating the force developed during a sideways fall of an old woman to the ground from standing height. Further advances in this field will come from basic biomechanical studies on the dynamics of falls which will help to better simulate and reproduce a fall by means of complex devices that have to take into account hip and pelvis geometry/stiffness, kinetic energy and the relative attenuation developed by a hip protector. For this reason, other attempts for standardization using mechanical testing methods validated for protective impact clothing have been criticized, given that the system is not suitable for properly studying the deflation of force during impact [31, 32]. To address the issue whether flooring properties could influence the force attenuation/deflection of hip protectors, the standardized pendulum technique mentioned above has recently been applied to testing different hip protectors against various flooring materials (i.e. concrete, wood and tatami flooring) using a simplified device. These Japanese authors concluded that soft protectors against tatami flooring offered the best force-attenuation effect [33]. It has also been suggested that the design and geometric parameters of the different hip pads could directly influence biomechanical effectiveness, depending on impact velocities [23]. These studies suggest that other parameters, other than force of impact and material, should be taken into consideration in the preclinical setting and in designing proper clinical trials.
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Soft hip protectors with air cushions seem to offer greater protection against a given impact by means of a better dual energy-absorbing and energy-shunting mechanism [34]. The next generation of hip protectors, still at the stage of prototypes, used only in the preclinical research setting and not yet commercialized, includes specific sensors able to monitor and record temperature, thereby indirectly measuring the amount of time the device is worn [35] and/or register the force of a given impact on the ground and monitor body sway/gait performance [36]. In general, combining electronic sensors in pre-existing hip pads offers the possibility to remotely monitor the patients for adherence, falls and muscular performance. Airbag inflation devices properly combined with fall-sensing mechanisms have also been patented, but not yet tested on a large scale in randomized trials [37].
Assessing Hip Protector Efficacy and Effectiveness in Reducing the Incidence of Hip Fractures in Clinical Studies Hip protectors were first developed in the late 1980s and have been tested in clinical trials since 1993. The first randomized controlled trials yielded promising results, since it was demonstrated that the use of hip protectors in nursing home residents could prevent hip fractures, consistently and similarly reducing the relative risk of hip fractures by nearly 50 % [38–41]. Notably, no fracture event was observed when a hip protector was worn. Conversely, fractures were observed in the intervention group when the pad was not in place. Nonetheless, all authors acknowledged that compliance to wear the device was crucial for hip fracture prevention, as shown by the fact that in less than 50 % of the people who fell, the hip protector was in a correct position. In addition, most of these initial studies could be biased by the fact that they were not individual but cluster randomized and small sized, since they included less than 200 participants [42, 43]. Nonetheless, an individual-randomized trial in female residents in Japanese nursing homes led to similar results, with a significant reduction in hip fracture events in the women who wore hip pads, independent of number of falls, anthropometric data and bone ultrasound parameters, as demonstrated by regression analysis [44]. Conversely, an Australian individual-randomized study carried out in a similar small-sized group of frail, higher-risk women admitted in aged care facilities (selected for having experienced two falls or one major fall requiring admission to hospital in the previous 3 months) failed to demonstrate a significant reduction of fall-related injuries in the group that was selected to receive the hip protector. This was probably also due to low compliance (57 %) in
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permanently wearing the hip protectors, as demonstrated by the percentage of falls (54 %) which occurred without hip protector in place in the women in the intervention group, despite having been appropriately encouraged to use it [45]. Similar negative results were obtained in a parallel study carried out in community-dwelling frail older women living in the community [46]. On the other hand, a randomized intervention trial carried out in 1725 frail community-dwelling elderly adults, including both sexes, demonstrated that the use of an external hip protector decreased the rate of hip fracture from 46/1000/year to 21.3/ 1000/year, although the reduction in the risk of pelvic fracture was not significant [47]. Since these first studies, a variety of clinical studies have further assessed the efficacy and effectiveness of hip protectors in reducing the risk of hip fractures, both in institutionalized subjects and in community-dwelling elderly, producing conflicting results [48–55]. This is mainly due to problems in the design of the trials and low adherence, i.e. scarce acceptance to wear the device permanently (as further addressed in this paper), together with a lack of a precise standardized validation of the device used by specific biomechanical characteristics and performance in preclinical testing, as previously described. A total of 16 individual or clustered randomized controlled trials on hip protectors have been considered eligible to be included in a recent Cochrane meta-analysis (totalling over 16,000 participants), 13 involving elderly living in aged care facilities (11,573 participants) and three including older adults living at home (5135 participants) [21, 38–41, 44–58]. These studies have been taken into account because their primary outcomes were the reduction of fractures and falls, with acceptance and adherence, side effects (e.g. skin irritation) and cost-effectiveness as secondary outcomes. The use of hip protectors was associated with a significant decrease in the incidence of hip fractures in six studies, including those previously described [38, 40, 41, 44, 47, 55] and with borderline significance in two [39, 50]. In eight studies, hip protectors failed to demonstrate a reduction in the risk of hip/pelvic fractures [45, 46, 48, 49, 51–54]. The conclusion of the meta-analysis by Gillespie et al. (with comment added in 2011, no change to conclusions), taken together with other systematic reviews of this kind, is that hip protectors are ineffective in decreasing the incidence of hip fractures in community-dwelling elderly subjects. Conversely, there is sufficient evidence of their efficacy in nursing homes or residential care settings in frail elderly at high risk for fractures. Nonetheless, the overall size of the reduction of hip fracture events in nursing home residents demonstrated by the systematic review by Gillespie et al. is smaller compared to the results of other meta-analyses, similar in the methods but with
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more stringent criteria for the inclusion of the trials for the pooled analysis [20, 21, 56–60]. After the first reports and initial enthusiasm about the use of hip pads to prevent fractures and their consequences, other well-designed, individually randomized large studies failed to confirm the positive results [48–52]. In the Amsterdam Hip Protector Project, an example of a well-designed study carried out in 561 subjects aged C70 years with low bone density (as assessed by calcaneous ultrasound) and/or at high risk for falling (excluding those who experienced previous hip fractures), the subjects included were residents in nursing homes or apartment houses/homes for the elderly who were randomized to receive and appropriately educated to wear a hard shell hip protector 24 h/day, or to a control group [49]. The adherence in the intervention group, which was supervised by nurses in nursing homes and in the houses for the elderly, decreased significantly to 37 % during the mean follow-up of 70 weeks (at least 1 year for each participant). Taking the measurement of the time to the first hip fracture as a primary outcome, there was no statistically significant difference between the two groups, both in the univariate and the multivariate analysis (HR 1.05; 95 % CI 0.55–2.03). Also, regarding the number of fractures, the number of events was comparable between the two groups (18 in the intervention group versus 20 in the control group). Even the per protocol analysis in the compliant subjects failed to show any statistical significance (HR, 0.77; 95 % CI 0.25–2.38) [49]. However, the results of this study are limited because of the small sample size, considering that hip fractures are a relatively rare event. For this reason, the observed 23 % reduction in fracture events in the group wearing the hip protectors did not reach statistical significance. In a subsequent cost-effectiveness analysis of this study, the use of hip protectors was not associated with lower costs compared to the cost of hip fracture and subsequent rehabilitation [61]. This was in contrast to a previous study, which demonstrated in a US setting the cost-effectiveness of an intervention with hip protectors when they achieved a risk of fracture less than 0.65 or adherence greater than 42 % [62]. A more recent study (Hip Impact Protection PROject, HIP PRO), adopting an innovative clustered match-pair design [63], has tested a biomechanically superior onesided hip protector harbouring energy-absorbing and energy-dispersing properties in 1042 subjects (mean age 85 years, 79 % women) in nursing homes in the US, which had been randomly selected to receive hip protectors for their residents, followed up for 20 months, with a mean adherence of 73.8 % [54]. The primary outcome was a reduction in the risk of hip fracture, with the main outcome measure being the number of fracture events on the padded
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hip versus fracture occurrence on non-padded hip. Since an interim analysis showed no statistical difference in terms of primary outcome, both in the whole group (3.1 %; 95 % CI 1.8–4.4 % vs. 2.5 %; 95 % CI 1.3–3.7 %; P = .70) and in the group of more compliant subjects (adherence C80 %), the study was discontinued due to the lack of efficacy [54]. This further demonstrated that, despite an overall mean adherence of 73.8 %, hip protectors as currently designed may not offer an advantage to nursing home residents in terms of protection from fractures. Because of the innovative design of this study with respect to other RCTs, no direct comparisons on the adherence results can be drawn at this stage. However, when both the professionals and the residents are trained by a dedicated, structured education programme regarding the meaning and usefulness of hip protectors, and provided with free devices, compliance can effectively increase, together with a significant rise in the protection against fractures, as demonstrated in a European individual-randomized trial in nursing home residents at high risk of falling [50]. Recently, a cluster randomized trial carried out in 76 Japanese nursing homes and aged care facilities, randomly allocated in a 3:1 ratio to intervention group or control group, has demonstrated that in institutionalized women at high risk of falls and hip fracture (low BMI), wearing hip protectors is significantly associated with a decrease in the incidence of fracture (HR of hip fracture in the intervention group 0.56; 95 % CI 0.31–1.03, P = 0.06) [55]. This latter study, appropriately included in the meta-analysis of Gillespie et al., has led to the concept that hip protectors may be effective when worn by frail institutionalized elderly subjects, while there is still no evidence that they could be of certain utility in older individuals living at home (Primary Care Hip Protector Trial) [51], even in the subgroup of frail people who had previously experienced a hip fracture [52]. Regarding this latter study, and as assessed in a retrospective observational study, the maximal preventive effect of a hip protector is around 50 %, since hip fractures often occur in people with low risk for hip fracture and in circumstances which prevent the use of hip protectors [64]. Two studies have recently addressed the prevention of hip fractures with hip protectors as secondary outcome, the first objective being the improvement of adherence. The intervention failed to increase adherence through specific educational programmes and by providing free devices, both in institutionalized subjects and older people living in the community, and no significant decrease in hip fracture was reported in the intervention groups [65, 66]. The latest update of the Cochrane meta-analysis on this matter included 19 studies, nine of which were cluster randomized, with a total of nearly 17,000 elderly subjects
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(mean age range of 78–86 years) [67]. Hip protectors were found to modestly decrease the risk of hip fractures in nursing homes or residential care settings, without affecting the rate of fracture in community dwellers. Wearing these devices did not influence the rate of falls, while there was an overall slight increase in the risk of pelvic fractures. Nonetheless, the evidence supporting this latter finding is still poor, given the small number of studies that included this information, and the small number of events [67].
Short- and Long-Term Adherence in Wearing Hip Protectors The clinical effectiveness of intervention studies employing hip protectors is clearly dampened by the lack of adherence, i.e. ‘‘the wearing of hip protectors in accordance with the recommendations of the study protocol, measured as the amount of time hip protectors are worn’’ [68], which has been proposed as a standard definition. Indeed, wearing time, which relies on user compliance, is crucial to obtain benefits from a hip protector in order to reduce the risk of fracture. According to the different types of measurements and definitions adopted and the different populations studied, the quantification of adherence to the wearing of hip pads varies greatly in the various trials [69]. This issue was addressed when intervention trials began to yield contradictory results. In a systematic review on this subject, which included early observational and intervention studies on this matter [70–72], primary acceptance with hip protectors was 68 % (ranging from 37 to 72 %), with a compliance of 56 % (ranging from 20 to 92 %) [69]. In the Amsterdam Hip Protector Project, compliance assessed by unannounced visits decreased steadily during the 12 months of observation (from 60.8 % at 1 month to 44.7 % at 6 months, and 37 % at 12 months). Among the compliant subjects, not all were wearing the device in a correct way, or during the night, despite the fact that they had been advised to use it 24 h/day at enrolment [73]. Several factors have been acknowledged as interfering with the compliance in wearing hip protecting pads. General discomfort, urinary incontinence, problems in correctly putting on and positioning the undergarment, along with poor health conditions and cognitive impairment, greatly decrease the overall time of using the devices [69, 74]. In addition, a general perception of low risk, in the absence of specific educational programmes, and coexistence of dementia may lead to non-acceptance and/or removal of the devices [69, 74]. Nonetheless, data on adherence to wear hip protectors in elders with cognitive impairment are contradictory. The largest study on this matter, in which an analysis of adherence by ‘‘intention to
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treat’’ has been performed, has indeed shown that institutionalized subjects with cognitive impairment at high risk for fall and fracture are more likely to not discontinue the use of hip protectors [75]. Initial acceptance to wear the device and subsequent compliance seem to strictly depend on the perceptiveness of the risk of hip fracture and/or the effectiveness of hip protectors in regard to reduction of fracture events, both from a patient and nurse viewpoint [76, 77]. With respect to the latter, staff could require further educational, financial and organizational support to increase adherence and appropriate training, in order to acquire the proper attitude in advising and supporting the use of hip protectors [78, 79]. Indeed, wearing hip protectors per se has been shown to increase fall self-efficacy, especially when specific educational programmes have been carried out [80, 81]. It has been postulated that wearing these devices can hamper the quality of life (QoL), thus decreasing compliance. A recent study has addressed this issue [82]. QoL, as assessed by specific questionnaires (i.e. EQ-5D questionnaire, developed by EuroQol Group-5 Dimension questionnaire, EQ-5D, encompassing self-care, mobility, usual activities, anxiety/depression and pain/discomfort), was not affected in patients adhering to wearing hip protectors. Although the lack of compliance is recognized as a major issue in intervention studies assessing effectiveness of hip protectors in preventing hip fractures, few randomized controlled trials have examined specific intervention to improve adherence as primary outcome. Two recent randomized trials, one cluster randomized performed in institutionalized elderly subjects and one individually randomized in older community-dwelling people, failed to show any benefit either in improving adherence or in reducing the incidence of hip fracture by means of appropriate educational programmes and/or providing hip protectors at no cost in the long term, although they can promote the initial acceptance [65, 66]. Monitoring compliance per se has been revealed to be a major issue in all the clinical studies testing the efficacy of hip protectors in preventing fractures. Adherence has been assessed mainly by self-reporting methods (e.g. by keeping a diary) or by indirect assessment by medical or paramedical personnel (e.g. by interviews, unannounced visits, assessment of hip pads wearing after a fall). With these methods, the quantification of adherence is frequently inaccurate and often overestimated. Moreover, it has been acknowledged that it is difficult to perform meta-analyses on adherence to hip protectors, since it is impossible to pool studies employing different assessment methods [69]. In this respect, the introduction of pads with sensors aimed to objectively monitor adherence and/or balance/falls is likely to increase compliance. As a matter of fact, a study in adolescents has shown that compliance to wear spinal
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Table 2 Key recommendations of the International Hip Protector Study Group for future clinical trials of hip protectors (source: Cameron et al. [85]) Further randomized trials should be conducted in nursing care facilities and possibly community settings for high-risk groups Participants in clinical trials of hip protectors should be at high risk (annual incidence [3 %) of proximal femoral fracture—suggested indicators are history of bone fragility fracture, low weight, functional impairment, increased fall risk and older age Hip protectors used in clinical trials should have been assessed using agreed international testing methods. ‘‘Sham’’ hip protectors should be used with intra-individual randomization (i.e. on random basis, the same person has an ‘‘active’’ protector on one hip and a ‘‘sham’’ protector on the other), and, in an ideal study design, a randomized comparison group without any protector should be used to clarify whether the use of hip protectors affects the general risk of hip fracture A ‘‘run-in’’ period prior to the clinical trial should occur with adequate adherence to be demonstrated Falls and, ideally, fall directionality should be monitored Adherence should be monitored by research staff across day- and night-time hours Economic analyses should be included in future clinical trials of hip protectors
orthoses equipped with sensors increased simply because of the awareness of being monitored [83]. Computer chips designed to be embedded in close proximity to the hip protector and able to detect and record temperature differentiate between environmental and skin surface temperature, thus giving a direct measurement of adherence (iButtonÒ Thermochron sensors) [35]. A recent study has shown a high compliance to custom-made monitors containing a combination of an accelerometer and a temperature sensor enclosed in a hard shell shield [36]. These devices have been tested in small groups of subjects wearing hip protectors and are likely to be tested in randomized controlled trials testing the overall effectiveness of hip protectors in preventing hip fractures in high-risk patients.
Evidence-Based Recommendations Given the absence of compelling evidence coming from the randomized controlled studies on the efficacy of hip protectors in preventing falls and fractures, definitive evidence-based recommendation on their use cannot be drawn. Heterogeneity in the studies, lack of compliance (also due to multimorbidities), different study populations and problems with the design of the trials (clustered versus individual), preventing an easy pooling of the results, prevent definitive conclusion about their use in clinical practice. Despite the fact that it has been demonstrated that hip protectors may be useful to the elderly living in aged care facilities, availability and use of these devices tend to be not homogeneous, and depend on sex (the likelihood of being offered a hip protector was lower for men), migration status, welfare aid and care needs (people with low and high care needs tended not to have hip protector offered) [84]. In this respect, specific instructions for nurses and frail individuals as to why the device must be worn, also during the night, are necessary in order to increase acceptance and overall compliance.
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It is likely that identifying and including in the intervention subjects at higher risk for fractures with objective measurements of muscular performance, muscle mass, gait analysis and bone density, in addition to qualitative or semi-quantitative measures, could increase the efficacy and the effectiveness of wearing hip protectors. However, few studies have been carried out in specific yet large subgroups of patients, such as those who have experienced a major osteoporotic fracture. Recently, recommendations as to how to optimize the devices in a preclinical setting from a biomechanical point of view according to agreed international testing methods [26] and how to correctly design and perform intervention trials [85] have been published (Tables 1, 2). These consensus statements acknowledge the opportunity to conduct further larger randomized trials in nursing care facilities, and possibly community settings, in high-risk individuals (estimated annual incidence of hip fracture [3 %). They advise to use ‘‘sham’’ hip protectors with intra-individual randomization, which could decrease the bias in cluster randomized trials which allow the inclusion of a larger number of subjects in institutionalized settings. An assessment of adherence with a given hip protector should precede the real intervention study in a ‘‘run in’’ period. Monitoring of falls and fall directionality, as well as monitoring of adherence throughout day- and night-time hours, is necessary. This could be more easily achieved by means of biosensors embedded in the device. Lastly, economic analysis on short- and long-term cost-effectiveness of hip protectors should always be included in future clinical trials.
Conclusions and Further Developments Despite current debate on the efficacy of hip protectors, mainly due to lack of adherence in the short and long term, they continue to demonstrate the potential of decreased hip fracture when correctly worn. In this regard, their use can
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be associated with a decrease in morbidity and mortality in elderly, especially in institutionalized individuals. Biosensors, by remotely tracking adherence to hip protectors in addition to monitoring gait, could represent a real turning point in this field. Inflatable airbag protection devices (patented), not yet tested in randomized trials, have the potential to significantly increase comfort, thus increasing overall compliance. Trials in particular settings, i.e. frail elderly at high risk of fall and fractures, are likely to achieve better statistical significance in demonstrating the usefulness of hip protectors. Optimizing adherence through specific educational programmes directed towards the elderly at higher risk of fracture and towards nursing staff, together with primary care physicians in community settings, could ultimately increase the effectiveness of intervention with hip protectors, making them a first-line intervention, in addition to rehabilitation procedures and medication, to reduce morbidity and mortality due to fragility fractures. Acknowledgments Luisella Cianferotti is the recipient of a grant on in vivo studies on bone and muscle crosstalk provided by the Italian Society for Osteoporosis, Mineral Metabolism and Bone Diseases (SIOMMMS). This work was also supported by an unrestricted grant from Fondazione Italiana sulla Ricerca delle Malattie dell’Osso (F.I.R.M.O. Foundation) to Maria Luisa Brandi. Conflict of interest Luisella Cianferotti and Maria Luisa Brandi declare that they have no disclosures to make relevant to work in this paper.
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Human and Animal Rights and Informed Consent This article does not contain any studies with human participants or animals performed by any of the authors.
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