Stress Fracture Risk in Military Trainees Is Associated With Modifiable Lifestyle and Training Factors: A Retrospective Case-Control Study.

Introduction/Objectives Stress fractures are a common and debilitating injury in military populations. Early identification of risk factors is critical for prevention. The purpose of this study was to identify demographic, clinical, lifestyle, and training-related factors associated with stress fractures in military trainees and to characterize their anatomical distribution. Methods  A retrospective case-control study was conducted at King Hussein Medical City from January 2021 to June 2023, including 600 military trainees (139 with stress fractures and 461 controls). Data collected included age, gender, training duration, prior conditioning, smoking status, vitamin D and calcium levels, previous joint injuries, and footwear usage. Statistical analysis was used to determine factors significantly associated with stress fracture risk (p < 0.05). Fracture locations were descriptively analyzed. Results The fracture group was younger (21.78 ± 3.70 vs 24.50 ± 3.33 years) and presented earlier in training (12.1 ± 1.2 days vs. 30.4 ± 22.5 days). They had higher rates of military shoe usage (70.5% vs. 23%), smoking history (64.03% vs. 20.4%), and lower vitamin D levels (26.63 ± 16.56 vs. 42.97 ± 13.75 ng/mL) (all p < 0.001). The most common fracture site was the tibial plateau (43.2%), and 23.0% of cases involved multiple sites. Most fractures (80.6%) were high-grade (Fredericson Grade 3 or 4). Conclusion In this retrospective case-control study, stress fracture occurrence among military trainees was significantly associated with younger age, the early phase of military training, vitamin D deficiency, smoking, use of standard-issue military footwear, and lack of prior physical training. These findings should be interpreted as associations and warrant confirmation in prospective studies with multivariable analyses.