Characteristics of falls and risk of hip fracture in elderly men

Hip fracture risk among community-dwelling elderly people in the United States: a prospective study of physical, cognitive, and socioeconomic indicators

OBJECTIVES

We determined risks of short-term (2-year) hip fracture in a nationally representative, prospective cohort of community-dwelling elderly people 70 years or older.

METHODS

We used self-report data from 2 waves of the Asset and Health Dynamics Survey (n = 5630). Sample-weighted logistic regression analyses were conducted to determine risk of hip fracture in relation to several demographic, cognitive, physical, and socioeconomic indicators.

RESULTS

During the 2-year study period, 102 participants reported a new hip fracture. Several indicators of physical functioning and cognitive status, including incorrect delayed word recall and inability to lift 10 lbs (4.5 kg), were significantly associated with hip fracture risk. In the final model, mobile home residents, individuals without Medicare part B insurance, and those without a high-school diploma were at more than a 2-fold risk of hip fracture. Educational level, physical functioning, and insurance status were the top 3 contributors to hip fracture risk.

CONCLUSIONS

In addition to functional status measures, health insurance status, educational level, and type of residence appear to be independent predictors of hip fracture.

Outdoor falls among middle-aged and older adults: a neglected public health problem

OBJECTIVES

Although risk factors for indoor falls among older individuals have been well studied, little is known about the etiology of outdoor falls. We examined risk factors for outdoor falls among middle-aged and older adults.

METHODS

We analyzed data on the most recent fall during the past year among participants aged 45 years and older in the control group (N=2193) of a case-control study of fractures. The study was conducted at 5 Northern California Kaiser Permanente Medical Centers between 1996 and 2001.

RESULTS

Falls occurred outdoors more often than indoors among most age groups. Study participants who reported more leisure-time physical activity had a higher risk for outdoor falls, and participants who were in poorer health had a greater risk for indoor falls. Most outdoor falls (73%) were precipitated by environmental factors, such as uneven surfaces and tripping or slipping on objects, and usually occurred on sidewalks, curbs, and streets. Walking (47.3%) was the most common fall-related activity.

CONCLUSIONS

Outdoor falls among adults aged 45 years and older were frequently attributable to modifiable environmental factors. With the widespread promotion of active lifestyles among older people, improvements in their outdoor environment are urgently needed.

Predictors of falls in a multiethnic population of older rural adults with diabetes

BACKGROUND

Falls are a recognized danger for older adults with diabetes. Persons in rural communities with diabetes may face additional risks from falling due to environmental and activity differences.

METHODS

Data were obtained in a cross-sectional survey of a stratified random sample of 691 community-dwelling adults (42.7% white, 31.4% African American, and 25.9% Native American) at least 65 years old with two or more Medicare claims for diabetes in 1998-2000, living in two rural counties in North Carolina. Falls data were self-reported for the previous year. Demographic data, foot-related symptoms, diabetes medications, and other health characteristics were reported.

RESULTS

Three hundred two persons (43.7%) reported falling at least once, including 171 (26.2%) who experienced two or more (frequent) falls. Frequent fallers were more likely to be male (odds ratio [OR] = 1.76; 95% confidence interval [CI] = 1.17, 2.66), report tingling or numbness in feet (OR = 1.75; 95% CI = 1.13, 2.70), have had a stroke (OR = 1.81; 95% CI = 1.19, 2.76), have longer duration of diabetes (OR = 1.21; 95% CI = 1.00, 1.47), have lower physical functioning (OR = 0.97; 95% CI = 0.96, 0.99) and mobility (OR = 0.89; 95% CI = 0.82, 0.96), and take a greater number of prescription medications (OR = 1.07; 95% CI = 1.01, 1.13).

CONCLUSIONS

For rural older adults with diabetes, falls history should be screened to identify those at risk. Further research should investigate unique environmental factors contributing to falls for rural elderly persons.

Association of geometric factors and failure load level with the distribution of cervical vs. trochanteric hip fractures

We experimentally studied the distribution of hip fracture types at different structural mechanical strength. Femoral neck fractures were dominant at the lowest structural strength levels, whereas trochanteric fractures were more common at high failure loads. The best predictor of fracture type across all failure loads and in both sexes was the neck-shaft angle.

INTRODUCTION

Bone geometry has been shown to be a potential risk factor for osteoporotic fractures. Risk factors have been shown to differ between cervical and trochanteric hip fractures. However, the determinants of cervical and trochanteric fractures at different levels of structural mechanical strength are currently unknown. In addition, it is not known if the distribution of fracture types differs between sexes. The aim of this experimental study on excised femora was to investigate whether there exist differences in the distribution of cervical and trochanteric fractures between different structural mechanical strength levels and different sexes and to identify the geometric determinants that predict a fracture type.

MATERIALS AND METHODS

The sample was comprised of 140 cadavers (77 females: mean age, 81.7 years; 63 males: mean age, 79.1 years) from whom the left femora were excised for analysis. The bones were radiographed, and geometrical parameters were determined from the digitized X-rays. The femora were mechanically tested in a side impact configuration, simulating a sideways fall. After the mechanical test, the fracture patterns were classified into cervical and trochanteric.

RESULTS

The overall proportion of cervical fractures was higher in females (74%) than in males (49%) (p = 0.002). The fracture type distribution differed significantly across load quartiles in females (p = 0.025), but not in males (p = 0.205). At the lowest load quartiles, 94.7% of fractures in female and 62.5% in males were femoral neck fractures. At the highest quartiles, in contrast, only 52.6% of fractures in females and 33.3% in males were cervical fractures. Among geometric variables, the neck-shaft angle was the best predictor of fracture type, with higher values in subjects with cervical fractures. This finding was made in females (p < 0.001) and males (p = 0.02) and was consistent across all failure load quartiles.

CONCLUSIONS

Femoral neck fractures predominate at the lowest structural mechanical strength levels, whereas trochanteric fractures are more common at high failure loads. Females are more susceptible to femoral neck fractures than males. The best predictor of fracture type across all structural strength levels and both sexes was the neck-shaft angle.

Update in the epidemiology of proximal humeral fractures

We sought to determine current trends in the number of fall-related and osteoporosis-related proximal humeral fractures in elderly Finns during last three decades. We collected data from the National Hospital Discharge Register on all patients 60 years or older who were admitted to Finnish hospitals from 1970 to 2002 for primary treatment of proximal humeral fractures. Fractures induced by traffic accidents or other high-energy traumas were excluded. The number and incidence (per 100,000 patients) of fractures increased from 208 (number) and 32 (incidence) in 1970 to 1120 (number) and 105 (incidence) in 2002. The age adjusted incidence of proximal humeral fractures also showed an increase, from 51 (1970) to 129 (2002) in women, and from 14 (1970) to 48 (2002) in men. In women 80 years or older, the age specific incidence of fracture increased from 90 (1970) to 294 (2002), while in the other age groups trend changes were less extensive. The mean patient age also increased, from 73 years (1970) to 78 years (2002) in women and from 70 years (1970) to 73 years (2002) in men. If these trends continue, the number of fractures in elderly Finns will triple during the next three decades.

LEVEL OF EVIDENCE

Prognostic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Time Requirement for Young and Elderly Women to Move Into a Position for Breaking a Fall With Outstretched Hands

BACKGROUND

Risk for hip fracture during a fall is reduced by contacting the ground first with the outstretched hands. However, it is unclear whether the time required for young and elderly individuals to move the hands into a protective position exceeds that available during a typical fall.

METHODS

We tested whether young (n = 30; aged 18-35 years) and elderly women (n = 30; aged 70-88 years) differed in the time required to move their hands into a protective position for breaking a fall. Participants stood either facing or sideways to shoulder-height targets (simulating forward and sideways falls, respectively), which they were instructed to contact as quickly as possible after hearing an aural go cue. Total contact time was partitioned into reaction time and movement time.

RESULTS

Young women contacted the targets faster than elderly women in both forward (530 +/- 60 vs 615 +/- 88 ms; p <.001) and sideways trials (658 +/- 80 vs 799 +/- 145 ms; p <.001). This difference was due to faster movement times for young participants. There was no difference between groups in reaction time.

CONCLUSIONS

Previous studies have shown that during actual falls from standing, wrist and pelvis contact occur at 680 +/- 116 and 715 +/- 160 ms, respectively. Comparing these values to our results suggests that the typical elderly woman should be able to move her hands quickly enough to break a forward fall, but not a sideways fall.

Prevention of falls and consequent injuries in elderly people

Injuries resulting from falls in elderly people are a major public-health concern, representing one of the main causes of longstanding pain, functional impairment, disability, and death in this population. The problem is going to worsen, since the rates of such injuries seem to be rising in many areas, as is the number of elderly people in both the developed and developing world. Many methods and programmes to prevent such injuries already exist, including regular exercise, vitamin D and calcium supplementation, withdrawal of psychotropic medication, cataract surgery, professional environment hazard assessment and modification, hip protectors, and multifactorial preventive programmes for simultaneous assessment and reduction of many of the predisposing and situational risk factors. To receive broader-scale effectiveness, these programmes will need systematic implementation. Care must be taken, however, to rigorously select the right actions for those people most likely to benefit, such as vitamin D and calcium supplementation and hip protectors for elderly people living in institutions.

Evaluation of hip fracture risk in relation to fall direction

The purpose of this study is to evaluate hip fracture risk in relation to fall direction, and to elucidate factors that influence the impact force in falls on the hip. Eight healthy volunteers performed deliberate falls in three directions (lateral, posterolateral and posterior) on a force platform covered by a mattress of 13 cm thickness. Fall descent motions and impact postures were examined by a three-dimensional analyzer. The maximum ground force reaction, velocity of the greater trochanter at impact, and activity of quadriceps and gluteus medius were measured. In all trials of lateral and posterolateral falls, but not of posterior falls, the subjects hit their greater trochanter directly on the mattress. The impact forces were between 2,000 N and 4,000 N. Posterolateral falls showed significantly higher velocity at impact than did posterior falls. The height and the lower limb length exhibited positive correlations with the impact force in all directions of fall. In the lateral fall, there was a positive correlation between the activity of quadriceps and the impact force. In view of the impact point, force, and velocity, the posterolateral fall seemed to carry the highest risk of hip fracture.

Risk factors for pelvis fracture in older persons

From 1996 to 2001, the authors undertook a case-control study of 192 pelvis fracture cases (men and women) and 2,402 controls aged > or = 45 years at five Kaiser Permanente medical centers in Northern California. Most information on potential risk factors was obtained by means of an interviewer-administered questionnaire. Number of fractures since age 45 years and a maternal history of hip fracture were associated with increased risks. Several factors thought to protect against loss of bone mass, including recent use of menopausal hormone therapy (adjusted odds ratio (OR) = 0.55, 95% confidence interval (CI): 0.33, 0.91) and high body mass index (weight (kg)/height (m)2; per 5-unit increase, adjusted OR = 0.65, 95% CI: 0.52, 0.81), were associated with decreased risks, while cigarette smoking (adjusted OR = 2.17, 95% CI: 1.34, 3.52) and hysterectomy (adjusted OR = 1.75, 95% CI: 1.15, 2.66) were associated with increased risks. Various conditions related to propensity to fall were associated with increased risks. Most indicators of frailty, including use of walking aids and needing help with or being unable to perform various activities of daily living, conferred increased risks. Thus, low bone mass, frailty, and probably a propensity to fall appear to be associated with increased risk of pelvis fracture.

Anatomical hip model for the mechanical testing of hip protectors

An anatomical hip model has been developed to simulate the impact load on the hip of a falling person wearing a hip protector. The hip consists of an artificial pelvis made of aluminium, linked by a ball-and-socket joint to an anatomically shaped steel femur (thigh bone). The femur is embedded in silicone material with a hip-shaped surface to allow realistic positioning of the protectors with accessory underwear. Additionally, the silicone simulates the damping and load-dispersal effect of soft tissue. A triaxial load sensor is integrated in the neck of the femur to measure the axial and cross-sectional force components in response to external impact forces on the hip. The performance of the hip model was investigated in drop tests and validated against biomechanical data. In a first series of measurements, the shock absorption of 10 different hip protectors, including both energy-absorbing and energy-shunting systems, was analysed. To determine the importance of hip protector placement, each protector was tested in the correct anatomical alignment over the hip and anteriorly displaced by 3 cm. Considerable differences were found between individual hip protectors in their effectiveness to reduce impact forces on the femur. Position of the hip protector also influenced the forces applied to the femur.

Reducing the risk for distal forearm fracture: preserve bone mass, slow down, and don't fall!

A case-control study of 1,150 female and male distal forearm cases and 2,331 controls of age 45 years and older was undertaken from 1996-2001 in five Northern California Kaiser Permanente Medical Centers. Most information on possible risk factors was obtained by an interviewer-administered questionnaire, supplemented by a few tests of lower extremity neurological function. Previous fractures since 45 years of age, a rough marker of osteoporosis, were associated with an increased risk (adjusted odds ratio [OR] [95% confidence interval] = 1.48 [1.20-1.84 ] per previous fracture). Several factors thought to protect against low bone mass were associated with a reduced risk, including current use of menopausal hormone therapy (adjusted OR = 0.60 [0.49-0.74]), ever used thiazide diuretics or water pills for at least 1 year (adjusted OR = 0.79 [0.64-0.97]), high body mass index (weight in kg/height in m2) (adjusted OR = 0.96 [0.89-1.04] per 5 unit increase), and high dietary calcium intake (adjusted OR = 0.88 [0.75-1.03] per 500 mg/day). Falls in the past year and conditions associated with falling, such as epilepsy and/or use of seizure medication (adjusted OR = 2.07 [1.35-3.17]) and a history of practitioner-diagnosed depression (adjusted OR = 1.40 [1.13-1.73]), were associated with increased risks. Having difficulty performing physical functions and all lower-extremity problems measured in this study were associated with reduced risks. The results from this and other studies indicate that distal forearm fractures tend to occur in people with low bone mass who are otherwise in relatively good health and are physically active, but who are somewhat prone to falling (particularly on an outstretched hand), and whose movements are not slowed by lower extremity problems and other debilities. Thus, measures to decrease fall frequency and to slow down the pace of relatively healthy people with low bone mass should lead to a lower frequency of distal forearm fracture.

Non-pharmacological means to prevent fractures among older adults

Bone fractures affecting elderly people are a true public health burden, because they represent one of the most important causes of long-standing pain, functional impairment, disability, and death among this population. Compromised bone strength (osteoporosis) and falling, alone, or more frequently in combination, are the two independent and immediate risk factors of elderly people's fractures through which all the other, more distant risk factors, such as aging, inactivity, poor nutrition, smoking, use of alcohol, diseases, medications, functional impairments, and disabilities, operate. Of these two, falling, not osteoporosis, is the strongest single risk factor for a fracture. The most usual occurrence resulting in a fracture of an older adult is a 'simple' fall from standing height or less. Although in general terms this type of trauma is mild or moderate only (compared with, for example, motor vehicle collisions), to the specific injury site these traumas are high-impact injuries often creating forces clearly exceeding the breaking strength of the bone. Therefore, fractures affecting elderly people should be called 'fall-induced high-impact injuries' instead of the commonly used, partly misleading terms of osteoporotic fractures or minimal-trauma fractures. Prevention of elderly people's fractures consists of prevention of osteoporosis and of falling, and prevention of fractures using injury-site protection. Concerning osteoporosis, maximizing peak bone mass and preventing bone loss by regular exercise, calcium, and vitamin D, and, treatment of established osteoporosis with bone-specific drugs, have a strong scientific basis. In fall prevention, regular strength and balance training, reducing psychotropic medication, and diet supplementation with vitamin D and calcium have been shown to be effective. The multifaceted risk factor-assessing and modifying interventions have also been successful in preventing falls among the older adults by simultaneously affecting many of the risk factors of falling. Finally, concerning injury-site protection, padded strong-shield hip protectors whose effectiveness is scientifically proven seem to be a promising option in preventing hip fractures.

Effects of combined sensory and muscular training on balance in Japanese older adults

BACKGROUND

Adequate levels of physical balance and muscular strength are necessary to live independently in old age. The effects of an exercise training program targeting the sensory and muscle systems on balance and strength in a group of older adults were determined in this study.

METHODS

Static balance (one-leg balance with eyes closed), dynamic balance (limits of stability [endpoint excursion [EPE], maximum excursion [MXE]]), and strength (chair stand) were assessed before and after the intervention. Volunteers were divided randomly into a training group (TR, n = 15, 76 +/- 4 years) and a control group (CN, n = 14, 76 +/- 7 years). TR performed 12-week (2 days/week, 60 min/day) supervised training while standing on the floor (first 4 weeks) and progressing to standing on foam pads of different compliances. Exercises included movements that challenged the sensory and muscle systems.

RESULTS

After 12 weeks of training, the TR demonstrated significant improvements in static balance (82%); EPE backward (72%), right (32%), and left (33%); MXE backward (74%), right (31%), and left (18%); and lower body muscle strength (20%) with no significant changes in CN.

CONCLUSION

These results indicate that this training program is very effective in improving balance and lower body strength in older adults.

Effect of the "squat protective response" on impact velocity during backward falls

Risk for injury during a fall depends on the position and velocity of the body segments at the moment of impact. One technique for reducing impact velocity is to absorb energy in the lower extremity muscles during descent, as occurs during squatting or sitting. However, the protective value of this response may depend on the time during descent when the response is initiated. We tested this hypothesis by conducting backward falling experiments with young women (n = 23; aged 21-29 years), who fell onto a soft gymnasium mattress after being suddenly releasing from an inclined position. In trials where subjects were released from a 5 degrees lean, average impact velocities were reduced by 18% when squatting was utilized as opposed to inhibited. Furthermore, increases in the release angle caused an increase in average impact velocity of 8% between lean angles of 2 degrees and 5 degrees, and 7% between lean angles of 5 degrees and 12 degrees. This was due to declines in peak extensor torques and peak flexion rotations, and corresponding reductions in both joint work and potential energy at impact. These results suggest that squatting during descent reduces impact severity, but the effectiveness of the response depends on the stage during descent when it is initiated, diminishing in benefit as the fall progresses and the state of imbalance grows increasingly severe.

Strategies for avoiding hip impact during sideways falls

During a fall, hip fracture risk increases 30-fold if there is direct impact to the hip. We conducted sideways falling experiments and found that subjects were able to avoid hip impact by rotating forward or by rotating backward during descent. These simple safe-landing strategies should be considered in designing hip fracture prevention programs.

INTRODUCTION

Ninety percent of hip fractures in the elderly are caused by falls. During a fall, hip fracture risk is increased 6-fold by falling sideways (instead of backward or forward) and 30-fold if direct impact occurs to the hip. Previous studies suggest that impact to the hip during a sideways fall can be avoided by rotating forward during descent to land on the outstretched hands. Presumably, an alternative strategy for avoiding hip impact is to rotate backward to land on the buttocks. We conducted sideways falling experiments to test the hypothesis that each of these falling strategies is equally effective in allowing one to avoid hip impact.

MATERIALS AND METHODS

Twenty-two young adult women participated in trials where they were released from an inclined standing position into a sideways fall onto a foam mattress. Subjects were instructed to "land as softly as possible" and to "avoid impacting the hip" by either rotating forward or rotating backward during descent.

RESULTS

We found that absolute values of the hip proximity angle, which described how close the impact site was to the lateral aspect of the pelvis, were not different in forward rotation and backward rotation trials (mean = 55.9 +/- 22.4 degrees versus 61.5 +/- 15.8 degrees, respectively). However, compared with forward rotation trials, backward rotation trials involved greater pelvis impact velocity (2.95 +/- 0.25 versus 2.45 +/- 0.77 m/s; p = 0.001) and greater whole-body kinetic energy at impact (238 +/- 70 versus 156 +/- 90 J; p = 0.001).

CONCLUSIONS

These results suggest that, during a sideways fall, individuals can avoid impact to the hip and thereby lower the risk for hip fracture by rotating forward or by rotating backward during descent. These simple yet effective safe-landing strategies should be considered in designing exercise-based hip fracture prevention programs.

Risk of hip fracture in disabled community-living older adults

OBJECTIVES

To determine the rate of hip fracture and risk factors associated with hip fractures in disabled older persons who enroll in the Program of All-Inclusive Care for the Elderly (PACE), a program providing comprehensive care to community-living nursing-home-eligible persons.

DESIGN

Prospective cohort study between January 1990 and December 1997.

SETTING

The twelve PACE demonstration sites: San Francisco, California; Columbia, South Carolina; Detroit, Michigan; Denver, Colorado; East Boston, Massachusetts; El Paso, Texas; Milwaukee, Wisconsin; Oakland, California; Portland, Oregon; Rochester, New York; Sacramento, California; and the Bronx, New York.

PARTICIPANTS

Five thousand one hundred eighty-seven individuals in PACE; mean age 79, 71% female, 49% white, 47% with dementia.

MEASUREMENTS

Functional status, cognitive status, demographics, and comorbid conditions were recorded on all the participants, who were tracked for occurrence of a hip fracture. The goals were to determine the rate of hip fracture and identify risk factors.

RESULTS

Two hundred thirty-eight hip fractures (4.6%) occurred during follow-up. The rate of hip fracture was 2.2% per person-year. Four independent predictors of hip fracture were identified using Cox proportional hazard analysis: age of 75 and older (adjusted hazard ratio (HR) = 2.0, 95% confidence interval (CI) = 1.4-2.8); white ethnicity (HR = 2.1, 95% CI = 1.6-2.8); ability to transfer independently to and from bed, chair, and toilet (HR = 3.0, 95% CI = 1.2-7.2); and five or more Short Portable Mental Status Questionnaire errors (HR = 1.6, 95% CI = 1.3-2.1). The incidence of hip fracture ranged from 0.5% per person-year in persons with zero to one independent risk factors to 4.7% per person-year in those with all four independent risk factors.

CONCLUSIONS

The rate of hip fracture in this cohort of disabled community-living older adults was similar to that reported in nursing home cohorts. Older age, white race, ability to transfer independently, and cognitive impairment were independent predictors of hip fracture. Persons with these risk factors should be targeted for preventive interventions, which should include strategies for making transferring safer.

Why is the age-standardized incidence of low-trauma fractures rising in many elderly populations?

Low-trauma fractures of elderly people are a major public health burden worldwide, and as the number and mean age of older adults in the population continue to increase, the number of fractures is also likely to increase. Epidemiologically, however, an additional concern is that, for unknown reasons, the age-standardized incidence (average individual risk) of fracture has also risen in many populations during the recent decades. Possible reasons for this rise include a birth cohort effect, deterioration in the average bone strength by time, and increased average risk of (serious) falls. Literature provides evidence that the rise is not due to a birth cohort effect, whereas no study shows whether bone fragility has increased during this relatively short period of time. This osteoporosis hypothesis could, however, be tested if researchers would now repeat the population measurements of bone mass and density that were made in the late 1980s and the 1990s. If such studies proved that women's and men's age-standardized mean values of bone mass and density have declined over time, the osteoporosis hypothesis would receive scientific support. The third explanation is based on the hypothesis that the number and/or severity of falls has risen in elderly populations during the recent decades. Although no study has directly tested this hypothesis, a great deal of indirect epidemiologic evidence supports this contention. For example, the age-standardized incidence of fall-induced severe head injuries, bruises and contusions, and joint distortions and dislocations has increased among elderly people similarly to the low-trauma fractures. The fall hypothesis could also be tested in the coming years because the 1990s saw many research teams reporting age- and sex-specific incidences of falling for elderly populations, and the same could be done now to provide data comparing the current incidence rates of falls with the earlier ones.

The Quick Step: A New Test for Measuring Reaction Time and Lateral Stepping Velocity

The Quick Step measures reaction time and lateral stepping velocity. Upon a visual cue, participants step to the side as quickly as possible. Instrumentation includes floor pads with pressure-sensitive switches and two timers. In all, 109 older adults who had experienced a recent fall, 46 older adult nonfallers, and 24 young adults volunteered for testing. Reliability for reaction time and stepping velocity was good to excellent (intraclass correlation = 0.69–0.85). Multivariate analysis of variance revealed a significant difference between groups, p < 0.01, but not between stepping directions, p = 0.62–0.72, for both reaction time and stepping velocity. Reaction times were different among the three groups, p < 0.01, with the young adults having the fastest times and the older adult fallers having the slowest times. Lateral stepping velocity was faster among the young adults than for the two older groups, p < 0.01, but did not differ between the older adults, p = 0.29. It is concluded that the Quick Step is a simple and reliable tool for determining reaction time and lateral stepping velocity, and that this test can be used to detect a significant difference in reaction time between older adult fallers and nonfallers.

An analysis of the effect of lower extremity strength on impact severity during a backward fall

At least 280 000 hip fractures occur annually in the U.S. at an estimated cost of $9 billion. While over 90 percent of these are caused by falls, only about 2 percent of all falls result in hip fracture. Evidence suggests that the most important determinants of hip fracture risk during a fall are the body's impact velocity and configuration. Accordingly, protective responses for reducing impact velocity and the likelihood for direct impact to the hip, strongly influence fracture risk. One method for reducing the body's impact velocity and kinetic energy during a fall is to absorb energy in the lower extremity muscles during descent, as occurs during sitting and squatting. In the present study, we employed a series of in verted pendulum models to determine: (a) the theoretical effect of this mechanism on impact severity during a backward fall, and (b) the effect on impact severity of age-related declines (or exercise-induced enhancements) in lower extremity strength. Compared to the case of a fall with zero energy absorption in the lower extremity joints, best-case falls (which involved 81 percent activation of ankle and hip muscles, but only 23 percent activation of knees muscles) involved 79 percent attenuation (from 352 J to 74 J) in the body's vertical kinetic energy at impact (KEv), and 48 percent attenuation (from 3.22 to 1.68 m/s) in the downward velocity of the pelvis at impact (v(v)). Among the mechanisms responsible for this were: (1) eccentric contraction of lower extremity muscles during descent, which resulted in up to 150 J of energy absorption; (2) impact with the trunk in an upright configuration, which reduced the change in potential energy associated with the fall by 100 J; and (3) knee extension during the final stage of descent, which "transferred" up to 90 J of impact energy into horizontal (as opposed to vertical) kinetic energy. Declines in joint strength reduced the effectiveness of mechanisms (1) and (3), and thereby increased impact severity However, even with reductions of 80 percent in available torques, KEv was attenuated by 50 percent. This indicates the importance of both technique and strength in reducing impact severity. These results provide motivation for attempts to reduce elderly individuals' risk for fall-related injury through the combination of instruction in safe falling techniques and exercises that enhance lower extremity strength.

Disturbance type and gait speed affect fall direction and impact location

Since falling to the side and impacting on or near the hip increase hip fracture risk, we examined the fall direction and pelvis impact location resulting from four disturbances (faint, slip, step down, trip) at three gait speeds (fast, normal, slow) in 14 young adults instructed not to attempt recovery. We hypothesized that certain disturbances such as faints and slips and slow walking speed were more likely to result in an impact on the hip. For each trial, the fall direction, impact location and pelvis impact velocity were measured. The results showed that both disturbance type and gait speed significantly affected fall direction and impact location (analysis of covariance with repeated measures, p< or =0.0001) with a significant interaction (p<0.05). Trips and steps down usually resulted in forward falls, with frontal impacts regardless of gait speed. At fast gait speed, slips and faints also usually resulted in forward falls, with frontal impacts. As gait speed decreased, however, slips usually resulted in sideways or backward falls, with impact on the hip or buttocks, and faints resulted in a greater number of sideways falls, with impact near the hip. Therefore, compared to other disturbances and gait speeds, slipping or fainting while walking slowly was more likely to result in an impact on the hip, suggesting a greater risk for hip fracture. Furthermore, 56% of the impact velocities generated were within one standard deviation of the estimate of the mean impact velocity needed to fracture an elderly femur.

Osteoporosis in men

Although less common than in women, osteoporosis in men is a prevalent worldwide problem with important socioeconomic implications. Our understanding of this condition in men is growing, but there remains a great deal more to be determined. Definitions for osteoporosis in men are needed. Cost-effective guidelines on who should be investigated and treated, and how, are clearly necessary. The role of bone mineral densitometry in diagnosis and treatment decisions needs to be clarified. The efficacy of drug therapies for osteoporosis in men requires greater attention. Currently, a large multicenter study is underway in the United States and should provide much needed insight into the epidemiology of osteoporosis in men.

Elderly subjects' ability to recover balance with a single backward step associates with body configuration at step contact

BACKGROUND

In the event of a slip or trip, one's ability to recover a stable upright stance by stepping should depend on (a) the configuration of the body at the instant of step contact and (b) the forces generated between the foot and ground during step contact. In this study, we tested whether these two variables associate with elderly subjects' ability to recover balance by taking a single backward step after sudden release from an inclined position.

METHODS

Twenty-six community-dwelling subjects (12 women, 14 men) of mean age 75+/-4 (SD) years each underwent five trials in which they were suddenly released from a backward inclination of 7 degrees and instructed to "recover balance with a single step." Body segment motions and foot contact forces were analyzed to determine step contact times, stepping angles, body lean angles at step contact, and the magnitudes and times (after step contact) of peak foot-floor contact forces and peak sagittal-plane torques at the ankle, knee, and hip of the stepping leg.

RESULTS

Fifty percent of subjects were predominantly single steppers (successful at recovering with a single step in greater than three of five trials), 27% were multiple steppers (successful in less than two of five trials), and 23% were mixed response steppers (successful in two of five or three of five trials). Recovery style associated with the ratio of stepping angle divided by body lean angle at step contact (p = .003), which averaged 1.4+/-0.5 for single steppers and 0.6+/-0.5 for multiple steppers, but not with step contact time, stepping angle, or contact forces and joint torques during step contact.

CONCLUSIONS

These results suggest that elderly subjects' ability to recover balance with a single backward step depends primarily on the configuration of the body (in particular, the ratio of stepping angle to body lean angle) at step contact.

Prevention of hip fracture in elderly people with use of a hip protector

BACKGROUND

Hip fractures are common in frail elderly adults worldwide. We investigated the effect of an anatomically designed external hip protector on the risk of these age-related fractures.

METHODS

We randomly assigned 1801 ambulatory but frail elderly adults (1409 women and 392 men; mean age, 82 years), in a 1:2 ratio, either to a group that wore a hip protector or to a control group. Fractures of the hip and all other fractures were recorded until the end of the first full month after 62 hip fractures had occurred in the control group. The risk of fracture in the two groups was compared, and in the hip-protector group the risk of fracture was also analyzed according to whether the protector had been in use at the time of a fall.

RESULTS

During follow-up, 13 subjects in the hip-protector group had a hip fracture, as compared with 67 subjects in the control group. The respective rates of hip fracture were 21.3 and 46.0 per 1000 person-years (relative hazard in the hip-protector group, 0.4; 95 percent confidence interval, 0.2 to 0.8; P=0.008). The risk of pelvic fracture was slightly but not significantly lower in the hip-protector group than in the control group (2 subjects and 12 subjects, respectively, had pelvic fracture) (relative hazard, 0.4; 95 percent confidence interval, 0.1 to 1.8; P > or = 0.05). The risk of other fractures was similar in the two groups. In the hip-protector group, four subjects had a hip fracture (among 1034 falls) while wearing the protector, and nine subjects had a hip fracture (among 370 falls) while not wearing the protector (relative hazard, 0.2; 95 percent confidence interval, 0.05 to 0.5; P=0.002).

CONCLUSIONS

The risk of hip fracture can be reduced in frail elderly adults by the use of an anatomically designed external hip protector.

Patients with prior fractures have an increased risk of future fractures: a summary of the literature and statistical synthesis

Numerous studies have reported increased risks of hip, spine, and other fractures among people who had previous clinically diagnosed fractures, or who have radiographic evidence of vertebral fractures. However, there is some variability in the magnitudes of associations among studies. We summarized the literature and performed a statistical synthesis of the risk of future fracture, given a history of prior fracture. The strongest associations were observed between prior and subsequent vertebral fractures; women with preexisting vertebral fractures (identified at baseline by vertebral morphometry) had approximately 4 times greater risk of subsequent vertebral fractures than those without prior fractures. This risk increases with the number of prior vertebral fractures. Most studies reported relative risks of approximately 2 for other combinations of prior and future fracture sites (hip, spine, wrist, or any site). The confidence profile method was used to derive a single pooled estimate from the studies that provided sufficient data for other combinations of prior and subsequent fracture sites. Studies of peri- and postmenopausal women with prior fractures had 2.0 (95 % CI = 1.8, 2.1) times the risk of subsequent fracture compared with women without prior fractures. For other studies (including men and women of all ages), the risk was increased by 2.2 (1.9, 2.6) times. We conclude that history of prior fracture at any site is an important risk factor for future fractures. Patients with a history of prior fracture, therefore, should receive further evaluation for osteoporosis and fracture risk.

Comparison of force attenuation properties of four different hip protectors under simulated falling conditions in the elderly: an in vitro biomechanical study

The purpose of this in vitro biomechanical study is to determine the force attenuation capacity of four different hip protectors (KPH1, KPH2, Safehip, and Safetypants) in falling simulations in elderly subjects (falls to the side). The simulated falling conditions were created by a biomechanical testing system, which consisted of an impact pendulum, surrogate pelvis and femur, and two load cells. Three series of impact experiments were conducted in an ascending order (low, moderate-, and high-force experiments), each exceeding the literature-provided average (+/- 1 SD) fracture threshold (3100 +/- 1200 N) of the proximal femur of elderly women with a mean age of 71 years. Using a low impact force of 4330 N, the trochanteric soft tissue (20-mm-thick polyethylene foam) attenuated the peak femoral impact force to 3740 N and, accordingly, the KPH1 protector to 590 N, KPH2 to 510 N, Safehip to 1080 N, and Safetypants to 790 N. Thus, in this low force experiment, all tested protectors could reduce the peak impact force entered into the proximal femur below the aforementioned average fracture threshold area (3100 +/-1200 N) of the proximal femur of elderly women. With a moderate impact force of 7230 N, the soft tissue attenuated the peak femoral impact force to 6130 N, and the protectors to 780 N, 760 N, 2240 N, and 2760 N, respectively. Thus, with this impact force, only the KPH hip protectors could reduce the impact force clearly below the fracture threshold area. In the final series of the experiment, the peak femoral impact force was set to be so high (10,840 N) that the protector, if effective, should prevent the hip fracture in almost all cases and situations. The trochanteric soft tissue attenuated this peak impact force to 9190 N, and the tested protectors to 1360 N, 1170 N, 4640 N, and 5770 N. Thus, with the KPH protectors the force received by the proximal femur remained below the average force required to fracture the proximal femur of elderly women, whereas with the two other protectors the impact force entered into the proximal femur clearly exceeded this threshold value. In conclusion, the test results showed that, of the four tested hip protectors, the anatomically designed energy-shunting and energy-absorbing KPH protectors can provide an effective impact force attenuation in a sideways-fall simulation in the elderly, whereas the force attenuation capacity of the two other protectors seems more limited. However, the true efficacy of any protector in the prevention of hip fractures can only be evaluated in randomized clinical trials.