1 Introduction to Clinical Epidemiology of Orthopaedic Trauma
Fractures Overview
Bone fractures occur when there is a break in the continuity and integrity of the bone as a result of excessive force. Fractures usually begin with intensive pain and swelling at the site of injury, along with some degree of loss of function. Furthermore, fractures can also present with shock and fever as seen in severe cases. Characteristics of fractures include deformities, abnormal movement, bony crepitus, and perception of friction between fracture fragments. Fractures that result in a deformed limb and severe pain often require immediate surgical intervention. In severe fractures, the circulation may become disrupted and lead to a loss of pulse distal to the fracture site. Fractures involving articulation sites may result in subsequent dysfunction of the joint.
Fractures can be classified into different categories based on the impact of the fracture. For example, they can be classified as open or closed, depending on the integrity of the skin tissue and mucosa; as complete or incomplete, depending on the severity of the fracture; or as stable or unstable in terms of displacement, angulation, and shortening. Fractures can also be described as traumatic or nontraumatic, the latter more commonly seen as a pathologic fracture. Traumatic fractures are seen more frequently in clinical practice than nontraumatic fractures.
Radiographic examination should include anteroposterior (AP) and lateral views of the fractured bone, along with the nearest joint. Some fractures require additional radiographic views, such as AP and oblique views for metacarpus and metatarsus, lateral and axial views for calcaneus, and AP and ulnar views for scaphoid deviations. Sometimes, if the injury is difficult to determine, comparison views of the contralateral uninvolved side will be helpful in reaching an accurate diagnosis. In cases with a clinically suspected fracture and negative or inconclusive findings on initial radiography, a radiographic examination should be repeated 2 weeks later, when the fracture line will emerge as healed fragments, as seen in carpal scaphoid fractures. For fractures adjacent to a joint or a complex anatomic structure, as X-ray examination provides limited information, computed tomography (CT) or magnetic resonance imaging (MRI) is therefore highly recommended to provide a clear depiction of the fracture.
The overall principles of fracture management are: restoration of anatomy, stable fracture fixation, and early mobilization of the limb and patient. Fracture reduction is a procedure to restore anatomy by positioning displaced bone fragments in the correct alignment, and to encourage healing and normal use of the bone and limb. Fixation is an attempt to maintain proper alignment of the fracture site until the bone becomes strong enough to support the union. Functional exercise must be started as soon as possible, to restore the functional ability of muscle, tendon, and joint ligaments without compromising the fixation hardware.
Fracture Classification
To understand the injury mechanism, select proper treatment options, and compare the outcomes of different treatments regimes, it is important to have a system of fracture classification. Numerous fracture classification systems have been proposed in orthopaedics. A standardized and widely accepted fracture classification system would facilitate communication between physicians and assist documentation and research. For clinical relevance, it should reflect the complexity of treatment planning and have prognostic value for patient outcome. Maurice E. Müller indicated that a classification is useful only if it considers the severity of the bone lesion and serves as a basis for treatment and for evaluation of results. The AO classification is currently in use along with conventional classification. The latest version of the Müller AO classification was published in 1996 in the form of a supplement to Volume 10 of The Journal of Orthopaedics Trauma, where the classifications for the long bones, spine, and pelvis were comprehensive; however, smaller bones such as those of the hand and foot were listed only with numbers indicating location. The Müller AO classification has become widely accepted and applicable in practice not only because of the great impact the AO Foundation has had over the years in the field of orthopaedics, but also because of scientific validation of the classification system itself. The strength of Müller’s system is that it provides a framework within which a surgeon can recognize, identify, and describe long bone injuries. The Orthopaedic Trauma Association (OTA) has established its own classification system, with the AO system as a reference. Essentially, the OTA system added to the AO system by classifying those bones that were never classified in the AO system; this ultimately led to the formation of the AO/OTA system. The OTA published the latest version of fracture classification in December 2007 in a supplement to Volume 21 of Journal of Orthopaedics Trauma. The OTA adopted the AO system of classifying long bones, spine, and pelvis, and significantly revised the classification for the clavicle and scapula, foot and hand, and patella.
The AO Foundation should be mentioned whenever the AO fracture classification system is discussed. In 1958, a group of Swiss general and orthopaedic surgeons led by Maurice E. Müller, Martin Allgower, and Hands Willenegger established the AO Foundation. The AO “pioneers” proposed a method of absolute stability through compression between fracture fragments to achieve a goal of rigid internal fixation of fractures. This concept may be less than perfect by modern standards, but it caused a revolution in the treatment of fractures. The most important contribution of the AO Foundation is to promote these original principles, which not only are of great practical and scientific value but also can be continually refined and improved with use. Over the past 10 years, the AO principles of fracture management have evolved in various ways, and have begun to advance internal fixation methods. Today, 56 years after its establishment, the AO principles for operative fracture fixation and the bone-healing concept are accepted worldwide. As research in the biomechanics of fractures has advanced, the AO principles and the hardware for internal fixation have seen dramatic improvement, with emphasis shifting from strong internal fixation based on pure mechanics to fixation based on biomechanics. The latest AO principles stress the pathophysiology and biology of the bone-healing process rather than its mechanics.
The AO classification system adopted a five-element alphanumeric code to describe each fracture as the following: ■ ■-□ □.□. The first two elements of the alphanumeric code describe the location (bone segment), followed by an alphabetic character for the fracture type (A, B, C), and lastly two numbers for morphological characteristics of the fracture (group and subgroup), as seen in ▶ Fig. 1.1.
Fig. 1.1 AO classification of fractures.
Fig. 1.2 Principles of the AO/OTA classification of fractures. All bones are coded by numbers that indicate the anatomical location. (a) The Müller AO classification system. (b) The OTA classification system. (c) The new unified classification system.
Bones
The numeric coding for every bone is seen in ▶ Fig. 1.2. It should be noted that the ulna/radius and tibia/fibula are each considered one long bone pair.
Segments
Each long bone is divided into three segments (proximal, diaphysis, and distal) which are numbered 1 to 3. Due to the complexity of a distal fracture of the tibia/fibula, the ankle joint is listed separately as segment 4. The anatomic delineation of the segments, proximal and distal, is performed according to “Heim’s square” as shown in ▶ Fig. 1.3; a square whose lateral sides equal the maximum width of the epiphysis, and delineates the proximal and distal segments of each bone (except for 31 and 44).
Fig. 1.3 Delineation of the proximal and distal segments of a long bone (“Heim’s square”).
Fig. 1.5 Fracture types of the proximal and distal segments, and intra-articular fracture.
Types
Fractures are divided into three types and coded with the letters A, B, and C, indicating increasing severity.
• Diaphyseal fractures of the long bones (based on surface contact between the main fragments after the fracture is reduced) (▶ Fig. 1.4):
– Type A: simple fracture; there is 90% surface contact between the main fragments
– Type B: wedge fracture; there is minimal surface contact between the main fragments
– Type C: complex fracture; there is no surface contact between the main fragments
• Fractures of the proximal and distal segments (based on the involvement of the articular surface) (▶ Fig. 1.5):
– Type A: extra-articular (or nonarticular) fracture; the fracture line does not pass through the articular surface
– Type B: partial articular fracture; the fracture line passes through the articular surface, with a portion of it still connected to the diaphysis
– Type C: complete articular fracture; the fracture line passes through the articular surface and separates it completely from the diaphysis
Group and Subgroup
When fractures occur, they can be divided into groups based on morphologic features, once their location and fracture type are determined. Each group can then be further divided into subgroups, indicating increasing severity. The division of groups and subgroups varies at different segments of each bone, and will be discussed in detail in the corresponding chapters of this book. For clinical practice, division by group is sufficient for appropriate diagnosis and treatment, while division by subgroup would be needed for research investigation.
Epidemiological Investigation and Analysis of Traumatic Fractures Incidence in China
Traumatic injury is a major cause of global mortality and disability. Injuries also impose a substantial burden for China, being the fifth most common cause of death and resulting in more fatalities than diabetes and infectious disease. As we know, injury-related fractures constitute a major drain on health-care resources. In addition, the formulation/adjustment of relevant national policies and health works are based on the scientific analysis of the status of the fracture. However, national epidemiological data for fracture incidence rates are not investigated in our country. There is lack of epidemiology study on traumatic fractures in China based on population, incidence, and risk factor involved. Countries without such data must infer statistics based on results from other regions or some small sample size studies, which is highly problematic because of substantial variations in incidence rates. Therefore, China urgently needs to set up a database of traumatic fractures and elaborate the status and trauma mechanism, to provide scientific basis for disease prevention and treatment.
With a population in excess of 1.36 billion people, China is a vast country with substantial diversity in terms of economic development, cultural practices, health-care systems, climate, and topography. Moreover, the data of different grades of hospitals cannot be shared. It is difficult to carry out the epidemiological survey of fracture. The design of this study was on the basis of the Sixth Population Census data and strictly followed the principle of epidemiological design and sampling method. A representative variety of people were field investigated with multistage stratified cluster random sampling. Under strict quality control, 51,2187 effective questionnaires were got at last. We analyzed the population-weighted incidences of traumatic fracture by the sex, age, part of fracture, and injury mechanism. The risk factors of different people were identified with multiple logistic regression analysis, establishing the biggest fracture epidemiological database in the world.
Methods
Respondents
The respondents of this study are from China’s 31 provinces, autonomous regions, and municipalities (except Taiwan, Hong Kong, and Macao). All eligible members in the selected families who had been living in their current residence for 6 months or more were invited to participate in the study, and single-member households were also included in the survey.
Sampling Method
A method of multistage stratified cluster random sampling was used in this study. Eight provinces and municipalities (three from the east region, two from the middle, and three from the west) were initially selected by stratified random sampling. According to the data of the sixth population census got in 2010, suitable sample size of each province was sampled by probability-proportional-to-size sampling method (PPS). Cities and counties of the chosen province were divided into large city, mid-sized city, small city, and rural area by the region type, population size, and level of economic development (▶ Fig. 1.6).
The Content and Method of this Investigation
1. For the field survey, a standardized questionnaire was administered by trained research teams. This questionnaire sought information about demographic characteristics such as age, sex, Chinese ethnic nationality, marital status, occupation, and residence.
2. Individuals who had traumatic fractures of the trunk, arms, or legs between January 1 and December 31, 2014 then answered a more detailed questionnaire between January 19 and May 16, 2015 regarding the date, fracture site, and injury mechanism. Participants were asked to provide medical records of their fractures, including radiographs, diagnostic reports, and medical reports. When such information was unavailable, the survey team paid the individual participants to obtain new radiographs of their reported fracture sites at a local hospital.
Quality Control and Evaluation
1. Strengthen the leadership of quality control organizations: In order to strengthen quality control organization’s leadership and guarantee the quality of this survey, execution group, quality control team, expert advisory committee, and project office were put directly under the project leader (professor). A remarkable organizational chart can supply a better leadership, coordination, and guarantee the smooth conduct of the study.
2. Set up working team system of three-level quality control system:
a) National quality control team led by epidemiological expert was responsible for the quality control method, the unified survey methods and survey form, the training of investigator, on-the-spot guidance, and the quality control of investigation process.
b) Eight quality control teams were established (one per province), and quality controller was appointed in accordance with sampling, field survey, imaging test, and data management. The quality controller cooperated with national quality control team to complete the quality control, according to the project quality control standards and methods.
c) A specialized quality controller was responsible for quality control in every investigation point. This quality controller was under the leadership of the provincial quality control working group to do a good job of quality control of the site.
3. Repeated program demonstration: The quality control methods in the phases of sampling, questionnaire survey, radiological examination, and data cleaning were determined. In order to ensure the quality of the investigation, we invited professor Derek Smith from James Cook University Australia, professors Guang Zeng and Ruotao Wang from the National Centers for Disease Control and Prevention, professor Qubing Shen from Nanjing Medical University, professor Changqing Zhang from Anhui Medical University, professors Dianwu Liu, Qingbao Tian, and Xu Liu from Hebei Medical University, professor Yichong Li from Beijing Medical University, and other famous epidemiologists in China to participate in our program. A pilot phase was undertaken to ameliorate this program in general in two urban communities and three administrative villages in Hebei Province.
4. Investigator training: All the investigators had to participate in the unified training and obtain the certificate at the project initiation. Each investigator had a clear understanding of the significance of the survey, principles of design, content of questionnaire, and method of inquiry.
Fig. 1.6 China National Fracture Study (CNFS) profile.
5. Establish supervision system of quality control: The supervision team supervised the national quality control section and subgroups of each province; the leading group invited specialist experts to supervise the implementation process of the project.
6. Enhance quality control of data input: Project office conducted centralized training of the data entry keyers, and the content of this training included the principle of questionnaire reorganization, method of input, and management of database. In order to ensure the quality of data input, each provincial unit conducted the data entry independently. All data were recorded on a written survey at each selected household and later entered into the EpiData 3.1 software program using the dual import program. Eight quality control teams were established (one per province), with 10% of all questionnaires collected in the field being sampled by the quality control team to check for omissions and errors. Participants reporting traumatic fractures had their clinical records, medical history, and radiographs interpreted by independent orthopaedic surgeons and radiologists to ensure the accuracy of the original diagnosis.
Data Statistics and Analysis
During the main sampling phase, 31 provinces (municipalities or autonomous regions) in mainland China were categorized into three regions (east, central, and west) according to socioeconomic development and climate, similar to the method used by the Chinese Statistical Bureau. Eight provinces and municipalities were initially selected by stratified random sampling: three from the east region (Hebei, Guangdong, Shanghai), two from the middle (Jilin, Hubei), and three from the west (Yunnan, Sichuan, Gansu) (▶ Fig. 1.7).
Twenty-four cities (large, mid-sized, and small cities), 41 streets and 112 community committees, and 24 counties, 67 towns, and 223 villages were selected from these 8 provinces were selected. A total of 535,836 questionnaires were collected. Following exclusions, 512,187 (96%) individuals participated in the China National Fracture Study (CNFS): 259,649 (51%) boys and men and 252,538 (49%) girls and women. The age and gender distributions of these patients in this national epidemiology of fracture survey are shown in ▶ Table 1.1.
The national epidemiological survey of fracture shows: 1,763 individuals (990 men and 773 women, mean age of 48.2 years [SD 18.9]) reported 1,833 traumatic fractures that had occurred in 2014. Among them were 117 (6%) children with 117 fractures, 1,303 (74%) young and middle-aged adults with 1,350 fractures, and 343 (19%) older individuals with 366 fractures. The population-weighted incidence rate of traumatic fractures of the trunk, arms, and legs in China was 3.21 per 1,000 population (▶ Table 1.2). It is estimated that about 4.4 million people in China suffered fractures of limbs and trunk in 2014.
Fig. 1.7 Distribution map of the selected provinces in this survey.
We also analyzed the population-weighted incidences of traumatic fracture by individual characteristics and regions. There was no significant difference in incidence between those of Han ethnicity and all other ethnicities combined, nor was there any significant difference according to geographical region or urbanization. Stratified by occupation, retired and unemployed individuals had the highest incidence rates (5.86 and 5.24 per 1,000 people, respectively), and the preschool and students had low incidence rates (1.76 and 0.79 per 1,000 people, respectively). According to education level, illiterate individuals had the highest incidence rate, 5.46 per 1,000 population (▶ Table 1.3).
The incidence of distal radial and ulnar fractures among all fractures is the highest in children (male 0.58%, female 0.51%). The incidence of tibiofibular fractures is the highest among middle-aged male (1.02%) and female (0.63%). The incidence of tibiofibular fractures is the highest among old male (1.30%). The incidence of distal ulnar and radius fracture is the highest among old female (1.72%; ▶ Table 1.4).
According to the causal mechanism, fracture patients are divided into six subgroups. Slip, trip, or fall is the most common injury mechanism in this investigation, accounting for 57.72% of all fractures. Traffic accidents, crushing injuries, and falls from heights accounted for 20.37%, 9.66%, and 20.37%, respectively. Analysis of risk factors shows that slip, trip, or fall is the most common injury mechanism among old women accounting for 83.03% of all fractures. The proportion of slip, trip, or fall is lower than 50% while the proportion of traffic accident is more than 25% in young and middle-aged males (▶ Table 1.5).
Five separate design-based multiple logistic regression models were constructed to explore the potential risk factors for traumatic fractures among children, young and middle-aged adults, and older people. In view of the complexity of the study’s sample design, weights were calculated for all analyses to reflect the entire population of China. Sample weighting comprised two components: sampling weight, which accounts for unequal probability of sample selection in each sampling stage, and poststratification weight, which harmonizes the sample structure of the survey with that of the standard Chinese population based on the most recent (2010) census. We specifically considered the age (5-year increments), sex, and geographical region simultaneously when undertaking the poststratification process. For 95% CIs, we estimated sampling error using Taylor series linearization, considering multistage sampling design. All statistical analyses were done with SAS (version 9.3) and Sudaan (version 11.01).
