The epidemiological status of osteoporotic hip fractures: A bicentric comparative and retrospective study

1. Introduction

Hip fracture, as a serious complication of osteoporosis, brings heavy nursing and economic burdens to patients, family members, and society. The number of hip fractures is increasing year after year as the world’s population ages [1]. According to reports, nearly 6.3 million hip fractures will occur each year in the world by 2050, with an estimated global total of 6.3 million hip fractures by 2050 [2]. Worldwide, there are significant differences in the epidemiology of hip fractures, such as age, sex ratio, incidence, and mortality, due to differences in culture, race, geography, economic level, and so on [3]. According to reports, Scandinavia has the highest incidence (439/10 5 inhabitants/year in Denmark, 420/10 5 inhabitants/year in Norway, 401/10 5 inhabitants/year in Sweden), and the lowest incidence are in Tunisia (50/10 5 inhabitants/year), Ecuador (55/10 5 inhabitants/year) and Morocco (69/10 5 inhabitants/year) [4].

Spain, as a developed country, has a large number of elderly people. According to data provided by Statistics National Institute, in 2020, the population over 65 years old was approximately 9.27 million, accounting for 19.58% (the total population was 47.35 million) [5]. This number will continue to increase in the next 30 years. A Spanish study showed that between 1999 and 2015, among people over 45 years of age with osteoporotic hip fractures, the average age was 83 years, of which 78% were women, and the overall incidence was 290/10 5 people (428 for women; 134 for men), and it was found that during this period, the incidence of fractures decreased by 3.6% per year [6]. This is consistent with the findings of recent Spanish scholars Aguilar [7] and Rey [8]. In other words, the number of hip fractures appears to be decreasing in Spain. In the mortality report, the one-year mortality rate of hip fracture patients in Spain is more than 20% to 33% [6, 9]. As the world’s most populous developing country, China’s aging problem is becoming increasingly serious as life expectancy rises and health care improves. China has a vast territory and the epidemiology of hip fractures varies. A large study of approximately 460 million Chinese residents found that the absolute number of hip fractures increased by approximately four times between 2012 and 2016. The overall incidence rate, however, has remained relatively stable, with 149 cases per 100,000 inhabitants in 2012 and 137 cases per 100,000 inhabitants in 2016. The average age of hip fracture patients was 77.05 ± 8.94 years, of which 63.99% were female [10]. The total number of hip fractures in people over the age of 65 in China is expected to be 1.3 million by 2050 [11]. A recent meta-analysis showed that the one-year mortality rate for hip fracture patients in China was 13.96% [12].

Currently, the treatment methods for femoral neck fractures are essentially the same; that is, relatively young patients are treated with methods that retain the femoral head, such as hollow screws, and artificial joint replacements are used for the rest. For intertrochanteric fractures, especially the instability of the elderly, many Chinese scholars have reported the use of artificial joint replacement treatment, and good results have been achieved [13]. When compared to internal fixation, patients with artificial joint replacement can begin weight-bearing activities sooner and have fewer bed-ridden complications. In Spain, however, there has been no report of artificial joint replacement for the treatment of elderly people with unstable intertrochanteric fractures.

The cost of hip fracture varies with each country’s economic level and purchasing power. The average cost of hip fractures in the first year for women is 9,690 €  and for men 9,019 €, according to a Spanish study. The main cost determinant is the first hospitalization (7,067 €  and 7,196 €  in women and men, respectively) [9]. According to a prospective study of the economic burden of hip fractures in western China, the total annual cost was $4,386 per person [14]. The cost is higher in China’s developed cities (such as Beijing or Shanghai), reaching $5,239 [15]. Most of the cost is associated with direct medical care. However, indirect costs cannot be ignored either. It can be seen that no matter in which country, the expensive cost of osteoporotic hip fractures has brought a huge economic burden to the family and the national health system.

Spain, as a typical representative of developed countries, and China is the largest developing country. There are differences in the epidemiology and mortality of hip fractures between these two countries. We selected two representative cities of these two countries to collect data on hip fracture patients in two large hospitals in order to gain insight into these differences and, to the greatest extent possible, reveal their causes, in order to provide reference and assistance for the epidemiology, prevention, and treatment of hip fractures.

2. Materials and methods

4. Discussion

This article is the first study that compares the epidemiology of hip fractures in Spain and China. We discovered that the epidemiology of hip fractures varies due to differences in the two countries’ economies, medical levels, and cultural concepts by collecting clinical data on hip fracture patients treated in two large hospitals.

First, we discovered the disparity in incidence of osteoporotic hip fractures between Seville, Spain and Xi’an, China. The incidence rate in Seville over the age of 50 was approximately 239 per 100,000 inhabitants, which is consistent with the previous findings in the same city [8], with 228 per 100,000 inhabitants. In Xi’an, there was approximately 158 per 100,000 inhabitants. This is consistent with the findings of another study conducted in the same location [17], which was 153/10 5 . It is also close to the results of a recent study involving 480 million people across the country [10], which was 149/10 5 .

In terms of demographic characteristics, Spanish women have a higher proportion of hip fractures, accounting for about three-quarters, while Chinese women account for about two-thirds. This is consistent with the results of other reports [6, 18]. Second, we discovered that in most countries, the average age of onset of hip fractures is close to the country’s average life expectancy. For example, in 2019, the average life expectancy of Spain, China and Egypt was 82.8, 76.1 and 72.0 years, respectively [19]. In recent years, reports from these three countries show that the average age of hip fractures is 82.3, 77.1, and 70.8 years [10, 20, 21], respectively. Therefore, the difference in age of hip fracture is mainly related to life expectancy.

Regarding anthropometric characteristics, the height, weight and BMI of Spanish patients are significantly higher than those of Chinese patients. The first reason is genetic: the average height of Europeans is higher than that of East Asians [22]. Another reason could be that the birth and development of Chinese patients in this age group were born and developed in a period of war and poverty, resulting in their height and weight being lower than Spanish patients. In terms of overweight and obesity rates, however, Spanish patients outnumber Chinese patients, particularly women. A meta-analysis found that there is a correlation between BMI and bone mass, that is, the higher the BMI, the better the bone density, which is considered to be a protective factor for osteoporotic hip fractures, and put forward the viewpoint of increasing the BMI of the elderly to reduce the incidence of hip fractures [23]. However, from the study we conducted, the percentage of overweight and obese patients with hip fractures in Spain was close to 60%, which is significantly higher than the 47% of the normal population [24]. Perhaps this is because obese patients have less flexibility, are more likely to fall, and their excessive weight at the time of injury exerts more force, which offsets the better bone density [25]. In addition, the BMI level is negatively correlated with the postoperative rehabilitation effect of hip fractures, that is, the higher the BMI, the worse the postoperative functional rehabilitation [26]. Moreover, as we all know, obesity is also a risk factor for many diseases, such as cardiovascular and cerebrovascular diseases, arthritis and diabetes [27]. For these reasons, we believe that maintaining a normal BMI is the healthiest option, rather than increasing BMI to reduce the risk of hip fractures.

Many studies have shown that alcohol affects bone metabolism, not only inhibiting bone synthesis but also increasing bone desorption via direct and indirect pathways, resulting in osteopenia and osteoporosis and increasing the risk of fractures [28, 29]. In our comparative study, we found that the proportion of Spanish women drinking is significantly higher than that of Chinese women. Smoking has a number of negative consequences, one of which is low bone density. Furthermore, smoking is linked to an increased fracture risk in both men and women, as well as delayed fracture healing [30]. Based on Dimitris’ research, ex-smokers and active smokers have an increased risk of hip fractures when compared to never-smokers, but the longer they quit smoking, the lower the risk of fractures [31]. Therefore, the higher consumption of tobacco and alcohol by Spanish women may be one of the reasons why they account for a higher proportion of hip fractures than Chinese women.

Hip fracture patients over 65 years of age often have multiple personal medical histories. The internal homeostasis of the patient is altered by the hip fracture, which causes a continuous deterioration of his general condition. It is worth noting that 75% of patients die as a result of a comorbidity that existed prior to the injury, rather than the pathology of the hip fracture itself [32]. Yoon et al. have shown that dementia and DM have a significant effect on postoperative functional outcomes [33]. Anemia will increase hospital complications as well as hospitalization costs [34]. A meta-analysis shows that malignant tumors, lung disease, DM, and cardiovascular disease significantly increase the risk of death after hip fracture surgery [35]. Studies have shown that personal history of fracture is one of the major risk factors for hip fractures [36]. In addition, some studies have shown that having more than 3 common comorbidities are risk factors that lead to the death of patients in one year [37]. In this study, we have found that the proportion of patients with 3 or more types of comorbidities is significantly higher in Spain than in China. This is especially true in the case of visual problems, diabetes, hypertension, cardiovascular disease, a personal history of fracture, osteoporosis, and so on, which may be one of the reasons why the mortality rate of Spanish patients is higher than that of Chinese patients. In summary, the comorbidities of elderly patients with hip fractures are not only related to the increased risk of osteoporosis and falls, but also to the increased risk of postoperative hip fracture death. Therefore, active prevention and treatment of elderly comorbidities can reduce the incidence and mortality of hip fractures.

Falls are the leading cause of hip fractures, which have serious psychological consequences for patients, such as a fear of falling and a loss of self-confidence. Walking is one of the most common causes of falls. In this study, we discovered an intriguing phenomenon: while pre-fracture activity in Spanish patients is lower than in Chinese patients (50.4% in Spain have no or little activity, compared to 40.3% in China), more Spanish patients fell during the day and outside. For example, in Seville, there are lanes dedicated to wheelchairs on both sides of the street; there are no steps on the bus, and it is more convenient for the elderly on crutches to get on and off the bus, and there is a ramp for wheelchairs on the bus. Another reason may be that older people in Spain have a more open perception and are more willing to enjoy a free and better life outdoors. In contrast, in Xi’an, China, the details of public transportation facilities are not friendly enough. For example, there are steps for getting on and off the bus, which is inconvenient for the elderly. In addition, in China, due to the conservative and traditional perception, more elderly people spend their time on the sofa watching TV or on the rocking chair on the balcony. All of this explains the interesting results we got in this study.

The primary method of treatment for elderly hip fracture patients is surgery, which can significantly reduce mortality and achieve treatment benefits. In our study, there are significant differences in the choice of surgical methods for patients between the two countries. In femoral neck fractures, although most patients in both countries have received more prosthetic treatment, 12 cases of fractures in China have received osteosynthesis, while only 5 cases in Spain. The main reason for this is that Chinese patients are younger, and osteosynthesis with femoral head preservation is the preferred treatment. However, for intertrochanteric fractures, all Spanish patients received osteosynthesis, while 31 Chinese patients received prostheses. Studies have shown that the use of prosthesis for the treatment of unstable intertrochanteric fractures is significantly better than internal fixation (DHS or PFNA) in terms of walking time, postoperative complications, Harris Hip Score and mortality [38]. Among Chinese patients with intertrochanteric fractures, 31 patients who received prostheses had a one-year mortality rate of 12.9%, while the remaining 116 patients who received osteosynthesis had a mortality rate of 22.4%. This indicates that the prosthesis is a good therapeutic alternative for unstable intertrochanteric fractures. Therefore, Spanish orthopedic surgeons should also consider the choice of prosthesis for intertrochanteric fractures.

In addition, we discovered that Spanish patients had longer surgery wait times than Chinese patients. This is because there are many patients in Spain waiting for surgery on weekends, while 14.8% of Chinese patients undergo surgery on weekends. The main reason for this difference is the healthcare system and the medical environment. In fact, in Spain, except for emergencies, they only perform operations on working days, while in China, they are also undergoing intensive operations on Saturdays. In the medical environment, Chinese patients and their families are more aggressive to medical staff forcing the doctors to urgently perform the procedudres [39]. A number of studies have shown that surgical delay is an independent risk factor for postoperative death in patients with hip fractures, and early surgery can reduce perioperative complications and mortality [40, 41]. This may also be a reason for the higher mortality rate among Spanish patients.

In terms of anesthesia, XDH prefers general anesthesia in China, whereas HUVM in Spain prefers regional anesthesia. This difference was only observed in the two hospitals studied and does not reflect the two countries. In fact, our review of Chinese literature revealed [42], many Chinese hospitals use more regional anesthesia than general anesthesia. However, more research evidence shows that different anesthesia methods will not affect the complications and mortality of patients with hip fractures [43]. In the comparison of ASA classification, the high-risk ratio of Spanish patients is significantly higher than that of Chinese patients, indicating that the overall condition of Spanish patients is worse. The Wang’s study shows that the high risk of ASA is an independent risk factor for death from hip fracture within one year [44]. In our study, there are more Chinese elderly people suffering from anemia, and the preoperative hemoglobin is significantly lower than that of the Spanish. Studies have shown that the higher the BMI, the lower the possibility of anemia [34], which may be the reason why the elderly in China are more likely to suffer from anemia. Therefore, more Chinese patients have to receive blood transfusions.

Patients with hip fractures have longer hospital stays than patients with other closed fractures because they have more comorbidities, longer surgical delays, and other postoperative complications [45]. In this study, the average hospital stay of Chinese patients is longer than that of Spanish patients. The main reason for this is that some Chinese patients do not have clinics or hospitals close to their homes, making it difficult for them to change dressings and remove sutures from wounds after surgery. However, a longer hospital stay may be beneficial to the patient. A South Korean study found that elderly patients with hip fractures who were hospitalized for less than 10 days had a higher mortality rate within one year after discharge [46]. Reducing the length of hospital stay entails shortening the time it takes for patients to receive nursing care in the hospital following surgery, as well as shortening the time it takes for a comprehensive assessment of the patient’s medical condition during this time. In fact, the amount of time spent in bed is directly related to the patient’s prognosis. Time spent in bed increases the risk of pressure ulcers, pulmonary infections, venous thrombosis, muscle atrophy, and cardiovascular complications [47]. In this study, the average number of days of bed rest for Chinese patients was significantly lower than that of Spanish patients, and the bed rest time of prosthesis treatment was significantly shorter than that of osteosynthesis treatment.

Regarding hospitalization costs, Spanish patients are significantly higher than Chinese patients. However, due to price and purchasing power differences, we must compare them in a different way. We believe that the average wage is an appropriate method in this case. For example, the average annual income of residents of Seville in 2019 was 16,271 euros [48], while in Xi’an it was 58,080 RMB, approximately 7,260 euros [49]. In other words, the hospitalization costs for hip fractures in the two countries are relatively similar, about 10 months’ salary. Finally, we must point out that as the elderly population increases, prevention has become the best strategy to reduce the cost of hip fractures, thereby reducing the high costs borne by the health system and families.

Because of the high mortality and disability rates, hip fracture is known as the “last fracture in life.” The one-year mortality rate following a hip fracture is 15% to 40%, which is 3 to 4 times higher than the general population [50, 51]. In this study we have seen one-year mortality rates of 19.01% in Spain and 12.99% in China. A recent meta-analysis carried out in China showed that the one-year mortality rate was 13.96% [12]. In Spain, a study using national data showed that the annual mortality rate for men and women under 80 years of age is 22%; that of women over this age was 25.2%, while that of men was 30.1% [52]. Based on these data, we can conclude that the one-year mortality rate of hip fracture patients in China is lower than that of Spain.

5. Conclusion

Our study found significant epidemiological differences between hip fracture patients in Seville, Spain and Xi’an, China. Gender, age, injury location, comorbidities, and other differences cannot be changed by admonishing patients or selecting treatment methods. We can, however, narrow the gap by advising patients to maintain a normal BMI, develop a healthy lifestyle, and select appropriate surgical methods to provide patients with a better foundation for rehabilitation and reduce mortality.