Fractured neck of the femur: the cause of the fall?

Prediction of proximal femur strength using a CT-based nonlinear finite element method: differences in predicted fracture load and site with changing load and boundary conditions

The annual occurrence of hip fracture due to osteoporosis as of 2002 had reached 120,000 in Japan. The increase has been very rapid. From a biomechanical perspective, hip fractures are thought to be caused in real settings by different directions of loading. Thus, clarification of the loading directions under which the proximal femur is most vulnerable to fracture would be helpful for elucidating fracture mechanics and establishing preventive interventions. The purpose of the current study was to clarify the influence of loading direction on strength and fracture site of the proximal femur using the CT-based nonlinear FE method to determine loading directions under which the proximal femur is most vulnerable to fracture. Contralateral femora were analyzed in 42 women with hip fracture (mean age, 82.4 years), comprising 20 neck fractures and 22 trochanteric fractures. Within 1 week after fracture, quantitative CT of the contralateral femur was performed in each patient and 3-dimensional FE models were created. One stance loading configuration (SC) and four different fall loading configurations (FC) were assigned. Nonlinear FE analysis was performed. Differences in fracture loads depending on differences in loading direction were analyzed and correlations among fracture loads in different loading directions were assessed. Next, fracture sites were also analyzed. Mean predicted fracture load in the SC was 3150 N. Mean fracture loads were 2270 N in FC1, 1060 N in FC2, 980 N in FC3, and 710 N in FC4. The correlation between predicted fracture loads in SC and those in each FC was significant with a correlation coefficient of 0.467-0.631. Predicted fracture sites in the SC appeared at the subcapital region in all patients and were categorized as neck fracture. However, trochanteric fractures occurred in all fall configurations except FC1. In FC1, a significant correlation was seen between real fracture type and predicted type. The current investigation could contribute to the acquisition of useful knowledge allowing the establishment of more efficacious means of preventing hip fractures.

Stress fractures

Stress fractures are common over-use injuries which include fatigue and insufficiency fractures. Athletes, soldiers and osteoporotic patients are some of the individuals at high risk for the development of this injury. Owing to the low sensitivity of plain radiography at the onset of symptoms the diagnosis of this entity may be easily overlooked. Occasionally, some of these fractures, such as tibial fracture in children and fractures in the clavicle and pelvic ring, can be misdiagnosed as tumoral or infectious processes; moreover, although most stress fractures are uncomplicated and can be managed by rest and restriction from precipitating activity, a subset of these fractures can present a high risk for progression to complete fracture or non-union problems. All of this indicates that the various types of stress fracture, owing to their different clinical characteristics and evolution, should be commented on in detail. In this chapter different types of stress fracture are described with special reference to their localization, clinical characteristics, evolution and treatment.

Effect of force direction on femoral fracture load for two types of loading conditions

Identifying the loading conditions under which the femur is most likely to fracture may aid the prevention of hip fracture. This study quantified the effect of force direction on fracture load, a factor inherently associated with fracture risk. Finite element (FE) models of four femora were used to determine the force directions associated with the lowest fracture loads. Force directions were varied three-dimensionally for two types of loading, one representing impact from a fall and one similar to joint loading during daily activities (atraumatic loading). For the fall configuration, the force direction with lowest fracture load corresponded to an impact onto the posterolateral aspect of the greater trochanter. For atraumatic loading, the lowest fracture loads for the force directions analyzed occurred when posterior force components were relatively large or when posterior and lateral components were both small, similar to conditions while standing on one leg or climbing stairs. When both fall and atraumatic configurations are considered, the type of loading associated with greatest fracture risk, i.e., with the greatest applied force and lowest fracture load, is impact from a fall onto the posterolateral aspect of the greater trochanter. Therefore, evaluation of hip fracture risk and development of fracture prevention technologies should focus on this high-risk loading condition.

Improved prediction of proximal femoral fracture load using nonlinear finite element models

Hip fracture, which is often due to osteoporosis or other conditions affecting bone strength, can lead to permanent disability, pneumonia, pulmonary embolism, and/or death. Great effort has been directed toward developing noninvasive methods for evaluating proximal femoral strength (fracture load), with the goal of assessing fracture risk. Previously, computed tomographic scan-based, linear finite element (FE) models were used to estimate proximal femoral fracture loads ex vivo in two load configurations, one approximating joint loading during single-limb stance and the other simulating impact from a fall. Measured and computed fracture loads were correlated (stance, r=0.867; fall, r=0.949). However, precision for the stance configuration was insufficient to identify subjects with below average fracture loads reliably. The present study examined whether, for this configuration, nonlinear FE models could be used to identify these subjects. These models were found to predict fracture load within +/-2.0 kN (r=0.962). This level of precision is sufficient to identify 97.5% of femora with fracture loads 1.3 standard deviations below the mean as having below average fracture loads. Accordingly, 20% of subjects with below average fracture loads, i.e. those with the lowest fracture loads and likely to be at greatest risk of fracture, would be correctly identified with at least 97.5% reliability. This FE modeling method will be a powerful tool for studies of hip fracture.

Spontaneous insufficiency fractures of long bones: a prospective epidemiological survey in nursing home subjects

A 30-month prospective observational cohort study was led to assess the prevalence of and describe the clinical features of spontaneous long bone insufficiency fractures (LBIF) in the 'oldest old' patients of long-term nursing homes (LTNH). The study was conducted in 30 LTNH in northeast France, which represented 3052 beds. Subjects aged 65 and more showing LBIF were included in the present study. Clinical data and outcome were collected. Fifty-five LBIF were found. The prevalence of LBIF calculated on the basis of the number of patients consecutively admitted in LTNH was 1%. The mean age of the subjects was 85+/-7 years. The LBIF sites were as follows (1) hip fractures in 15 subjects (27%); (2) femoral shaft fractures in 13 subjects (24%); (3) tibia and/or fibula fractures in 14 subjects (25%); (4) humerus fractures in 11 subjects (20%); (5) cubitus in 2 subjects. The global mortality at 2 months was 24%. The poorest outcome was observed in the group with femoral shaft fracture who showed mortality of 54% at 2 months. The dramatic repercussions in outcome and quality of life in bedridden patients show that the detection of LBIF should not be neglected in nursing homes. There is no consensus for a preventive pharmacological treatment in these patients. Educational programs for 'proper handling' by the nursing staff are highly recommended.

[Clinical and prognostic aspects of spontaneous fractures in long term care units: a thirty month prospective study. Eastern Gerontology Society]

PURPOSE

Spontaneous fractures (stress and bone insufficiency fractures) are well described in young healthy patients; however, few studies were conducted in the elderly.

METHODS

A 30-month prospective clinical and epidemiological survey including elderly patients from long-term nursing homes (LTNH) of the Société de Gérontologie de l'Est (70 centers; 11,495 elderly patients in total) was conducted.

RESULTS

Sixty-seven spontaneous fractures were encountered in 30 LTNH (3,052 elderly patients) (five stress fractures of the foot, 62 bone insufficiency fractures). The mean age of bedridden patients was 85 +/- 7 years. The prevalence of spontaneous fractures (calculated from the number of patients admitted consecutively in LTNHs) was 0.34% in the whole population (11,495 beds). When the calculation was based on LTNH reports of spontaneous fractures (3,052 elderly patients), the prevalence reached 1.3%. Fractures of long bones were common in elderly patients and included 15 fractures of the femoral neck, 14 fractures of either the tibia or fibula, 13 fractures of the femoral shaft, and 11 fractures of the humerus. Fractures of the femoral shaft were associated with the highest mortality: seven out of 13 patients died versus two out of 15 patients with regard to fractures of the femoral neck (P < 0.05).

CONCLUSION

Bone insufficiency fractures have not the same course in young healthy patients as those in elderly nursing home patients: they more often concern long bones and their prognosis is worse. Means of prevention still have to be defined.

Falls reported among elderly Norwegians living at home

BACKGROUND AND PURPOSE

Norway has the highest reported incidence of hip fractures in western Europe. Little is known about the epidemiology of falls in Norway where the winter season is long and dark. The objective of this work was to study reported falls and their consequences among elderly Norwegians living at home.

METHODS

A cross-sectional design was used for the study. Interviews were performed in the homes of 431 subjects, aged 67-97 years, living at home. Information on falling was gathered through six questions: whether the subject had fallen during the last six months, and if so, how many falls they had, where the last fall occurred, its perceived reason, the activity the subject had been engaged in when the fall occurred, and the resulting injury.

RESULTS

In all, 24.1% of subjects reported falling during the last six months, and 9.5% had suffered more than one fall. Falls were most frequently linked to external events (63.1%). Outdoor falls were more frequent (59.0%; 95% CI = 51.2-82.0) than indoor falls. Older subjects were associated with more frequent indoor falls (p < 0.05), but gender was not significant. Fifty-one per cent of subjects had fallen while walking and 53% had suffered an injury from the last fall. In 13.4% of the women and 16.2% of the men, the last fall had resulted in a fracture.

CONCLUSIONS

Compared to the results of other studies from industrialized Western countries, a similar crude fall rate, similar frequency and similar type of injury were found. However, in contrast to other studies, no gender difference was observed with regard to falling, place of falling and fracture rate.

Spontaneous hip fractures, 44/872 in a prospective study

We assessed the relationship between the onset of pain and the fall in a consecutive series of 1,212 patients admitted to a single hospital with an acute hip fracture. 915 patients could be evaluated. The overall incidence of spontaneous fractures was 7%, but this fell to 5% if pathological fractures were excluded. The incidence of fractures without a fall was 6%. 2% of patients gave a history of pain for up to 8 weeks before the fall and only 2 of the patients gave a history of acute pain in the hip, causing them to fall. Physicians should be aware that a spontaneous hip fracture can occur without any history of trauma and such fractures are likely to be pathological or intracapsular.

The relationship between loading conditions and fracture patterns of the proximal femur

In an attempt to test the hypothesis of spontaneous hip fracture, seven pairs of femurs, with ages ranging from 59 to 90, were tested under two loading conditions designed to simulate muscular contraction. Simulated iliopsoas contraction produced femoral neck fractures at an average normalized ultimate load of 5.2 +/- 0.8 times body weight. Simulated gluteus medius contraction produced sub-/inter-trochanteric fractures at an average normalized ultimate load of 4.1 +/- 0.6 times body weight. The average ultimate load for all specimens was 3040 +/- 720 N. Fracture patterns produced by both loading conditions were clinically relevant. The results from this study suggest that abnormal contraction produced by major rotator muscles could induce hip fracture.

Femoral neck fractures in the elderly patient: a preventable injury

There is growing evidence that many fractures of the femoral neck in the elderly occur spontaneously because of stresses imposed on osteoporotic bone, rather than because of the trauma of the fall. A case of a spontaneous femoral neck fracture (Garden type IV) in an elderly woman with osteoporosis is presented. Early detection and medical management of osteoporosis complemented with assistive technology could have prevented this common injury.

Falls leading to femoral neck fractures in lucid older people

OBJECTIVE

To analyze the mechanisms of falls that result in femoral neck fractures among lucid older people.

DESIGN

A cross-sectional study.

SETTING

An orthopedic university hospital department.

PARTICIPANTS

A consecutive series of 123 lucid patients, 65 years of age or more, who were admitted for femoral neck fractures.

MEASUREMENTS

On admission, the subjects were interviewed about fracture accident characteristics, and falling mechanisms were classified. An arterial blood gas sample was taken from each patient soon after admission. Based on data regarding drug consumption and social and medical characteristics, a fall-risk index was calculated for each subject.

RESULTS

It was ascertained that 95% of the fractures were caused by falls and < 2% were spontaneous. Most accidents (68%) took place indoors, 47% of the falls were classified as extrinsic, 24% as intrinsic, 7% as nonbipedal, and 22% remained unclassified. Almost all outdoor falls were extrinsic; however, intrinsic falls were as common as extrinsic falls indoors (P < .001). Extrinsic fallers presented a significantly lower fall-risk index score than subjects with fractures caused by intrinsic, nonbipedal, and unclassifiable falls. A large proportion of subjects (24%) wre hypoxemic (pO2 < 8 kPa) on admission, and patients who sustained fractures at night had lower oxygen tension than that of daytime fallers (P = .006).

CONCLUSIONS

Accidental falls are the primary cause of femoral neck fractures. Preventive actions should be directed toward intrinsic, as well as extrinsic, risk factors for falls. Hypoxemia might be a risk factor for falls, especially those falls that occur at night.

Hip fractures--patient background

A consecutive series of 282 patients with hip fractures, with a mean age of 76 years, was studied. Two-thirds of the patients (182) lived in their own homes, half of them alone and one-third of the 182 requiring regular help. Widows were more common in the age group 75-84 years and widowers and single men in the age group 65-74 years. Thirty % of the patients used walking aids and had previously sustained fractures of the osteoporotic type. One-fourth of the patients were confused on arrival at hospital. Laboratory tests differed little from values in the normal population. Chest X-ray was of value and cardiac decompensation was diagnosed in a small group. Time aspects of the hip fracture accident are discussed. No increase in incidence in the age group over 70 years was found during the period 1971-1981.

Spontaneous fractures of the hip in the elderly

The authors found 41 patients with 42 fractures of the hip who had no distinct history of trauma in the total of 1,449 hip fractures treated. They were all women ranging in age from 64 to 91 years. Most of the fractures were of intracapsular type. Three extracapsular fractures, however, were found. Fractures were randomly selected with clear history of trauma, which were matched to the patients with no trauma for age, sex, and type of fracture as a control group. The grades of osteoporosis of the femoral neck, estimated with the Singh index, and of the spine, estimated with the spinal score, were noted statistically significantly higher in the patients than those in the control group. Most of spontaneous fractures of the hip in the elderly are considered similar phenomena to the compression fractures of the dorsolumbar spine.

Role of drugs in fractures of the femoral neck

To investigate the role of drugs in the rising incidence of fractures of the femoral neck in the elderly a case-control study inquiring about the use of prescribed drugs was carried out. The drug histories of 102 patients with femoral neck fractures were obtained from general practice records and compared with those of 204 controls matched for age and sex from the same practices. At the time of fracture 41 patients with fractures and 126 controls were receiving at least one prescription (relative risk of fracture of the femoral neck in patients taking drugs = 0.42, p = 0.0006). For all types of prescribed drugs except antibiotics the risk of fracture of the femoral neck was less in patients taking drugs than in those not doing so, and this was true at all times in the year before fracture. Six patients with fractures were receiving thiazide diuretics compared with 37 controls (relative risk 0.28, p = 0.004). These results indicate that, contrary to popular belief, drugs that sedate or that impair postural control are not important factors in fractures of the femoral neck. The results are consistent with the hypothesis that the hypocalciuria induced by thiazides protects against fracture, but the degree of protection is not significantly greater than that associated with other drugs.