Injury Surveillance and Reporting for Trainees with Bone Stress Injury: Current Practices and Recommendations

Incidence and Risk Factors for Bone Stress Injuries in United States Air Force Special Warfare Trainees

OBJECTIVES

To determine (1) the incidence rate of lower extremity (LE) bone stress injuries (BSIs) in United States Air Force Special Warfare (AFSPECWAR) trainees during the first 120 days of training, and (2) factors associated with sustaining a LE BSI.

DESIGN

Retrospective cohort study.

METHODS

AFSPECWAR Airmen (n = 2,290, mean age = 23.7 ± 3.6 years) entering an intensive 8-week preparatory course "SW-Prep" between October 2017 and May 2021. We compared anthropometric measurements, previous musculoskeletal injury (MSKI), fitness measures, and prior high-impact sports participation in those that did and did not suffer a BSI during the 120-day observation period using independent t-tests and chi-square tests. A multivariable binary logistic regression was used to determine factors associated with suffering a BSI.

RESULTS

A total of 124 AFSPECWAR trainees suffered a BSI during the surveillance period, yielding an incidence proportion of 5.41% and an incidence rate of 1.4 BSIs per 100 person-months. The multivariate logistic regression revealed that lower 2-minute sit-up scores, no prior history of participation in a high-impact high-school sport, and a history of prior LE MSKI were associated with suffering a BSI. A receiver operator characteristic curve analysis yielded an area under the curve (AUC) of 0.727.

CONCLUSION

BSI incidence proportion for our sample was similar to those seen in other military settings. Military trainees without a history of high-impact sports participation who achieve lower scores on sit-ups tests and have a history of LE MSKI have a higher risk for developing a LE BSI during the first 120 days of AFSPECWAR training.

A Case-Control Analysis of Bone Stress Injury on Advancement and Health Care Utilization in US Air Force Basic Military Trainees

INTRODUCTION

Every year, approximately 35,000 recruits enter the United States Air Force Basic Military Training (BMT). Musculoskeletal problems are particularly vexing for BMT because a broad array of differentials render definitive diagnosis burdensome and while most sufferers will fully recover, healing often requires protracted training delays resulting in increased unrecoverable training costs to the program. The purpose of this study is to conduct a case-control study of basic military trainees entering service from 2012 to 2015 to assess detectable differences in demographics, retention, and health care utilization.

MATERIALS AND METHODS

This is a retrospective case-control study of existing data and records obtained from existing and active information record systems for individuals who attended BMT between the years 2012 and 2015. Cohort assignment was based on incidence of first stress fracture diagnosis (i.e., having a select diagnosis code in one's medical record) relative to arrival at BMT. Health care utilization is operationalized as medical encounter frequencies and associated international classification of disease (ICD) codes occurring for all patients from BMT recruit date of arrival to 6 months post-graduation (i.e., 180 days).

RESULTS

The primary dataset includes 132,359 distinct individuals, of which 129,637 (98%) had no history of stress fracture diagnosis and 1,487 (1%) of which have a diagnosis of stress fracture more than 60 days after arrival at BMT; these are assigned to the CONTROL group. There are 1,235 (0.9%) assigned to the CASE group. CASE members presented with 30.1 unique ICD-10 codes post-graduation compared to 6.3 in the CONTROL group. Six of the top thirteen ICD-10 codes were musculoskeletal in nature and all presented significantly higher rates for the CASE group.

CONCLUSIONS

Trainees who suffered a bone stress injury (BSI) during the United States Air Force BMT advanced in rank on par with trainees who did not, but BSI sufferers exhibited greater health care utilization than those who did not suffer BSI. The cost to replace a trainee unable to complete BMT is considerable; however, it is also important to consider the reduction in resiliency and readiness to the Department of Defense and the financial burdens from increased health care utilization. The 2-fold increase in BSI presentation in the graduated control group reflects that more needs to be done for all populations to identify better proactive efforts to foundationally support wellness and prevention rather than accept injury as the status quo.

Diagnosis of Stress fractures in military trainees: a large-scale cohort

INTRODUCTION

The Israel Defense Forces (IDF) has strict protocols for the diagnosis and treatment of stress fractures wherein diagnosis is clinical with imaging used for persistent symptoms only. The purpose of this study was to examine the incidence of clinical and radiological stress fractures during IDF combat training.

METHODS

Medical records of all soldiers enlisted to combat training between 2014 and 2017 were scanned for the diagnosis of stress fractures. We examined the imaging tests ordered (plain radiographs and bone scans) and their results and the time between the clinical diagnosis to imaging tests.

RESULTS

During 4 years, 62 371 soldiers (10.1% women) had started combat training, and 3672 of them (5.9%) were diagnosed with clinical stress fractures. Radiographs were ordered for 53.5% of those diagnosed, of whom 29.7% also had a bone scan. Some 42% of radiographs were taken within 21 days. Radiographs were positive for stress fractures in 11.1% of tests. Bone scans showed evidence of stress fractures in 49.7%, of which 49.2% diagnosed stress fractures in multiple bones.

CONCLUSION

The high percentage of negative radiographs may indicate towards alternative causes for symptoms. Performing the radiograph before or after 21 days did not affect workup results diverting from current belief that later radiographs will be more sensitive. Multiple stress fractures are a common finding, indicating that the increased training load puts the whole musculoskeletal system at increased risk for injury. Research results may necessitate a revision of clinical guidelines for the diagnosis of stress fractures in military trainees.