UK combat casualties see improved survival 2003-2012

Improved survival in UK combat casualties from Iraq
and Afghanistan: 2003Y2012
Jowan G. Penn-Barwell, MB ChB, Stuart A.G. Roberts, MB ChB, Jon R.B. Bishop, PhD,
and Mark J. Midwinter, CBE MD, Birmingham, United Kingdom
BACKGROUND: The United Kingdom was at war in Iraq and Afghanistan for more than a decade. Despite assertions regarding advances in
military trauma care during these wars, thus far, no studies have examined survival in UK troops during this sustained period of
combat. The aims of this study were to examine temporal changes of injury patterns defined by body region and survival in a
population of UK Military casualties between 2003 and 2012 in Iraq and Afghanistan.
METHODS: The UK Military Joint Theatre Trauma Registry was searched for all UK Military casualties (survivors and fatalities) sustained
on operations between January 1, 2003, and December 31, 2012. The New Injury Severity Score (NISS) was used to stratify
injury severity.
RESULTS: There were 2,792 UK Military casualties sustaining 14,252 separate injuries during the study period. There were 608 fatalities
(22% of all casualties). Approximately 70% of casualties injured in hostile action resulted from explosive munitions. The
extremities were the most commonly injured body region, involved in 43% of all injuries. The NISS associated with a
50% chance of survival rose each year from 32 in 2003 to 60 in 2012.
CONCLUSION: An improvement in survival during the 10-year period is demonstrated. A majority of wounds are a result of explosive
munitions, and the extremities are the most commonly affected body region. The authors recommend the development of more
sophisticated techniques for the measuring of the performance of combat casualty care systems to include measures of
morbidity and functional recovery as well as survival. (J Trauma Acute Care Surg. 2015;78: 00Y00. Copyright * 2015 Wolters
Kluwer Health, Inc. All rights reserved.)
LEVEL OF EVIDENCE: Level III.
KEY WORDS: Combat injuries; survival; war; injury severity.
The decade since the invasion of Iraq in 2003 (Operation
Telic) and the subsequent widening of operations in Af-
ghanistan (Operation Herrick) has resulted in a sustained level
of casualties not seen by the UK Military since the Korean War,
when the United Kingdom suffered 1,078 killed in action,
2,674 wounded, and 1,060 missing or taken prisoner.1
The UK Defence Medical Services (DMS) have taken a
deliberate approach to continuous performance improvement
by measurement, identification, and promulgation of effective
techniques and serially developing medical training to reflect
recent practice to improve trauma team preparation. This
process is collectively known as the Major Trauma Audit for
Clinical Effectiveness (MACE).2
During the decade of conflict, the UK DMS trauma
system, through a process of critical analyses of injuries and
outcomes, has evolved to include advanced ‘‘buddy-buddy’’
care, where fighting troops deliver first responder assistance
to a wounded colleague (including use of hemostatic dressings
and application of tourniquets); the prehospital deployment of
physicians delivering advanced resuscitation skills and decision
making to the point of wounding via retrieval helicopter (e.g.,
airway interventions, including rapid sequence induction and
intubation, transfusion of blood and fresh frozen plasma, ability
to perform thoracostomies); field hospital damage-control re-
suscitation and damage-control surgery protocols with measures
to recognize and mitigate against acute traumatic coagulopa-
thy; continuing intensive care in flight during repatriation to the
ORIGINAL ARTICLE
J Trauma Acute Care Surg
Volume 78, Number 5 1
Submitted: July 16, 2014, Revised: December 8, 2014, Accepted: January 12,
2015.
From the National Institute of Health Research (NIHR) Surgical Reconstruction &
Microbiological Research Centre (SRMRC) (J.P.B., M.J.M.); Royal Centre for
Defence Medicine and Royal College of Surgeons of England (S.A.G.R.)
University of Birmingham Clinical Trials Unit (J.R.B.B.).
On behalf of the Severe Lower Extremity Combat Trauma (SeLECT) Study Group:
Surg Lt Cdr J.G. Penn-Barwell, Surg Lt P.M. Bennett, Surg Lt Cdr C.A. Fries, Wg
Cdr J.M. Kendrew, Surg Capt M. Midwinter, Dr J. Bishop, Surg Capt R.F. Rickard,
Gp Capt I.D. Sargeant OBE, Prof Sir K. Porter KBE, Lt Col T. Rowlands, Lt Col A.
Mountain, Lt Col S. Jeffrey, Dr D. Mortiboy, Mr A.F.G. Groom, Surg Lt R. Myatt,
Lt Col M. Foster, Surg Capt SA Stapley.
The opinions or assertions contained herein are the private views of the authors and
are not to be construed as official or as reflecting the views of the Ministry of
Defence or Her Majesty’s Government.
The guarantor, on behalf of all the authors confirms that the manuscript is an honest,
accurate, and transparent account of the study being reported; that no important
aspects of the study have been omitted.
This work has previously been presented at the Combined Services Orthopaedic
Society Conference, Portmouth, United Kingdom, May 2013, and the Military
Health Systems Research Symposium, Fort Lauderdale, Florida, 2013.
Supplemental digital content is available for this article. Direct URL citations appear
in the printed text, and links to the digital files are provided in the HTML text of
this article on the journal’s Web site (www.jtrauma.com).
This is an open access article distributed under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivatives 3.0 License, where it is permissible
to download and share the work provided it is properly cited. The work cannot be
changed in any way or used commercially.
Address for reprints: Surg Lt Cdr Jowan Penn-Barwell Royal Navy, Academic De-
partment of Military Surgery and Trauma, Royal Centre for Defence Medicine
(RCDM), ICT Research Park Vincent Dr, Edgbaston, Birmingham B15 2SQ,
United Kingdom; email: Jowan@doctors.net.uk.
DOI: 10.1097/TA.0000000000000580

United Kingdom and integrated National Health Service de-
livered continuing care in a single center concentrating expe-
rience and expertise in contemporary injuries of combat.
This study sought to examine and report the temporal
changes in the injury patterns of UK Military casualties from
the conflicts of Iraq and Afghanistan during the last decade.
The secondary aim was to determine changes in survival fol-
lowing combat trauma during this period.
PATIENTS AND METHODS
The study was registered and approved by the Joint
Medical Command institutional review process. The UK Mili-
tary Joint Theatre Trauma Registry (JTTR) is an electronic
database of prospectively gathered information on all casualties
collected by trained trauma nurse coordinators working both in
deployed medical facilities in Iraq and Afghanistan and in the
Royal Centre for Defence Medicine (RCDM) in Birmingham,
United Kingdom. Information on those killed in action is pro-
vided following post mortem. All fatalities and traumatically
injured casualties that trigger a ‘‘trauma alert’’ on presentation to
deployed UK medical facilities or subsequently requiring return
to the UK following injury are included. The military definition
of casualty to encompass those both killed and injured is used
throughout this study. The database is managed by the Clinical
Information and Exploitation Team and administered by UK
Defence Statistics.2
The JTTR was searched for all UK casualties injured or
killed in Iraq and Afghanistan between 2003 and 2012. Injuries
were coded between 2003 and 2007 using the 1998 revision3
of
the Abbreviated Injury Scale (AIS), which was also used to
define the distribution of injuries about specific body regions.3
From 2007 to 2012, a military specific version of the AIS was
adopted, and the new weighted scoring was retrospectively
applied, so all injury data in this study were based on AIS 2005-
Military scores.5
New Injury Severity Scores were used as an
anatomic measure of injury.6
Personnel years at risk (PYAR) were calculated between
2008 and 2012 from UK Defence Statistics data. This was
based on computerized records of every day spent in either of
the two operational theaters by each service person; these
figures were summed for each calendar year and divided by 365
to give the PYAR, that is, the equivalent number of personnel
deployed for 12 months. For 2003 to 2007, detailed pay records
were not available; hence, the information was extrapolated
from the Ministry of Defence figures on troop levels contained
in memoranda to the UK Parliament and was regarded as less
precise.7,8
All PYAR figures exclude Special Forces because
possible Special Forces deployments are not released by the
Ministry of Defence.
Statistical Analysis
Data were grouped into calendar year cohorts according
to date of injury, and logistic regression was used to examine
relationships between year of injury and specific variables. In
all models, year of injury was coded as a continuous variable
on the range 1 to 10 corresponding to years 2003 to 2012.
In Model 1, multinomial log linear regression was used
to examine the distribution of total recorded injuries across
body regions by year of injury. The categorical outcome var-
iable, body region of injury, was coded with ‘‘abdomen’’set as
the reference level. Year of injury was modeled using a re-
stricted cubic spline to allow for flexible nonlinear relation-
ships between time and region of body injury. Model fitting of
this complex data was performed using a quasi-Newton opti-
mization method because of the potential for convergence
problems using standard optimization algorithms. Injuries to
body regions were assumed to be clustered by individual, and
SEs were estimated using a cluster bootstrap approach based
on 10,000 samples to account for this. In Model 2, New Injury
Severity Score (NISS) was included as a continuous variable as
both a main effect and as part of an interaction term with year of
injury. The interaction between year of injury and NISS was
statistically significant (p = 0.009). In each model, year of
injury was modeled using restricted cubic splines to allow for
flexible relationships. Model selection was based on Akaike
information criterion.9
Logistic regression was used for this
analysis, and fitting was performed using maximum likelihood
estimation. In Model 2, the reference level of the outcome
variable was coded as ‘‘fatality’’ (vs. ‘‘survival’’).
Analyses were conducted using R and the libraries:
stats,10
rms,11
effects,12
and nnet.13
RESULTS
The JTTR recorded 2,792 casualties injured or killed
during service in Iraq and Afghanistan. These consisted of all
those who killed or were injured following trauma. The mean
(SD) age was 25.7 (5.9), and 2,746 (99%) were male. Of these
casualties, 2,227 (80%) were a result of hostile action, with the
remaining 565 (20%) resulting from incidents not involving
enemy forces, for example, road traffic collisions. There were
608 fatalities (22% of all casualties) during this decade. The
distribution of casualties and fatalities throughout the 10-year
study period is shown in Table 1.
The most common mechanism of injury was caused by
explosive weapons, causing 1,592 casualties, representing 56%
of the total casualties and 65% of those from hostile action.
Gunshot wounds (GSWs) were the next most significant
mechanism of injury, being the cause of 684 casualties, 28% of
total casualties, and 31% of those from hostile action. Aside
from the increased proportion of GSWs in 2003 during the
invasion of Iraq, the relative proportion of casualties of GSW to
injuries from explosive weapons remained approximately
consistent as the conflicts in Iraq and Afghanistan evolved at
approximately 1:3.
There were 14,071 injuries sustained in the 2,792 casu-
alties over the study period, distributed across body regions as
shown in Table 2. The extremities were the most commonly
injured body regions, constituting 43% of all injuries. The
relative distributions of injuries affecting the abdomen, thorax,
spine, face, neck, and upper extremity remained relatively
constant during the study period.
Observed proportions of injuries by body region and year
of study were analyzed for temporal trend using the Cochran-
Armitage test. Although there is evidence that the proportion
of injuries by body region is associated with year (p G 1e-11),
the Cochrane-Armitage test is restricted to testing for linear
Volume 78, Number 5Penn-Barwell et al.
2 * 2015 Wolters Kluwer Health, Inc. All rights reserved.

monotonic trends. We wished to examine how the relative dis-
tribution of injuries across body regions has changed over time.
Models that included nonlinear functions of time provided an
improved fit to the data and were used for the analyses.
The relative risk ratio (RR) of sustaining an injury to the
head, relative to sustaining an injury to the abdomen (which
remained relatively constant), changed by a factor between 0.87
(95% confidence interval [CI], 0.78Y0.97) and 0.79 (95% CI,
0.68Y0.92) per year from 2006 to 2010. Relative risk ratios for
head injuries for all unit changes in year are presented in Sup-
plemental Digital Content 1 (http://links.lww.com/TA/A530).
The RR of sustaining an injury to the lower extremity, relative to
the abdomen, remained statistically indistinguishable from 0 be-
tween 2003 and 2010. The RRs changed by 1.44 (95% CI,
1.25Y1.68) from 2010 to 2011 and by 1.80 (95% CI, 1.41Y2.30)
from 2011 to 2012. RRs for lower extremity injuries for all unit
changes in year are presented in Supplemental Digital Content 2
(http://links.lww.com/TA/A531). The predicted probabilities from
Model 1 display the negative trend in the proportion of head
injuries (Supplemental Digital Content 3, http://links.lww.com/
TA/A532) and the positive trend in the proportion of lower
extremity injuries (Fig. 1) during the study period. Predicted
probabilities and corresponding 95% CIs for receiving an injury
to a specific body region for each year are presented in Supple-
mental Digital Content 4 (http://links.lww.com/TA/A533).
The odds of surviving a given injury severity was ex-
amined by analyzing NISS as a continuous variable (Model 2).
Analyses demonstrate a consistent improvement in survival
year-on-year during the decade of the study as shown in Figure
2. Model 2 can be used to estimate the NISS value associated
with a 50% probability of fatality for each year in the study
period. The estimated probabilities of survival were obtained
from Model 2 for every possible NISS value in each year. The
smallest NISS value with a corresponding 95% CI lower limit
that exceeds 50% was identified in each year. This 50% survival
NISS value rose from 32.5 in 2003 to 59.6 in 2012 (Fig. 3).
DISCUSSION
This study is the first that accurately quantifies a marked
improvement in survival following major trauma on UK com-
bat operations during the last decade. These findings provide
TABLE 2. Injured Regions as Defined by AIS System5
per Year
Total Injuries Head, % Face, % Neck, % Thorax, % Abdomen, % Spine, % Lower Extremity, % Upper Extremity, %
2003 320 43 (13) 25 (8) 15 (5) 78 (24) 41 (13) 15 (5) 59 (18) 25 (8)
2004 263 54 (21) 25 (10) 16 (6) 40 (15) 16 (6) 12 (5) 45 (17) 37 (14)
2005 241 13 (5) 19 (8) 20 (8) 27 (11) 26 (11) 10 (4) 50 (21) 58 (24)
2006 741 140 (19) 75 (10) 36 (5) 118 (16) 57 (8) 35 (5) 116 (16) 86 (12)
2007 1,964 284 (14) 224 (11) 65 (3) 228 (12) 179 (9) 91 (5) 490 (25) 321 (16)
2008 1,503 126 (8) 143 (10) 29 (2) 233 (16) 191 (13) 74 (5) 465 (31) 199 (13)
2009 3,320 282 (8) 422 (13) 95 (3) 414 (12) 470 (14) 225 (7) 842 (25) 501 (15)
2010 2,599 196 (8) 299 (12) 85 (3) 279 (11) 368 (14) 161 (6) 758 (29) 404 (16)
2011 1,787 140 (8) 194 (11) 45 (3) 156 (9) 177 (10) 75 (4) 649 (36) 326 (18)
2012 1,333 117 (9) 134 (10) 47 (4) 204 (15) 91 (7) 58 (4) 393 (29) 250 (19)
Total 14,071 1,395 (10) 1,560 (11) 453 (3) 1,777 (13) 1,616 (11) 756 (5) 3,867 (27) 2,207 (16)
More than one injury possible per region and casualty.
TABLE 1. Number of Fatalities and Injured Survivors per Year in Respective Conflicts
Iraq Afghanistan Total
Fatalities Injured Survivors PYAR CFR Fatalities Injured Survivors PYAR CFR Fatalities Injured Survivors PYAR CFR
2003 50 43 17,820 54 0 0 0 V 50 43 17,820 54
2004 22 47 9,583 32 1 0 900 100 23 47 10,483 33
2005 23 74 9,867 24 1 2 900 33 24 76 10,767 24
2006 29 57 7,200 34 39 52 5,800 43 68 109 13,000 38
2007 46 137 5,500 25 42 183 7,800 19 88 320 13,300 22
2008 4 26 5,723 13 51 188 7,790 21 55 214 13,513 20
2009 1 11 2,636 8 108 424 9,273 20 109 435 11,909 20
2010 0 0 963 V 104 418 10,694 20 104 418 11,657 20
2011 0 1 224 0 46 300 11,547 13 46 301 11,771 13
2012 0 0 0 V 41 221 11,488 16 41 221 11,488 16
Total 175 396 59,517 31 433 1,788 66,192 19 608 2184 125,708 22
CFR, case-fatality rate (expressed as a percentage).
Volume 78, Number 5 Penn-Barwell et al.
* 2015 Wolters Kluwer Health, Inc. All rights reserved. 3

unprecedented detail on the military casualties sustained by the
UK Armed Services on combat operations. The results dem-
onstrate that a majority of injuries from hostile action were
primarily from blast and fragmentation trauma resulting from
explosive devices, with the extremities being more likely than
any other region to be injured.
This study echoes the finding of our US colleagues that
support the belief that survival has improved over the conflict.14
However, previous attempts to quantify this improvement have
relied on the case-fatality rate, that is, the ratio of fatalities to
total casualties (killed and wounded). While we cite this figure
in Table 1, the authors regard this methodology as vulnerable to
multiple confounders, although it has the advantage of com-
parison with historical records, which is impossible with more
sophisticated techniques such as NISS.
It is important to acknowledge that although obviously
very important, mortality is a crude outcome measure. The UK
JTTR is investigating the possibility of measuring subsequent
disability, functional recovery, or patient-reported quality of life,
but this has inherent challenges, and no major trauma registry has
successfully incorporated this. There is limited evidence that ca-
sualties with severe injuries have returned to military service, and
thiscan be regarded as asurrogate marker offunctional recovery.15
The UK Military trauma system is not analogous to a
civilian trauma network. Aside from the initial invasion of Iraq
and special operations, the UK DMS did not deploy forward
surgical teams and instead relied on rapid transit from point of
wounding to a single field hospital in each operational theater.
The distinction between prehospital and hospital care has be-
come blurred with ‘‘hospital techniques,’’ that is, resuscitation
with blood (from 2008), intubation, and thoracostomies being
taken into the prehospital environment, with the overwhelming
majority of UK casualty retrieval helicopters carrying a doctor
capable of delivering these techniques with demonstrable im-
provements is survival.16
There is some distinction between the UK and US strat-
egies in this regard. By virtue of the larger area of operations of
US forces and resultant longer transit times, the US Military
trauma system deploys forward surgical teams that perform
initial damage-control procedures before transfer on to a field
hospital.17,18
A further distinction is that US helicopters trans-
ferring casualties from point of wounding to a forward surgical
team and onward to the field hospital are staffed by emergency
medical technicians and paramedics rather than physicians.16
The UK also returns patients direct to a single treatment facility
(the Royal Centre for Defence Medicine, Birmingham, United
Kingdom), whereas the US returns patients to three main US-
based hospitals after transit via the Landstuhl Regional Medical
Center (Rhineland-Palatinate, Germany).
The structured MACE approach to improving combat
casualty care is similar between the UK and US military
medical services. Both operate a JTTR that are sufficiently
aligned to allow coordinated joint research.16,19Y21
Figure 2. Plot of predicted probability of survival by NISS value
for each year. Shaded regions indicate the 95% CIs for the
predicted values obtained from the logistic regression
model summarized in Supplemental Digital Content 5,
http://links.lww.com/TA/A534 (Model 2).
Figure 1. Distribution of upper and lower extremity injuries
over time as proportion of total injuries. Shaded regions denote
95% CIs about the predicted values obtained from the
multinomial logistic regression (Model 1). Dots denote observed
proportions.
Figure 3. NISS values associated with a predicted 50% or
greater probability of survival predicted by the logistic
regression model summarized in Supplemental Digital Content 5,
http://links.lww.com/TA/A534 (Model 2).

The finding of this study that 70% of injuries resulting
from hostile action are from explosive weapons is entirely con-
sistent with the experience from the previous half century of
conflict. In modern warfare, the majority of injuries have simi-
larly resulted from explosive weapons, that is, landmines,
rockets, grenades, improvised explosive devices, and mortars as
demonstrated in Table 3. Our findings that the extremities are the
most likely body region to be injured are consistent with the
published literature from recent conflicts. Interestingly however,
extremity injuries form a relatively smaller proportion of all
injuries in this study (Table 3) compared with previous studies.
The management of polytrauma is complex, and when
casualties are injured on an overseas battlefield, this complexity
is increased significantly. In an already complex system of care,
pinpointing specific factors responsible for improved odds of
survival is challenging. From the presented results, it is not
possible to conclude which specific intervention and system
changes improved outcomes. We propose that the improvement
in survival demonstrated in this study is likely caused by the
aggregation of multiple summative improvements in tech-
niques across a system that adopts an ‘‘end-to-end’’ approach,
blurring the boundaries between point of wounding treatment,
prehospital en route care, receiving field hospital management,
and in-flight care during repatriation to continuing care in the
National Health Service.
If such results are to be achieved in the already fast im-
proving civilian trauma sector, no single or limited number of
advances are necessarily required or indeed expected in the near
future; rather, smaller cumulative improvements across the care
pathway could yield significant benefit in trauma outcomes.
Management of trauma in deployed UK Military medical
facilities is both consultant led and consultant delivered. With
the high tempo and unpredictability of military operations
during the last decade, consultants have gained experience
across multiple previous deployments. This knowledge is
further consolidated by the cyclical predeployment training
system through which clinicians returning from deployment
instruct their colleagues about to deploy via the bespoke
Military Operational Surgical Training (MOST) course run
with the assistance of the Royal College of Surgeons of En-
gland since 2007. This team-based training involves rehearsing
damage-control resuscitation and surgical techniques on ca-
daveric material and third-generation simulation mannequins
with the complete team of surgeons, anesthetists, emergency
physicians, and theater staff using current equipment and
protocols. It is possible that improvements in UK Military
trauma system performance achieved during the last 10 years
might be lost at the cessation of hostilities. The associated
decreased exposure to severe combat trauma may result in a
loss of some of the gains in survival demonstrated by this study
in the initial phases of subsequent conflicts.
There has been a significant improvement in the un-
derstanding of resuscitation with blood products during the last
10 years. The traditional concept of restoring a casualty’s he-
moglobin concentration by administering packed red blood
cells has been augmented by the administration of packed red
blood cells and fresh frozen plasma at approximately a 1:1 ratio
with early platelet administration.27
This strategy was improved
in the second half of the study period by massive transfusions
being guided by real-time, near-patient thromboelastography
(introduced from 2009), which has supplanted traditional
measures of ‘‘clotting,’’ allowing a tailored correction of
coagulopathy as part of the resuscitation phase.28
Large vol-
umes of blood products that are often required in catastrophic
exsanguinating hemorrhage are infused through high-volume
blood warmers at rates of up to 1 L/min. In addition, the
use of tranexamic acid has been shown to improve survival
following major trauma in both civilian and military studies
and is now routinely administered at the prehospital setting
within the military trauma system.19,29
These improvements in
care were directly resulting from the systematic MACE system
of analyzing practice and outcomes and rapidly altering doc-
trine and training accordingly as well as the ability to increase
the numbers available for analyses by pooling UK and US
JTTR data.16,19
Two or more anesthetists manage the casualty’s airway,
ventilation, anesthetic, and resuscitation. An operating de-
partment practitioner and a transfusion technician aid them.
Adapting these structures to the civilian setting will require
recognition that a team of doctors and technicians, rather than a
single doctor, is required for the anesthetic/resuscitation of the
severely injured patient in the way described.30
Helicopters have been routinely used by the military to
transport casualties from near point of wounding to surgical
facilities since the US-Vietnam conflict.31
During the conflicts
of the last decade, the UK Military developed a consultant-led
retrieval service that permits prehospital advanced inter-
ventions. This service has been shown to improve outcomes
when compared with nonYphysician-led conventional heli-
copter casualty retrieval in a selected group of patients with
Injury Severity Scores (ISSs) between 16 and 50.16
Personal protective equipment improved during the study
period and now offers protection to the head, eyes, and torso
as standard with personnel able to increase protection of
the neck, shoulders, thorax, groin, and thighs, depending on
perceived threat.
We would like to acknowledge the inherent weaknesses
of this study. First, although our results quantify improved
survival, an observational study of this type is clearly unable to
identify specific treatment or intervention responsible for this
effect. Second, data modeling is inherently imperfect. The high
shrinkage estimate of Model 2 implies that it does not dem-
onstrate significant overfitting; therefore, we are confident that
the model estimates are reliable.
TABLE 3. Relative Proportions of GSW to Blast Injuries, and
Proportion of Wounds Involving the Extremities
Current
study
US OIF/OEF
2001Y200522,23
Falklands24
US-
Vietnam25
US-
Korea26
GSW 30% 19% 29% 35% 31%
Blast 70% 81% 71% 65% 69%
n 2,276 1,416 48 13,050 111,716
Extremity
wounds
43% 54% 75% 61% 65%
n 14,252 6,609 233 17,726 111,716
OEF, Operation Enduring Freedom (US operations in Afghanistan); OIF, Operation
Iraqi Freedom (US-led invasion of Iraq 2003).

Third, we acknowledge that NISS is an anatomic mea-
sure only and might underestimate survival in a young and
physically robust military population. Both the UK and US
JTTR collect Trauma and Injury Severity Scores (TRISS),
which also incorporates physiologic variables; however, these
calculations are both based on coefficients for either blunt or
penetrating injury developed in the 1980s. There is currently no
coefficient for explosive injury, and given that this is the most
common injury mechanism in the registry, we regard this as a
significant limitation with the use of TRISS in this population.
The output from Model 2 in which NISS is incorporated
as a continuous variable is summarized in Supplemental Digital
Content 5 (http://links.lww.com/TA/A534). For this model, the
likelihood ratio test comparing the specified model against
the null model returned p values of less than 0.0001. The le
CessieYVan HouwelingenYCopasYHosmer goodness-of-fit test
statistics for Model 2 gives a p value of 0.314. In addition, this
model exhibits high discriminatory power with a C statistic of
0.982 and a shrinkage estimate of 0.9944.
This study shows a dramatic improvement in survival over
the 10 years, caring for UK casualties across the conflicts in
Iraq and Afghanistan. These results suggest that future military
trauma system performance metrics will need reconsideration to
be sensitive to change from the current performance level. More
sophisticated outcome measures the performance of combat
casualty care systems including morbidity and functional re-
covery are required to drive future improvement.
AUTHORSHIP
J.P.B. contributed in the study conception, study design, and manuscript
preparation S.A.G.R. contributed in the study design and manuscript
preparation J.R.B.B. contributed in the data analyses and graph prepa-
ration M.J.M. contributed in the study design and manuscript preparation
ACKNOWLEDGMENT
We acknowledge the hard work, dedication, and professionalism of all
the members of the Defence Medical Services and the National Health
Service that cared for the casualties described in this work. We also thank
the Clinical Information and Exploitation Team, Joint Medical Com-
mand, and UK Defence Statistics (Health) for collecting, collating, and
identifying appropriate data for this article. We also thank Brig. Tim
Hodgetts L/RAMC for his role in leading the development of the Joint
Theatre Trauma Register and Major Trauma Audit for Clinical Effec-
tiveness (MACE) process.
DISCLOSURE
J.P.B., S.A.R. and M.J.M. are serving officers in the Royal Navy. All authors
have completed the ICMJE uniform disclosure form and declare no
support from any organization for the submitted work; no financial
relationships with any organizations that might have an interest in the
submitted work in the previous 3 years; and no other relationships or
activities that could seem to have influenced the submitted work.
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