The data were extracted from the registered data bank system from the KMTBI study. Ten institutions (eight university hospitals and two military hospitals) are participated in the KMTBI study. The patients, who were admitted to the hospitals and diagnosed with definitive TBI from January 2016 to December 2018, were retrospectively enrolled. Patients, who were aged under 15 or who had poor medical records, were excluded. In this study, the data were registered online and were freely accessible to the research team of the institutions. The extracted data contained age, sex, past medical histories, mechanism of trauma, diagnosis, neurologic status including Glasgow coma scale (GCS) scores, treatment modality, and outcomes. The outcome was measured by the modified Rankin Scale scores on discharging date in mild TBI and at six-month in moderate to severe TBIs. In addition, the neurological deterioration was defined when the GCS score decrement is larger than 2 points. The previous study was approved by the Institutional Review Board of the Human Research Center of each institution. The requirement for obtaining informed consent was omitted because it is a retrospective design.

In the current study, the patients were divided into “Military Hospital” group and “Other Hospital” group according to the institution that the patients are admitted to. In addition, patients were classified as mild (13-15) and moderate/severe TBIs (3-12) according to their GCS scores.

Baseline characteristics of military hospital groups were examined. Furthermore, comparison analyses between the groups were conducted by two steps; “mild” and “moderate/severe” TBIs according to the GCS scores. Continuous values were presented as mean and standard deviation, and they were compared by using independent t-test. Discontinuous variable data were presented as numbers and percentages, and they were compared by using Chi-square analysis. Statistical analyses were conducted using a standard software (version 23.0, SPSS, IBM, Chicago, IL, USA), and the significance was considered if p < 0.05.

The result of the current study would be a good reference for the military doctors working in the military hospitals. In order to identify the clinical characteristics of the military TBI patients, the optimized military medical system can be equipped during this non-war years in ROK. They can place the medical resources in the right place with the most efficient ways. Specifically, the most of the patients in military group are young male soldiers, and they show the clinical differences: lesser past medical diseases, higher incidence of sports-related trauma, lower incidence of traffic accidents, and lesser frequent diagnosis of chronic subdural hematoma^12,13). We conclude that the military hospital usually cares mild TBI patients, that the most of them is young male soldiers. Only 10% of the military patients had severe TBI, and others had favorable outcomes which means non-severe TBI (Table 1).

From the ‘mild TBI’ comparison (Table 2), we can draw a conclusion that the clinical manifestation, clinical courses, and outcomes of military mild TBI patients are related to ‘young male’ patients. The patients significantly complain bitterly of non-specific symptoms: headache, dizziness, nausea and vomiting, and loss of consciousness. A larger number of young patients might be related to the sensitive detection of increased intracranial pressure, and the symptoms can be frequently observed among the young age group. On contrary, ‘motor weakness’ is significantly highly observed among other hospital groups: it might be related to the chronic subdural hemorrhage which frequently occurred in elderly patients¹⁰⁾. Therefore, the treatment such as burr-hole trephination is more frequently conducted in other hospital groups. In terms of outcome, we can find that no military patients were deteriorated, which means that the military personnel in mild TBI have rarely been worsened to moderate or severe TBIs.

In moderate to severe TBIs (Table 3), the favorable clinical courses and outcome in military personnel are identified. The initial neurologic status, including GCS scores, level of consciousness, and neurological symptom and signs, have no differences between the groups. Treatment modality does not vary among the groups, neither. However, the mRS score in military group is approximately 1 point higher than that in other hospital groups. Because more than a half of the military patients who had no symptoms or had mild symptoms (mRS 0 to 1) were treated, physicians should actively treat the patients.

We identify the low incidence of TBI in military personnel and small numbers of ‘severe’ patients which requires the human as well as medical resources for treating. In non-wartime years, the military hospitals in ROK divided their works and specialties for better efficacy. If we have TBI patients (especially, severe), they initially visit the nearest military hospital and are transferred to the superior hospitals. Consequently, AFCH carries on providing the medical service as the supremacy hospital. In addition, AFYH is located on front lines and usually prepare for the potential combat injuries. Maybe this systematic difference leads to the higher transfer rates of military hospitals (55.3%). Instead, the medical command operates an all-time helicopter emergency transporting systems in order to assess and manage the patients better²⁾. The fastest transporting system may enable the better clinical outcomes. According to our results, two hospitals greatly manage the military TBI patients, and the outcomes are favorable.

The present study has several limitations. First, the data were extracted from the databank system of KMTBI, and they did not include radiological images. Therefore, known prognostic factors observed in brain computed tomography (CT), such as poor Marshall or Rotterdam CT scores, were omitted^5,8). Second, the data were registered from each different hospital’s reviewers, and there might be an inter-observer bias.