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School of Medicine
January 2019
Demographics, Mechanism Of Injury, Injury
Severity, And Associated Injury Profiles Of Patients
With Femoral And Tibial Shaft Fractures: A Study
Of The National Trauma Databank
Nidharshan Anandasivam
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Recommended Citation
Anandasivam, Nidharshan, “Demographics, Mechanism Of Injury, Injury Severity, And Associated Injury Profiles Of Patients With
Femoral And Tibial Shaft Fractures: A Study Of The National Trauma Databank” (2019). Yale Medicine Thesis Digital Library. 3473.
https://elischolar.library.yale.edu/ymtdl/3473
1
Demographics, mechanism of injury, injury severity,
and associated injury profiles of patients with femoral
and tibial shaft fractures: a study of the National
Trauma Databank
A Thesis Submitted to the
Yale University School of Medicine
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Medicine
by
Nidharshan Subra Anandasivam
2019
2
Abstract
Introduction:
Traumatic injuries, such as fractures, are known for having defined associated
injury patterns. These can alter management and affect outcome if not promptly
recognized and managed. There are limited large-scale studies of demographics,
mechanism of injury, and injuries associated with femoral and tibial shaft fractures.
Objectives:
1. To determine the demographics, mechanism of injury, injury severity score, and
associated injuries in those with femoral and tibial shaft fractures in a large
national sample.
2. To determine the relationship between associated injuries and in-hospital
mortality.
Methods:
In two separate studies, patients in the 2011 and 2012 National Trauma Data Bank
were analyzed for demographics, mechanism of injury, injury severity score, and
associated injuries. Using ICD-9 diagnosis codes, the first study examined patients with
tibial shaft fractures, while the second study examined patients with femoral shaft
fractures. Descriptive analyses were performed for each of the cohorts, and multivariate
regression was utilized to understand relationships between associated injuries and in-
hospital mortality.
Results:
A total of 26,357 adult patients with femoral shaft fractures were analyzed. The
primary mechanisms of injury for these fractures were motor vehicle accidents and falls
(predominantly in those above 65 years of age). Generally, those with motor vehicle
accidents tended to be younger males with more associated injuries. Associated injuries
tended to concentrate based on proximity to the femoral shaft fracture. The highest
frequencies of associated injuries are the following: upper extremity (22.4%), thoracic
organ (19.5%), spine (16.8%), and intracranial (13.5%).
A total of 27,706 adult patients with tibial shaft fractures were analyzed. There
was a bimodal age distribution with peaks at 20 and 50 years of age. Falls were the most
common mechanism in the older age groups, while motor vehicle accidents dominated
the younger age groups. Overall, 59.6% of patients had at least one associated injury. The
highest frequencies of associated injuries are the following: upper extremity (16.3%),
spine (14.0%), thoracic organ (12.9%), and intracranial (11.3%). The presence of an
associated injury correlated with mortality (odds ratio = 12.9).
Conclusion:
Overall, the current study describes the cohorts of patients who sustain femoral
and tibial shaft fractures. The significant incidences and patterns associated with these
fractures are described. Furthermore, the significantly increased odds of mortality
associated with these injuries underscores the importance of recognizing and managing
associated injures in the trauma population.
3
Acknowledgements
This work would not have been possible without the generous contributions of
several individuals. First, I would like to extend a warm thank you to Dr. Jonathan Grauer
who has been an inspirational mentor to me and a formative part of my orthopaedic
education at the Yale School of Medicine. In addition, I thank my colleagues who are a
part of the clinical research team of Dr. Grauer. The collegial atmosphere created here is
like no other, and I am grateful for my opportunities to collaborate in the works of several
esteemed individuals, including Dr. Daniel Bohl and Dr. Andre Samuel.
I am also grateful for the mentorship of the Yale orthopaedics faculty including
Dr. Brian Smith and Dr. Michael Baumgaertner, as I really appreciate the support they
have provided during my time at the Yale School of Medicine.
4
Table of Contents
Abstract……………………………………………………………………………………..2
Acknowledgements………………………………………………………………………….3
Introduction to Thesis……………………………………………………………………….5
Sections (each containing an introduction, methods, results, discussion,
tables, figures, and appendices)
Section I: Analysis of Bony and Internal Organ Injuries…………………………..6
Associated with 26,357 Adult Femoral Shaft Fractures and
Their Impact on Mortality.
Section II: Tibial Shaft Fracture: A Large-scale Study Defining………………..28
the Injured Population and Associated Injuries
Conclusion to Thesis………………………………………………………………………52
References………………………………………………………………………………………….53
5
Introduction to Thesis
Femoral and tibial shaft fractures are relatively common injuries, with incidences
of 10.3 and 21.5, respectively, per 100,000 people per year.1,2 Furthermore, these injuries
are associated with several complications and significant costs.3,4 The average
incremental direct cost increase during the six months after a polytrauma with a long
bone fracture was estimated to be $39,041, with absenteeism and short-term disability
costs amounting to an additional $7,200.3
The orthopaedic trauma population can present with isolated injuries or defined
patterns of associated injuries. For example, there is a known correlation between clavicle
fractures and thoracic injuries, as well as a known correlation between calcaneus
fractures and lumbar spine injuries.5,6 By appreciating these known associations,
orthopaedic traumatologists are able to conduct a more focused evaluation for these
injuries.
Although associated injuries have been examined in patients with femoral and
tibial fractures, these studies are limited because they involve small sample sizes and do
not examine all associated bony and internal organ injuries. For example, Bennett et al.
focused on femoral shaft fractures and only associated ipsilateral femoral neck fractures
in a total of only 250 patients.7 As another example, Jung et al. examined 71 patients with
tibial shaft fractures to determine the frequency of concomitant ankle injuries.8 Although
these studies provide useful information about specific associated injuries, they lack the
statistical power to determine common associated injury patterns in patients with femoral
and tibial shaft fractures.
In light of this dearth of knowledge, the current thesis utilizes a large national
sample from the National Trauma Data Bank (NTDB) to examine associated injuries in
patients with femoral and tibial shaft fractures. The NTDB was constructed and is
currently maintained by the American College of Surgeons, and is a database that utilizes
registrar-abstracted data from over 900 US trauma centers and contains over five million
cases.9,10,11 Because of its volume and national representation, it was specifically chosen
to obtain an adequate study sample to analyze these fracture patients on a large scale.
Section 1 of this thesis examines demographics, mechanism of injury, injury
severity, associated injuries, and mortality in adult patients with femoral shaft fractures.
Section 2 examines demographics, mechanism of injury, injury severity, associated
injuries, and mortality in adult patients with tibial shaft fractures This information will be
essential in guiding the orthopaedic traumatologist and emergency medicine physician in
deciding when to have a low threshold for suspecting associated injuries.
6
Section I
Analysis of Bony and Internal Organ Injuries Associated with 26,357
Adult Femoral Shaft Fractures and Their Impact on Mortality.
This section was published as follows:
Anandasivam NS, Russo GS, Fischer JM, Samuel AM, Ondeck, NT,
Swallow MS, Chung SH, Bohl DD, Grauer JN. Analysis of Bony and
Internal Organ Injuries Associated with 26,357 Adult Femoral Shaft
Fractures and Their Impact on Mortality. Orthopedics 2017;40(3): 506-512.
PubMed ID: 28358976
Introduction
Femoral shaft fractures are common following major traumas, such as motor
vehicle accidents.1 In fact, a femoral shaft fracture occurs in approximately one in every
ten road injuries.2 A recent study estimated that the incidence of femoral shaft fractures is
about 1 to 2.9 million per year worldwide.2 The preferred treatment option of these severe
injuries is intramedullary nails.3-5 This surgery has been shown to have good healing and
recovery.6
Oftentimes fractures are not isolated injuries, and identifying associated injuries is
important for patient care, especially in the seriously injured patient.7 For given injuries,
there are often specific known patterns of associated injuries that can help direct patient
workups and management. For example, such patterns of associated injuries have been
described for calcaneus fractures (known association with lumbar fractures)8,9 and
clavicle fractures (known association with lung injuries).10 Along with comorbidities and
the patient’s general condition, associated injuries can impact the fracture management,
time to surgery, and outcomes.
7
Given that femoral shaft fractures typically result from major trauma, they are
frequently seen in polytrauma patients.11 However, to the best of our knowledge, no study
has identified the associated injury profile for femoral shaft fractures.
To address the lack of literature in this area, the current study sought to utilize the
National Trauma Data Bank (NTDB), the largest multi-center trauma repository, to
define a large cohort of patients with femoral shaft fractures and assess associated injury
profiles. Furthermore, in order to assess the impact of such associated injuries, the
correlations of such associated injuries with mortality were defined and compared to
other factors believed to affect mortality in this patient population.
8
Methods
The NTDB, created by the American College of Surgeons, is the largest national,
multi-center trauma database and includes registrar abstracted and administratively coded
data.12 It was established as a “repository of trauma related data voluntarily reported by
participating trauma centers.”13 The current study utilized the NTDB to identify adult (18
years of age and older) patients with femoral shaft fractures from 2011 and 2012. This
was based on International Classification of Disease, 9th Revision (ICD-9) codes for
either open or closed femoral shaft fractures (821.01, 821.11).
Patient age, gender, and comorbidities were characterized. Age was stratified into
the following groups: 18 – 39 years old, 40 – 64 years old, and 65+ years old. The
following comorbidities contained in NTDB were used to calculate a modified Charlson
Comorbidity Index (CCI): hypertension, alcoholism, diabetes, respiratory disease,
obesity, congestive heart failure, coronary artery disease, prior cerebrovascular accident,
liver disease, functionally dependent status, cancer, renal disease dementia, and
peripheral vascular disease. These variables were used to calculate CCI based on a
previously described algorithm.14 Of note, this modified CCI did not include an age
component, and any mention of “CCI” in this paper always refers to this modified
Charlson Comorbidity Index.
Mechanism of injury was then determined from ICD-9 e-codes. Patients were
categorized into “fall”, motor vehicle accident (“MVA”), or “other.” Patients with a fall
mechanism of injury were determined based on the following ICD-9 e-code ranges:
880.00 – 889.99, 833.00 – 835.99, 844.7, 881, 882, 917.5, 957.00 – 957.99, 968.1, 987.00
– 987.99. These primarily contained falls from standing height, ladders, buildings, and
9
sports. Patients with an MVA mechanism of injury were determined based on the
following ICD-9 e-code ranges: 800-826, 829-830, 840-845, 958.5, and 988.5. These
included patients who were involved in accidents as motor vehicle drivers, motorcyclists,
bicyclists, and pedestrians. All other e-codes were counted as “other”. These included
firearm and machinery-related injuries, among others.
Injury severity score (ISS) and mortality were data elements directly abstracted
from NTDB. Associated injuries were identified by ICD-9 codes. The diagnosis codes
that were used to identify associated bony and internal organ injuries are shown in
Appendices 1 and 2 (which have been used for a previously submitted associated injuries
study).15
For analysis, Adobe® Photoshop® CS3 was used to visually demonstrate the
associated injury frequencies by shadings on the skeleton and internal organ figures. The
range of shadings from white to black represented increasing injury frequency.
Multivariate logistic regression was used to determine the association of age, modified
CCI, and various associated injuries with mortality. All statistical analyses were
conducted using Stata® version 13.0 statistical software (StataCorp LP, College Station,
TX). All tests were two-tailed and a two-sided α level of 0.05 was taken as statistically
significant. A waiver for this study was issued by our institution’s Human Investigations
Committee.
10
Results
Patient demographics
For 2011 and 2012, the NTDB included 26,357 adult patients (16,717 males and
9,640 females) who had femoral shaft fractures. The age distribution of all adult femoral
shaft fracture patients is shown in Figure 1. The highest incidences were between the
ages of 18 and 39. The primary incidence peak was around 20 years of age. It was found
that the younger patients were predominantly male (10,448 males and 3,220 females in
the 18-39 age group), while the older patients were predominantly female (3,823 females
and 1,586 males in the 65+ age group). The middle group (ages 40-65) contained 4,683
males and 2,597 females.
Comorbidity index and injury severity
The medians of modified Charlson Comorbidity Index (CCI) for age categories
18-39, 40-64, and 65+ were all 0 (Table 1). However, comorbidity burden did generally
increase with age for this cohort.
The medians of Injury Severity Score (ISS), for these three categories were
between 10-19 for the first two, and between 0-9 for ages 65 and over (Table 2). This is
consistent with decreasing injury severity with increasing age for this cohort.
Mechanism of Injury
Mechanism of injury distribution by age group is shown in Figure 2. Younger
adults sustaining femur fractures and had predominantly been involved in MVAs, while
older adults had predominantly been involved in falls. The middle age category (40-64)
11
had a distribution more similar to the younger adults than the older adults, with MVAs
dominating the distribution.
Associated Injuries by Age
On average, younger adults (ages 18-39, who as a group had a predominate MVA
mechanism of injury) sustained higher frequencies of bony and internal organ associated
injuries across the board compared to the older adults (65+ years of age). The middle age
group (40-64 years of age) had associated injury frequencies more comparable to the
younger group (ages 18-39) than the older age group (age 65+ years old). Table 3
summarizes the associated injury frequencies by age category.
Figures 3 and 4 show the associated bony and internal organ injury profiles for the
total adult femoral shaft fracture population (18 years of age and older). The darker
shadings correspond to higher frequencies. Overall, among associated bony injuries, the
top three were tibia/fibula (20.5%), rib/sternum (19.1%), and non-shaft femur (18.9%, of
which 5.8% of the total cohort were femoral neck) fractures. Among associated internal
organ injuries, the top three were lung (18.9%), intracranial (13.5%), and liver (6.2%)
injuries. In general, the most common associated injuries were found in the thoracic area
(lungs and ribs) and in the lower extremity, especially near the femoral shaft fracture.
Effects of associated injuries on mortality
The overall mortality after femoral shaft fractures was 4.3%. Multivariate
analysis was used to determine the independent effects of age, modified CCI, and specific
associated injuries on mortality (Table 4).
12
With regards to age (while controlling for modified CCI and associated injuries),
compared to the 18-39 year old reference group, the 40-64 age group had a 1.92 times
increased odds of death and 65+ age group had a 4.29 increased odds of death. With
regards to modified CCI (while controlling for age and associated injuries), values of 2
and above all had increased odds of death compared to a modified CCI of zero. Both age
and modified CCI had a statistically significant correlation with mortality (p<0.05).
Lastly, the effects of associated injuries (by anatomic region) on the odds of death
were assessed (while controlling for age and modified CCI). These are shown in order of
increasing odds of mortality in Table 4. The associated injuries by anatomic area that
correlated with the greatest increase in odds of death were thoracic organ injuries
(adjusted odds ratio [AOR]=3.53), head injuries (AOR=2.93), abdominal organ injuries
(AOR=2.78), and pelvic fractures (AOR=1.80).
13
Discussion
Femoral shaft fractures are relatively common injuries that can result from high-
energy trauma. Noting that there can be associated injuries with femoral shaft fractures,
traditional teaching demands a thoughtful evaluation of the femoral neck, as the
incidence of this concomitant injury with femoral shaft fractures has been documented
anywhere from 2.5% to 9%.16-19 However, to our knowledge, there has been no reported
compelling data defining the likelihood of the overall spectrum of injuries that can be
associated with femoral shaft fractures.
The current study utilized the NTDB to identify a cohort of 26,357 adult femoral
shaft fractures patients. This is a much large sample size than those found in previous
femoral shaft studies.20,21 That said, the demographics of the identified cohort were in
line with the prior studies. For example, the majority of these femoral shaft fractures
occurred in patients between 18 and 39 years of age, which is comparable to previously
identified peak incidences between 15 and 24 years of age.21 As another example, the
identified cohort had a male-to-female ratio of 1.7:1, which is comparable to a previously
reported ratio of 1.4:1.20 Furthermore, consistent with what would be anticipated,
modified CCI was found to increase with age, and the predominant mechanism of injury
was found to transition from MVAs to falls with increasing age.
ISS gives us an overview of the severity of both the femoral shaft fracture and
associated injuries. In our study, ISS was found to be higher in younger patients than
older patients, consistent with the expected higher energy mechanisms and greater overall
injury level for younger patients.22 However, importantly, ISS alone does not define the
specific injuries associated with femoral shaft fractures, which was the focus of our work.
14
Specific associated injuries were evaluated and results are presented in tabular and
graphic formats in the current paper.
As an example of a specific associated injury, femoral neck fractures have been
reported to be associated with femoral shaft fractures with an incidence ranging from
2.5%-9%. This was confirmed by our analysis, which showed that 5.8% of femoral shaft
fractures had concomitant femoral neck fractures (completely in line with prior
reports).16,23 This is clearly of clinical importance for the treating surgeon, who should be
aware of this when managing patients with this combination of injuries.
From our analyses of bony injuries associated with femoral shaft fractures, it was
found that 38.1% had other lower extremity fractures (notably 20.5% had tibia/fibula
fractures), while 22.4% had upper extremity fractures. These high incidences suggest that
the extremities need to be thoroughly assessed for concomitant injuries and that there
should be a low threshold for imaging any area of question.
In addition, spinal injuries were relatively common in this population (16.8% of
patients with femoral shaft fractures had a concomitant spinal fracture). This is notable
since this incidence is comparable to that of patients with a known spine fracture who
also have a non-contiguous spinal fracture (reported ranges from 6.4% to 19%).24,25 For
patients with a spine fracture, conventional teaching promotes a low threshold to evaluate
for non-contiguous fractures. The same appears to be true for the need to evaluate for any
spine fracture in the femoral shaft fracture patient as well.
From our analysis of internal organ injuries associated with femoral shaft
fractures, it was found that thoracic injuries (19.5%), abdominal injuries (14.2%), and
intracranial injuries (13.5%) were quite common. This suggests a higher incidence than a
15
previous study that showed concomitant thoraco-abdominal injuries (10.9%) with
femoral shaft fractures.21 The high incidence of internal organ injuries identified
underscores the importance of the “pan scan” for patients with high energy injuries when
clinically appropriate to ensure that such associated internal organ injuries are not missed.
Finally, multivariate analysis showed that increasing age, increasing modified
CCI, and many of the associated injuries (most notably thoracic organ, head, and
abdominal organ injuries) had significant associations with higher risk of mortality. This
underscores the importance and impact of associated injuries, highlighting the clinical
importance of appreciating the associated injuries defined in the current study.
The major limitation of the current study deals with the data acquired from
NTDB. Since NTDB focuses on trauma patients, the studied population may be biased
towards femoral shaft fractures that occur in the setting of more severely injured patients
than the general population. Also, because NTDB is a “convenience sample,” the data
“may not be representative of all hospitals.”13 It is important to note that trauma victims
who die before transport to a hospital are not included in the NTDB, and so this study
does not represent those femoral shaft fractures that result in immediate death.13 Lastly,
although we gathered all femoral shaft fracture patients in the NTDB by ICD-9 diagnosis
coding, it is crucial that we emphasize the potential variability within this group, as
fracture classification was not available in the data set.
16
Tables
Table 1: Distribution of modified Charlson comorbidity index (CCI)
CCI
Age
18-39
40-64
65+
Total
0
93.7%
77.8%
56.5%
81.7%
1
5.6%
15.5%
25.4%
12.4%
2
0.6%
3.6%
10.0%
3.3%
3
0.1%
1.7%
4.2%
1.4%
>=4
0.0%
1.4%
3.9%
1.2%
Total
100%
100%
100%
100%
Note: Underlined values represent median CCI values for each age group.
17
Table 2: Distribution of Injury Severity Score (ISS)
ISS
Age
18-39
40-64
65+
Total
0-9
30.7%
41.0%
73.0%
42.2%
10-19
40.1%
33.9%
18.7%
34.0%
20-29
16.6%
14.5%
5.4%
13.7%
30+
12.6%
10.6%
3.0%
10.1%
Total
100%
100%
100%
100%
Note: Underlined values represent ISS ranges containing median values for each age
group.
18
Table 3: Percent Incidence of Injuries for Each Age Group
18-39
40-64
65+
Total
Head Injury
26.2
21.4
7.0
21.0
Skull Fracture
14.9
11.2
3.0
11.4
Intracranial Injury
16.5
14.3
5.0
13.5
Spinal Injury
18.1
20.9
7.7
16.8
Cervical Spine
5.4
6.5
2.9
5.2
Thoracic Spine
5.3
6.7
2.4
5.1
Lumbar Spine
9.5
11.6
3.8
8.9
Sacral Spine
4.6
4.8
1.4
4.0
Ribs/Sternum
18.9
26.5
9.7
19.1
Pelvic Fracture
15.6
15.2
5.8
13.5
Acetabulum
8.4
7.1
2.4
6.8
Pubis
5.9
6.2
2.7
5.4
Ilium
2.0
2.4
0.7
1.8
Ischium
0.5
0.6
0.3
0.5
Upper Extremity Fracture
25.8
24.5
10.8
22.4
Clavicle
4.2
4.2
1.6
3.7
Scapula
3.6
3.5
1.0
3.0
Humerus
5.8
6.6
3.5
5.5
Proximal Humerus
1.6
2.6
2.0
2.0
Humeral Shaft
2.7
2.5
0.8
2.2
Distal Humerus
1.4
1.5
0.7
1.3
Radius/Ulna
12.7
12.2
5.0
11.0
Proximal Radius/Ulna
2.9
2.7
0.8
2.4
Radial/Ulnar Shaft
4.3
3.6
1.1
3.4
Distal Radius/Ulna
6.1
6.4
3.0
5.6
Hand
7.3
5.9
2.3
5.8
Lower Extremity Fracture
38.0
47.1
26.2
38.1
Other Femur Fracture
15.1
25.6
19.5
18.9
Proximal Femur
9.5
16.1
10.5
11.6
Femoral Neck
5.8
6.8
4.5
5.8
Distal Femur
5.4
10.3
8.7
7.5
Patella
5.8
5.0
1.8
4.8
Tibia/Fibula Fracture
22.1
26.6
8.4
20.5
Proximal Tibia/Fibula
6.5
10.9
3.4
7.1
Tibial/Fibular Shaft
8.8
10.6
2.7
8.1
Ankle
8.5
9.8
3.3
7.8
Foot
10.1
10.2
2.4
8.6
Thoracic Organ Injury
25.3
18.6
6.0
19.5
Heart
0.8
1.2
0.4
0.8
19
Lung
24.7
17.8
5.7
18.9
Pneumothorax
15.1
12.6
4.3
12.2
Diaphragm
0.8
1.0
0.2
0.7
Abdominal Organ Injury
18.4
14.2
3.6
14.2
GI Tract
4.7
4.5
0.9
3.8
Liver
8.7
5.0
1.4
6.2
Spleen
7.9
5.5
1.1
5.9
Kidney
3.7
2.0
0.5
2.6
Pelvic Organ Injury
1.5
1.4
0.2
1.2
Note: All values are percentages.
20
Table 4: Multivariate Mortality Analysis
Outcome: Mortality
Adjusted
Odds Ratio
95% CI*
P-value
Age (reference=18-39)
<0.001 40-64 1.92 1.65-2.23 65+ 4.27 3.55-5.16 Modified CCI (reference=0) <0.001 1 0.70 0.56-0.88 2 1.45 1.04-2.03 3 2.88 1.95-4.27 4+ 2.69 1.78-4.07 Associated Injuries (in increasing order of odds of mortality) Lumbar Spine 0.72 0.60-0.86 <0.001 Lower Extremity 0.96 0.84-1.10 0.541 Thoracic Spine 1.11 0.90-1.36 0.342 Upper Extremity 1.30 1.13-1.50 <0.001 Cervical Spine 1.40 1.15-1.70 0.001 Pelvic Fracture 1.80 1.55-2.08 <0.001 Abdominal Organ 2.78 2.39-3.23 <0.001 Head 2.93 2.54-3.38 <0.001 Thoracic Organ 3.53 3.01-4.14 <0.001 * CI = Confidence Interval 21 Figures Figure Captions Figure 1: Distribution of ages of femoral shaft fracture patients by gender. Figure 2: Distribution of femoral shaft fracture patients by mechanism of injury and age groups. Figure 3: Schematic representation of percentages of adult (18 years and older) femoral shaft fracture patients with incidence of associated bony injuries in different regions of the skeleton. Darker shadings in grayscale correspond to higher frequencies of associated injuries. Figure 4: Schematic representation of percentages of adult (18 years and older) femoral shaft fracture patients with incidence of associated internal organ injuries in different regions of the body. Darker shadings in grayscale correspond to higher frequencies of associated injuries. 22 23 24
