Epidemiological patterns of traumatic musculoskeletal injuries and non-traumatic disorders in Japan Self-Defense Forces.

BACKGROUND: The epidemiological patterns of musculoskeletal injuries or disorders in military personnel have not been well documented and a better understanding is required for proper preventative measures and treatment. Here, we investigated musculoskeletal injuries or disorders among members of the Japan Self-Defense Forces. METHODS: All orthopedic patients (n = 22,340) who consulted to Japan Self-Defense Forces Hospitals were investigated for their type of injury or disorder, the injured body part, the mechanism, and the cause of injuries. RESULTS: Thirty-nine percent of the cases were classified as traumatic injuries, and 61% were classified as non-traumatic disorders. Of the traumatic injury patients, the injured body part was the upper extremity in 32%, the trunk in 23%, and the lower extremities in 45% of the cases. The most common injured body location was the knee followed by the hand/finger and ankle. Exercise was the most common cause of injury, followed by traffic accident and military training. Contusions were the most common traumatic injuries, followed by sprains and fractures. Of non-traumatic disorders, the lower extremities were reported as the injured part in 43% of the disorders. Lumbar spine disorders were the most common non-traumatic disorders, followed by tendon and joint disorders. CONCLUSIONS: Over one-third of orthopedic cases among members of the Japan Self-Defense Forces are traumatic injuries, with the knee being the body part most commonly injured and exercise being the leading cause of injury.

Incidence and Characteristics of Traumatic Shoulder Instability in Japanese Military Cadets.

Little is known regarding the incidence of the shoulder instability in Japan. The aim of this study was to evaluate the incidence of traumatic shoulder instability among Japanese military cadets. A prospective cohort study was performed to capture all traumatic shoulder instability events between 2009 and 2012 among cadets in a military educational academy of the Japan Self Defense Forces. The total number of cadets in the cohort was 5,402 (average age 20.6 years). The incidence of instability events, including dislocation or subluxation, was calculated. Chronicity, demographics of participants, mechanism of injury, and athletic events were also evaluated. The incidence of traumatic dislocation was 4.1/1,000 person-years and that of subluxation was 6.1/1,000 person-years. The incidence of primary dislocation or subluxation was 5.4/1,000 person-years and that of recurrent dislocation or subluxation was 4.7/1,000 person-years. Of first dislocations or subluxations, 92% occurred during sports activities, including after-school sports activities, military training, and gym classes. In conclusion, the overall incidence of shoulder instability events among Japanese military cadets was 10.3/1,000 person-years, and was extremely high. Most shoulder instability events occurred during sports activities, and a program to prevent such injuries during sports activities is necessary for young participants.

Incidence and Risk Factors of Adjacent Cranial Facet Joint Violation Following Pedicle Screw Insertion Using Cortical Bone Trajectory Technique.

STUDY DESIGN: Retrospective study evaluating cranial facet joint violation (FJV) by pedicle screws. OBJECTIVE: The aim of the study was to determine the incidence and risk factors of FJV following screw placement via cortical bone trajectory (CBT). SUMMARY OF BACKGROUND DATA: CBT is a new minimally invasive technique for lumbar pedicle screw insertion that minimizes muscle dissection. Inserting a screw from a more caudal entry point can reduce iatrogenic damage to the cranial facet joint; however, no previous reports exist describing the incidence of FJV secondary to the CBT technique. METHODS: We reviewed 202 consecutive patients who underwent lumbar pedicle screw instrumentation using CBT from October 2011 to June 2015. Postoperative CT scans were obtained to determine the degree and incidence of FJV. Clinical and imaging data were analyzed to clarify the risk factors of FJV. The detailed positions of the proximal screws were also investigated and compared between the FJV and non-FJV groups. RESULTS: The incidence of FJV by the proximal screws was 11.8% (48/404), with no occurrence of intra-articular FJV. Multiple logistic regression analysis revealed that age >70 years, vertebral slip >10%, and adjacent facet joint degeneration (Pathria's grade 2 or 3) were independent factors significantly affecting FJV. There were statistically significant differences between the FJV and non-FJV groups in the facet-screw distance (3.2 ±â€Š1.0 vs. 8.1 ±â€Š2.3 mm, P < 0.01), the cranial angle (25.8 ±â€Š6.3° vs. 29.9 ±â€Š7.6°, P < 0.01), and the lamina-screw head distance (5.6 ±â€Š1.6 vs. 6.4 ±â€Š1.9 mm, P < 0.01). CONCLUSION: Lumbar pedicle screw placement via CBT would reduce FJV; however, special care should be taken in patients with age >70 years, vertebral slip >10%, and facet degeneration. LEVEL OF EVIDENCE: 3.