Biomechanical comparison of hard and soft hip protectors, and the influence of soft tissue

Does hip protector prevent falls and hip fractures? An umbrella review of meta-analyses

BACKGROUND

Wearing hip protectors is a measure used to prevent hip fractures caused by falls. However, its protective effect has remained controversial in previous studies. This study provides a rationale for the use of hip protectors by pooling all the current meta-analysis evidence.

METHODS

We conducted an umbrella review of all the current meta-analysis articles about the efficacy of hip protectors to reduce hip fractures and falls in communities and/or institutions. Major databases including EMBASE, Cochrane Library, PubMed and Web of Science, were searched up to June 2022. Two reviewers screened the studies, extracted the data, and conducted the methodological quality assessment independently. The primary outcome was the association statistic (odds ratio (OR), relative risk (RR), etc.) reported in the meta-analysis that quantified the influence of the intervention on hip fractures and falls compared to that of the control group. Narrative synthesis was also conducted. Forest plots and the AMSTAR score were used to describe the results and quality of the pooled literature, respectively.

RESULTS

A total of six meta-analysis articles were included in the study. Hip protectors were effective at reducing hip fractures in older individuals who were in institutions (nursing or residential care settings) but not in communities (RR = 0.70, 95% CI 0.58 to 0.85, I2 = 42%, P < 0.001) (RR = 1.12, 95% CI 0.94 to 1.34, I2 = 0%, P = 0.20), and they did not reduce falls (RR = 1.01, 95% CI 0.90 to 1.13, I2 = 0%, P = 0.89).

CONCLUSIONS

Hip protectors are effective at preventing hip fractures in institutionalized older adults but not in community-dwelling older adults.

TRIAL REGISTRATION

This study has been registered in PROSPERO (PROSPERO ID: CRD42022351773).

Potential Solutions for the Mitigation of Hip Injuries Caused by Falls in Older Adults: A Narrative Review

BACKGROUND

Hip injuries caused by falling are common and often catastrophic for older adults. There is thus an urgent need to develop solutions designed to mitigate fall injuries to the hip by reducing the forces created on the body by ground impact.

METHODS

The goal of this narrative review was to synthesize published literature on available products developed with the expressed goal of reducing fall-related hip injuries.

RESULTS

Three categories were identified: passive wearables (eg, hip protectors), active wearables (eg, instrumented belts with deployable airbags), and compliant flooring. Laboratory studies indicate that each technology can reduce peak forces induced by simulated falls. Considerable preliminary data suggest that passive wearables and compliant flooring may reduce fall-related injuries within long-term care facilities. Controlled trials of specific types of these 2 technologies, however, have produced inconsistent results. While little is known about the effectiveness of active wearables, promising early data indicate the feasibility of an instrumented belt worn around the waist to effectively deploy an airbag to protect the hips prior to ground impact. Important challenges associated with one or more identified technologies included poor adherence to instructed wear as well as the potential for significant physical or time burden to caregivers or health care professionals.

CONCLUSIONS

Passive wearables, active wearables, and compliant flooring have shown promise in reducing fall-related hip injuries in older adults. Still, each type of product is accompanied by limited real-world data and/or significant challenges that must be overcome to maximize effectiveness and minimize unintended side effects.

Shock-absorbing effect of flooring-adopted mechanical metamaterial technology and its influence on the gait and balance of older adults

Objective

To elucidate the performance of a shock-absorbing floor material with a mechanical metamaterial (MM-flooring) structure and its effect on the gait and balance of older adults.

Methods

The drop-weight impact was applied to evaluate the shock-absorbing performance. The falling weight was adjusted equivalent to the energy exerted on the femur of an older woman when she falls, which was evaluated on the MM-flooring and six other flooring materials.

Nineteen healthy people over the age of 65 years participated in the gait and balance evaluations. The timed up and go and two-step tests were adopted as gait performance tests, and the sway-during-quiet-balance test with force plates and the functional reach test (FRT) were adopted as balance tests. All the participants underwent these tests on the MM-flooring, shock-absorbing mat and rigid flooring.

Results

The shock-absorbing performance test revealed that MM-flooring has sufficient shock-absorbing performance, and suggesting that it may reduce the probability of fractures in the older people when they fall. The results of the gait performance test showed that the participants demonstrated the same gait performance on the MM-flooring and the rigid floor. In the quiet standing test, MM-flooring did not affect the balance function of the participants to the same extent as the rigid floor, compared with the shock-absorbing mat. In the FRT, no significant differences were found for any of the flooring conditions.

Conclusions

MM-flooring has the potential to prevent fractures attributed to falls and does not affect the gait or balance of older adults.

Analysis of loading to the hip joint in fall using whole-body FE model

Hip fractures caused by falls are important health problems for the elderly. Many studies used finite element (FE) models of the femur and its surroundings to evaluate the hip fracture risk during the impact phase in a fall. In this study, the whole-body human FE model (THUMS) of a small female was applied from the descent to the impact phase in a fall to understand the effect of the whole body. Brosh's material model was used for the soft tissue of the hip. A low-BMI and high-BMI model were developed based on THUMS (middle-BMI). For the middle-BMI model, the torso angle and the pelvis impact velocity were 45.2° and 2.62 m/s at the time of pelvis impact. The effective mass changed with time, and was 18.3 kg when the femoral neck force was maximum. The femoral neck force was 2.11 kN for the low-BMI model. The femoral neck forces when wearing a soft and a hard hip protector, and when falling on an energy-absorbing floor were compared for the FE models of human and a hip protector testing system. Though the force attenuation of the protective devices was 32.0-44.3 % in the testing system, the force attenuation in the middle-BMI was 0.1-22.2 %. In the low-BMI model, the attenuation of the soft protector was limited (4.2 %) because the hip protector protruded from the outer surface, so the contact force was concentrated at the hip region. This research suggests the importance of including the whole body to evaluate the hip fracture risk.

Aerobic Dance on an Air Dissipation Platform Improves Cardiorespiratory, Muscular and Cellular Fitness in the Overweight and Obese Elderly

Background: Obesity is a global health problem associated with a high number of comorbidities that decrease functional capacity, especially in elderly people. Aerobic dance is considered a viable strategy to prevent the effects of aging, mainly in obese and overweight elderly people. This study aimed to evaluate the effects of aerobic dance on an air dissipation platform (ADP) on body composition, oxidative stress and muscular and cardiorespiratory fitness in elderly people. Methods: In total, 32 elderly adults (67.1 ± 3.6) were divided into 3 groups based on body mass index: healthy (HG), overweight (OWG) and obese (OG). Training program of aerobic dance on an ADP was carried out twice a week for 12 weeks. Results: OWG (p = 0.016) and OG decreased their weight (p < 0.001). There was a significant decrease in malondialdehyde concentrations in all experimental groups (p < 0.05). OWG and OG significantly improved their peak oxygen uptake (p < 0.01). HG increased the vertical jump height (p < 0.05), and HG and OG improved the power output of the lower extremities (p < 0.05). Conclusions: The aerobic dance on an ADP may be an effective alternative to lose weight, prevent oxidative stress and improve cardiorespiratory fitness in obese and overweight elderly people.

A Single Axial Impact Load Causes Articular Damage That Is Not Visible with Micro-Computed Tomography: An Ex Vivo Study on Caprine Tibiotalar Joints

OBJECTIVE

Excessive articular loading, for example, an ankle sprain, may result in focal osteochondral damage, initiating a vicious degenerative process resulting in posttraumatic osteoarthritis (PTOA). Better understanding of this degenerative process would allow improving posttraumatic care with the aim to prevent PTOA. The primary objective of this study was to establish a drop-weight impact testing model with controllable, reproducible and quantitative axial impact loads to induce osteochondral damage in caprine tibiotalar joints. We aimed to induce osteochondral damage on microscale level of the tibiotalar joint without gross intra-articular fractures of the tibial plafond.

DESIGN

Fresh-frozen tibiotalar joints of mature goats were used as ex vivo articulating joint models. Specimens were axially impacted by a mass of 10.5 kg dropped from a height of 0.3 m, resulting in a speed of 2.4 m/s, an impact energy of 31.1 J and an impact impulse of 25.6 N·s. Potential osteochondral damage of the caprine tibiotalar joints was assessed using contrast-enhanced high-resolution micro-computed tomography (micro-CT). Subsequently, we performed quasi-static loading experiments to determine postimpact mechanical behavior of the tibiotalar joints.

RESULTS

Single axial impact loads with a mass of 15.5 kg dropped from 0.3 m, resulted in intra-articular fractures of the tibial plafond, where a mass of 10.55 kg dropped from 0.3 m did not result in any macroscopic damage. In addition, contrast-enhanced high-resolution micro-CT imaging neither reveal any acute microdamage (i.e., microcracks) of the subchondral bone nor any (micro)structural changes in articular cartilage. The Hexabrix content or voxel density (i.e., proteoglycan content of the articular cartilage) on micro-CT did not show any differences between intact and impacted specimens. However, quasi-static whole-tibiotalar-joint loading showed an altered biomechanical behavior after application of a single axial impact (i.e., increased hysteresis when compared with the intact or nonimpacted specimens).

CONCLUSIONS

Single axial impact loads did not induce osteochondral damage visible with high-resolution contrast-enhanced micro-CT. However, despite the lack of damage on macro- and even microscale, the single axial impact loads resulted in "invisible injuries" because of the observed changes in the whole-joint biomechanics of the caprine tibiotalar joints. Future research must focus on diagnostic tools for the detection of early changes in articular cartilage after a traumatic impact (i.e., ankle sprains or ankle fractures), as it is well known that this could result in PTOA.

Cardiorespiratory, Metabolic and Muscular Responses during a Video-Recorded Aerobic Dance Session on an Air Dissipation Platform

BACKGROUND

Aerobic dance (AD) is an appropriate physical activity for improving cardiorespiratory fitness. This study aimed to compare cardiorespiratory and metabolic responses, and muscle fatigue between an air dissipation platform (ADP) and a hard surface during a video-recorded AD session.

METHODS

25 healthy young women (23.3 ± 2.5 years) completed three sessions. In session 1, participants performed an incremental test to exhaustion on a treadmill. One week after session 1, participants were randomly assigned in a crossover design to perform video-recorded AD sessions on an ADP and on a hard surface (sessions 2 and 3). Cardiorespiratory and metabolic responses were assessed during AD sessions. Muscular fatigue was measured before and after AD sessions by a countermovement jump test.

RESULTS

Significantly higher heart rate, respiratory exchange ratio, pulmonary ventilation, ventilatory oxygen equivalent, and ventilatory carbon dioxide equivalent were observed on an ADP than on a hard surface (p < 0.05). Despite a significant increase in lactate levels on an ADP (p ≤ 0.01), muscular fatigue and perceived exertion rating were similar on both surfaces (p > 0.05).

CONCLUSIONS

Video-recorded AD on an ADP increased the cardioventilatory and metabolic responses compared to a hard surface, preventing further muscle fatigue.

Hip protectors are cost-effective in the prevention of hip fractures in patients with high fracture risk

Cost-effective preventive interventions are necessary for tackling the increasing number of hip fractures, which are frequently occuring as a serious consequence of osteoporosis. Several interventions have been available for preventing and treating osteoporosis. The aim of this study was to systematically review and critically appraise studies that assessed cost-effectiveness of hip protectors for the prevention of hip fractures and to investigate the effects of age, gender and residence situation on cost-effectiveness. A systematic review was conducted in order to identify economic evaluation studies examining the hip protector solely or compared to no treatment according to the Preferred Reported Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Synthesis of results was performed to observe trends between the studies. Methodological quality of the studies was assessed by the use of the Quality of Health Economic Studies (QHES) instrument. A total of 15 economic evaluation studies were included for analysis. The methodological quality was high in most studies (13/15). The hip protector was solely evaluated in three studies and within 12 other studies compared with no intervention. All studies that investigated the cost-effectiveness in long-term care facilities revealed that hip protector use is a cost-effective strategy for the prevention of hip fractures in elderly. Cost-effectiveness was also observed in two studies that provided hip protectors in a geriatric hospital ward. Four studies included both community-dwelling residents and residents living in a long-term care facility in their study. These studies showed more variability regarding cost-effectiveness. One study did not report information regarding the residence situation of their cohort, but also observed cost-effectiveness. In conclusion, this review suggests that hip protectors are a cost-effective approach in the prevention of hip fractures in populations with high risk of hip fractures especially in long-term care facilities and a geriatric ward in a hospital.

Test systems for the biomechanical evaluation of hip protectors: a systematic review

Various mechanical and biomechanical test systems to evaluate the effectiveness of hip protectors designed to prevent hip fracture as a result of falls were examined in this review. The articles considered were selected systematically. The effect of differences in design criteria was demonstrated, and it was observed that the impact energy employed during testing dramatically affects the performance of the hip protector. Over the past three decades, researchers have continuously experimented with various systems to determine the efficacy of various hip protectors. The primary aim has been to make informed decisions in optimizing hip protector design. This article provides a systematic review of various test systems employed in the determination of the biomechanical efficacy of hip protectors. A systematic literature search was carried out, and 28 relevant articles were included to demonstrate the effect of test systems in the evaluation of the biomechanical effectiveness of hip protectors. Methodological studies illustrated the appropriate use of impact testing systems for the simulation of hip anatomy and fall dynamics in evaluating the effectiveness of hip protectors in preventing a hip fracture. This systematic review has demonstrated the effect of the variability of test systems on the evaluation of impact attenuation by various hip protectors. The lack of standardized test systems accounts for the inconsistencies in the test results of the efficacy of hip protectors. This has been a major challenge in the efforts of researchers to optimize the interventions. The standardization of test systems may require needed improvements immediately as opposed to the development of new interventions in order to ensure that only hip protectors with adequately proven efficacies are deployed for clinical trials or for the protection of the hips of vulnerable individuals from sideways impact.

Development of a stick-on hip protector: A multiple methods study to improve hip protector design for older adults in the acute care environment

Introduction

Over 90% of hip fractures in older adults result from falls, and hospital patients are at especially high risk. Specific types of wearable hip protectors have been shown to reduce hip fracture risk during a fall by up to 80%, but user compliance has averaged less than 50%. We describe the development and evaluation of a "stick-on" hip protector (secured over the hip with a skin-friendly adhesive) for older patients in acute care.

Methods

An initial version of the product was evaluated with six female patients (aged 76-91) in a hospital ward, who were asked to wear it for one week. We subsequently refined the product through biomechanical testing and solicited feedback from 43 health professionals on a second prototype.

Results

The first prototype was worn by five of six patients for the full week or duration of their hospital stay. The second prototype (20 mm thick, surface area 19 × 15.5 cm) provided 36% force attenuation, more than common garment-based models (20-21%). Feedback from patients and health professionals highlighted usability, comfort, cost, and appearance.

Conclusions

Our results from biomechanical and user testing support the need for further work to determine the value of stick-on hip protectors in acute care.

Developing Fall-impact Protection Pad with 3D Mesh Curved Surface Structure using 3D Printing Technology

In this study, we present the development of fall-impact protection pads for elderly people using three-dimensional (3D) printing technology. To develop fall-impact protection clothing, it is important to maintain the functionality of the protection pad while ensuring that its effectiveness and appearance remain optimal in the process of inserting it. Therefore, this study explores the benefit of exploiting 3D scan data of the human body using 3D printing technology to develop a fall-impact protection pad that is highly suited to the human body shape. The purpose of this study was to present a 3D modeling process for creating curved protective pads comprising a hexagonal mesh with a spacer fabric structure and to verify the impact protection performance by printing curved pads. To this end, we set up a section that includes pads in the 3D human body scan data and extracted body surface information to be applied in the generation of the pad surface. The sheet-shaped hexagonal mesh structure was cut and separated according to the pad outline, and then deformed according to the curved surface of the human body. The pads were printed, and their protection performance was evaluated; a 79.2–81.8% reduction in impact force was observed compared to similar cases in which the pads were not used.

Development and Evaluation of Fall Impact Protection Pads Using Additive Manufacturing

This paper presents the development and evaluation of fall-impact protection pants for elderly women using additive manufacturing. The protective pants were designed incorporating a protective pad in the hip area to reduce the impact of falls on the human body. The protective pad is a 3D mesh structure with a curved surface to fit the human body. Pads printed with flexible thermoplastic polyurethane were combined with foam to create the final pad. The impact-absorbing performance of the pad was verified through physical impact experiments. When dropping a bowling ball onto the protective pad from heights of 15, 20, and 25 cm, the protective pad was found to reduce the impact force by more than 82% in all cases. The impact force was less than the average fracture threshold of 3472 N. A subject group and an expert group evaluated the appearance, pad characteristics, motion functionality, and the wearability of the protection pants. Despite the insertion of a pad, the pants appeared natural and had a good fit. The pads were evaluated as being well-designed in terms of their position, shape, area, thickness, weight, flexibility, ease of insertion, and ease of use. Users were comfortable performing various motions when wearing the designed protective clothing. Therefore, this work can be considered to have developed protective clothing that provides satisfactory impact-protection performance and comfort thereby advancing the possibility of applying additive manufacturing to the creation of functional garments.

Biomechanical testing of hip protectors following the Canadian Standards Association express document

A variety of hip protectors are available, but it is not clear which is the most effective and there is no standard test to evaluate their performance. This is the first study that uses a standard mechanical test on hip protectors. Some protectors perform well but others are almost ineffective, providing little to no protection to the wearer during a fall.

INTRODUCTION

Each year, over 70,000 patients are admitted to hospital in the UK with hip fractures. There are a variety of commercial hip protectors currently available. However, it is not explicitly clear which is the most effective with regard to maximum force attenuation, whilst still being both comfortable for the user and providing reasonable force reduction if misplaced from the intended position. The numerous test methods reported in the literature have given conflicting results, making objective comparison difficult for users, researchers, and manufacturers alike. The Canadian Standards Association (CSA) has therefore published an express document (EXP-08-17) with a draft standard test method. This paper presents initial results for a range of hip protectors.

METHODS

Eighteen commercially available hip protectors were tested according to EXP-08-17. Each hip protector was impacted five times in correct anatomical alignment over the greater trochanter and once at 50 mm displacements in the anterior, posterior, and lateral directions.

RESULTS

Considerable differences were identified between individual hip protectors in their ability to reduce impact forces on the femur (between 3% and 36% reduction in peak force). The performance was reduced when misplaced in many cases (maximum reduction only 20%).

CONCLUSIONS

This is the first study that uses a standard mechanical test on hip protectors. Previous studies have used a variety of methods, making it difficult to interpret results. We hope that these results using a standard test method will facilitate the effective comparison of results, as well as providing useful data for clinicians, users, and purchasers.

Study on buffer characteristics of air cushion used as hip protector

INTRODUCTION

In order to develop a good hip protector to prevent in the elderly hip fracture as a result of a fall, we studied the buffer characteristics of sponges and air cushions.

METHODS

The buffer rate of material was defined, and the absorption ability of the material to instantaneous impact was evaluated. An experimental device was developed and used to measure the buffer rates of sponges and leak-allowed air cushions with orifice(s).

RESULTS

According to the experimental results, the buffer rate largely depended on the hardness of the sponge materials, and on the total area of the orifice(s) for the leak-allowed air cushions. Compared with the sponge with correct hardness and thickness, the buffer characteristic of the air cushion seems slightly inferior.

CONCLUSIONS

Nevertheless, the air cushion's overall performance, including the better buffer rate, ultra-lightness, flexibility, and low cost, makes it a potentially useful material for hip protectors and other sport protectors.

Hip Protectors: Are They Worth it?

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, well-designed studies following specific guidelines are strongly 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.

A procedure for a mechanical evaluation of an undefined osteo-protective material

Falls represent a major care and cost problem to health and social services world-widely, since 50% of falls result in an injury. In this work, is proposed a methodology to evaluate protective pads materials and geometry performance, in order to reduce impact results in a fall event. Since the material properties and the pad geometry are the key factors to make the protection possible when a fall event occurs, our approach relies on the use of mechanical tests to evaluate the properties of the material and in the study of the pad response during a fall. For this, were used compression, tensile and instrumented falling weight tests, that allow a fully characterization of the materials that can be employed in the protective pads. Likewise, to gather precise information on falls events, in order to study the pad response during a fall, a set of laboratory fall trials were created using a camera-less inertial motion capture (mocap) system. This allow the acquisition of dynamic information of falls, namely acceleration and velocity that can be used to create a finite element analysis (FEA) model, where different segments from the human body can be evaluated when the protective pad is associated to it. Through the proposed methodology, different materials and pad geometries can be studied towards maximizing the performance of protection pads for falls. The mocap system allows the acquisition of fall data, and also the creation of a human body geometrical model, representative of the fall. From the mechanical trials, was showed that the spacer fabric embedded with silicone has the higher ability to reduce the peak force in case of impact when compared with all the other specimens. The compression and the tensile tests allow the mechanical definition of the material, and with this the material definition on the FEA model.

Energy absorption during impact on the proximal femur is affected by body mass index and flooring surface

Impact mechanics theory suggests that peak loads should decrease with increase in system energy absorption. In light of the reduced hip fracture risk for persons with high body mass index (BMI) and for falls on soft surfaces, the purpose of this study was to characterize the effects of participant BMI, gender, and flooring surface on system energy absorption during lateral falls on the hip with human volunteers. Twenty university-aged participants completed the study with five men and five women in both low BMI (<22.5 kg/m(2)) and high BMI (>27.5 kg/m(2)) groups. Participants underwent lateral pelvis release experiments from a height of 5 cm onto two common floors and four safety floors mounted on a force plate. A motion-capture system measured pelvic deflection. The energy absorbed during the initial compressive phase of impact was calculated as the area under the force-deflection curve. System energy absorption was (on average) 3-fold greater for high compared to low BMI participants, but no effects of gender were observed. Even after normalizing for body mass, high BMI participants absorbed 1.8-fold more energy per unit mass. Additionally, three of four safety floors demonstrated significantly increased energy absorption compared to a baseline resilient-rolled-sheeting system (% increases ranging from 20.7 to 28.3). Peak system deflection was larger for high BMI persons and for impacts on several safety floors. This study indicates that energy absorption may be a common mechanism underlying the reduced risk of hip fracture for persons with high BMI and for those who fall on soft surfaces.

The influence of body mass index and gender on the impact attenuation properties of flooring systems

The biomechanical effectiveness of safety floors has never been assessed during sideways falls with human volunteers. Furthermore, the influence of body mass index (BMI) and gender on the protective capacity of safety floors is unknown. The purpose of this study was to test whether safety floors provide greater impact attenuation compared with traditional flooring, and whether BMI and gender modify their impact attenuation properties. Thirty participants (7 men and 7 women of low BMI; 7 men and 9 women of high BMI) underwent lateral pelvis release trials on 2 common floors and 4 safety floors. As a group, the safety floors reduced peak force (by up to 11.7%), and increased the time to peak force (by up to 25.5%) compared with a traditional institutional grade floor. Force attenuation was significantly higher for the low BMI group, and for males. Force attenuation was greatest for the low BMI males, averaging 26.5% (SD = 3.0) across the safety floors. These findings demonstrate an overall protective effect of safety floors during lateral falls on the pelvis, but also suggest augmented benefits for frail older adults (often with low body mass) who are at an increased risk of hip fracture.

The effects of pad geometry and material properties on the biomechanical effectiveness of 26 commercially available hip protectors

Wearable hip protectors (padded garments) represent a promising strategy to decrease impact force and hip fracture risk during falls, and a wide range of products are currently marketed. However, little is known about how design features of hip protectors influence biomechanical effectiveness. We used a mechanical test system (simulating sideways falls) to measure the attenuation in femoral neck force provided by 26 commercially available hip protectors at three impact velocities (2, 3, and 4m/s). We also used a materials testing machine to characterize the force-deflection properties of each device. Regression analyses were performed to determine which geometric (e.g., height, width, thickness, volume) and force-deflection properties were associated with force attenuation. At an impact velocity of 3m/s, the force attenuation provided by the various hip protectors ranged between 2.5% and 40%. Hip protectors with lower stiffness (measured at 500N) provided greater force attenuation at all velocities. Protectors that absorbed more energy demonstrated greater force attenuation at the higher impact velocities (3 and 4m/s conditions), while protectors that did not directly contact (but instead bridged) the skin overlying the greater trochanter attenuated more force at velocities of 2 and 3m/s. At these lower velocities, the force attenuation provided by protectors that contacted the skin overlying the greater trochanter increased with increasing pad width, thickness, and energy dissipation. By providing a comparison of the protective value of a large range of existing hip protectors, these results can help to guide consumers and researchers in selecting hip protectors, and in interpreting the results of previous clinical trials. Furthermore, by determining geometric and material parameters that influence biomechanical performance, our results should assist manufacturers in designing devices that offer improved performance and clinical effectiveness.

Increasing adherence with the use of hip protectors for older people living in the community

For people at high risk of hip fracture living in community settings, providing hip protectors at no cost increased adherence, but the additional effect of an educational programme was limited. Overall, the level of adherence was modest.

INTRODUCTION

The objective of the study was to increase adherence with hip protector use by older people at high risk of hip fracture. The study included two randomised controlled trials with 308 older people recruited from three hospital rehabilitation wards and 171 older people recruited from the community.

METHODS

Participants were randomised into three groups. The control group received a brochure about hip protectors. The no cost group were fitted with free hip protectors and asked to use them. The combined group received free hip protectors and education sessions about their use. Adherence with the use of hip protectors at 3 and 6 months after recruitment was measured. Secondary outcomes were falls, fractures and hospitalisations.

RESULTS

Very few participants in the two control groups bought a hip protector. Overall adherence in the four intervention groups was modest, but higher in the community recruitment setting (49%) than in the hospital recruitment setting (36%) at 6 months. In the community recruitment group, at 3 months of follow-up, a significantly higher number of participants in the combined group (62%) were wearing hip protectors compared to the no cost group (43%, p=0.04). Five hip fractures occurred during the study, with four sustained whilst not wearing the hip protectors.

CONCLUSION

Providing hip protectors at no cost to community living older people at high risk of hip fractures modestly increases initial acceptance and adherence with hip protector use. Additional education may further increase hip protector use in people living in the community in the short term.

Mechanical evaluation of polymer composite hip protectors

Hip fractures often result in serious health implications, particularly in the geriatric population, and have been related to long-term morbidity and death. In most cases, these fractures are caused by impact loads in the area of the greater trochanter, which are produced in a fall. This work is aimed at developing hip protectors using composite materials and evaluating their effectiveness in preventing hip fractures under high impact energy (120 J). The hip protectors were developed with an inner layer of energy absorbing soft material and an outer rigid shell of fiberglass-reinforced polymer composite. According to the experimental results, all tested configurations proved to be effective at reducing the impact load to below the average fracture threshold of proximal femur. Furthermore, an addition of Ethylene Vinyl Acetate (EVA) to the impacted area of the composite shell proved to be beneficial to increase impact strength of the hip protectors. Thus, composite hip protectors proved to be a viable alternative for a mechanically efficient and cost-effective solution to prevent hip fractures.

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

BACKGROUND

Hip fractures represent an increasing public health burden with a simple fall to the floor as the most common cause. Because nursing home residents are particularly at risk, nursing homes should implement a broad range of fall prevention strategies. However, not all fall incidents can be avoided and external hip protectors may contribute to prevent hip fractures. A major problem in studying the effectiveness of hip protectors is residents' poor adherence. In nursing homes, adherence is dependent not only on the resident, but also on staff knowledge of and attitudes about hip protectors.

OBJECTIVES

To describe (1) attitudes of day versus night shift caregivers towards the use of a soft hip protector, (2) residents' adherence about the use of such protectors, and (3) differences in characteristics between adherent and non-adherent residents.

DESIGN

Survey and observational study.

SETTING

Nursing home.

PARTICIPANTS/METHODS

: Survey of care staff (n=37) in a nursing home after 8 months of continued application of a soft hip protector policy in residents (n=68). Adherence to wearing the hip protector, measured by weekly unannounced, randomly determined checks during day and night in the 8 months after the start of the study.

RESULTS

Overall, 85% agreed to wear a hip protector. At 8 months, only 29% was still wearing their hip protector; with significant differences between day and night shifts. Although virtually all caregivers (97%) considered a hip protector policy in residential care as feasible, the attitude towards hip protectors was found to be significantly different between day and night caregivers. Pain and discomfort, patient insight in the usefulness of these devices, interference with incontinence materials, and the overall resident mix and care acuity were reported as major barriers.

CONCLUSION

Implementing a hip protector policy for injury prevention in long-term care is not an issue of whether or not to use the devices. Rather, it is a continued clinical nursing decision process about when and when not, by whom and by whom not, why and why not, for how long, and to what clinical benefit--considering both the needs of the individual resident and the feasibility of such a policy in the context of resident mix and nursing staff.

Hip protectors in fracture prevention for aging adults at risk of falling: a study of user compliance

PURPOSE

A compliance survey was conducted to establish factors that influence low user compliance with hip protectors amongst aging adults at risk of hip fracture. Medical professionals who deal with patients at risk of hip facture were also included in this survey.

METHODS

For this descriptive study 2 questionnaires were designed, 1 for community dwelling aging adults at high risk of fall and hip fracture and 1 for medical professionals dealing with these patients. The questionnaires were presented, completed, and collected at individual appointments with aging adults and by group appointments with medical professionals. All data was statistically analysed to detect the most significant factors related to poor user compliance with hip protectors. For this descriptive study, frequency tests were used to analyse the data and therefore percentage of response was also reported. Certain demographic data such as age and gender was also collected.

RESULTS

The outcomes in both interviewed groups were very similar. The main findings demonstrate that 51% of users find hip protectors very valuable while 41% reported the product to be uncomfortable and 29% of users found them difficult to put on. For potential users the high cost of the product and its appearance remains an issue. Also negative psychological aspects of wearing the hip orthoses appear to be common reasons for not wearing a hip protector.

CONCLUSION

The study confirmed poor user compliance with hip protectors (18.9%). The information gathered from users and medical professionals regarding hip protectors provides valuable information which allows for the identification and development of new design features.

Characterizing the effective stiffness of the pelvis during sideways falls on the hip

The force applied to the proximal femur during a fall, and thus hip fracture risk, is dependent on the effective stiffness of the body during impact. Accurate estimates of pelvis stiffness are required to predict fracture risk in a fall. However, the dynamic force-deflection properties of the human pelvis have never been measured in-vivo. Our objectives were to (1) measure the force-deflection properties of the pelvis during lateral impact to the hip, and (2) determine whether the accuracy of a mass-spring model of impact in predicting peak force depends on the characterization of non-linearities in stiffness. We used a sling and electromagnet to release the participant's pelvis from heights up to 5 cm, simulating low-severity sideways falls. We measured applied loads with a force plate, and pelvis deformation with a motion capture system. In the 5 cm trials peak force averaged 1004 (SD 115)N and peak deflection averaged 26.3 (5.1)mm. We observed minimal non-linearities in pelvic force-deflection properties characterized by an 8% increase in the coefficient of determination for non-linear compared to linear regression equations fit to the data. Our model consistently overestimated peak force (by 49%) when using a non-linear stiffness equation, while a piece-wise non-linear fit (non-linear for low forces, linear for loads exceeding 300 N) predicted peak force to within 1% at our highest drop height. This study has important implications for mathematical and physical models of falls, including mechanical systems that assess the biomechanical effectiveness of protective devices aimed at reducing hip fracture risk.

Martial arts fall training to prevent hip fractures in the elderly

Hip fractures are a common and serious consequence of falls. Training of proper fall techniques may be useful to prevent hip fractures in the elderly. The results suggested that martial arts fall techniques may be trainable in older individuals. Better performance resulted in a reduced impact force.

INTRODUCTION

Hip fractures are a common and serious consequence of falls. Fall training may be useful to prevent hip fractures in the elderly. This pilot study determined whether older individuals could learn martial arts (MA) fall techniques and whether this resulted in a reduced hip impact force during a sideways fall.

METHODS

Six male and nineteen female healthy older individuals completed a five-session MA fall training. Before and after training, force and kinematic data were collected during volitional sideways falls from kneeling position. Two MA experts evaluated the fall performance. Fear of falling was measured with a visual analog scale (VAS).

RESULTS

After fall training, fall performance from a kneeling position was improved by a mean increase of 1.6 on a ten-point scale (P < 0.001). Hip impact force was reduced by a mean of 8% (0.20 N/N, P = 0.016). Fear of falling was reduced by 0.88 on a VAS scale (P = 0.005).

CONCLUSION

MA techniques may be trainable in older individuals, and a better performance may reduce the hip impact force in a volitional sideways fall from a kneeling position. The additional reduction of fear of falling might result in the prevention of falls and related injuries.

Hip protectors: recommendations for conducting clinical trials--an international consensus statement (part II)

INTRODUCTION

While hip protectors are effective in some clinical trials, many, including all in community settings, have been unable to demonstrate effectiveness. This is due partly to differences in the design and analysis. The aim of this report is to develop recommendations for subsequent clinical research.

METHODS

In November of 2007, the International Hip Protector Research Group met to address barriers to the clinical effectiveness of hip protectors. This paper represents a consensus statement from the group on recommended methods for conducting future clinical trials of hip protectors.

RESULTS AND CONCLUSIONS

Consensus recommendations include the following: the use of a hip protector that has undergone adequate biomechanical testing, the use of sham hip protectors, the conduct of clinical trials in populations with annual hip fracture incidence of at least 3%, a run-in period with demonstration of adequate adherence, surveillance of falls and adherence, and the inclusion of economic analyses. Larger and more costly clinical trials are required to definitively investigate effectiveness of hip protectors.

Hip protectors: recommendations for biomechanical testing--an international consensus statement (part I)

INTRODUCTION

Hip protectors represent a promising strategy for preventing fall-related hip fractures. However, clinical trials have yielded conflicting results due, in part, to lack of agreement on techniques for measuring and optimizing the biomechanical performance of hip protectors as a prerequisite to clinical trials.

METHODS

In November 2007, the International Hip Protector Research Group met in Copenhagen to address barriers to the clinical effectiveness of hip protectors. This paper represents an evidence-based consensus statement from the group on recommended methods for evaluating the biomechanical performance of hip protectors.

RESULTS AND CONCLUSIONS

The primary outcome of testing should be the percent reduction (compared with the unpadded condition) in peak value of the axial compressive force applied to the femoral neck during a simulated fall on the greater trochanter. To provide reasonable results, the test system should accurately simulate the pelvic anatomy, and the impact velocity (3.4 m/s), pelvic stiffness (acceptable range: 39-55 kN/m), and effective mass of the body (acceptable range: 22-33 kg) during impact. Given the current lack of clear evidence regarding the clinical efficacy of specific hip protectors, the primary value of biomechanical testing at present is to compare the protective value of different products, as opposed to rejecting or accepting specific devices for market use.

Mechanical testing of different hip protectors according to a European Standard

The effect of hip protectors depends on two factors: (1) mechanical features and (2) wearing time, which depends on the user's compliance. Various biomechanical studies have been performed to test hip protectors' ability in reducing impacts. However, none of these has shown the ability to simulate a fall in a natural way. Therefore, we tested conventional and newly designed hip protectors that might raise user's compliance using a standardised mechanical test.

MATERIALS AND METHODS

Mechanical testing was performed according to a European Standard testing method for protective impact clothing (EN 1621-1) where an impact is released vertically onto the hip protectors with an energy of 50J. Seven different hip protectors were tested three times each.

RESULTS

Using this test, four of the hip protectors were able to reduce the impact below a suggested fracture threshold. The two newly designed hip protectors using special absorption materials were superior (9.10kN, 12.65kN) to the other commercially available hip protectors (21.97-50.62kN), which differ in their mechanical testing performance.

DISCUSSION

This is the first study using a standardised mechanical test on hip protectors and allows an objective comparison because only mechanical properties are tested. New hip protectors with improved mechanical properties are superior to conventional hip protectors. Furthermore, they allow a more appealing design that increases the comfort of the wearer. Mechanical testing should be performed as a first step and has to be followed up by clinical trials to determine and clarify their overall effect.

Hip protectors for preventing hip fractures among elderly adults

Prevention of fractures in the elderly consists of prevention and treatment of osteoporosis, prevention of falling and prevention of fractures using injury-site protection. Since the majority of hip fractures in elderly people are caused by a sideways fall with direct impact on the greater trochanter of the proximal femur, one option to prevent the fracture is a biomechanically effective external hip protector. The biomechanical test results of an energy-shunting and energy-absorbing hip protector have demonstrated that this type of hip protector can provide an effective impact force attenuation in typical falling conditions of older adults by reducing the initial force down to the seventh part. Recent meta-analyses and systematic reviews combining findings of all different types of hip protectors suggest that in care homes and institutions with high rates of hip fracture, the use of hip protectors might help to reduce the risk of fracture to 20–60%, but there is no evidence of a public health level benefit from hip protectors for lower-risk (usually home-dwelling) elderly people.

The challenges of interpreting efficacy of hip protector pads in fracture prevention in high-risk seniors

Efficacy of hip protector pads to prevent hip fracture is controversial. This study was done to evaluate two comparable groups for fracture risk. Two matched cohorts of long-term care residents in Canada, assessing the efficacy of hip protector pads. Evaluation included demographics, medications/diagnoses, cognition (Mini Mental Status Examination (MMSE)), balance (Berg), bone mineral density (calcaneal ultrasound), falls/injuries at baseline and completion. Of the 58 participants, there were two confirmed hip fractures (8%) in the hip pad (one while wearing the pad) and eight (24%) in the control groups. But baseline demographics showed significant differences between hip pad (25) and control groups (33) in MMSE, Berg and osteoporosis treatment, all being less in the hip pad group. This persisted at completion, with a higher mortality in the hip pad group. Baseline differences predisposed the hip pad group to a higher fracture risk, but there were fewer hip fractures in this group. Small numbers, multifactorial nature of hip fractures and the inability to control for many of these variables in the real world make efficacy of hip protector pads difficult to confirm. Hip protector pads should be offered as part of the osteoporosis management of frail elderly, especially in those unable/unwilling to take pharmacotherapy.

The force attenuation provided by hip protectors depends on impact velocity, pelvic size, and soft tissue stiffness

Wearable hip protectors represent a promising strategy for preventing hip fractures. However, there is lack of agreement on biomechanical testing standards and subsequent uncertainty about the ability of hip protectors to attenuate impact force during a fall. To address this issue, we designed a fall impact simulator that incorporated a "biofidelic" surrogate pelvis, which matched the surface geometry and soft tissue stiffness measured in elderly women (n=15). We then used this system to measure the attenuation in peak femoral neck force provided by two commercially available soft shell protectors (Safehip Soft and Hipsaver) and one rigid shell protector (Safehip Classic). Finally, we examined how the force attenuation provided by each protector was influenced by systematic changes in fall severity (impact velocity), body size (pelvis size), and soft tissue stiffness. With the biofidelic pelvis, the force attenuation averaged over all impact velocities was 27% for Safehip Soft, 17% for Safehip Classic, and 19% for Hipsaver. However, the rank order of hip protectors (and especially the performance of Safehip Classic) varied with the test conditions. Safehip Classic attenuated force by 33% during a low velocity (1 ms) fall, but only by 8% for a high velocity (4 ms) fall. In the latter condition, improved attenuation was provided by the soft shell hip protectors (19% by Safehip Soft and 21% by Hipsaver). As soft tissue stiffness increased from softest to most rigid, the attenuation provided by Safehip Classic increased 2.9-fold (from 26% to 76%), while Safehip Soft increased 1.7-fold (from 36% to 60%) and Hipsaver increased 1.1-fold (from 36% to 38%). As pelvis size decreased from largest to smallest, the attenuation provided by Safehip Classic increased 8-fold, but for a high velocity fall and moderate tissue stiffness, never exceeded that provided by Safehip Soft and Hipsaver. Our results indicate that, under biofidelic testing conditions, the soft shell hip protectors we examined generally provided greater force attenuation (averaging up to 27%) than the hard shell protector. Measured values of force attenuation were highly sensitive to variations in impact velocity, pelvic size, and pelvic soft tissue stiffness. This indicates the need to develop international testing standards to guide market approval, the selection of protectors for clinical trials, and the design of improved hip protectors.

Effect of soft shell hip protectors on pressure distribution to the hip during sideways falls

INTRODUCTION

While hip protectors represent a promising strategy for preventing hip fractures, clinical efficacy has been limited by poor user compliance. Soft shell protectors may be more acceptable to users than traditional hard shell designs. However, before embarking on clinical trials to assess efficacy, laboratory experiments are required to determine how soft shell protectors affect the force applied during impact to the hip. This was the goal of the current study.

METHODS

Fifteen women participated in "pelvis release experiments," which safely simulate the impact stage of a sideways fall. During the trials, we measured total impact force and mean pressure over the greater trochanter with the participant unpadded, and while wearing two commercially available soft shell protectors.

RESULTS

Mean pressure over the greater trochanter was reduced by 76% by a 14-mm thick horseshoe-shaped protector and by 73% by a 16-mm thick continuous protector. Total force was reduced by 9% by the horseshoe and by 19% by the continuous protector.

CONCLUSIONS

Soft shell hip protectors substantially reduce the pressure over the greater trochanter, while only modestly reducing total impact force during simulated sideways falls. These data support the need for clinical trials to determine whether soft shell protectors reduce hip fracture risk in vulnerable populations.

Development of a new design of hip protectors using finite element analysis and mechanical tests

The rate of hip fractures due to falls increases with age. External hip protectors placed over the greater trochanter can prevent hip fractures, but the willingness to wear such protective devices is rather low. Most of the commercially available hip protectors consist either of an energy-absorbing foam pad or of a hard shell that distributes the load to the surrounding tissue. In the present study, a fibre-reinforced shell composed of three curved strips bonded with a ring, was designed and lined with shock absorbing foam. The development of the new shell design was based on quasi-static and impact tests of manufactured shells in combination with finite element simulations. The results of the numerical analysis showed the potential protection effect of the shell and indicated how the design can be further improved. First impact tests on an anatomical hip model showed promising results of the new protector shell in combination with a foam pad.

Contribution of trochanteric soft tissues to fall force estimates, the factor of risk, and prediction of hip fracture risk

We compared trochanteric soft tissue thickness, femoral aBMD, and the ratio of fall force to femoral strength (i.e., factor of risk) in 21 postmenopausal women with incident hip fracture and 42 age-matched controls. Reduced trochanteric soft tissue thickness, low femoral aBMD, and increased ratio of fall force to femoral strength (i.e., factor of risk) were associated with increased risk of hip fracture.

INTRODUCTION

The contribution of trochanteric soft tissue thickness to hip fracture risk is incompletely understood. A biomechanical approach to assessing hip fracture risk that compares forces applied to the hip during a sideways fall to femoral strength may by improved by incorporating the force-attenuating effects of trochanteric soft tissues.

MATERIALS AND METHODS

We determined the relationship between femoral areal BMD (aBMD) and femoral failure load in 49 human cadaveric specimens, 53-99 yr of age. We compared femoral aBMD, trochanteric soft tissue thickness, and the ratio of fall forces to bone strength (i.e., the factor of risk for hip fracture, phi), before and after accounting for the force-attenuating properties of trochanteric soft tissue in 21 postmenopausal women with incident hip fracture and 42 age-matched controls.

RESULTS

Femoral aBMD correlated strongly with femoral failure load (r2 = 0.73-0.83). Age, height, and weight did not differ; however, women with hip fracture had lower total femur aBMD (OR = 2.06; 95% CI, 1.19-3.56) and trochanteric soft tissue thickness (OR = 1.82; 95% CI, 1.01, 3.31). Incorporation of trochanteric soft tissue thickness measurements reduced the estimates of fall forces by approximately 50%. After accounting for force-attenuating properties of trochanteric soft tissue, the ratio of fall forces to femoral strength was 50% higher in cases than controls (0.92 +/- 0.44 versus 0.65 +/- 0.50, respectively; p = 0.04).

CONCLUSIONS

It is possible to compute a biomechanically based estimate of hip fracture risk by combining estimates of femoral strength based on an empirical relationship between femoral aBMD and bone strength in cadaveric femora, along with estimates of loads applied to the hip during a sideways fall that account for thickness of trochanteric soft tissues. Our findings suggest that trochanteric soft tissue thickness may influence hip fracture risk by attenuating forces applied to the femur during a sideways fall and provide rationale for developing improved measurements of trochanteric soft tissue and for studying a larger cohort to determine whether trochanteric soft tissue thickness contributes to hip fracture risk independently of aBMD.

Hip protectors in the elderly: lack of effectiveness or just suboptimal implementation?

Hip protectors seemed to be the only non-pharmacological intervention to effectively prevent hip fractures in high-risk populations. In contrast, recently published trials did not find hip fracture reduction through hip protector interventions. An updated Cochrane review concluded that the device is ineffective for community-dwelling elderly and of uncertain effectiveness for institutionalised elderly. However, some primary studies used suboptimal implementation of hip protectors, which has led to low adherence and ineffectiveness of the intervention. Shortcomings in implementation techniques have not been assessed by the Cochrane review. Therefore, reviewers should explicitly assess whether the intervention was well planned and competently administered. As a checklist cannot adequately assess individual, study-specific implementation flaws, we suggest narrative expert review and feedback to the authors of the primary study.