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Ann Thorac Surg 2006;82:444-450
© 2006 The Society of Thoracic Surgeons

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Original Articles: General Thoracic

Sternal Fractures Occur Most Often in Old Cars to Seat-Belted Drivers Without Any Airbag Often With Concomitant Spinal Injuries: Clinical Findings and Technical Collision Variables Among 42,055 Crash Victims

^a Trauma Department, Medical School Hannover, Hannover, Germany
^b Accident Research Unit, Medical School Hannover, Hannover, Germany

Accepted for publication March 17, 2006.

^_* Address correspondence to Dr Knobloch, Trauma Department, Medical School Hannover, Carl-Neuberg-Str 1, Hannover 30625, Germany (Email: kknobi{at}yahoo.com).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Footnotes References

 
BACKGROUND: The incidence and treatment of sternal fractures caused by traffic accidents is of increasing importance to ensure best possible outcomes.

METHODS: Analysis of technical indicators of the collision, preclinical, and clinical data of patients with sternal fractures from 1985 to 2004 among 42,055 injured patients was assessed by an Accident Research Unit. Two time groups were categorized: 1985 to 1994 (group A) versus 1995 to 2004 (group B).

RESULTS: Of 42,055 patients, 267 (0.64%) suffered a sternal fracture. Regarding the vehicle type, the majority occurred after car accidents in 0.81% (251 of 31,183 patients), followed by 0.19% (5 of 2,633 patients) driving motorbike, and 0.11% (4 of 3,258 patients) driving a truck. Ninety-one percent wore a safety belt. Only 13% of all passengers suffering a sternal fracture had an airbag on board (33 of 255 car/trucks), with an airbag malfunction in 18%. The steering column was deformed in 39%, the steering wheel in 36%. Cars in the recent years were significantly older (group B, 7.67 ± 5 years, versus group A, 5.88 ± 5 years; p = 0.003). Cervical spine injuries are frequent (23% versus 22%), followed by multiple rib fractures (14% versus 12%) and lung contusions (12% versus 11%). We found 9 of 146 (6%) and 3 of 121 patients (3%) with heart contusion among the 267 sternal fractures. Maximal abbreviated injury scale score was 2.56 ± 1.3 versus 2.62 ± 1.3 (group A versus B, p = 0.349). Eighteen percent of patients were polytraumatized, with 11.2% dying at the scene, 2.3% in the hospital.

CONCLUSIONS: Sternal fractures occur most often in old cars to seat-belted drivers often without any airbag. Severe multiple rib fractures and lung contusion are concomitant injuries in more than 10% each, indicating the severity of the crash. Over a 20-year period, the injury severity encountered was not different, with 18% polytrauma patients suffering sternal fractures.

	Introduction

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Throughout the last decades, the rate of sternal fractures has increased owing to the introduction of seat belts [1] in cars and trucks as well as by further thorough clinical investigations in the emergency room using sternal sonography [2] and thoracic computed tomography [3] after traffic accidents. The role of airbags in reducing thoracic injuries is still debated controversially [4, 5].

Among 200 sternal fractures [6] with predominant traffic accidents (83%), 179 sternal fractures were located in the corpus sterni, 21 fractures in the manubrium sterni, and 11 in the xiphoid process. Another study supported the predominant location of the sternum body (83%), followed by 11% manubrium sterni and 6% xiphoid fractures among 100 patients [7]. Although 67% of these patients had isolated sternal fractures, one third had concomitant injuries. Rib fractures have been reported in 28% without any clarification regarding the number of ribs involved; cardiac injury as hemopericardium was encountered in 1%.

Fowler [8] found that 43% of sternal fractures were associated with a spinal injury. Other reports are limited owing to small sample groups, with one study of blunt trauma by Hills and colleagues [9] reporting that 5 of 27 patients with thoracic spine fractures had associated sternal fractures. Brookes and associates [10] showed 4.8% incidence of thoracic spine fractures in patients with sternal fractures. In a retrospective study between 1981 and 1987, Jones and associates [11] discovered 8 patients with indirect sternal fractures and concomitant fractures of the spine (5 thoracic and 3 lumbar).

The evidence regarding concomitant multiple rib fractures as well as lung contusion associated with sternal fractures is limited, however. Furthermore, to date, no thorough information is available regarding the circumstances of collisions causing a sternal fracture in traffic accidents. A technical analysis of the accident scene and the vehicle are pending. We therefore performed a thorough analysis of 20 years of accident research in a given regional area around Hannover in Germany with special emphasis regarding a technical accident analysis and attention as to clinical information and outcome of 267 patients suffering a sternal fracture among 42,055 injured and documented patients from 1985 to 2004 in a rural area around Hannover, Germany.

	Material and Methods

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In a statistical retrospective analysis of car collision files from January 1, 1985, to December 31, 2004, the incidence and mechanism of 267 sternal fractures among a total number of 42,055 injured patients involved in a vehicle accident were examined. Regarding the data used from this governmental database, the local ethical committee agreed to use the data without the individual consent of each patient; all data were used anonymously. The accident files had been prepared by scientific teams of the Accident Research Unit, which is run by the government. The teams had been informed through police dispatch and quickly arrived at the accident scenes in their own squad vehicles.

Since 1972, this local traffic accident research unit has collected prospective data for all reported traffic accidents in the rural area of Hannover, Germany [12]. The Accident and Research Unit is alarmed randomly on every third traffic accident with casualties regardless of the type of injury, number of injured patients, or severity of injuries. In addition to technical indications and an evaluation of the damage to the car, the files also included medical records outlining the types and severity of the injuries to the occupants. Seatbelt use was determined by history or assessment of the injury pattern. The first medical institution providing care for the injured people documented the diagnosis and types of injury. Pictures of the vehicular collision scene and the inside and outside of the cars and the relevant radiographs were collected by the staff of the Accident Research Unit.

Through this database, we were able to reconstruct the injury mechanisms in detail. This reconstruction was performed by the staff of the Accident Research Unit under the direction of the technical author (D.O.). The injury severity was classified with the abbreviated injury scale (AIS). These classifications were performed by the staff of the Accident Research Unit. To estimate the relevance of the improvements of the passive car safety and any change over time, accidents occurring from January 1, 1985, to December 31, 1994 (group A), and from January 1, 1995, and December 31, 2004 (group B) were compared.

Statistics
The data are presented as median and range for continuous variables or number and percentages for dichotomous variables. Median values were displayed for the percent change of parameters of microcirculation. Univariate analysis of categorical data was carried out using the ² or Fisher exact tests. Univariate analysis of metrical data was carried out by one-way analysis of variance, Student's t test, and the Mann-Whitney U test. Student's t test for paired samples was used for parametric, ordinal, and metrical variables of connected samples. The SPSS statistical software package 11.5 for Windows (SPSS, Chicago, Illinois) was used for statistical analysis.

	Results

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In all, 42,055 injured patients were included in this study from 1985 to 2004, where technical and medical information was available for assessment. Of these, 267 patients (0.64%) suffered a sternal fracture, and 41,788 patients were injured in a traffic accident and assessed without a sternal fracture. The distribution regarding the type of vehicle in sternal fractures is displayed in Table 1, demonstrating cars as the main vehicle involved in sternal fractures.

Seating Position of Patients Suffering Sternal Fractures
Of all car passengers, 65.4% were seated at the drivers' position, 26.7% at the front right position; 92.1% of all patients suffering a sternal fracture were therefore seated in the front seat.

Crash Vehicle Characteristics
Cars in the recent years between 1995 and 2004 were significantly older than those between 1985 and 1994 (7.67 ± 5 years, group B, versus 5.88 ± 5 years, group A; p = 0.003) with patients suffering sternal fractures. The majority of crashes were head-on crashes into another vehicle, followed by crashes by leaving the road, crossing-vehicle crashes, and rear-end crashes, as indicated in Table 2.

Polytrauma and Glasgow Coma Scale at the Scene Among Patients With Sternal Fractures
Forty-seven of 267 patients (17.6%) were classified as polytraumatized, where at least one or the combination of more injuries was supposed to be life threatening. Mean Glasgow Coma Scale (GCS) score was 13.1 ± 4 at the scene: 85.1% (n = 223) were GCS 11 to 15, 1.9% (n = 5) were GCS 6 to 10, and 13% (n = 34) were GCS less than 5.

Concomitant Injuries in 267 Patients With Sternal Fractures
The major concomitant injury associated with sternal fractures were bruises of soft tissue with 84 of 146 cases (57.5%) in 1985 to 1994 and 65 of 121 cases (53.7%) in 1995 to 2004 (Table 3). The second frequent concomitant injury to sternal fractures were spine injuries with 47 of 146 (32.2%) and 32 of 121 (26.5%), respectively. Regarding spine injuries, the cervical spine was most often involved (22.6% versus 22.3%) with distortions predominantly (Table 6). There was no change in the frequency of cervical spine injuries over the 20-year-observation period. Injuries of the thoracic spine followed the cervical spine injuries without any change over time (9.6% versus 8.3%), but thoracic spine injuries were almost all fractures. Lumbar spine injuries accounted for 4.8% and 1.7% as a concomitant injury to sternal fractures with lumbar fractures being often encountered. Following bruises and spinal injuries head injuries were found third as concomitant injury among the 267 sternal fractures (28% versus 18%), followed by multiple rib fractures (13.7% versus 12.4%) and lung contusions (12.3% versus 10.7%). We found 9 of 146 patients (6.2%, 1985 to 1994) and 3 of 121 patients (2.5%, 1995 to 2004) with myocardial contusions among the 267 sternal fractures.

The AIS score for thorax/shoulder injury was on average 2.47 ± 1.1. Categorized, 75% of all 267 patients suffering a sternal fracture were AIS 2 (Table 4). The AIS score for arms was 0.5 ± 0.8 versus 0.6 ± 0.8 (p = 0.312); and 97 of 146 patients (66.9%, 1985 to 1994) versus 75 of 121 patients (62%, 1995 to 2004) were rated AIS arms 0. The highest scores were AIS 3, with 9 of 146 (6.2%, 1985 to 1994) versus 4 of 121 (3.3%, 1995 to 2004). The AIS score for abdomen was 0.62 ± 1.5 in 1985 to 1994 and 0.29 ± 1 in 1995 to 2004, which was significantly decreased over time (p = 0.016); 81.4% (118 of 146 patients) versus 89.5% (102 of 121) were AIS 0. Whereas 12 of 146 (8.3%) were AIS 5 in 1985 to 1994, no one was AIS 5 in 1995 to 2004.

Procedures Performed in the Hospital
Of 267 patients with a sternal fracture, 195 (79.6%) had no operation at all during the hospital stay; 12.7% were operated on within the first 24 hours of admission, and 2% were operated on within the second to the seventh hospital day.

Hospital Stay and Intensive Care Unit Stay
Hospital stay was on average 9.7 ± 16.5 days, with 18.7% (n = 29) being on an outpatient basis, 11% (n = 17) admitted for 48 hours, 22.6% (n = 35) admitted from 3 to 5 days, 25.8% (n = 40) for 6 to 10 days, and 21.9% (n = 34) for more than 10 days. Among 121 patients, 5% (n = 6) were admitted to the intensive care unit for as long as 48 hours, 4.1% (n = 5) for 3 to 5 days, 1.7% (n = 2) for 6 to 10 days, and 5% (n = 6) for longer than 10 days (Table 5).

	Comment

Top Abstract Introduction Material and Methods Results Comment Footnotes References

 
Sternal fractures occur most often in old cars to seat-belted drivers. Severe multiple rib fractures and lung contusion are concomitant injuries in more than 10%, indicating the severity of the crash. Eighteen percent of all patients having a sternal fracture were classified as polytrauma patients, with an overall survival rate of 86.1%. We found that 11.2% die at the scene, and we found a 30-day mortality rate of 2.3%.

These data reveal that sternal fractures oftentimes are associated with concomitant significant injuries and a remarkable mortality rate. The high mortality rate found in our study may indicate that a sternal fracture could be interpreted as a marker lesion for a severe trauma. A recent autopsy study [13] after fatal falls from height found sternal fractures to be present in 25 cases involving heart injuries (76%), with 16% of these with multiple sternal fractures, and in only 5 cases without heart injuries (18%). It was concluded that the presence of severe sternal fractures can be used as an indicator of possible cardiac trauma, a conclusion supported by data of De Waele and colleagues [14] as well as by our high overall mortality rate.

Concomitant Injuries
The major concomitant injuries associated with sternal fractures in our study among 42,055 patients were bruises of soft tissue without any significant change over time within the 20 years of observation. The second frequent concomitant injury associated with sternal fractures were spine injuries in one third of all cases, with cervical whiplash injuries dominating, followed by thoracic and lumbar spine fractures. Others have reported a lower rate of whiplash injury (3%, Athanassiadi and coworkers [7], 15.5%; von Garrel and colleagues [6]) and fractures of the spine (4%, Athanassiadi data [7], 13%; von Garrel data [6]) with predominant thoracic spine fractures.

Concomitant spinal injuries are evident in case of sternal fractures, with certain implications for the spinal stability. In a cadaver study [15] to determine the amount of stability the rib cage imparts to the thoracic spine and to show the amount of stability lost by a sternal fracture, it was recently found that the rib cage and sternum provide 40% of the stability of the thoracic spine in flexion-extension, 35% of the stability in lateral bending, and 31% in axial rotation. An indirect flexion-compression type of sternal fracture decreases the stability of the thoracic spine by 42% in flexion-extension, 22% in lateral bending, and 15% in axial rotation. A sternal fracture decreases, therefore, the stability of the thorax dramatically; thus, a sternal fracture associated with a thoracic spine injury or a multiple rib fracture could be an unstable combination of injuries after accidents, as seen in a case of multiple thoracic spine wedge fractures and sternal fracture [16]. Multiple rib fractures have been reported in 10.5% by von Garrel and associates [6], which is somewhat the same occurrence rate as observed by us (1985 to 1994, 13.7%; 1995 to 2004, 12.4%). Regarding the 11.2% of patients dying at the scene with a sternal fracture, 39.1% had fatal thoracic injuries, 13% fatal head injuries, 8.7% fatal abdominal injuries, 34.8% died because of a combination as polytraumatized. Among 99 patients with sternal fractures, no significant increase of aortic ruptures has been reported by Sturm and colleagues [17]. However, currently no data regarding these preclinical dead patients have yet been reported after car crashes.

Treatment
Sternal fractures are most often treated conservatively with reasonable results regarding complete bony union and pain control [18]. Surgery is indicated in case of severe displacement, impairment due to severe pain limiting ventilation, or in case of nonunion of the sternum due to a pseudarthrosis sterni [19], oftentimes in a delayed fashion. Different operative techniques have been reported only in small series so far, such as circumferential wiring as in cardiac surgery or plates [20]. Based on our results, one cannot derive a straight and strong recommendation for a surgical approach to stabilize any sternal fracture occurring in traffic accidents. However, given the significant loss of thoracic spine stability after a sternal fracture, which itself is often associated with spinal injuries in one third of the cases, the restoration of the thoracic cage support the goal of sternal and spinal repair. Future outcome studies should focus this issue in more detail.

Limitations
Certain limitations have to be mentioned. The data collection was done by specially trained personal of the Accident Research Unit. Nevertheless, the data collected by the specialized personal might be influenced in that patients were transported and treated by different physicians in various hospitals in the Hannover region. It has been shown that diagnosis can be made best with computed tomography and ultrasonography rather that conventional roentgenography, but we cannot exclude from our data that patients might be undiagnosed regarding a sternal fracture. Furthermore, the important question of preclinical rescue time in case of polytraumatized patients might affect outcome, which has to be taken into account regarding the mortality rate. Based on the fact that the patients were transferred in different hospitals, the indications for sternal and spinal surgery might vary to some degree. However, this study among a patient group of 42,055 patients over a 20-year-period adds information regarding the effect of evolutional aspects of the vehicles as well as the distribution of concomitant injuries.

In conclusion, sternal fractures occur most often in old cars to seat-belted drivers in frontal crashes. Severe multiple rib fractures and lung contusion are concomitant injuries, each in more than 10%, indicating the severity of the car crash. Concomitant spinal injuries, occurring in one third of all cases, may deteriorate thoracic stability significantly, indicating the need for further emphasis on a thorough clinical examination in case of a sternal fracture.

	Footnotes

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^_* Both authors contributed equally to this work.

	References

Top Abstract Introduction Material and Methods Results Comment Footnotes References

 

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