Age‐ and Gender‐Specific Epidemiologic Characteristics of Major Intra‐Articular Fractures: Five‐Year Data from a Level 1 Trauma Center

Objective To investigate the epidemiological characteristics of major intra‐articular fractures. Methods This retrospective study enrolled patients with major intra‐articular fractures who were treated in the Third Hospital of Hebei Medical University from January 2015 to December 2019. A total of 11,084 patients (7,338 [66.20%] males and 3,746 [33.80%] females) meeting the inclusion and exclusion criteria were included. The distribution characteristics of intra‐articular fractures involving shoulder, elbow, wrist, hip, knee, ankle, and subtalar joints were identified.The potential associations between fractures and various other factors, such as age, gender, sites, were explored. Results There were 74 cases (0.67%) of shoulder fractures, 1,941 cases (17.51%) of elbow fractures, 1,155 cases (10.42%) of wrist fractures, 520 cases (4.69%) of hip fractures, 3,118 cases (28.13%) of knee fractures, 2,156 cases (19.45%) of ankle fractures, and 2,120 cases (19.13%) of subtalar fractures. The overall male‐to‐female ratio was 1.96:1. The highest proportion age group of major intra‐articular fractures included the ages 45–54 years. For males, the highest proportion age group was 45–54 years, for females, it was 55–64 years. The knee joint fracture was the most common type, accounting for 28.13%. For male and female patients, knee fractures accounted for 26.19% and 31.93%, respectively, with a male to female ratio of 1.13:1. The proportion of shoulder fractures was the smallest among this investigation, accounting for 0.67%. For male and female patients, shoulder fractures accounted for 0.44% and 1.12%, respectively, with a male to female ratio of 0.76:1. The age group with the highest proportion of shoulder joint fractures was ≥65 year olds (41.89%), with a male to female ratio of 0.76:1. The age group with the highest risk of elbow, wrist, hip, knee, ankle, and subtalar joint fracture was 5–14 year olds (33.59%) with a male to female ratio of 3.29:1, 5–14 year olds (23.98%) with a male to female ratio of 6.91:1, 45–54 year olds (26.92%) with a male to female ratio of 5.67:1, 45–54 year olds (24.60%) with a male to female ratio of 1.68:1, 25–34 year olds (20.36%) with a male to female ratio of 2.30:1, 45–54 year olds (27.41%) with a male to female ratio of 9.02:1, respectively. The most common site of intra‐articular fractures in different age groups was corresponding as follows: 0–4 year olds (elbow), 5–14 year olds (elbow), 15–24 year olds (ankle), 25–34 year olds (subtalar joint), 35–44 year olds (subtalar joint), 45–54 year olds (knee), 55–64 year olds (knee), 65–74 year olds (knee), and ≥75 year olds (knee). Conclusion The current study revealed the age‐ and gender‐specific epidemiological characteristics of major intra‐articular fractures, providing a basis for clinical evaluation and practices.


Introduction
I ntra-articular fracture refers to a fracture involving the articular surface, which belongs to a common type of fracture in clinical practice. It is mostly caused by high-energy injuries or falling injuries, and the treatment requires a high standard of expertise; otherwise, improper handling often creates functional obstacles of different levels. At present, most studies focus on conservative or surgical treatment, and there remains a lack of large-sample epidemiological investigation; furthermore, a substantial proportion of epidemiological studies focus on a specific location (e.g. knee joint fracture), rather than investigating the epidemiological characteristics of major intra-articular fractures in the whole body.
As early as 1832, Astley Cooper 1 recognized the influence of age on bone strength in the study of femoral neck fractures in elderly patients. In 1882, Bruns 2 first discussed the influence of age and gender on the incidence of various types of fractures. Alffram 3 studied the age and gender differences of 2672 cases of forearm fractures that occurred in 5 years and found that before the age of 40, the incidence of distal forearm fractures in males and females was approximately equal, while after the age of 60, the number of female patients with fractures was more than seven times that of males. Singer 2 conducted an epidemiological survey on 15,000 adult fracture patients in the Edinburgh area, and found that between 15 and 49 years old, males were 2.9 times more likely to have fractures than females, while after 60 years old, the situation was reversed, with females 2.3 times more likely to have fractures than males. The influence of age and gender on the incidence and location of fractures also exists in the adolescent population. An epidemiological survey of 6% of the population of Britain 4 showed that the incidence of fractures in adolescent boys was higher than that in girls, and the peak time was 14 and 11 years old, respectively, with significant differences between them.
Studies have shown that age and gender are closely related to intra-articular fractures at specific sites [5][6][7][8] . Therefore, it is necessary to conduct relevant epidemiological investigation into these factors to identify the aggregation of intra-articular fractures at different ages and genders, so as to provide effective targeted preventive measures. Therefore, we conducted this retrospective study on the clinical data of 11,084 patients with major intra-articular fractures with the aim to clarify: (i) which joint of intra-articular fracture is most common and the incidence of other intra-articular fractures; (ii) which age group is most likely to experience the major intra-articular fractures; and (iii) the distribution of major intra-articular fractures in different age groups.

Patients Inclusion
Patients with major intra-articular fractures of the limbs were selected to be included in this study.
Patients were sourced through the picture archiving and communication systems (PACS) and the medical record inquiry systems of the Third Hospital of Hebei Medical University from January 2015 to December 2019.
Exclusion criteria: (i) patients with pathological fractures; (ii)patients with old fractures.

Demographic Information and Fracture Classification
The medical records of enrolled patients were retrieved using the medical record inquiry system. The demographic characteristics of patients and detailed information on major intraarticular fractures were recorded. The preoperative radiographs, computed tomography (CT), and magnetic resonance imaging (MRI) of the intra-articular fractures were collected with the use of the picture archiving and communication systems. The X-ray films, CT, and MRI scans of the intra-articular fractures were reviewed by five orthopaedic surgeons with more than 10 years of experience. Intraarticular fractures are divided into shoulder intra-articular fractures, elbow intra-articular fractures, wrist intra-articular fractures, hip intra-articular fractures, knee intra-articular fractures, ankle intra-articular, and subtalar intra-articular fractures according to the fracture site. If there was any disagreement in the diagnosis of intra-articular fractures, a final decision would be made through discussion, with consensus achieved by at least three surgeons.

Indicators Measures
An intra-articular fracture is a fracture that crosses a joint surface, so all the patients we included met the definition of intra-articular fracture. Preoperative X-ray, CT, and MRI were used for auxiliary diagnosis of intra-articular fractures. Intra-articular fractures in seven major sites of the human body were selected for analysis and each intra-articular fracture included the following fracture type:

Intra-articular Fractures of Shoulder
Intra-articular fractures of shoulder include humeral head, humeral anatomic neck and glenoid.

Intra-articular Fractures of Wrist
Intra-articular fractures of wrist include distal radial articular surface.

Intra-articular Fractures of Hip
Intra-articular fractures of hip include femoral head, acetabulum.

Intra-articular Fractures of Subtalar joint
Intra-articular fractures of subtalar joint include calcaneus and talus.

Statistical Analysis
All the analyses were performed with the use of SPSS 22.0 (IBM, Chicago,USA). A P-value of <0.05 was considered significant. Descriptive data were presented as numbers. The number of major intra-articular fractures and composition ratios in each year were analyzed. The distribution of male and female patients in different age groups and the distribution of intra-articular fractures in different age groups were all accessed. The Kolmogorov-Smirnov test was used to check whether results were in accordance with the normal distribution. The compositions of intra-articular fractures in different years were analyzed by Analysis of Variance (ANOVA) test, and the comparison between pairs was performed by Student-Newman-Keuls Q test (SNK-Q test) or Least Significant Difference test (LSD test). The compositions of intra-articular fractures in different genders over 5 five years were compared by Pearson chi-square test.

Result
Demographic Information and Fracture Classification A total of 11,084 patients with major joint fractures were identified over the 5-year period, accounting for 17.08% (11084/64885) of the total fractures at the whole skeleton sites in the same period, including 7338 males and 3746 females. The overall male-to-female ratio was 1.96:1. The highest proportion age group was 45-54 years (20.49%), the male and female patients were 45-54 years (20.89%) and 5564 years (23.63%), respectively. There were 74 cases (0.67%) of shoulder fractures, 1,941 cases (17.51%) of elbow fractures, 1,155 cases (10.42%) of wrist fractures, 520 cases year by year. There was no significant difference in the composition of intra-articular fractures over the 5 years (P > 0.05), and there was a significant difference in the composition of intra-articular fractures between men and women (χ2 = 764.06, P = 0.000). The proportion of intra-articular fractures in each year and in different genders is shown in Tables 1 and 2 and Figs 1-3.

The Most Affected Age Group and Its Gender Distribution for Each Intra-articular Fracture
The knee fractures were the most common among the seven intra-articular fractures, accounting for 28.13%, and the ratio of males to females was 1.13:1. The least common fracture was shoulder fractures, accounting for 0.67%, 0.44% in male and 1.12% in female, with a male to female ratio of 0.76:1. The age group with the highest proportion of shoulder fractures were ≥65 year olds (41.89%), with a male to female ratio of 0.76:1. The peak incidence occurred at 5-14 years of age (33.59%) in elbow fractures, with a male to female ratio of 3.29:1. For other joints, such as wrist, hip, knee, ankle, and subtalar joint, the age groups with the highest proportion of fractures were 5-14 years (23.98%), 45-54 years (26.92%), 45-54 years (24.60%), 25-34 years (20.36%), 45-54 years (27.41%), respectively, and the male-to-female ratio was 6.91:1, 5.67:1, 1.68:1, 2.30:1, and 9.02:1, respectively.

Discussion
I ntra-articular fracture is a common type of injury in trauma and orthopaedics. The principle of treatment requires precise reduction of the articular surface; improper treatment can likely result in postoperative complications, such as pain and dysfunction, which will increase the burden on society and family. At present, more attention has been paid to the treatment of intra-articular fractures in clinic, but less to primary prevention. Furthermore, existing epidemiological studies are mostly concerning with the individual intra-articular fractures and there are only rare epidemiological holistic studies on whole major intra-articular fractures. Although this is not a national investigation study, it includes a large number of cases over a long time span. For the first time, this study elaborates on age and gender as factors that influence different intra-articular fractures, making it a valuable reference for the prevention of these types of fractures.

Overall Age and Sex Distribution Characteristics of Major Intra-articular Fractures in the Human Body
Male patients were about twice as likely as females to experience these fractures, possibly because they offen participate in sports or jobs that were vulnerable to injury. A total of 3118 patients with intra-articular knee fractures were treated in the past 5 years, accounting for 28.13% of fractures, making them the most common intra-articular fractures. The reason may the high proportion of patellar and tibial plateau fractures, with incidence rates of 2.73% 9 and 1.66% 10 , respectively. Previous studies showed that patellar fractures and tibial plateau fractures were more common in males 9, 10 , and the highest proportion age group was 41-59 years, which was basically consistent with the findings of our study. A study 11 based on 576,364 patients in the northern region of Denmark showed that the incidence of tibial plateau  Fig. 4 The proportion of intra-articular fractures in different age groups, showing that the highest proportion age group was 45-54 years (20.49%). While 0-4 years rarely experienced intra-articular fractures.
fractures was 10.3 per 100,000, and the highest frequency was in 40-60 year olds for both men and women. At the same time, that study pointed out that fracture rates were higher in men under age 50, but after age 50, fracture rates increased significantly in women and decreased in men. The main causes of injury for men were falls from a height or accidents involving cars, motorcycles, or other motorized vehicles. Women were injured primarily while bicycling, walking, and during indoor activities. This indicated that close attention should be paid to the prevention of knee fractures in this age group, such as avoiding falls, traffic injuries, preventing osteoporosis, and so on.
Age and Gender Characteristics of Intra-articular Fractures at Different Sites This study showed that the age group with the highest proportion of shoulder fractures was ≥65 year olds (41.89%) and the male-to-female ratio was 0.76:1, which was the only age group where the number of female patients exceeded that of male patients. The reason may be that osteoporosis of females was more severe in older women than in older men [12][13][14] . A Finnish study 15 showed that age and gender were both independent risk factors in patients over the age of 60 with proximal humerus fractures caused by low energy.
The age group at risk of elbow and wrist joint fractures was 5-14 year olds, and males were significantly more prone to these fractures than females, which was related to the lively and active character of boys in this age group 16 . Therefore, attention should be paid to popularizing relevant sport protection knowledge, wearing protective gear, etc. The findings are consistent with the investigation by Erik 17 , who conducted an epidemiological survey of fractures in children and adolescents in Sweden during the past 10 years, showing that the most common fracture site was the distal forearm, the peak incidence occurring at 1112 years in females and at 13 14 years in males. The most common risk factors were various sports.
The age group with the highest proportion of hip, knee, and subtalar joint fractures was 45-54 year olds, with more males than females experiencing these fractures. Obviously, this age group includes first-home owners. Therefore, it is necessary to strengthen the protection of lower limb joints in this age group. This study also showed that peak incidences of ankle fractures occurred at 25-34 years, especially in men, suggesting that attention should be paid to the protection of ankle joints in young men who engage in more construction and transportation activities. Similar to previous studies, Liu 14 retrospectively analyzed the data of 7742 ankle fractures and concluded that the highest-proportion age group was 21-30 year olds, with a male-to-female incidence ratio of 1.36. However, a nationwide epidemiological survey of ankle fractures based on the basic population by Liu 9 showed that the peak incidence occurred at 4150 years, which was different from our study because of the different study population. Another 18 epidemiological survey of ankle fractures in 673,214 cases in American hospitals showed that the highest incidence age group was 10-19 year olds (23.5%), followed by 20-29 year olds (12.0%), with females (56%) more likely to experience these fractures than males (44%). The common causes were falls and sports injuries, and occurred more usually in white people than other races. The difference between the two studies was possibly that ours was a single-center study, while the American study was a multi-center study. In future research, the sample should be expanded and multi-center data should be included.

Distribution Characteristics of Intra-articular Fractures in Different Age Groups
The elbow fractures were the most common in 0-4 year olds and 5-14 year olds, which may be related to more activity patterns and high incidences of humeral condyle and olecranon 19 in this age group. The results are consistent with another investigation 20 , which included 8987 fractures over a 5-year period, showing that school-age patients aged 7-11 years accounted for the most fractures (32.86%), and the most common fracture site was the distal humerus (22.4%). Intra-articular fracture of the ankle was the most common in 15-24 year olds, followed by elbow fractures. While intra-articular fractures of the subtalar joints were common in 25-44 year olds, the reason may be that the age groups were young adults, belonging to the main labor force in society, which exposed them to the risk of high-energy trauma, such as crashes and falls from height, resulting in calcaneal and talus fractures. The epidemiological study, which included 3881 calcaneal fractures, showed that the age group with the highest propotion was 31-40 year olds 21 . Dong 22 analyzed 1014 cases of talar fracture, showing that the peak incidence occurred at 21-40 years, and the median age at 35-36 years. Knee fractures were most common in patients over 45 years of age, as the incidence of osteoporotic fractures around the knee increased with age 23 .
By dividing patients into age groups, we defined the most common intra-articular fracture sites in each age group, which would be helpful to institute preventive and protective measures in order to reduce the incidence of intra-articular fractures and avoid complications such as deformity, dysfunction, and pain. Finally, the burden on both families and society will be reduced.

Limitations
Several limitations of this study should be noted. First, because it was a retrospective study, recall bias is inevitable. Second, the cases were only from a single center and other factors such as mechanism of injury, occupation, classification of fractures were not taken into account. Therefore, the next step is to expand the sample size through a multi-center study and consider more related factors.

Conclusion
The most common fracture site among major intra-articular fractures is in the knee, while the least common major intraarticular fracture site is the shoulder. Male patients are more likely to experience these fractures than females. At 0-4 years and 5-14 years, the most common intra-articular fractures occur in the elbow. However, ankle fractures, subtalar fractures, and knee fractures are most common in 15-24 year olds, 25-44 year olds, and >45 year olds, respectively. Targeted preventive measures can be formulated according to the above characteristics.