Owen T. Hill

Rhabdomyolysis in the Us Active Duty Army, 2004–2006

PURPOSE Rhabdomyolysis (RM) is a skeletal muscle disorder resulting in severe cellular injury caused by vigorous physical activity and other systemic etiologies. RM is associated with significant morbidity, such as acute renal failure, and can be fatal. RM that occurs in the US Active Duty Army (ADA) results in time lost from training, deployment, and combat. We sought to systemically describe the epidemiology of ADA clinical RM by quantifying RM in terms of absolute numbers, examine rate trends, and identify soldiers at elevated risk. METHODS We used data from the Total Army Injury and Health Outcomes Database to calculate yearly RM rates in the overall ADA, as well as adjusted RM rates within soldier subpopulations for 2003-2006. RESULTS During this period, the absolute numbers of clinically diagnosed ADA RM ranged between 382 and 419 cases per year. Annual rates were 7-8 per 10,000, which is 300%-400% higher than the estimated US civilian population (2 per 10,000). In soldiers with a history of a prior heat injury, RM rates climbed to 52-86 per 10,000, a 7- to 11-fold increase. Increased RM rates were seen in soldiers who are male, African American, younger, less educated, and with a shorter length of service. Approximately 8% of yearly ADA RM cases resulted in acute renal failure, an estimate lower than that for the US civilian population. CONCLUSIONS Our findings suggest that rates of RM are higher in the ADA than in the US civilian population. Rates remained fairly stable; however, relative to other ADA soldiers, those with prior heat injury, who are African American, or who have a length of service of less than 90 d are at the highest risk for RM development.

Risk Factors for Soft Tissue Knee Injuries in Active Duty U.S. Army Soldiers, 2000–2005

BACKGROUND There is a scarcity of analytic research on active duty Army (ADA) knee injuries (KI), such as soft tissue knee injuries (STKI), which are the predominant ADA KI pattern. PURPOSE To quantify the independent adjusted association of significant ADA STKI risk factors, 2000-2005. MATERIALS/METHODS Using the Total Army Injury and Health Outcomes Database, we (1) captured absolute STKI numbers and rates (N = 83,323) and (2) developed regression models to determine significant STKI risk factors. Models included STKI overall and subcategories: meniscus, patella, anterior/posterior cruciate ligament, and medial/lateral cruciate ligament. RESULTS Eight risk factors significantly increased STKI. They are: (1) prior KI (within 2 years) (odds ratio [OR] 9.83, 95% confidence interval [CI] 9.67-10.00); (2) increasing length of service (OR 1.83, 95% CI 1.76-1.90); (3) increasing age (OR 1.57, 95% CI 1.50-1.65); (4) prior deployment (OR 1.39, 95% CI 1.36-1.41); (5) prior ankle injury (OR 1.16, 95% CI 1.14-1.19); (6) Infantry occupation (OR 1.12, 95% CI 1.04-1.21); (7) marital status (OR 1.10, 95% CI 1.08-1.12); (8) and prior hip injury (OR 1.08, 95% CI 1.03-1.12). MAJOR CONCLUSION Soldiers with a prior KI have nearly a 10-fold increased relative risk of developing a subsequent STKI.

Rates of Knee Injury in the U.S. Active Duty Army, 2000–2005

We sought to summarize knee injuries (KI) in the U.S. Active Duty Army (ADA) in terms of absolute numbers, examine current rate trends, and identify ADA who were at increased risk for experiencing a KI. We used the Total Army Injury and Health Outcomes Database (TAIHOD) to compute unadjusted and adjusted rates of KI, categorized by the Barell Matrix, within the ADA for the years 2000-2005. During this period, 21 to 25 per 1,000 ADA suffered from KI. The highest yearly rates were observed for knee dislocation and sprains/strains (31 per 1,000 ADA). In ADA with a history of a KI (within 2 years), rates increased nearly tenfold. Elevated KI rates were also seen in ADA with prior upper or lower leg injuries, those > 30 years of age, and those with a category IV Armed Forces Qualification Test score (lowest admissible in Army). ADA KI rates remained fairly stable throughout the study period. Relative to other ADA Soldiers, those with prior knee, upper leg, or lower leg injuries are at increased risk for subsequent KI.

Trends in overweight and obesity in soldiers entering the US Army, 1989-2012.

The US Army recruits new soldiers from an increasingly obese civilian population. The change in weight status at entry into the Army between 1989 and 2012 and the demographic characteristics associated with overweight/obesity at entry were examined.

BMI and Lower Extremity Injury in U.S. Army Soldiers, 2001–2011

INTRODUCTION Little data exist regarding the long-term impact of excess weight on lower extremity musculoskeletal injury/disorder (MID) in U.S. Army Soldiers. This prospective analysis examines the association between BMI of Soldiers at accession and risk of MID. METHODS A total of 736,608 Soldiers were followed from accession into the Army, 2001-2011. Data were analyzed January through March 2015. MID was categorized as any first incident lower extremity musculoskeletal injury/disorder, and secondarily, as first incident injury/disorder at a specific site (i.e., hips, upper legs/thighs, knees, lower legs/ankles, feet/toes). Multivariable-adjusted proportional hazards models estimated associations between BMI category at accession and MID risk. RESULTS During 15,678,743 person-months of follow-up, 411,413 cases of any first MID were documented (70,578 hip, 77,050 upper leg, 162,041 knee, 338,080 lower leg, and 100,935 foot injuries in secondary analyses). The overall MID rate was 2.62 per 100 person-months. Relative to Soldiers with normal BMI (18.5 to <25 kg/m(2)) at accession, those who were underweight (<18.5); overweight (25 to <30); or obese (≥30) had 7%, 11%, and 33% higher risk of MID, respectively, after adjustment. Risks were highest in Soldiers who were obese at accession, and lowest in those with a BMI of 21-23 kg/m(2). CONCLUSIONS Soldier BMI at accession has important implications for MID. A BMI of 21-23 kg/m(2) in newly accessing Soldiers was associated with the lowest risk of incident MID, suggesting that accession be limited to people within this range to reduce overall incidence of MID among service personnel.

Epidemiology of Ankle Sprains and the Risk of Separation From Service in US Army Soldiers

STUDY DESIGN Retrospective cohort study. OBJECTIVES To report the incidence rate of ankle sprains in active-duty soldiers and to examine if soldiers who sustain ankle sprain injuries are more likely to leave the Army than those who do not sustain an ankle sprain. BACKGROUND Ankle sprains are one of the most common musculoskeletal injuries in physically active people and have been identified as the most common foot or ankle injury in active-duty Army personnel, with a rate of 103 sprains per 1000 soldiers per year. METHODS Data were analyzed on the entire active-duty US Army population from 2000 to 2006 (n = 1 014 042). A semi-parametric Cox proportional hazard model was built. RESULTS The overall incidence rate for ankle sprains was 45.14 per 1000 person-years. After controlling for length of service prior to the study period, soldiers who sustained a single ankle sprain were 27% less likely (relative risk ratio = 0.73; 95% confidence interval: 0.73, 0.75) to leave the service than soldiers who had no documented history of an ankle sprain. However, this trend toward increased service time no longer held true for those who sustained a recurrent sprain (risk ratio = 1.07; 95% confidence interval: 0.99, 1.15). CONCLUSION It appears that individuals who sustain an incident ankle sprain have longer time in service in the Army than those who do not sustain this injury. However, this trend toward longer service time no longer held true for soldiers who sustained a recurrent. LEVEL OF EVIDENCE Prognosis, level 2b.

Body Mass Index at Accession and Incident Cardiometabolic Risk Factors in US Army Soldiers, 2001-2011.

Individuals entering US Army service are generally young and healthy, but many are overweight, which may impact cardiometabolic risk despite physical activity and fitness requirements. This analysis examines the association between Soldiers’ BMI at accession and incident cardiometabolic risk factors (CRF) using longitudinal data from 731,014 Soldiers (17.0% female; age: 21.6 [3.9] years; BMI: 24.7 [3.8] kg/m2) who were assessed at Army accession, 2001–2011. CRF were defined as incident diagnoses through 2011, by ICD-9 code, of metabolic syndrome, glucose/insulin disorder, hypertension, dyslipidemia, or overweight/obesity (in those not initially overweight/obese). Multivariable-adjusted proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) between BMI categories at accession and CRF. Initially underweight (BMI<18.5 kg/m2) were 2.4% of Soldiers, 53.5% were normal weight (18.5−<25), 34.2% were overweight (25−<30), and 10.0% were obese (≥30). Mean age range at CRF diagnosis was 24–29 years old, with generally low CRF incidence: 228 with metabolic syndrome, 3,880 with a glucose/insulin disorder, 26,373 with hypertension, and 13,404 with dyslipidemia. Of the Soldiers who were not overweight or obese at accession, 5,361 were eventually diagnosed as overweight or obese. Relative to Soldiers who were normal weight at accession, those who were overweight or obese, respectively, had significantly higher risk of developing each CRF after multivariable adjustment (HR [95% CI]: metabolic syndrome: 4.13 [2.87–5.94], 13.36 [9.00–19.83]; glucose/insulin disorder: 1.39 [1.30–1.50], 2.76 [2.52–3.04]; hypertension: 1.85 [1.80–1.90], 3.31 [3.20–3.42]; dyslipidemia: 1.81 [1.75–1.89], 3.19 [3.04–3.35]). Risk of hypertension, dyslipidemia, and overweight/obesity in initially underweight Soldiers was 40%, 31%, and 79% lower, respectively, versus normal-weight Soldiers. BMI in early adulthood has important implications for cardiometabolic health, even within young, physically active populations.

Outcomes Associated With the Intrepid Dynamic Exoskeletal Orthosis (IDEO): A Systematic Review of the Literature

High-energy lower extremity trauma is a consequence of modern war and it is unclear if limb amputation or limb salvage enables greater recovery. To improve function in the injured extremity, a passive dynamic ankle-foot orthosis, the Intrepid Dynamic Exoskeletal Orthosis (IDEO), was introduced with specialized return to run (RTR) therapy program. Recent research suggests, these interventions may improve function and return to duty rates. This systematic literature review sought to rate available evidence and formulate empirical evidence statements (EESs), regarding outcomes associated with IDEO utilization. PubMed, CINAHL, and Google Scholar were systematically searched for pertinent articles. Articles were screened and rated. EESs were formulated based upon data and conclusions from included studies. Twelve studies were identified and rated. Subjects (n = 487, 6 females, mean age 29.4 year) were studied following limb trauma and salvage. All included studies had high external validity, whereas internal validity was mixed because of reporting issues. Moderate evidence supported development of four EESs regarding IDEO use with specialized therapy. Following high-energy lower extremity trauma and limb salvage, use of IDEO with RTR therapy can enable return to duty, return to recreation and physical activity, and decrease pain in some high-functioning patients. In higher functioning patients following limb salvage or trauma, IDEO use improved agility, power and speed, compared with no-brace or conventional bracing alternatives.

The Extremity Trauma and Amputation Center of Excellence: Overview of the Research and Surveillance Division

Congress authorized creation of the Extremity Trauma and Amputation Center of Excellence (EACE) as part of the 2009 National Defense Authorization Act. The legislation mandated the Department of Defense (DoD) and Department of Veterans Affairs (VA) to implement a comprehensive plan and strategy for the mitigation, treatment, and rehabilitation of traumatic extremity injuries and amputation. The EACE also was tasked with conducting clinically relevant research, fostering collaborations, and building partnerships across multidisciplinary international, federal, and academic networks to optimize the quality of life of service members and veterans who have sustained extremity trauma or amputations. To fulfill the mandate to conduct research, the EACE developed a Research and Surveillance Division that complements and collaborates with outstanding DoD, VA, and academic research programs across the globe. The EACE researchers have efforts in four key research focus areas relevant to extremity trauma and amputation: (1) Novel Rehabilitation Interventions, (2) Advanced Prosthetic and Orthotic Technologies, (3) Epidemiology and Surveillance, and (4) Medical and Surgical Innovations. This overview describes the EACE efforts to innovate, discover, and translate knowledge gleaned from collaborative research partnerships into clinical practice and policy.

Methodological challenges of using U.S. army administrative data to identify a cohort of basic combat trainees and descriptive analysis of trends in characteristics that are potential risk factors for training-related injury

OBJECTIVES Training-related injury is a threat to military health and readiness. Prevalence of potential risk factors for training-related injury can change with U.S. Army recruitment goals and may influence basic combat training (BCT) injury rates. This article describes challenges of using administrative data to identify a trainee cohort and describes demographic and training characteristics across the five BCT locations. METHODS Data from the Total Army Injury and Health Outcomes Database were used to identify a U.S. Army-wide cohort of first-time trainees from January 1, 2002 to September 30, 2007 and describe its characteristics. RESULTS The cohort includes 368,102 first-time trainees. The annual number starting BCT increased from 52,187 in 2002 to 68,808 in 2004. The proportion of males increased from 81.57% in 2003 to 83.84% in 2007. Mean (SD) age increased from 20.67 (3.55) years in 2002 to 20.94 (3.65) years in 2007. Mean (SD) body mass index increased from 24.53 (3.56) kg/m(2) in 2002 to 24.94 (3.84) kg/m(2) in 2006. Other characteristics fluctuated by year, including proportions of race/ethnicity, accession waivers, and confirmed graduates. CONCLUSIONS Fluctuations in trainee characteristics warrant further analysis of potential influence on BCT injury rates. For research uses, careful acquisition of administrative data is needed.