Characterization of Limited Duty Neuromusculoskeletal Injuries and Return to Duty Times in the U.S. Army During 2017-2018

Can a Psychologic Profile Predict Successful Return to Full Duty After a Musculoskeletal Injury?

BACKGROUND

Psychologic variables have been shown to have a strong relationship with recovery from injury and return to work or sports. The extent to which psychologic variables predict successful return to work in military settings is unknown.

QUESTIONS/PURPOSES

In a population of active duty soldiers, (1) can a psychologic profile determine the risk of injury after return to full duty? (2) Do psychologic profiles differ between soldiers sustaining injuries in the spine (thoracic or lumbar) and those with injuries to the lower extremities?

METHODS

Psychologic variables were assessed in soldiers returning to full, unrestricted duty after a recent musculoskeletal injury. Most of these were noncombat injuries from work-related physical activity. Between February 2016 and September 2017, 480 service members who were cleared to return to duty after musculoskeletal injuries (excluding those with high-velocity collisions, pregnancy, or amputation) were enrolled in a study that tracked subsequent injuries over the following year. Of those, we considered individuals with complete 12-month follow-up data as potentially eligible for analysis. Based on that, approximately 2% (8 of 480) were excluded because they did not complete baseline surveys, approximately 2% (11 of 480) were separated from the military during the follow-up period and had incomplete injury data, 1% (3 of 480) were excluded for not serving in the Army branch of the military, and approximately 2% (8 of 480) were excluded because they were not cleared to return to full duty. This resulted in 450 soldiers analyzed. Individuals were 86% (385 of 450) men; 74% (331 of 450) had lower extremity injuries and 26% (119 of 450) had spinal injuries, including soft tissue aches and pains (for example, strains and sprains), fractures, and disc herniations. Time-loss injury within 1 year was the primary outcome. While creating and validating a new prediction model using only psychological variables, 19 variables were assessed for nonlinearity, further factor selection was performed through elastic net, and models were internally validated through 2000 bootstrap iterations. Performance was deciphered through calibration, discrimination (area under the curve [AUC]), R 2 , and calibration in the large. Calibration assesses predicted versus actual risk by plotting the x and y intersection of these values; the more similar predicted risk values are to actual ones, the closer the slope of the line formed by the intersection points of all subjects is to equaling "1" (optimal calibration). Likewise, perfect discrimination (predicted injured versus actual injured) presents as an AUC of 1. Perfect calibration in the large would equal 0 because it represents the average predicted risk versus the actual outcome rate. Sensitivity analyses stratified groups by prior injury region (thoracic or lumbar spine and lower extremity) as well as the severity of injury by days of limited duty (moderate [7-27 days] and severe [28 + days]).

RESULTS

A model comprising primarily psychologic variables including depression, anxiety, kinesiophobia, fear avoidance beliefs, and mood did not adequately determine the risk of subsequent injury. The derived logistic prediction model had 18 variables: R 2 = 0.03, calibration = 0.63 (95% confidence interval [CI] 0.30 to 0.97), AUC = 0.62 (95% CI 0.52 to 0.72), and calibration in the large = -0.17. Baseline psychologic profiles between body regions differed only for depression severity (mean difference 1 [95% CI 0 to 1]; p = 0.04), with greater mean scores for spine injuries than for lower extremity injuries. Performance was poor for those with prior spine injuries compared with those with lower extremity injuries (AUC 0.50 [95% CI 0.42 to 0.58] and 0.63 [95% CI 0.57 to 0.69], respectively) and moderate versus severe injury during the 1-year follow-up (AUC 0.61 [95% CI 0.51 to 0.71] versus 0.64 [95% CI 0.64 to 0.74], respectively).

CONCLUSION

The psychologically based model poorly predicted subsequent injury. This study does not minimize the value of assessing the psychologic profiles of injured athletes, but rather suggests that models looking to identify injury risk should consider a multifactorial approach that also includes other nonpsychologic factors such as injury history. Future studies should refine the most important psychologic constructs that can add the most value and precision to multifactorial models aimed at identifying the risk of injury.

LEVEL OF EVIDENCE

Level III, prognostic study.

Overview of Navy Medicine's Limited Duty Patient Population

INTRODUCTION

U.S. Navy Medicine's temporary limited duty (LIMDU) program is the primary vehicle for managing the medical care and subsequent career outcomes of the ill and injured active component (AC) Sailors and Marines to ensure a medically ready force. Before the LIMDU Sailor and Marine Readiness Tracker System (SMART) came online, it was very difficult to examine LIMDU program administration metrics, patients' experiences during LIMDU, and their subsequent health and career outcomes. This study examined the LIMDU patient population's demographic, military career, and LIMDU-specific characteristics; identified characteristics that differed significantly by military service; and evaluated potentially modifiable factors associated with patient outcomes.

MATERIALS AND METHODS

A comprehensive SMART extract was used to identify all AC Sailors and Marines in active LIMDU status between October 1, 2016, and September 30, 2019. The SMART extract was merged with comprehensive administrative military personnel data by patient identifiers to create a longitudinal dataset and to conduct descriptive statistics, bivariate, and multivariate logistic regression analyses for this study. The sample included 26,591 AC Sailors and Marines with complete SMART and military personnel records who ended LIMDU on or before September 30, 2019.

RESULTS

During the study's 3-year period, Navy Medicine's rate of initial LIMDU entry by AC personnel increased each year from 2,041 in FY2017 to 2,424 in FY2019 per 100,000 personnel. At the time of initial entry, most LIMDU patients were male (76%), E4-E6 paygrades (54%), and had a single diagnosis recorded in their SMART records (66%). Pain patients (23%) constituted the largest diagnostic group, followed closely by musculoskeletal patients (23%), and then mental and behavioral health patients (20%). Variables that might reflect administration practices of the program did not differ significantly by service, suggesting good internal standardization of LIMDU administration across Navy Medicine. However, bivariate and multivariate analyses identified significant differences by service for almost all personal demographic, LIMDU-specific, and post-LIMDU military career sample characteristics measured at the last LIMDU close date or later. Study results suggested that the Navy and Marine Corps referred Sailors and Marines to start LIMDU for different medical reasons; to receive care from different military treatment facilities; to close LIMDU with different final actions; and to experience different post-LIMDU career outcomes.

CONCLUSION

Navy Medicine's SMART data is an important new resource for LIMDU program evaluation and population-level patient research, despite the data limitations and concerns identified and addressed by this study. The study results provide a baseline empirical understanding about the LIMDU patient population. Further research is necessary to interrogate the validity of these results over a longer period and to initiate other lines of inquiry. While the construction of the larger project's LIMDU patient population longitudinal dataset required a significant initial investment, future dividends from ongoing work are anticipated. Results derived from verified SMART data will benefit Navy Medicine, operational commands, and LIMDU patients alike by informing continuing efforts to improve patient health and career outcomes, identify and implement best clinical and administrative practices, and optimize force readiness.

Quantitative Analysis of Condition-based Limited Duty Duration of Musculoskeletal Conditions

INTRODUCTION

Musculoskeletal injuries affect nearly a million service members annually within the DoD, ultimately costing the U.S. Military half a billion dollars in direct patient costs and a significant loss to fleet readiness as many members are assigned days on limited duty (LIMDU) until they are deemed medically fit to return to duty (RTD). The new approach implemented by Navy Medicine in 2022, called "condition-based LIMDU," aims to drastically impact the time in which Sailors and Marines spend under a provider's care by assigning LIMDU days based on a standardized set of guidelines. This study provides a quantitative analysis on LIMDU duration, before and after implementation of the new condition-based LIMDU paradigm, to increase the understanding on the effectiveness and impact to fleet readiness and to assess the accuracy of suggested patient outcome timelines.

MATERIALS AND METHODS

De-identified and aggregated data were obtained from the Naval Medical Forces Atlantic's (NMFL) LIMDU Sailor and Marine Readiness Tracker System (SMART) program for all active duty military patients with ICD-10 code for musculoskeletal conditions. Only closed LIMDU cases in which active duty patients were given a final status of RTD were included. This study analyzed top musculoskeletal ICD-10 codes, optimum period (weeks), maximum period (weeks), and average days on LIMDU assigned at NMFL centers (medical and non-medical) for fiscal years 2021 (FY21) and 2022 (FY22). As well as descriptive statistics, t-test analysis was used to test if there was a difference between FY21 and FY22 and at what point the difference was no longer significant. Critical value method was then used to compare the top five most common musculoskeletal injuries to determine the accuracy of recommended LIMDU days to actual average assigned LIMDU per injury type. A color-coded compliance chart was created based on the results.

RESULTS

The results showed that for RTD population, the implementation of condition-based LIMDU significantly decreased average days assigned on LIMDU by 33%. In fact, there is a 35-day (5-week) difference before we can confidently say that the difference between FY21 and FY22 is no longer statistically significant. This significant decrease in LIMDU days, before and after implementation, is a trend consistent at both medical and non-medical NMFL centers; however, medical centers reported significantly more assigned LIMDU days for both years. The five most common injuries of FY21 and FY22 were low back pain, pain in shoulder, pain in hip, pain in knee, and pain in ankle. Before implementation, all five of these injury types far exceeded the recommended amount of LIMDU days. With the new condition-based LIMDU paradigm, the average assigned LIMDU days for pain in hip, pain in knee, and pain in ankle were all found to be in compliance with the recommended LIMDU days within a 99% confidence level.

CONCLUSIONS

The new condition-based LIMDU paradigm is successful in its aim to improve fleet readiness by returning Sailors and Marines to full duty status significantly faster. Regular assessment of ICD-10 diagnosis codes and update to recommended LIMDU assignment timelines should be conducted to maximize the effectiveness and accuracy for all medical conditions.

Timing of Outcomes and Expectations After Knee Surgery in the US Military: A Systematic Review

CONTEXT

Knee injury and subsequent surgery are widespread in the military setting. Associations between knee surgery and expected outcomes over time have not been consolidated and characterized systematically by procedure type across the body of literature, and the temporal expectations of these outcomes remain unclear.

OBJECTIVE

To summarize common postoperative follow-up times and associated outcomes that determine clinical or surgical failure in US service members after elective knee surgery.

DATA SOURCES

A systematic search was conducted with 3 bibliographic databases of published research reports from 2010 through 2021.

STUDY SELECTION

Studies in US military service members undergoing elective knee surgery, with a minimum of 1-year follow-up, and reporting on a functional/occupational outcome were included. Three reviewers screened all abstracts and full-text articles to determine eligibility.

STUDY DESIGN

Systematic review of longitudinal cohort studies.

LEVEL OF EVIDENCE

Level 2a.

DATA EXTRACTION

Extracted data included military demographics, surgical procedure variables, surveillance period, and outcome measures. The Newcastle-Ottawa Scale and the Grading of Recommendations Assessment, Development, and Evaluation approach were used to determine study quality and risk of bias.

RESULTS

A total of 22 studies (mean follow-up time of 40.7 months) met the inclusion criteria. For cruciate ligament repair, approximately one-third of patients required a second surgery or were medically separated from military service by 2 years from surgery; 100% were reinjured by 4 years, and 85% sustained a new injury within 5 years of surgery. For meniscal repair, nearly one-third of patients were medically separated, and half were placed on activity restrictions within 3 years of surgery. For articular cartilage repair, within 5 years, 39% of patients required a second surgery, 30% were placed on activity restrictions, and 36% were medically separated. For patellar repair, 37% of patients were medically separated and over half were placed on activity restrictions within 5 years.

CONCLUSION

Common knee surgeries can have long-term implications for military careers that may not become apparent with shorter follow-up periods (<2 years). When longer surveillance periods are used (eg, up to 5 years), additional surgical procedures are more common and the likelihood of being injured or medically separated from military service is higher.

Behavioral Health-related Reasons for Permanent Duty Limitation Profiles in the U.S. Army: Population-Based Data from 2017 to 2019

INTRODUCTION

When warfighters are unable to fight, they are formally removed from battle through temporary or permanent duty limitation profiles. This study uses a population-based data repository to characterize permanent behavioral health (BH)-related profiles across the army for an identified 2-year period. The absolute risk of a permanent duty limitation for specific BH categories was also examined.

MATERIALS AND METHODS

This study utilized a retrospective population-based design to identify all new BH diagnoses across the U.S. Army. Service members identified as having a new BH diagnosis were tracked for 12 months following the diagnosis to determine the recommendation of a permanent duty limitation profile.

RESULTS

From 2017 to 2018, 16% (n = 102,440) of service members received a "new" BH diagnosis. Less than 10% (9.5%; n = 9,752) of soldiers diagnosed with a BH disorder were issued a permanent BH-related duty profile within 12 months of the initial diagnosis. The absolute risk of a permanent profile was highest for soldiers diagnosed with a psychotic or delusional disorder (42%; n = 324) followed by dissociative or somatoform disorders (26%; n = 178) and eating disorders (23%; n = 108).

CONCLUSIONS

Military regulations dictating medical readiness and retention standards reflect both the standards required for mission readiness and a layer of medical protection for the service member. This study provides important information on the relationship between a new BH diagnosis and the likelihood that a service member will be referred for a retirement evaluation.

Surveillance is the first step to preventing injury among fast jet aircrew: results of a 2-year prospective cohort study

OBJECTIVES

Injury surveillance is imperative for injury prevention but difficult in military populations. Our objective was to accurately describe the pattern of musculoskeletal complaints among Royal Australian Air Force (RAAF) fast jet aircrew (FJA) using the validated University of Canberra Fast Jet Aircrew Musculoskeletal Questionnaire (UC-FJAMQ) over a 2-year period, and determine injury burden on the workforce and operational capability.

METHODS

306 RAAF FJA were monitored over a 2-year period (4×5 month reporting periods). Musculoskeletal complaint episodes (MCEs) were captured weekly using the UC-FJAMQ. Time loss episodes (TLEs) were captured from the UC-FJAMQ and injury registers completed by embedded physiotherapists. Cumulative severity and operational impact scores from the UC-FJAMQ, and time loss duration, were used to describe severity and calculate burden.

RESULTS

Mean weekly UC-FJAMQ response rate was 62%. 1012 MCEs were captured, with a mean weekly prevalence of 14.9% (95% CI 14.2-15.6), and incidence of 4.1 episodes per person-year (95% CI 3.9-4.4). A total of 145 TLEs were captured, with a mean 5-month prevalence of 12.4% (range 8.9-15.3%), and incidence of 0.37 episodes per person-year (95% CI 0.31-0.43). Spinal regions accounted for 81% of MCEs and contributed 76% and 85% of burden in relation to cumulative severity and operational impact, respectively. 57% of TLE burden came from spinal regions.

CONCLUSIONS

Despite modest weekly UC-FJAMQ response rates, musculoskeletal complaints were shown to be widespread and negatively impact operational capability. Future injury prevention efforts among FJA should focus on spinal regions, particularly the neck.

Predicting Postoperative Injury and Military Discharge Status After Knee Surgery in the US Army

BACKGROUND

Researchers have assessed postoperative injury or disability predictors in the military setting but typically focused on 1 type of surgical procedure at a time, used relatively small sample sizes, or investigated mixed cohorts with civilian populations.

PURPOSE

To identify the relationship between baseline variables and injury incidence or military discharge status in US Army soldiers after knee surgery.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Data were obtained from a repository containing personnel, performance, and medical records for all active-duty US Army soldiers. Multivariate logistic regressions were used to estimate the effects of numerous variables on postoperative injury or on medical discharge. Variable selection and model validation were conducted using the k-fold method.

RESULTS

A total of 7567 soldiers underwent knee surgery between 2017 and 2019. Meniscal procedures were the most common type of surgery (39%), and approximately 71% of the cohort had a postoperative injury. Significant predictors for sustaining a postoperative injury included having a previous nonknee injury (odds ratio [OR], 1.5), female sex (OR, 1.3), and Black race (OR, 1.2). Within 4 years after surgery, 17% of soldiers were discharged from the military because of knee-related disability. Significant predictors for discharge from duty included enlisted rank (OR, 2.3), recent fitness test failure (OR, 1.9), number of previous knee surgeries (OR, 1.7), and having a previous nonknee injury (OR, 1.6).

CONCLUSION

After knee surgery, nearly three-fourths of the soldiers in this cohort sustained a postoperative injury and almost one-fifth of soldiers were medically discharged from the military within 4 years. This study identified variables that indicate statistically increased risk for these postoperative outcomes and highlighted potentially modifiable factors.

Association of clinically-measured and dynamic ankle dorsiflexion assessed by markerless motion capture during the drop-jump task on landing biomechanics and risk of ankle injury in military personnel undergoing 10 weeks of physical training

OBJECTIVES

Determine the influence of clinically-measured maximum dorsiflexion, dynamic peak dorsiflexion and percent of clinically-measured maximum dorsiflexion used during a drop-jump task on landing biomechanics and risk of ankle injury in military personnel.

DESIGN

Prospective cohort study.

METHODS

672 participants (122 women) enrolled. The weightbearing lunge test assessed clinically-measured maximum dorsiflexion averaged across limbs (degrees). Markerless motion capture and force plates collected lower extremity kinematic and kinetic data during a drop-jump task. Percent of clinically-measured maximum dorsiflexion used during landing was calculated as dynamic peak dorsiflexion divided by clinically-measured value, multiplied by 100 (%). De-identified injury data was derived from military physical therapists. Simple linear regression analysis determined the association between dorsiflexion measures and landing biomechanics. Simple binary logistic regression analyses identified predictors of ankle injuries. Statistical significance was set at α = 0.05.

RESULTS

Eighteen participants sustained a traumatic ankle injury from a landing. All measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy with dynamic measures showing a higher predictive value. Protective factors against ankle injury included height (odds ratio: 0.818, p = 0.006) and weight (odds ratio: 0.824, p = 0.023) for women. Relative braking impulse was a risk factor for men (odds ratio: 1.890, p = 0.001).

CONCLUSIONS

Greater clinically-measured and dynamic measures of dorsiflexion were associated with movement patterns that countered the stiff-legged landing strategy but neither measure of dorsiflexion predicted ankle injury risk. Resultant biomechanics and anthropometrics influenced ankle injury risk to warrant recognition for injury prevention initiatives.

Diagnosed Behavioral Health Disorders, Related Duty Limitations, and Return to Duty Time in the U.S. Army: Population-based Data, from 2017 to 2019

INTRODUCTION

Less than half of service members with a behavioral health (BH) problem seek care. Soldiers may avoid seeking needed care because of concerns related to being placed on a duty-limiting profile and the related medical disclosures that follow.

MATERIALS AND METHODS

This study used a retrospective population-based design to identify all new BH diagnoses across the U.S. Army. The relationship between diagnostic category, risk of being issued a duty limitation (profile), and time until return to full duty was also examined. Data were collected from a comprehensive data repository that includes medical and administrative records. Soldiers with a new BH diagnosis were identified from 2017 to 2018. All duty limitation profiles within 12 months of initial diagnosis were identified.

RESULTS

Records for 614,107 unique service members were reviewed. This cohort was mostly male, enlisted, unmarried, and White. The mean age was 27.13 years (SD = 8.05). Soldiers with a new BH diagnosis accounted for 16.7% (n = 102,440) of the population. The most common diagnostic category was adjustment disorder (55.7%). About a quarter (23.6%) of soldiers with a new diagnosis were issued a related profile. The mean length of these profiles was 98.55 days (SD = 56.91). Of those with a new diagnosis, sex and race failed to have an effect on the odds of being placed on a profile. Overall, enlisted, unmarried, or younger soldiers had greater odds of being placed on a profile.

CONCLUSION

These data provide relevant information for both the service member who seeks care and command teams seeking readiness projections.

Evaluation of U.S. Army Soldiers wearing a back exosuit during a field training exercise

Back overuse injuries are a significant problem in the U.S. Army, responsible for nearly a quarter of musculoskeletal injuries. Back exosuits are wearable devices that relieve musculoskeletal strain, make lifting easier, and could potentially reduce Soldier overuse injuries. But published studies have not evaluated exosuits during realistic field operations to assess acceptability to Soldiers. We tested a back exosuit on field artillery Soldiers during a field training exercise. Afterward, Soldiers completed a survey to quantify their satisfaction, intent to use, and performance impact of the exosuit. Feedback was overwhelmingly positive: Approximately 90% of Soldiers reported that exosuits increased their ability to perform their duties, and 100% said that if the exosuit were further developed and made available to them, they would be likely to wear it. These numerical survey results indicated that exosuits can provide a practical and acceptable way to assist lifting and augment physical performance during realistic Army operations without interfering with other duties.

Musculoskeletal injuries in US Air Force Tactical Air Control Party trainees: an 11-year longitudinal retrospective cohort study and presentation of a musculoskeletal injury classification matrix

INTRODUCTION

Little is known of the epidemiology of musculoskeletal injuries (MSKIs) in US Air Force Special Warfare (AFSPECWAR) Tactical Air Control Party trainees. The purpose of this longitudinal retrospective cohort study was to (1) report the incidence and type of MSKI sustained by AFSPECWAR trainees during and up to 1 year following training, (2) identify factors associated with MSKI, and (3) develop and present the MSKI classification matrix used to identify and categorise injuries in this study.

METHODS

Trainees in the Tactical Air Control Party Apprentice Course between fiscal years 2010-2020 were included. Diagnosis codes were classified as MSKI or non-MSKI using a classification matrix. Incidence rates and incidence proportion for injury types and regions were calculated. Measures were compared for differences between those who did and did not sustain an MSKI during training. A Cox proportional hazards model was used to identify factors associated with MSKI.

RESULTS

Of the 3242 trainees, 1588 (49%) sustained an MSKI during training and the cohort sustained MSKIs at a rate of 16 MSKI per 100 person-months. Overuse/non-specific lower extremity injuries predominated. Differences were seen in some baseline measures between those who did and did not sustain an MSKI. Factors retained in the final Cox regression model were age, 1.5-mile run times and prior MSKI.

CONCLUSION

Slower run times and higher age were associated with an increased likelihood of MSKI. Prior MSKI was the strongest predictor of MSKI during training. Trainees sustained MSKIs at a higher rate than graduates in their first year in the career field. The MSKI matrix was effective in identifying and categorising MSKI over a prolonged (12-year) surveillance period and could be useful for future injury surveillance efforts in the military or civilian settings. Findings from this study could inform future injury mitigation efforts in military training environments.

Wearable technology assessing running biomechanics and prospective running-related injuries in Active Duty Soldiers

The purpose of this study was to determine if running biomechanical variables measured by wearable technology were prospectively associated with running injuries in Active Duty Soldiers. A total of 171 Soldiers wore a shoe pod that collected data on running foot strike pattern, step rate, step length and contact time for 6 weeks. Running-related injuries were determined by medical record review 12 months post-study enrollment. Differences in running biomechanics between injured and non-injured runners were compared using independent t-tests or ANCOVA for continuous variables and chi-square analyses for the association of categorical variables. Kaplan-Meier survival curves were used to estimate the time to a running-related injury. Risk factors were carried forward to estimate hazard ratios using Cox proportional hazard regression models. Forty-one participants (24%) sustained a running-related injury. Injured participants had a lower step rate than non-injured participants, but step rate did not have a significant effect on time to injury. Participants with the longest contact time were at a 2.25 times greater risk for a running-related injury; they were also relatively slower, heavier, and older. Concomitant with known demographic risk factors for injury, contact time may be an additional indicator of a running-related injury risk in Active Duty Soldiers.

Use of Non-Specific Knee Diagnoses and Incidence of Obscure Knee Injuries in a Large Government Health System

Purpose

Within a large government health system, to assess the practice of using non-specific diagnoses for knee disorders and determine how often they appear as the only diagnosis without more specificity. The secondary purpose was to identify the incidence of obscure knee disorders diagnosed: pes anserine bursitis, prepatellar bursitis, pigmented villonodular synovitis, and plica syndrome.

Patients and Methods

Eligible beneficiaries of the Military Health System (MHS) seeking care for a knee disorder between 1 January 2009 and 31 December 2013 with at least 2-year follow-up. Data were sourced from the MHS Data Repository. The study outcomes were 1) utilization rate of non-specific knee diagnosis codes, 2) proportion of cases that never received a specific knee diagnosis, 3) incidence of obscure knee pathology in this cohort.

Results

There were 127,570 beneficiaries seeking care for knee pain during this period. While the majority (99.7%) initially received a non-specific knee diagnosis, these occurred in isolation for only 16.5% of the cases (n=20,042) over two-year follow-up. The use of non-specific codes was similar between military and civilian clinic settings (45.3% and 47.0%, respectively, of all knee disorders diagnosed), which appears to reflect clinical practice in which diagnoses become more specified over time and diagnostic workup aims to exclude competing diagnoses. The incidence of obscure knee pathology was small (0.2% to 4.0%).

Conclusion

Most of the cohort (99.7%) received a non-specific diagnosis at their initial visit, but only 15% did not eventually receive a more specific diagnostic code. These findings suggest that diagnoses may become more specific over time as condition-specific signs and symptoms become more evident, and diagnostic workup excludes competing diagnoses. A better understanding of diagnostic patterns and criteria for knee pain will improve the quality and interpretation from epidemiological studies.

How Common is Subsequent Posterior Tibial Tendon Dysfunction or Tarsal Tunnel Syndrome After Ankle Sprain Injury?

Posterior tibial tendon dysfunction (PTTD) and tarsal tunnel syndrome (TTS) are debilitating conditions reported to occur after ankle sprain due to their proximity to the ankle complex. The objective of this study was to investigate the incidence of PTTD and TTS in the 2 years following an ankle sprain and which variables are associated with its onset. In total, 22,966 individuals in the Military Health System diagnosed with ankle sprain between 2010 and 2011 were followed for 2 years. The incidence of PTTD and TTS after ankle sprain was identified. Binary logistic regression was used to identify potential demographic or medical history factors associated with PTTD or TTS. In total, 617 (2.7%) received a PTTD diagnosis and 127 (0.6%) received a TTS diagnosis. Active-duty status (odds ratio [OR] 2.18, 95% confidence interval [CI] 1.70-2.79), increasing age (OR 1.03, 95% CI 1.02-1.04), female sex (OR 1.58, 95% CI 1.28-1.95), and if the sprain location was specified by the diagnosis (versus unspecified location) and did not include a fracture contributed to significantly higher (p < 0.001) risk of developing PTTD. Greater age (OR 1.06, 95% CI 1.03-1.09), female sex (OR 2.73, 95% CI 1.74-4.29), history of metabolic syndrome (OR 1.73, 95% CI 1.03-2.89), and active-duty status (OR 2.28, 95% CI 1.38-3.77) also significantly increased the odds of developing TTS, while sustaining a concurrent ankle fracture with the initial ankle sprain (OR 0.45, 95% CI 0.28-0.70) significantly decreased the odds. PTTD and TTS were not common after ankle sprain. However, they still merit consideration as postinjury sequelae, especially in patients with persistent symptoms. Increasing age, type of sprain, female sex, metabolic syndrome, and active-duty status were all significantly associated with the development of one or both subsequent injuries. This work provides normative data for incidence rates of these subsequent injuries and can help increase awareness of these conditions, leading to improved management of refractory ankle sprain injuries.

The Impact of Footwear on Occupational Task Performance and Musculoskeletal Injury Risk: A Scoping Review to Inform Tactical Footwear

The aim of this scoping review was to investigate the impact of footwear on worker physical task performance and injury risk. The review was guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews protocol and registered in the Open Science Framework. Key search terms were entered into five academic databases. Following a dedicated screening process and critical appraisal, data from the final articles informing this review were extracted, tabulated, and synthesised. Of 19,614 identified articles, 50 articles informed this review. Representing 16 countries, the most common populations investigated were military and firefighter populations, but a wide range of general occupations (e.g., shipping, mining, hairdressing, and healthcare workers) were represented. Footwear types included work safety boots/shoes (e.g., industrial, gumboots, steel capped, etc.), military and firefighter boots, sports shoes (trainers, tennis, basketball, etc.) and various other types (e.g., sandals, etc.). Occupational footwear was found to impact gait and angular velocities, joint ranges of motion, posture and balance, physiological measures (like aerobic capacity, heart rates, temperatures, etc.), muscle activity, and selected occupational tasks. Occupational footwear associated with injuries included boots, conventional running shoes, shoes with inserts, harder/stiffer outsoles or thin soles, and shoes with low comfort scores-although the findings were mixed. Occupational footwear was also linked to potentially causing injuries directly (e.g., musculoskeletal injuries) as well as leading to mechanisms associated with causing injuries (like tripping and slipping).

The Use of Force Plate Vertical Jump Scans to Identify Special Warfare Trainees at Risk for Musculoskeletal Injury: A Large Cohort Study

BACKGROUND

Vertical jump scans from commercially available force plate systems are increasingly used in military settings to screen for musculoskeletal injury (MSKI) risk. However, to date, no studies have determined the ability of these tools to identify tactical athletes at elevated risk for MSKI.

PURPOSE

To (1) determine associations between scores from a force plate vertical jump test and the likelihood of experiencing an MSKI and to (2) establish the test-retest reliability of the output scores from the force plate system used.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 823 male Air Force Special Warfare trainees underwent force plate vertical jump screenings before entering an 8-week training course at US Air Force Special Warfare Training Wing. MSKI data were collected for the 8-week surveillance period for each trainee. Logistic regression analyses were used to identify associations between baseline force plate jump scores and the likelihood of MSKI (any region) or a lower extremity MSKI (significance level, P = .05). The test-retest portion of the study collected force plate output scores from 12 trainees performing 3 trials of the standard test procedures. The reliability of 5 output scores was assessed with intraclass correlation coefficients (ICCs) using a single rater.

RESULTS

All force plate output scores demonstrated excellent test-retest reliability (ICC >0.90). Overall 308 (36.4%) trainees had an MSKI during the surveillance period. However, no significant associations were found between the proprietary force plate vertical jump scan output scores and the likelihood of experiencing either an MSKI or a lower extremity MSKI.

CONCLUSION

Output scores from this commercially available force plate system did not identify Air Force Special Warfare trainees at elevated risk of experiencing an MSKI.

Sex Differences in the Incidence and Risk of Ankle-Foot Complex Stress Fractures Among U.S. Military Personnel

Background: The objective of this study was to evaluate sex differences in the incidence and risk of ankle-foot complex (AFC) stress fractures among U.S. military personnel, which could assist in developing management strategies as females assume a greater role in U.S. military operations. Materials and Methods: The Defense Medical Epidemiology Database was used to identify all diagnosed AFC stress fractures in military personnel from 2006 to 2015. Cumulative incidence of AFC stress fractures was calculated and compared by year, service branch, and military rank. Sex differences in the risk of AFC stress fractures by occupation were examined, and integrated (i.e., male and female) occupations were compared with nonintegrated (i.e., male only) occupations. Results: A total of 43,990 AFC stress fractures were identified. The overall incidence rate was 2.76 per 1,000 person-years (p-y) for males and 5.78 per 1,000 p-y for females. Females consistently had higher incidence of AFC stress fractures across all subgroups, particularly among enlisted personnel. Female enlisted service members had the highest risk of AFC stress fractures in aviation (relative risk [RR] = 5.74; 95% confidence interval [CI]: 4.80-6.87) and artillery/gunnery (RR = 5.15; 95% CI: 4.62-5.75) occupations. Females in integrated occupations had significantly higher rates of AFC stress fractures than males in both integrated and nonintegrated occupations (i.e., special forces, infantry, and mechanized/armor). Conclusions: Females in the U.S. military have a higher risk of AFC stress fractures than males. As integration of females into previously sex-restricted occupations continues, focused prevention efforts may be needed to reduce injury burden and maximize medical readiness.

Association Between Markerless Motion Capture Screenings and Musculoskeletal Injury Risk for Military Trainees: A Large Cohort and Reliability Study

Background:

Markerless motion capture (MMC) systems used to screen for musculoskeletal injury (MSKI) risk have become popular in military and collegiate athletic settings. However, little is known regarding the test-retest reliability or, more importantly, the ability of these systems to accurately identify individuals at risk for MSKI.

Purpose:

To determine the association between scores from a proprietary MMC movement screen test and the likelihood of suffering a subsequent MSKI and establish the test-retest reliability of the MMC system used.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Trainees for the Air Force Special Warfare program underwent MMC screenings immediately before entering the 8-week training course. MSKI data were extracted from a database for the surveillance period for each trainee. Logistic regression analyses were performed to identify associations between baseline MMC scores and the likelihood of suffering any MSKI or, specifically, a lower extremity MSKI. The test-retest portion of the study collected MMC scores from 10 separate participants performing 4 trials of the standard test procedures. Reliability was assessed using intraclass correlation coefficients by a single rater.

Results:

Overall, 1570 trainees, of whom 800 (51%) suffered an MSKI, were included in the analysis. MMC scores poorly predicted the likelihood of any or a lower extremity MSKI (odds ratio, 1.01-1.02). Further, receiver operating characteristic curve analyses demonstrated poor sensitivity and specificity for prediction of MSKI with MMC scores (area under the curve = 0.53). Finally, intraclass correlation coefficients from the test-retest analysis of MMC scores ranged from 0.157 to 0.602.

Conclusion:

This MMC system displayed poor to moderate test-retest reliability and did not demonstrate the ability to discriminate between individuals who were and were not likely to suffer an MSKI.

Fractures and Chronic Recurrence are Commonly Associated with Ankle Sprains: a 5-year Population-level Cohort of Patients Seen in the U.S. Military Health System

BACKGROUND

Whereas ankle-foot injuries are ubiquitous and affect ~16% of military service-members, granularity of information pertaining to ankle sprain subgroups and associated variables is lacking. The purpose of this study was to characterize and contextualize the burden of ankle sprain injuries in the U.S. Military Health System.

METHODS

This was a retrospective cohort study of beneficiaries seeking care for ankle sprains, utilizing data from the Military Health System Data Repository from 2009 to 2013. Diagnosis and procedural codes were used to identify and categorize ankle sprains as isolated lateral, isolated medial, concomitant medial/lateral, unspecified, or concomitant ankle sprain with a malleolar or fibular fracture. Patient characteristics, frequency of recurrence, operative cases, and injury-related healthcare costs were analyzed.

RESULTS

Of 30,910 patients included, 68.4% were diagnosed with unspecified ankle sprains, 22.8% with concomitant fractures, (6.9%) with isolated lateral sprains, (1.7%) with isolated medial sprains and 0.3% with combined medial/lateral sprains. Pertaining to recurrence, 44.2% had at least one recurrence. Sprains with fractures were ~2-4 times more likely to have surgery within one year following injury (36.2% with fractures; 9.7% with unspecified sprains) and had the highest ankle-related downstream costs.

CONCLUSION

Fractures were a common comorbidity of ankle sprain (one in five injuries), and operative care occurred in 16.4% of cases. Recurrence in this cohort approximates the 40% previously reported in individuals with first-time ankle sprain who progress to chronic ankle instability. Future epidemiological studies should consider reporting on subcategories of ankle sprain injuries to provide a more granular assessment of the distribution of severity.

LEVEL OF EVIDENCE

3b.