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Epidemiology of Osteoporotic Ankle Fractures in Elderly Persons in Finland
- Pekka Kannus, MD, PhD;
- Jari Parkkari, MD;
- Seppo Niemi; and
- Mika Palvanen, MD
- From UKK Institute for Health Promotion Research, Tampere, Finland. Acknowledgments: The authors thank the Finnish Ministry of Health for its cooperation. Grant Support: By grants 95/3/15, 95/9/27, and 96/3/22 from the Medical Research Fund of Tampere University Hospital, Tampere, Finland. Requests for Reprints: Pekka Kannus, MD, PhD, UKK Institute, Kaupinpuistonkatu 1, FIN-33500 Tampere, Finland. Current Author Addresses: Drs. Kannus, Parkkari, and Palvanen and Mr. Niemi: UKK Institute, Kaupinpuistonkatu 1, FIN-33500 Tampere, Finland.
Abstract
Background: Although osteoporotic or minimal trauma fractures among elderly persons are a major public health problem worldwide, epidemiologic information on these fractures is limited.
Objective: To determine the current trend in the number and incidence of osteoporotic ankle fractures in the elderly. A fracture was defined as osteoporotic only if it occurred as a result of minimal trauma in a person 60 years of age or older.
Design: National hospital discharge register.
Setting: Finland, a country with approximately 5 million inhabitants.
Participants: All patients 60 years of age or older who were admitted to hospitals in Finland for primary treatment of first osteoporotic ankle fracture in 1970 to 1972, 1974, 1975, 1978 to 1980, 1983 to 1985, 1988 to 1989, and 1991 to 1994.
Measurements: The number and the age-specific and age-adjusted incidence of osteoporotic ankle fractures in each year of the study.
Results: For the study period, the number and incidence (per 100 000 persons) of osteoporosis-related ankle fractures in Finnish persons 60 years of age or older increased considerably (370 and 57, respectively, in 1970 compared with 1243 and 130, respectively, in 1994). The age-adjusted incidence of these fractures also increased in women, from 66 in 1970 to 162 in 1994, and in men, from 38 in 1970 to 82 in 1994.
Conclusion: The number of osteoporotic ankle fractures in Finland is increasing at a rate that cannot be explained simply by demographic changes. Vigorous preventive measures are needed to control the increasing burden of this type of fracture.
Osteoporosis, with its sequelae of fracture, is a major public health problem, especially in contemporary western societies that have aging populations [1]. As the number of elderly persons in these populations continues to increase, the number of osteoporotic problems will also increase. In the United States, approximately 15 to 20 million adults are affected by osteoporosis, and as many as 1.2 to 1.3 million osteoporotic fractures occur annually [2-6]. Given an average life expectancy, a white person who is 60 years of age has a high residual lifetime risk for fracture (56% for women and 29% for men [1]). Osteoporosis is therefore an important cause of morbid conditions and (indirectly) death among these persons [2-5].
Osteoporotic fractures (also called age-related fractures or minimal-trauma fractures) increase in number and incidence with age, have a higher incidence in women than in men, occur at sites containing substantial amounts of trabecular bone, and are associated with only minimal to moderate trauma (typically a fall from standing height or less) [1, 4]. The most common and well-known forms of these fractures occur at the distal forearm, spine, and hip [1, 4, 7]; many osteoporotic fractures also occur at the ankle (distal tibia and fibula), knee, pelvis, and proximal humerus [1, 8-13]. Treatment of these fractures is expensive and often requires surgery, long-term immobilization, or both.
Epidemiologic information on these latter fractures is scarce, and no nationwide study investigating the number, incidence, and secular trends of osteoporotic ankle fractures has been published. Therefore, we determined trends in the absolute number of osteoporotic ankle fractures and age-specific and age-adjusted ankle fracture incidence rates in Finland, a country with a population of 5 million persons, between 1970 and 1994.
Methods
In accord with other epidemiologic studies of osteoporotic fractures [1, 2, 4, 13], we defined an osteoporotic ankle fracture to be a fracture that occurs in a person 60 years of age or older as a consequence of minimal trauma (such as an ankle sprain or a fall from standing height or less). We therefore selected all patients 60 years of age or older who were admitted to hospitals in Finland for primary treatment of a first ankle fracture in 1970 to 1972, 1974, 1975, 1978 to 1980, 1983 to 1985, 1988 to 1989, and 1991 to 1994 from the National Hospital Discharge Register (NHDR). These intervals were randomly selected. Unique personal identification numbers allowed us to focus our analysis on each patient's first recorded admission. The NHDR contains data on age, sex, place of residence, hospital and department, day of admission and discharge, place and cause of injury, and place of further treatment. Injuries caused by a vehicular accident or other high-impact trauma were excluded. The Finnish NHDR is the oldest nationwide discharge register in the world, and the data provided by this register are well suited to epidemiologic purposes: The register has been shown to cover the population adequately and accurately (≥ 95% of the population), especially for such severe injuries as ankle fractures [14-16].
Fractures were recorded by evaluating primary and secondary diagnoses. According to the directives given by the Finnish National Board of Health, the first diagnosis describes the main reason for the hospital stay. The second, third, and fourth diagnoses indicate other possible diseases or injuries. The diagnoses were labeled with a five-digit code according to the eighth and ninth revisions of the International Classification of Diseases (ICD) that indicated the type of malleolar ankle fracture (fractures occurring at the distal tibia, distal fibula, or both). Between 1970 and 1986, the eighth revision of the ICD and its two codes for malleolar fractures (82400 and 82410) were used. In 1987 and after, the following codes from the ninth revision of the ICD were used: 8240A to 8247A, 8248X, and 8249X. The data were taken from the entire population of Finland; absolute numbers and incidences of ankle fractures are therefore not cohort-based estimates.
Annual midyear population figures for each 5-year age group between 1970 and 1994 were taken from The Official Statistics of Finland [17]. Fracture incidences were calculated for both sexes and were expressed as the number of cases per 100 000 persons per year. To establish age-and sex-specific incidences for the selected age groups (60 to 69 years of age, 70 to 79 years of age, and 80 years of age or older), the annual numbers of ankle fractures were divided by the midyear population for each sex and age group. The rates were expressed as the number of cases per 100 000 persons per year, by sex and age group. We used direct standardization to calculate age-adjusted fracture incidences, using the mean population between 1970 and 1994 as the standard population.
Results
Absolute Number and Incidence of Osteoporotic Ankle Fractures
The total annual number of osteoporotic ankle fractures increased during the study period, from 370 in 1970 to 1243 in 1994 (Figure 1). The average increase was 9.8% per year. The incidence curve for fractures followed the absolute number curve, although the Finnish population of persons 60 years of age or older increased 47% (from 652 000 to 958 000) during this 24-year period. The overall incidence (per 100 000 persons) of osteoporotic ankle fractures in persons 60 years of age and older was 57 in 1970 and 130 in 1994. For women, it was 68 in 1970 and 161 in 1994; for men, it was 39 in 1970 and 81 in 1994.
In persons 60 years of age and older, the proportion of all first ankle fractures (including those caused by severe, high-impact injuries) that were osteoporotic ankle fractures increased steadily during the study period-from 81% (370 of 455) in 1970 to 88% (1243 of 1408) in 1994. The mean age of patients with an osteoporotic ankle fracture also increased during the study period, from 67.7 years in 1970 to 70.7 years in 1994. In women, the mean age increased from 68.1 years in 1970 to 71.5 years in 1994; in men, the mean age increased from 66.7 years in 1970 to 68.4 years in 1994.
Age-Adjusted Incidence of Osteoporotic Ankle Fractures
During the study period, the age-adjusted incidence of osteoporotic ankle fractures in persons 60 years of age and older increased. In women, the incidence per 100 000 increased from 66 in 1970 to 162 in 1994; in men, it increased from 38 in 1970 to 82 in 1994 (Figure 2). The relative increases were 145% in women and 116% in men.
Age-Specific Incidence of Osteoporotic Ankle Fractures
The age-specific incidence of osteoporotic ankle fractures increased in all age groups during the study period. In women 60 to 69 years of age, the incidence of fractures per 100 000 persons was 74 in 1970 and 161 in 1994; in women 70 to 79 years of age, it was 63 in 1970 and 168 in 1994; and in women 80 years of age or older, it was 50 in 1970 and 150 in 1994. For men 60 to 69 years of age, the incidence of fractures per 100 000 persons was 42 in 1970 and 90 in 1994; for men 70 to 79 years of age, it was 36 in 1970 and 68 in 1994; and for men 80 years of age or older, it was 26 in 1970 and 71 in 1994.
Thus, the age-specific incidence of fractures increased over time but showed no consistent changes across age groups. The group of men and women 60 to 69 years of age had a somewhat higher incidence than did the older age groups. Fracture incidence therefore increased over time in all age groups, but it did not increase with age in general.
Discussion
We studied all persons 60 years of age or older in Finland to describe the trends over time for the absolute number and incidence of osteoporotic ankle fractures. The overall incidence of fractures per 100 000 persons among women 60 years of age or older increased steadily from 68 in 1970 to 161 in 1994. The relative increases seen for men were almost as great (from 39 to 81), but the absolute increase in the incidence and number of these fractures was much lower for men than for women. In both sexes, an increase in fracture incidence was seen in all age groups older than 60 years of age. Our observations are similar to those of previous studies from Sweden [10] and the United States [11], which suggest that the incidence of ankle fractures is increasing, especially in elderly women [10].
Our study is limited because the numbers, incidences, and secular trends of osteoporotic ankle fractures in Finland cannot be directly generalized to other populations. However, the incidence of fractures will probably develop similarly in other western countries. Further studies are required to show precise results for each population. In addition, it should be noted that our database of fractures did not include information on comorbid illnesses, medications, and lifestyles. In other words, our finding that the incidence of osteoporotic ankle fractures is increasing among elderly persons in Finland remains unexplained.
Our findings on osteoporotic fractures are frightening for two reasons. First, not only is the incidence of fractures increasing, but the population at risk is constantly expanding and will expand more rapidly in the near future. As a result, the largest age group in Finland (the 10-year cohort born after World War II) will reach the age at which persons are most prone to osteoporotic ankle fractures around the year 2020. Second, the increasing mean age of the patients presenting with these fractures is likely to mean more difficulties in the treatment of these fractures (longer time for fracture healing, longer rehabilitation period, and an increasing number of such treatment complications as infection and nonunion) and increasing rates of general morbid conditions and (indirectly) death of the patients.
As we have noted, the precise reasons for the increasing age-adjusted and age-specific incidence of osteoporotic ankle fractures in elderly women and men are not known. In hip fractures (for which a similar secular trend has been reported [7, 18]), deterioration in the age-adjusted bone quality (caused by decreased bone mineral density and bone strength) and an increase in the age-adjusted incidence of falls in the elderly (caused by impaired balance, coordination, proprioception, reaction time, and muscle strength) have been the most commonly offered explanations [5, 12, 18-20]. In other words, elderly persons may be less healthy today than in the past; thus, persons who now survive to old age are more prone to osteoporosis, falls, and fractures than were elderly persons in the past. Decreased bone quality and an increased propensity for falls in the elderly have, in turn, been explained by such factors as less-active lifestyles, poorer nutrition, greater consumption of tobacco and alcohol, greater occurrence of coexisting medical problems, and more frequent use of drugs [6, 12].
For the year 2000, the annual number of first osteoporotic ankle fractures in Finland for persons 60 years of age and older is estimated to be more than 1400. However, the age group that is most prone to osteoporotic ankle fractures will be the largest age group in Finland after the year 2000, and the number of these fractures is therefore expected to increase exponentially during the first two decades of the new millennium. For this reason, vigorous prevention of osteoporosis and falls in elderly persons and support and protection of critical anatomical sites should be implemented to control the increasing burden of these fractures.
- Copyright ©2004 by the American College of Physicians
