SciELO - Scientific Electronic Library Online

 
vol.49 issue5Use of adrenalin with lidocaine in hand surgery ,Densitometric study of the clavicle: bone mineral density explains the laterality of the fractures, author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Revista Brasileira de Ortopedia

Print version ISSN 0102-3616On-line version ISSN 1982-4378

Rev. bras. ortop. vol.49 no.5 São Paulo Sept./Oct. 2014

http://dx.doi.org/10.1016/j.rboe.2014.09.004 

Original Article

Body mass index as a prognostic factor for fracturing of the proximal extremity of the femur: a case-control study,☆☆

Renato Cavanus Pagani a  

Rodrigo Ernesto Kunz b   * 

Ricardo Girardi b  

Marcelo Guerra a   c  

aUniversidade Luterana do Brasil (ULBRA), Canoas, RS, Brazil

bUniversity Hospital, Universidade Luterana do Brasil (ULBRA), Canoas, RS, Brazil

cUniversidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil

ABSTRACT

Objectives:

To compare the body mass index (BMI) of patients with fractures in the proximal extremity of the femur with the BMI of patients without any previous history of fractures.

Methods:

We investigated patients of both sexes, aged 65 years or over, who were admitted to Hospital Independência, Hospital Beneficência Portuguesa or ULBRA University Hospital, between December 2007 and December 2010, with histories of low-energy trauma such as falling from a standingposition. These individuals were compared with patients of the same age but without any history of fracturing of the proximal extremity of the femur (n = 89), who were attended at the geriatrics outpatient clinic of the Sociedade Porto-Alegrense de Auxílio aos Necessitados (SPAAN).

Results:

The age group of the patients with fractures in the proximal extremity of the femur ranged from 65 to 96 years (mean: 77.58). The main type of fracture was trochanteric (47; 62.2%), followed by femoral neck fractures (27; 36%). Among the patients who presented on fracturing the proximal extremity of the femur, 12% had low weight, 62.7% normal weight, 24% overweight, and 1.3% obesity. Among the patients without any history of fractures, 5.6% presented low weight, 43.8% normal weight, 33.7% overweight, and 9.8% obesity. It was observed that the patients with fractures in the proximal extremity of the femur (n = 75) presented a mean BMI of 22.6, while the patients without fractures presented a mean BMI of 25.5.

Conclusion:

The patients in the group with fractures were significantly taller than those in the group without fractures and presented significantly lower BMI than those in the group without fractures.

Key words: Hip fracture; Elderly person; Body mass index

Introduction

Fractures of the proximal extremity of the femur are among the commonest traumatic injuries today, not only because of their high incidence in the elderly population but also because of the accompanying morbidity and mortality.

It has been estimated that the incidence of hip fractures will increase dramatically over the next 20 years. This increase will be most evident among individuals over the age of 85 years.1 It has also been estimated that nine out of every 10 hip fractures occur in individuals over the age of 65 years.2 The World Health Organization (WHO) has predicted that by the year 2050, the annual incidence will be 6.26 million.3

Fractures of the proximal extremity of the femur are a public health problem worldwide.4,5 In addition to the high mortality rate, these patients require intensive medical care and functional rehabilitation over long periods.6

They are associated with considerable functional incapacity, diminished independence and quality of life and, especially, decreased life expectancy.7,8

Fractures of the proximal extremity of the femur comprise those of the head, neck, trochanteric region and subtrochanteric region.9

It is observed that these fractures in the elderly population are generally caused by small and unintentional traumatic events, such as falling from a standing position, which occur through the debility resulting from senescence and also depend on extrinsic factors.10 A well-documented report has suggested that body mass index (BMI) is a significant prognostic factor for hip fractures.

In this context, fractures of the proximal femur may be associated with low BMI, which is considered to be a risk factor. Some authors have reported that the ideal BMI is 25-27.4kg/m2. Lower indices than this are considered to be important prognostic factors for mortality among young and old hospitalized patients.11

It is suspected that obesity provides protection against fractures, but the mechanisms for such an association still remain poorly understood.12

Estrogen may protect against hip fractures in various manners, by increasing bone resistance, improving neuromuscular function, modifying fat deposition and improving the viscoelastic properties of the soft tissues.13

The possible hypotheses for the situation of greater risk of hip fracture among thin elderly people include: the role of adipose tissue in producing estrogen, which reduces the risk of hip fractures; greater weight increases the mechanical tension on bones and stimulates bone remodeling; and low weight may be an indicator or debilitated health, which in itself is a risk factor for falls and fractures.

Thus, the aim of the present study was to compare the BMI of patients of both sexes over the age of 65 years who were hospitalized between December 2007 and December 2010, with a diagnosis of fracture in the proximal extremity of the femur and a history of low-energy trauma (such as falling from a standing position), in relation to patients of the same age without any previous history of fracturing in the extremity of the proximal femur, who were attended at the geriatric outpatient service of Sociedade Porto-Alegrense de Auxílio aos Necessitados (SPAAN).

Materials

This was a case-control scientific study in which 75 patients who were hospitalized between December 2007 and December 2010 due to fracturing the proximal extremity of the femur were assessed.

The patients were selected in accordance with the following criteria: age greater than or equal to 65 years; diagnosis for hospitalization relating to fracturing of the proximal extremity of the femur; and presence of a history of low-energy trauma such as falling from a standing position.

The criteria for excluding patients were: the presence of pathological fractures, distal fractures and fractures of the femoral diaphysis; situations of high-energy trauma; age under 65 years; presence of specific conditions that accentuate bone mass loss; and use of drugs that cause bone mass reduction.

Methods

The patients studied were compared with a group of patients of the same age who did not have fractures of the proximal femur (n = 89) and who were attended at the geriatric outpatient service of SPAAN.

Data such as weight and height were ascertained from the medical files or were furnished by the patients, because of the difficulty of assessing these parameters among bedridden patients. Data such as age, sex, type of fracture (transtrochanteric, subtrochanteric or femoral neck) and fracture mechanism (falling) were recorded.

The BMI was calculated by dividing weight in kilograms by height in meters, squared. Four BMI categories were created: low weight (<18.5 kg/m2); normal weight (18.5-25 kg/m2); overweight (25-30 kg/m2); and obese (>30 kg/m2).

The data were analyzed by means of table, graphs and descriptive statistics. The following statistical tests were performed:

Chi-square test was used to ascertain whether there was any significant association among the qualitative variables between the study groups (with and without fractures), and, in relation to the group with fractures alone, to ascertain whether any association existed between the type of fracture and the other variables;

Student's t test was used to compare mean age, height, weight and BMI between the study groups (with and without fractures).

For all the abovementioned tests, the maximum significance level taken was 5% (p ≤ 0.05). The software used for the statistical analysis was SPSS version 10.0.

The data were stored in a specific database using the Microsoft Excel 2010 for Windows® software.

A search for articles relating to the study topic was conducted in electronic filing systems such as Pubmed, Lilacs and Scielo.

Proper authorization was obtained from the institutions for data gathering in their filing systems, and the project was approved by the ULBRA research ethics committee under protocol number 2010-237H.

Results

In this section, the results relating to data gathered at the institutions investigated are presented and discussed (Table 1).

Table 1 Description of the sample investigated according to the variables of age and sex for the groups with fractures (n = 75) and without fractures (n = 89). 

Variable Category Group(%) Total p a
With fractures Without fractures
Sex Female 74.7 62.9 68.3 0.107
Male 25.3 37.1 31.7
Age Up to 70 years 17.3 14.6 15.9 0.864
From 71 to 80 years 45.3 44.9 45.1
Over 80 years 37.3 40.4 39.0

Source: data gathered in 2011.

ap value (significance level). For associations to be considered significant, the p value needed to be a maximum of 5% (p ≤ 0.05).

Through the results from the chi-square test, it was found that there were no significant associations in relation to the variables of age and sex between the groups (with and without fractures). In other words, there was no relationship between occurrences of fractures and these patients' sex and age. This test aims to ascertain whether any significant association exists between two qualitative variables. It is sought to find out whether any patient characteristic is more frequent in one given group than in another.

The age group of the patients with diagnoses of fractures of the proximal extremity of the femur ranged from 65 to 96 years, with a mean of 77.58.

In relation to sex among the patients with fractures, it was found that 56 (74.7%) were female and 19 (25.3%) were male (Fig. 1and Table 2).

Fig. 1 Description of the sample investigated according to the variables of age and sex for the groups with fractures (n =75 cases) and without fractures (n = 89 cases).
Source: data gathered in 2011. 

Table 2 Comparison of the means for the quantitative variables of age, height and weight between the study groups. 

Variable Group n Mean Standard deviation p
Age With fractures 75 77.6 7.6 0.491 (NS)
Without fractures 89 78.4 7.3
Height With fractures 75 1.62 0.11 0.000a
Without fractures 89 1.54 0.09
Weight With fractures 75 59.7 13.2 0.784 (NS)
Without fractures 89 60.3 13.5
BMI With fractures 75 22.6 3.9 0.000a
Without fractures 89 25.5 5.3

Source: data gathered in 2011.

NS, not significant.

aSignificant at the significance level of p ≤ 0.0001.

Through the results from the independent Student's t test, it was found in comparison between the above variables that the ones presenting a significant difference between the groups with and without fractures were the following:

    –. Height: it was observed that the patients in the group with fractures were significantly taller than those in the group without fractures;

    –. BMI: it was observed that the patients in the group with fractures presented significantly lower BMI than those in the group without fractures (Table 3).

Table 3 Description of the sample investigated according to the variable of BMI classification for the groups with fractures (n = 75) and without fractures (n = 89). 

BMI classification Group (%) Total p
With fractures Without fractures
Low weight 12.0 5.6 8.5 0.003a
Normal weight 62.7 43.8 52.4
Overweight 24.0 33.7 29.3
Obese 1.3 16.9 9.8

Source: data gathered in 2011.

aSignificant at the significance level of p ≤ 0.01. To perform the test on the BMI variable, the categories of overweight and obesity were grouped.

The Student's t test aims at comparing values coming from two independent groups. It compares the values in each group (in this case, with and without fractures) with the aim of ascertaining whether there is any significant difference between these values.

Through the results from the chi-square test, it was found that there was a significant association between the variable of BMI classification and the group (with or without fracture). It was observed that normal weight was significantly associated with the group with fractures, while patients who were overweight or obese were associated with the group without fractures.

Among the patients who presented fractures of the proximal extremity of the femur, 12% presented low weight, 62.7% normal weight, 24% overweight, and 1.3% obesity. Among the patients without any history of fractures of the proximal extremity of the femur, 5.6% presented low weight, 43.8% normal weight, 33.7% overweight, and 9.8% obesity. It was found that the patients with fractures of the proximal extremity of the femur (n = 75) presented mean BMI of 22.6, while the patients without fractures presented mean BMI of 25.5 (Fig. 2 and Table 4).

Fig. 2 Description of the sample investigated according to the variable of BMI classification for the groups with fractures (n = 75 cases) and without fractures (n = 89 cases).
Source: data gathered in 2011. 

Table 4 Comparison of sex, BMI and age in relation to the types of fracture that occurred, for the group with fractures alone (n = 75). 

Variable Category Type of fracture p
Femoral neck Subtrochanteric Trochanteric
Sex Female 70.4 100.0 76.6 0.693(NS)
Male 29.6 23.4
Age Up to 70 years 33.3 8.5 0.010a
From 71 to 80 years 48.1 44.7
Over 80 years 18.5 100.0 46.8
BMI classificationb Low weight 14.8 10.6 0.256(NS)
Normal weight 70.4 59.6
Overweight/obese 14.8 100.0 29.8

Source: data gathered in 2011.

NS, not significant

aSignificant at the significance level of p ≤ 0.01.

bTo perform the test on the BMI variable, the categories of overweight and obesity were grouped.

Through the results from the chi-square test, it was found that there was a significant association between the variable of patient's age and the type of fracture. It was observed that patients up to the age of 70 years presented an association with femoral neck fractures, while those aged over 80 years presented an association with trochanteric fractures.

The main types of fracture presented in this study were trochanteric (47 cases; 62.2%), femoral neck (27; 36%) and subtrochanteric (1; 1.8%) (Fig. 3).

Fig. 3 Comparison of sex, BMI and age in relation to the types of fracture that occurred, for the group with fractures alone (n = 75 cases).
Source: Data gathered in 2011. 

Discussion

A total of 164 medical files were selected: 75 relating to patients aged 65 years and over with a diagnosis of fracture in the proximal extremity of the femur; and 89 relating to patients without a previous history of fractures of the proximal extremity of the femur.

The ages of the patients with a diagnosis of fracture in the proximal extremity of the femur ranged from 65 to 96 years, with a mean of 77.58. The fracture cases were predominantly in the age range from 71 to 80 years (45.3%). Vilas Bôas Junior et al.14 reported that the age range from 60 to 69 years was the one most affected (36.64%). Rocha et al.15 found that the greatest incidence of fractures among their elderly patients was in the age range from 71 to 80 years (27.99%). Benetos et al.13 observed that around 80% of the hip fractures occurred in women over the age of 70 years. Among the men, 50% were over the age of 70 years. The mean age at which hip fractures occurred was 81 years among women and 78 years among men.

In relation to sex, we found that 56 (74.7%) were female and 19 (25.3%) were male. According to Eisler et al.,16 in a sample of 571 patients with proximal fractures of the femur, the observed incidence was 86% among females and 14% among males. Pereira et al.17 also found that femoral fractures were predominantly among women. Espino et al.18 reported that the incidence of fractures in women was 66% and that it was 34% in men. Aharonoff et al.19 found that the incidence among women was 78.6%. Ramalho et al.20 noted that femoral fractures occurred predominantly among women. Benetos et al.13 found that the incidence of hip fractures was twice as high among women than among men.

The main types of fracture presented in this study were trochanteric fractures, with 47 cases (62.2%), femoral neck fractures, with 27 cases (36%) and subtrochanteric fractures, with one case (1.8%). In the literature, trochanteric fractures are presented as the most frequent type. Cunha and Veado21 analyzed 190 patients (142 women and 48 men; mean age of 79 years) in the state of Minas Gerais who were hospitalized with fractures in the proximal extremity of the femur in the orthopedic ward of the State Public Servants' Hospital, among whom the incidence of trochanteric fractures was 50%, femoral neck fractures 44% and subtrochanteric fractures 6%.

IN relation to BMI, the patients were divided into four categories: low weight (<18.5 kg/m2), normal weight (18.5–25 kg/m2), overweight (25-30 kg/m2) and obese (>30 kg/m2). Among the patients with proximal fractures of the femur, 12% presented low weight, 62.7% normal weight, 24% overweight, and 1.3% obesity. Among the patients without any history of proximal fractures of the femur, 5.6% presented low weight, 43.8% normal weight, 33.7% overweight, and 9.8% obesity. It was found that the patients with fractures of the proximal extremity of the femur (n = 75) presented mean BMI of 22.6, while the patients without fractures (n = 89) presented mean BMI of 25.5.

A study conducted by Alfaro-Acha et al.1 also confirmed that there was an inverse relationship between body weight and the risk of fracturing of the proximal extremity of the femur and reported that a 10% weight loss significantly increased the risk of hip fractures among individuals aged 65 years and over. De Laet et al.22 found a small difference in the risk of fractures among their patients, in relation to an increase in BMI of five units, from 25 kg/m2 to 30 kg/m2, the difference observed was a 17% decrease in the risk of hip fractures. In relation to an increase in BMI of ten units, the difference observed was a 25% decrease in the risk of hip fractures. At the lower extremity of the BMI spectrum, a change of five BMI units from 25 kg/m2 to 20 kg/m2 corresponded to doubling the risk of hip fractures. Folsom et al.23confirmed that there was an inverse relationship between BMI and occurrences of hip fractures. Young et al.24 reported that low BMI was a risk factor for hip fractures, while high BMI was a protective factor. Margolis et al.25 found an association between low BMI or body size and increased risk of hip fractures. White et al.26 only demonstrated a benefit from increased BMI among women, while there was no change in risk among men. Holm-bergetal.27 reported that increased BMI was protective against hip fractures in both men and women.

Conclusion

The patients in the group with fractures were significantly taller than those in the group without fractures. In relation to BMI, the patients in the group with fractures presented significantly lower BMI than those in the group without fractures.

In view of the growing numbers of elderly people over recent years and the consequent increased frequency of hospital admissions due to fractures of the proximal extremity of the femur, which directly influence elderly people's quality of life and independence, early detection of risk factors is needed in order to select treatments better, diminish the morbidity and mortality rates and reduce costs. These factures have a direct bearing on society's economic situation, given that they lead to billions of dollars of expenditure on medical care.

Please cite this article as: Pagani RC, Kunz RE, Girardi R, Guerra M. Índice de massa corporal como fator prognóstico para fratura da extremidade proximal do fêmur: um estudo de caso-controle. Rev Bras Ortop. 2014;49(5):461–7.

☆☆Work developed at Hospital Independência, Hospital Beneficência Portuguesa and ULBRA University Hospital, Canoas, RS, Brazil.

REFERENCES

1. Alfaro-Acha A, Ostir GV, Markides KS, Ottenbacher KJ. Cognitive status, body mass index, and hip fracture in older Hispanic adults. J Am Geriatr Soc. 2006;54(8):1251-5. [ Links ]

2. Hinton RY, Smith GS. The association of age, race, and sex with the location of proximal femoral fractures in the elderly. J Bone Joint Surg Am. 1993;75(5):752-9. [ Links ]

3. World Health Organization. Prevention and management of osteoporosis. Geneva: WHO Technical Report Series; 2003. [ Links ]

4. Kannus P, Niemi S, Parkkari J, Palvanen M, Vuori I, Jarvinen M. Hip fractures in Finland between 1970 and 1997 and predictions for the future. Lancet. 1999;353(9155):802-5. [ Links ]

5. Kannus P, Parkkari J, Niemi S, Pasanen M, Palvanen M, Jarvinen M, et al. Prevention of hip fracture in elderly people with use of a hip protector. N Engl J Med. 2000;343(21):1506-13. [ Links ]

6. Hannan EL, Magaziner J, Wang JJ, Eastwood EA, Silberzweig SB, Gilbert M, et al. Mortality and locomotion 6 months after hospitalization for hip fracture: risk factors and risk-adjusted hospital outcomes. JAMA. 2001;285(21):2736-42. [ Links ]

7. Kannus P, Parkkari J, Sievanen H, Heinonen A, Vuori I, Jarvinen M. Epidemiology of hip fractures. Bone. 1996;18 Suppl. 1:57S-63S. [ Links ]

8. Richmond J, Aharonoff GB, Zuckerman JD, Koval KJ. Mortality risk after hip fracture. J Orthop Trauma. 2003;17(1):53-6. [ Links ]

9. Schwartsmann CR, Oliveira GK, Oliveira RK, Boschin LC, Mothes FC, Silva RC. A verdadeira fratura do colo do fêmur. Acta Orthop Bras. 2000;8(3):108-11. [ Links ]

10. Muniz C, Arnaut A, Yoshida M, Trelha C. Caracterização dos idosos com fratura de fêmur proximal atendidos em hospital escola público. Rev Espaço Saúde. 2000;8(2):33-8. [ Links ]

11. Berral FJ, Moreno M, Berral CJ, Contreras MEK, Carpintero P. Composição corporal de pacientes acamados por fraturas do quadril. Acta Ortop Bras. 2008;16(3):148-51. [ Links ]

12. Cunha DF, Cunha SFC, Piloto PE, Santos NP, Barros JW. Estado nutricional e resposta de fase aguda em pacientes com fratura do terço proximal do fêmur. Rev Bras Ortop. 1998;33(4):321-4. [ Links ]

13. Benetos IS, Babis GC, Zoubos AB, Benetou V, Soucacos PN. Factors affecting the risk of hip fractures. Injury. 2007;38(7):735-44. [ Links ]

14. Vilas-Bôas A Jr, Vercesi AE, Bodachne L, Vialle LRG. Estudo epidemiológico de fraturas de femur proximal em idosos. Acta Ortop Bras. 1996;4(3):122-6. [ Links ]

15. Rocha MA, Carvalho WS, Zanqueta C, Lemos SC. Estudo epidemiológico retrospectivo das fraturas do fêmur proximal tratados no Hospital Escola da Faculdade de Medicina do Triângulo Mineir. Rev Bras Ortop. 2001;36(8):311-6. [ Links ]

16. Eisler J, Cornwall R, Strauss E, Koval K, Siu A, Gilbert M. Outcomes of elderly patients with nondisplaced femoral neck fractures. Clin Orthop Relat Res. 2002;(399):52-8. [ Links ]

17. Pereira GJC, Barrreto AA, Curcelli EC, Pereira HDR, Gérios JC, Galväo MPL, et al. Estudo epidemiológico retrospectivo das fraturas do terço proximal do fêmur na região de Botucatu. Rev Bras Ortop. 1993;28(7):504-10. [ Links ]

18. Espino DV, Palmer RF, Miles TP, Mouton CP, Wood RC, Bayne NS, et al. Prevalence, incidence, and risk factors associated with hip fractures in community-dwelling older Mexican Americans: results of the Hispanic EPESE study. Establish Population for the Epidemiologic Study for the Elderly. J Am Geriatr Soc. 2000;48(10):1252-60. [ Links ]

19. Aharonoff GB, Dennis MG, Elshinawy A, Zuckerman JD, Koval KJ. Circumstances of falls causing hip fractures in the elderly. Clin Orthop Relat Res. 1998;348:10-4. [ Links ]

20. Ramalho AC, Lazaretti-Castro M, Hauache O, Vieira JG, Takata E, Cafalli F, et al. Osteoporotic fractures of proximal femur: clinical and epidemiological features in a population of the city of Sao Paulo. Sao Paulo Med J. 2001;119(2):48-53. [ Links ]

21. Cunha U, Veado MAC. Fratura da extremidade proximal do fêmur em idosos: independência funcional e mortalidade em um ano. Rev Bras Ortop. 2006;41(6):195-9. [ Links ]

22. De Laet C, Kanis JA, Oden A, Johanson H, Johnell O, Delmas P, et al. Body mass index as a predictor of fracture risk: a meta-analysis. Osteoporos Int. 2005;16(11):1330-8. [ Links ]

23. Folsom AR, Kushi LH, Anderson KE, Mink PJ, Olson JE, Hong CP, et al. Associations of general and abdominal obesity with multiple health outcomes in older women: the Iowa Women's Health Study. Arch Intern Med. 2000;160(14):2117-28. [ Links ]

24. Young Y, Myers AH, Provenzano G. Factors associated with time to first hip fracture. J Aging Health. 2001;13(4):511-26. [ Links ]

25. Margolis DJ, Kantor J, Santanna J, Strom BL, Berlin JA. Risk factors for delayed healing of neuropathic diabetic foot ulcers: a pooled analysis. Arch Dermatol. 2000;136(12):1531-5. [ Links ]

26. White SC, Atchison KA, Gornbein JA, Nattiv A, Paganini-Hill A, Service SK. Risk factors for fractures in older men and women: The Leisure World Cohort Study. Gend Med. 2006;3(2):110-23. [ Links ]

27. Holmberg AH, Johnell O, Nilsson PM, Nilsson J, Berglund G, Akesson K. Risk factors for fragility fracture in middle age. A prospective population-based study of 33,000 men and women. Osteoporos Int. 2006;17(7):1065-77. [ Links ]

Received: July 19, 2013; Accepted: August 27, 2013

* Corresponding author. E-mail: digokunz@yahoo.com.br (R.E. Kunz).

Conflicts of interest

The authors declare no conflicts of interest.

Creative Commons License This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License which permits unrestricted non-commercial use, distribution, and reproduction in any medium provided the original work is properly cited.