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Editorial Manager(tm) for Annals of Emergency Medicine Manuscript Draft Manuscript Number: Title: Injury Patterns in Frontal Crashes: The Association between Knee-Thigh-Hip (KTH) and Serious Intra-abdominal Injury Article Type: Original Research Section/Category: Trauma Corresponding Author: Dr. Carol Conroy, MPH, PhD Corresponding Author's Institution: University of California at San Diego First Author: Jeanne Lee, MD Order of Authors: Jeanne Lee, MD; Carol Conroy, MPH, PhD; Raul Coimbra, MD, PhD, FACS; Gail Tominaga, MD; David B Hoyt, MD, FACS Abstract: Abstract Objective: Safety belts protect occupants in frontal impacts by slowing occupant deceleration and preventing the occupant from hitting interior vehicle components likely to cause injury. However, occupants moving forward during the impact may contact the safety belt webbing across their chest and abdomen. We hypothesized that if the occupant loaded their knee-thigh-hip (KTH) region with enough force to result in injury to this region---it might prevent compression (and injury) of their abdomen by the safety belt. Methods: Crash Injury Research and Engineering Network (CIREN) data were used to test the association between KTH and intra-abdominal injury. Chi square statistics and unadjusted Odds Ratios with % Confidence Limits (CL) were used to assess statistical significance. Logistic

regression models were used to further determine whether KTH injury was associated with serious intra-abdominal injury while controlling for other potential predictive factors. Results: Almost 0% of occupants sustained KTH injury or intra-abdominal injury, but only % had both KTH and serious intra-abdominal injury. Occupants with KTH injury were four times less likely (adjusted Odds Ratio=0., % CL 0., 0.) to have concomitant serious intra-abdominal injury caused by the safety belt. Conclusions: Although safety belts save lives and prevent serious injury, some occupants may sustain serious intra-abdominal injury when the abdomen is loaded by the safety belt during a frontal impact. We found occupants sustaining KTH injury are less likely to have serious intraabdominal injury caused by their safety belt. These results may be useful to motor vehicle manufacturers and others who design and test motor vehicle safety systems. Suggested Reviewers: Opposed Reviewers:

* Cover Letter UNIVERSITY OF CALIFORNIA, SAN DIEGO UCSD BERKELEY DAVIS IRVINE LOS ANGELES RIVERSIDE SAN DIEGO SAN FRANCISCO SANTA BARBARA SANTA CRUZ Mail address: Carol Conroy MPH, PhD Emergency Medical Services San Diego CIREN Program Mission Gorge Road Division of Trauma, Surgery & Critical Care San Diego, CA - Department of Surgery, School of Medicine Phone:.. Fax:..1 e-mail: carol.conroy@sdcounty.ca.gov October, 0 Dear Editor, Annals of Emergency Medicine: Thank you for considering this manuscript, Injury Patterns in Frontal Crashes: The Association between Knee-Thigh- Hip (KTH) and Serious Intra-abdominal Injury for publication. We wish to submit this study under the Original Research category. This study has not been presented, submitted, or published elsewhere. We are not aware of any conflicts of interest and there are no copyright constraints. Dr. Conroy provided statistical support for the analyses and interpretation of results. The corresponding author is: Dr. Carol Conroy County of San Diego Emergency Medical Services Mission Gorge Road San Diego, CA Telephone:.. Fax:..1 e-mail: carol.conroy@sdcounty.ca.gov Please do not hesitate to contact us if additional information is required. Kindest regards, Carol Conroy, MPH, PhD

* Title Page Injury Patterns in Frontal Crashes: The Association between Knee-Thigh-Hip (KTH) and Serious Intra-abdominal Injury Authors: Jeanne Lee, MD Division of Trauma, Burns & Critical Care, Department of Surgery, School of Medicine, University of California at San Diego, San Diego, California, USA Carol Conroy, MPH, PhD Division of Trauma, Burns & Critical Care, Department of Surgery, School of Medicine, University of California at San Diego, San Diego, California, USA Raul Coimbra, MD, PhD, FACS Division of Trauma, Burns & Critical Care, Department of Surgery, School of Medicine, University of California at San Diego, San Diego, California, USA Gail T. Tominaga, MD, FACS Scripps Memorial Hospital, La Jolla, California, USA David B. Hoyt, MD, FACS Department of Surgery, School of Medicine, University of California at Irvine, Orange, California, USA Word count:,

Reprints not available from the authors Corresponding author: Carol Conroy, MPH, PhD University of California, San Diego County of San Diego Emergency Medical Services Mission Gorge Road San Diego, CA Telephone:.. Fax:..1 carol.conroy@sdcounty.ca.gov Funding was provided by Department of Transportation/National Highway Safety Administration (USDOT/NHTSA) under Cooperative Agreement Number DTNH-0-H-001. Views expressed are those of the authors and do not represent the views of any of the sponsors or NHTSA. Key words: intra-abdominal injuries, KTH injuries, vehicle safety, motor vehicle crashes

* Abstract, Article, References 1 1 0 1 0 1 0 1 0 1 Abstract Objective: Safety belts protect occupants in frontal impacts by slowing occupant deceleration and preventing the occupant from hitting interior vehicle components likely to cause injury. However, occupants moving forward during the impact may contact the safety belt webbing across their chest and abdomen. We hypothesized that if the occupant loaded their knee-thigh-hip (KTH) region with enough force to result in injury to this region---it might prevent compression (and injury) of their abdomen by the safety belt. Methods: Crash Injury Research and Engineering Network (CIREN) data were used to test the association between KTH and intra-abdominal injury. Chi square statistics and unadjusted Odds Ratios with % Confidence Limits (CL) were used to assess statistical significance. Logistic regression models were used to further determine whether KTH injury was associated with serious intra-abdominal injury while controlling for other potential predictive factors. Results: Almost 0% of occupants sustained KTH injury or intra-abdominal injury, but only % had both KTH and serious intra-abdominal injury. Occupants with KTH injury were four times less likely (adjusted Odds Ratio=0., % CL 0., 0.) to have concomitant serious intra-abdominal injury caused by the safety belt. Conclusions: Although safety belts save lives and prevent serious injury, some occupants may sustain serious intra-abdominal injury when the abdomen is loaded by the safety belt during a frontal impact. We found occupants sustaining KTH injury are less likely to have serious intra-abdominal injury caused by their safety belt. These results may be useful to motor vehicle manufacturers and others who design and test motor vehicle safety systems. 1

1 0 1 0 1 0 1 0 1 Introduction Background Safety belts are designed to prevent serious injuries occurring to the head, thorax, and abdomen. The National Highway Traffic Safety Administration (NHTSA) estimates that in the last 0 years, safety belts have saved more lives than all other safety systems together 1. Frontal impacts result in rapid deceleration of the vehicle when it hits another vehicle or object. Safety belts protect occupants in frontal crashes by slowing occupant deceleration and preventing the occupant from hitting vehicle components likely to cause injury. However, occupants moving forward during the impact will contact the safety belt webbing across their chest (shoulder belt) and abdomen (lap belt) and this results in loading (energy transfer) to these regions. Importance Safety belts have previously been documented as a source of intra-abdominal injury,. Compression of the abdominal organs during loading by the safety belt may result in injury when the pressure within these organs is rapidly increased. Frontal impacts also are often associated with lower extremity injuries. Knee-Thigh-Hip (KTH) injuries may occur if the occupant strikes their knee against the lower instrument panel (knee bolster), steering wheel rim, or column -. The energy is then transmitted upwards through the femur into the hip joint,, possibly resulting in knee, femur, or acetabulum fractures. One study, using CIREN data, found that knee-thigh-hip (KTH) fractures were the most common lower extremity region injured in frontal crashes.

1 0 1 0 1 0 1 0 1 Another study based on National Automotive Sampling system (NASS) data, estimated over 0,000 KTH injuries occur every year during frontal motor vehicle crashes in the United States. Occupant characteristics, including age, gender, height, weight, and Body Mass Index (BMI), have been shown to be associated with lower extremity fracture severity,,,. Previous research looking at injury patterns, have considered the concomitant occurrence of lower extremity fractures and other injuries. Adili, et al. found that occupants with femur fractures had significantly more bowel injuries 1. A more recent study, found that only % of occupants with intra-abdominal injury had femur fractures and only % had knee injuries. However, it may be more pertinent to consider the entire knee-thigh-hip region together when assessing injury patterns. Goals of This Investigation We used data from the Crash Injury Research and Engineering Network (CIREN) to assess whether occupants with knee-thigh-hip (KTH) injuries were less likely to have serious (Abbreviated Injury Scale (AIS) >= ) intra-abdominal injury. We hypothesized that if an occupant loads their knee-thigh-hip with enough force to result in injury to this region, it prevents loading and compression of their abdomen by the lap portion of the safety belt thus preventing a more serious, life threatening intra-abdominal injury.

1 0 1 0 1 0 1 0 1 Methods Study Design A case-control study design was used to test the association between KTH injury and serious intra-abdominal injury. Selection of participants We used all available Crash Injury Research and Engineering Network (CIREN) data ( - 0) to identify occupants in frontal crashes. In crashes with multiple impacts, the frontal impact ranked as the most severe by the crash investigator was selected for study. The Collision Deformation Classification (CDC) is the standard used by crash investigators to categorize motor vehicle crashes on the basis of direction of force and other crash characteristics. We used the CDC to identify vehicles that were in frontal crashes with a Principal Direction of Force (PDOF) equal to, 1, or 1 o clock (using a clock face superimposed along the longitudinal axis of the vehicle with the center at the point of impact). Cases were further restricted to include only adult (> years old) drivers (sitting in the left outboard position of the first row) or passengers (sitting in the right front outboard position) who were wearing a safety belt.

1 0 1 0 1 0 1 0 1 Data collection and processing Multiple CIREN Centers throughout the United States participate in this multidisciplinary research program to study severe motor vehicle crashes and the resulting occupant injuries using a modified National Automotive Sampling System (NASS) protocol. Trauma centers and medical examiners identify potential cases for inclusion in the CIREN program. All trauma centers participating in CIREN have Institutional Review Board approval for the CIREN Program and each case is recruited using informed consent. Both occupants dying at the scene and those transported to Level One or Level Two trauma centers are included. Case selection criteria for frontal crashes are restricted to non-ejected occupants who are either wearing a safety belt or are protected by a deploying frontal airbag or both. The occupant must be in a vehicle that is no older than six to eight years from the crash date. Cases must also meet injury severity criteria. Specifically, cases must have at least one Abbreviated Injury Scale (AIS) >= injury or AIS injuries in two different AIS body regions to be included in the CIREN database. Medical data are obtained by personal interviews with occupants, medical chart review, and evaluation of diagnostic images including radiographs, Computed Tomography (CT) images, and Magnetic Resonance Imaging (MRI) scans. A NASS trained crash investigator does a detailed evaluation of the vehicle the occupant was in at the time of the crash and also collects measurements at the scene. This information is used to determine how the crash occurred and the vehicle dynamics during the crash. After all crash and medical data are obtained, a multidisciplinary team (trauma surgeons,

1 0 1 0 1 0 1 0 1 orthopedic surgeons, nurses, biomechanical engineers, and crash investigators) at each center reviews each case. This review allows each case to be discussed in detail to determine the occupant kinematics, how injury occurred during the crash, and the cause of each injury. This information regarding injury causation is unique to the CIREN database and provides information regarding which vehicle component causes a specific injury. An independent external quality control review of all data for each case is conducted after data entry is complete. Methods of measurement Occupant variables used in the analyses include age (years), gender, height (centimeters), weight (kilograms), Body Mass Index (BMI), co-morbidity, and seat position (driver or passenger). BMI (weight in kilograms (kg) divided by the height (in meters) squared) was used to classify occupants on the basis of weight scaled to their height. BMI is a numeric measure of stature that is considered both age and gender independent. The BMI categories (based on World Health Organization guidelines) used were: Underweight: <., Normal:. -., Overweight: -., Obese: => 0. AIS codes were assigned using medical records and diagnostic tests (e.g., radiographs, CT scans, MRI). Currently, CIREN injuries are coded using the 00 NASS version of the Abbreviated Injury Scale (AIS) ( edition) manual. The AIS is an anatomical injury scoring system ranging from minor (AIS 1), moderate (AIS ), serious (AIS ), severe (AIS ), critical (AIS ) to maximum (AIS ) severity. It was originally developed by the Association for the Advancement of Automotive Medicine (AAAM) as

1 0 1 0 1 0 1 0 1 a measure of severity for injuries sustained during motor vehicle crashes. For logistic regression analyses, we defined serious intra-abdominal injury as AIS >=. The Injury Severity Score (ISS) was used to provide an assessment of overall body damage. The ISS is the sum of the squares of the highest AIS codes in each of the three most severely injured AIS body regions. The definition of the knee-thigh-hip (KTH) body region was based on an anatomical classification consistent with other research on this region,. Proximal fibula or tibia fractures, femur fractures, patella fractures, knee ligament/meniscus injury, and acetabulum fractures were classified together as KTH injuries. These injuries were identified by either AIS codes or International Classification for Disease (ICD--CM) codes (for the acetabulum fractures because there is currently no AIS code specific for this injury in the CIREN database). Intra-abdominal injuries also were identified using AIS codes. Crash related variables used in the analysis were: Principal direction of force (PDOF), delta V (change in velocity at the time of impact), and frontal air bag deployment. If the delta V was not available, the Barrier Equivalent Speed (BES) was used. Delta V is commonly used as a measure of crash severity. Both delta V and BES for CIREN crashes are determined by WinSmash software. This software uses vehicle parameters and vehicle crush information to determine the change in velocity during impact. BES is calculated for multi-vehicle crashes when there is insufficient information regarding the second vehicle to calculate the delta V. BES is the speed at which the vehicle would

1 0 1 0 1 0 1 0 1 have had to impact a fixed barrier to produce the measured amount of external crush. The WinSmash software takes into account the stiffness of the vehicle based on the specific make and model. Primary data analysis Open (i.e., incomplete) CIREN cases were excluded from all analyses. Minor (AIS 1) injuries of the abdomen and KTH region were excluded from analyses. Occupants with missing data for specific variables were excluded only from analyses based on those variables. Therefore, the numbers may vary for some analyses. SAS software (Release.1.) was used to extract data from the CIREN Oracle database and for data analyses. Detailed case summaries were reviewed as necessary to validate data. Chi square statistics and unadjusted Odds Ratios (OR) with % Confidence Limits (CL) were used to assess statistical differences comparing occupants with KTH and intra-abdominal injuries and to test the association between KTH and serious intra-abdominal injuries. Differences were considered statistically significant based on a 0.0 level. Logistic regression models were used to further determine whether KTH injury was associated with serious (AIS >= ) intra-abdominal injury while controlling for other potential predictive factors or confounders (i.e., age, delta V, occupant stature, occupant seat position, age, and front airbag deployment). Adjusted odds ratios were used to explain the importance of the predictor variables (i.e., estimating the odds of an occupant

1 0 1 0 1 0 1 0 1 having serious intra-abdominal injury). The Hosmer-Lemshow Goodness-of-Fit (Chi square) was used to test the fit of the logistic regression model. A non-significant Chi square supports that the model adequately fit the data. Results Characteristics of study subjects There were 0 occupants in the CIREN database who met study criteria (adult drivers or front seat passengers who were wearing their safety belt and injured in a frontal crash). Figure 1 summarizes the frequency and percent of occupants meeting study criteria who had intra-abdominal injury, KTH injury, or both. Main results KTH injury decreases the odds of sustaining serious intra-abdominal injury caused by the safety belt (unadjusted OR=0., % CL=0., 0.). However, we found no significant protective effect of KTH when we considered intra-abdominal injury caused by other sources (e.g., steering wheel rim) (unadjusted OR=1., % CL=0.0,.). The study participants were divided into three groups for further analyses. These were: (1) Occupants with KTH injury but no serious intra-abdominal injury (n= 0); () Occupants with serious intra-abdominal injury but no KTH injury (n=); and, () Occupants with both KTH and serious intra-abdominal injury (n= ). Table 1 shows demographic, vehicle, and crash characteristics for all 0 occupants and the three groups. There were significant differences in age and Body Mass Index (BMI)

1 0 1 0 1 0 1 0 1 comparing the three groups. There were proportionally more drivers among those with isolated KTH injury. Overall body damage based on the mean Injury Severity Score (ISS) was significantly different for the three groups. Occupants with intra-abdominal injury, regardless of whether they had concomitant KTH injury, had greater overall body damage. Not surprisingly, crash severity was significantly greater (based on mean delta V) for occupants with both KTH and serious intra-abdominal injury compared to the other two groups. Vehicle model year also was statistically different. Vehicle curb weight differed significantly although most vehicles were in the medium range for each group. As expected, occupants without serious intra-abdominal injury (regardless of KTH injury status) were more likely to have a frontal airbag deploy during the impact. Multivariate analyses Table shows the models used to assess potential predictors of serious (AIS >= ) intraabdominal injury based on logistic regression modeling. Variables were included in the model if they were potential confounders or known a priori to be associated with serious injury during motor vehicle crashes. Occupant factors included age, Body Mass Index (BMI), and safety belt use. Height and weight also were included in a different model instead of BMI. Crash factors included in the model were delta V (as a proxy measure of crash severity) and whether the frontal airbag deployed. The adjusted Odds Ratio showed KTH injury was associated with a significant decrease in the odds of serious intra-abdominal injuries caused by the safety belt. Frontal airbag

1 0 1 0 1 0 1 0 1 deployment also protected the occupant from serious intra-abdominal injury (adjusted OR=0.). Logistic Regression models including height and weight, instead of BMI, were similar with neither height nor weight being independent predictive factors. Logistic regression also was used to predict the presence of serious intra-abdominal injury from other injury sources. We found that only the deployed frontal airbag (adjusted OR=0.) protected the occupant from serious intra-abdominal injury from sources other than the safety belt. Occupant position (adjusted OR=1.) was significantly associated with serious intra-abdominal injury caused by vehicle components other than the safety belt. Limitations CIREN based studies may have bias related to selection criteria because cases are not selected in a statistically random method. In general, CIREN cases are occupants (with at least AIS (serious)) injuries who are in severe motor vehicle crashes. However, selection criteria vary from year-to-year and some cases are enrolled as special interest cases. For example, occupants with potentially disabling lower extremity fractures have previously been included even if their injuries were only AIS (moderate). Additionally, some occupants with AIS injuries in different body regions (based on the AIS) have been included. Because our study focused on occupants sustaining serious (AIS >= ) intra-abdominal injury this limitation may not have resulted in biased results. However, some KTH injuries are only AIS (moderate) injuries and would not always be sufficient to include the occupant in the CIREN database. These occupants would need to have at least AIS injury in another body region to qualify. We did not differentiate between

1 0 1 0 1 0 1 0 1 occupants with or without thoracic injury in our study due to insufficient numbers. However, future research may be needed to determine whether concomitant thoracic injury influences the association between KTH injury and serious intra-abdominal injury. As the number of CIREN cases with refinements in safety systems increases, it would be important to reconsider these results based on whether the safety belt had load-limiters or pre-tensioners and whether the vehicle had knee bolster airbags. Possible bias also may occur when CIREN cases with missing data are excluded from analyses based on specific variables. Discussion This study, using CIREN data, showed both KTH injury and intra-abdominal injury were common following frontal crashes. Almost 0% of occupants sustained KTH injury or intra-abdominal injury, although only % had both KTH and serious intra-abdominal injury. We found that occupants with KTH injury were four times less likely to have concomitant serious (AIS >= ) intra-abdominal injury caused by the safety belt. This finding suggests the need for more in-depth bio-mechanical research to further explore this observational study result. It is outside the scope of this study to determine if the protective effect is due to the decreased force load on the abdomen or because there is less forward movement of the occupant when their knee is trapped against the lower instrument panel. If the protective effect is due to less force transmitted to the abdomen, then efforts to better protect the occupant from loading against the lap portion of the safety belt may help prevent serious intra-abdominal injury. 1

1 0 1 0 1 0 1 0 1 Safety belts are considered the primary safety system used by the occupant and should always be worn. Although unlikely, the current -point lap and shoulder safety belt design in most vehicles may cause intra-abdominal organ injury. Motor vehicle manufacturers have responded to the need to improve safety belt design by incorporating load-limiting devices and pre-tensioners in some vehicles. Pre-tensioners improve safety belt function by tightening slack in the belt during the impact. Other research has demonstrated that dual pre-tensioners decrease the occurrence of lower extremity injuries. Load-limiters are another example of a recent safety belt refinement that allows excess webbing to release in response to the deceleration during a crash. Loadlimiters are designed to allow the occupant s torso to move forward when a threshold load is exceeded. The impact of load-limiters on the lap portion of the safety belt across the abdomen is not well documented, but may play a role in decreasing the safety belt load on the abdomen. As crashes involving more recent model year vehicles equipped with these safety belt design features are included in the CIREN database, their association with intra-abdominal injuries can be studied further. Knee bolsters (typically metal plates covered by foam and plastic) were developed to absorb crash energy and help maintain the upright seated position of the occupant. However, as our study shows, KTH injuries may still occur during frontal crashes. Redesign of the knee bolster has previously been suggested as a way to decrease these injuries. Some recent model year vehicles are now being equipped with knee bolster airbags that may help absorb energy without causing injury while still maintaining the

1 0 1 0 1 0 1 0 1 upright position of the occupant. Previous research has also suggested revising the current Federal Motor Vehicle Safety Standard standard regarding kilo-neuton maximum femur loading criteria to help reduce the frequency of KTH injuries,. Our results indicate that it may be important to consider how any new crashworthiness feature (e.g., knee bolster airbags) directed towards a specific body region (KTH) may influence injury occurrence in other regions such as the abdomen. As more vehicles with knee bolster airbags are included in the CIREN database, it may be feasible to further study the effect of knee bolster airbags on KTH and serious intra-abdominal injury. Airbags are an important component of vehicle crashworthiness design and have been shown to help prevent injury, especially when the occupant is also restrained by a safety belt. Regardless of the source of intra-abdominal injury, this study confirms the important role that airbags play in preventing intra-abdominal injury during frontal impacts. Although hard contact with the lower instrument panel (knee bolster) may result in injury to the patella, femur, acetabulum, and other components of the knee-thigh-hip region, it may prevent a more serious, life threatening intra-abdominal injury. Serious intraabdominal injury presents a diagnostic challenge in the emergency department and may require operative intervention to prevent death, 0. We are not suggesting it is acceptable for occupants to sustain KTH injuries, which may be disabling and impact quality of life, to protect them against serious intra-abdominal injuries. Not only do KTH injuries occur frequently, but they also may require expensive rehabilitation and may

1 0 1 0 1 0 1 0 1 result in long term disability,. Clearly, the ultimate goal is to develop safer vehicles and crashworthiness features that protect the occupant from any serious or disabling injury. Our hope is that these study results may help promote a better understanding of the importance of limiting energy forces on all body regions to prevent injury during motor vehicle crashes.

1 0 1 0 1 0 1 0 1 References 1. NHTSA, 0. Lives saved by the federal motor vehicle safety standards and other vehicle safety technologies, 0-0. Washington DC. US DOT.. Campbell DJ, Sprouse LR, Smith LA, Kelley JE, Carr MG. Injuries in pediatric patients with seatbelt contusions. Am Surgeon. 0; : -.. Munshi IA, Patton W. A unique Pattern of Injury secondary to Seatbelt-related Blunt Abdominal Trauma. J Emerg Med. 0; :-.. Eid HO, Abu-Zidan FM. Biomechanics of road traffic collision injuries: A Clinician s Perspective. Singapore Med J. 0: : -00.. Chong M, Sochor M, Ipaktchi K, Brede C, Poster C, Wang S. The Interaction of Occupant Factors on the Lower Extremity Fractures in Frontal Collision of Motor Vehicle Crashes based on a Level 1 Trauma Center. J Trauma. 0; : -.. Huelke D, Compton CP, Compton TW. Lower Extremity Injuries in Frontal Crashes: Injuries, Locations, AIS, and Contacts. Soc Auto Eng. 1; Paper 0.. Kuppa S, Fessahaie O. An Overview of Knee-Thigh-Hip Injuries in Frontal Crashes in the United States. Proceedings th International Technical Conference on Experimental Safety Vehicles. Washington DC; 0. Paper.

1 0 1 0 1 0 1 0 1. Rupp JD, Schneider LW. Injuries to the Hip Joint in Frontal Motor-vehicle Crashes: Biomechanical and Real-World Perspectives. Ortho Clin N Am. 0; : -0.. Rupp J, Read MP, Van Ee CA. The tolerance of the human hip to dynamic knee loading. Stapp Car Crash J. 0; : 1-.. Laituri TR, Henry S, Sullivan K, Prasad P. Derivation and Theoretical Assessment of a Set of Biomechanics-based, AIS+ Risk Equations for the Knee-Thigh-Hip Complex. Stapp Car Crash J. 0; 0:-0.. Ore L, States J, Tanner B. Accident Investigation and Impairment Study of Lower Extremity Injury. Soc Auto Eng Paper.. Paper 00. 1. Adili A, Bhandari M, Lachowski RJ, Kwok DC, Dunlop RB. Organ Injuries associated with Femoral fractures: Implications for Severity of Injury in Motor Vehicle Collisions. J Trauma. ; :-1.. Gonzalez RP, Han M, Turk B, Letterman A. Screening for abdominal injury prior to emergent extra-abdominal trauma surgery: A Prospective Study. J Trauma. ; : -1.

1 0 1 0 1 0 1 0 1. NHTSA and CIREN Center Staffs. NHTSA Crash Injury Research and Engineering Network (CIREN) Program Report, 0. DOT HS 0. 0. http://wwwnrd.nhtsa.dot.gov/departments /nrd-0/ciren/ciren.html. Society of Automotive Engineers (SAE). Recommended Practice J, Collision Deformation Classification. 0. Soc Auto Eng.. National Center for Statistics and Analysis. National Highway Traffic Safety Administration. http://www-nrd.nhtsa.dot.gov/departments /nrd-0/ncsa/nass-html.. World Health Organization. Physical status: the use and interpretation of anthropometry. Geneva, Switzerland.. WHO Technical Report Series... Association for the Advancement of Automotive Medicine. The Abbreviated Injury Scale. Des Plaines, IL.. Association for the Advancement of Automotive Medicine.. Baker SP, O Neill B, Haddon W, Long WB,. The Injury Severity Score: a Method for Describing Patients with Multiple Injuries and Evaluating Emergency Care. J Trauma. ; : -.

1 0 1 0 1 0 1 0 1. ICD--CM: international classification of diseases, th revision; clinical modification. Los Angeles, CA: Practice Management Information Corporation (PMIC); 0.. Stuck SL, Fessahaie O. Comparison of Measured Velocity Change in Frontal Crash tests to NASS Computed Velocity Change. Soc Auto Eng Paper -0, Warrendale, PA... SAS Software Version.1 Cary, NC:.SAS Institute, Inc. Copyright 0-0.. Homer DW, Tabor S, Lemeshow S. The importance of assessing the fit of logistic regression models: A case study. AJPH. 1; 1: 0-.. Faure J, Couturier S, Page Y, Labrousse M. The Benefits of Double Pretension in Decreasing Knees and Lower Leg Injuries in Frontal Impacts. Proceedings th International Technical Conference on Experimental Safety Vehicles. 0. Lyon, France. Paper 0.. Brumbelow, ML, Baker BC, Nolan JM. Effects of Seat Belt Load Limiters on Driver Fatalities in Frontal Crashes of Passenger Cars. Insurance Institute for Highway Safety. 0. Arlington, VA. Paper 0-00.

1 0 1 0 1 0 1 0 1. Atkinson, PJ, Garcia, JJ, Altiero, NJ, and Haut, RC. The influence of impact interface on human knee injury: Implications for instrument panel design and the lower extremity injury criterion.. Proceedings 1st Step Car Crash Conference. Paper -. Society of Automotive Engineers, Warrendale, PA.. Soochow MR, Faust DP, Schneider LW, Wang S. Knee, Thigh, and Hip Injury Patterns for Drivers and Right Front Passengers in Frontal Impacts. 0. Detroit, MI. Soc Auto Eng 0-01-0. World Congress & Exhibition.. Mayberry JC. Blunt Injury Mechanisms. In: Trunkey DD, Lewis FR. Current Therapy of trauma, th ed.. St. Louis, MO. Mosby: 0-.. Holbrook TL, Hoyt DB, Eastman AB, Sise MJ, Kennedy F, Velky T, Conroy C, Pacyna S, Erwin S. The Impact of Safety Belt Use on Liver Injuries in Motor Vehicle Crashes: The Importance of Motor Vehicle Safety Systems. J Trauma. 0; : 00-0. 0. Mackenzie EJ, Fowler CJ. Epidemiology. In: Moore EE, Feliciano DV, Mattox KL, editors. Trauma. th Edition. 0. NY, NY: McGraw-Hill : -.

1 0 1 0 1 0 1 0 1 Figure 1. Occupants with Knee-Thigh-Hip (KTH) and Intra-abdominal Injuries sustained in Frontal Impacts, CIREN -0 AIS >= N=0 (.%) Safety Belt source of injury N= (.%) Intra-abdominal Injury N= (.%) AIS < N= (.%) All Occupants N=0 No intraabdominal Injury N= (0.%) No intraabdominal Injury N=0 (.%) KTH injury N=1 (.%) Intra-abdominal Injury N= (0.%) AIS >= Intraabdominal Injury (.1%)

1 0 1 0 1 0 1 0 1 Table 1. Occupant, Vehicle, and Crash Characteristics of Occupants in Frontal Impacts, CIREN -0 All occupants Knee-Thigh- Hip Injury Only Serious (AIS >= ) Intraabdominal Injury Only KTH and Serious (AIS >= ) Intra-abdominal Injury Number (%) Number (%) Number (%) Number (%) 0 (0.0) (0.) (.) (.1) Occupant Characteristics Age (years)* - - 0-0- 0-0- 0+ 1 (.1) 1 (.) 1 (.) 1 (.) (.1) (.) (1.) (.1) 1 (.) (.1) 1 (.) (.) (.0) (.) (.) (.) (.0) (.) (.0) (.) (.) (.) 1 (.) (.) (.0) (.) (.) (.0) Male Gender (1.) (.) (.) (.) Height (centimeters) Mean, standard deviation, range,, - 0, 1, - 0,, - 1,., - Weight (kilograms) Mean, median, range 1,, -,, 1 -,, -,, -

1 0 1 0 1 0 1 0 1 Body Mass Index (BMI)* Underweight/Normal Overweight Obese (.) (.0) (0.) (.) (.) (.0) (.) (.) (.) 1 (.) 1 (.) (.) Driver* (0.) 0 (.) (.) (.) Injury Severity Score (ISS)* Mean, median, range,, -, 1, -,, -,, - Vehicle and Crash Characteristics Delta V (km/hour)* <. >. Mean, median, range Vehicle model year* 0 00-0 Vehicle curb weight* Light (<) Medium (0 ) Heavy (> ) Mean, median, range (.) (.),, -1 (.) (.) (.) (.) (.) (.), 0, -0 1 (.) 1 (0.).1,., -1 (.) (.) 1 (.) (.) (.) (.) 1, 1, - (.) (.).,, -1 (1.) 0 (.) (.) (.) (.) 1 (.),, -0 (1.) (.1),, -1 (.) (.) (.) (.) (.1) (.) 0, 1, 00- Frontal Air Bag Deployed* 0 (.) (1.) (.1) (.1) *Statistically significant difference between occupants with KTH only, serious intra-abdominal injury only, or both (p < 0.0)

1 0 1 0 1 0 1 0 1 Table. Adjusted Odds Ratios predicting Serious (AIS >= ) Intra-abdominal Injury for Occupants in Frontal Impacts Independent variables Safety Belt Source All Sources Adjusted Odds Ratio % Confidence Interval Adjusted Odds Ratio % Confidence Interval KTH Injury 0.* 0., 0. 0. 0., 1.0 Deployed frontal airbag 0.* 0.0, 0. 0.0* 0., 0. Body Mass Index 0. 0., 1.0 0. 0., 1.0 Driver or Passenger 1. 0.,. 1.* 1., 1. Age 0. 0., 1.0 0. 0., 1.00 Gender 0. 0.0, 1.1 0. 0., 1. delta V 1.00 0., 1.0 1.0 1.01, 1.0 * Statistically significant Adjusted Odds Ratio

1 0 1 0 1 0 1 0 1 Acknowledgements Special thanks to the other San Diego County Trauma Center Directors and staff participating in the San Diego CIREN Program (Dr. Kennedy, Sharp Memorial Hospital; Dr. Sise, Scripps Mercy Hospital; Dr. Steele, Palomar Medical Center; Dr. Hilfiker, Rady s Children s Hospital and Health Center). The authors also thank Dr. Troy L. Holbrook (Epi-Soar Consulting, San Diego, California) for conducting preliminary analyses on the association between lower extremity fractures and intra-abdominal injuries. We also wish to thank all the other previous and current CIREN Centers who contributed data to the CIREN Program: (Mercedes-Benz CIREN Center, University of Alabama at Birmingham; William Lehman Injury Research Center, University of Miami, Miami, Florida; University of Maryland CIREN Center, Baltimore, Maryland; University of Michigan Program for Injury Research and Education, Ann Arbor, Michigan; Froedtert Hospital and Medical College of Wisconsin, Milwaukee; UMDNJ-New Jersey Medical School, Newark, NJ; Honda Inova Fairfax Hospital CIREN Center, Falls Church, VA; Harborview Injury and Research Center, Seattle WA; Children s National Medical Center, CIREN Center; The Children s Hospital of Philadelphia, Philadelphia, PA; Wake Forest University Health Sciences, Winston Salem, NC.) Also, thank you to Volpe National Transportation Systems Center, Cambridge, MA, and National Highway Traffic Safety Administration staff, Washington DC.

* Author Contributions Information Injury Patterns in Frontal Crashes: The association between Knee-Thigh-Hip (KTH) and Serious Intra-abdominal Injury Author contributions: RC, GT, and DH obtained research funding. DH conceived of the study hypothesis and reviewed the manuscript. JL and CC drafted the manuscript and take responsibility of the manuscript as a whole. CC edited and analyzed the data. RC and GT reviewed the manuscript.