Spinal injuries after ejection seat evacuation in fighter aircraft of the German Armed Forces between 1975 and 2021.

OBJECTIVE: The ejection seat is one of the most important rescue tools for military aircrews. However, the high ejection speeds place high loads on the pilots, which is mainly absorbed by the pilot's spine. The differentiated evaluation of spinal injuries is of particular importance because this has a decisive influence on the further personal life and career of the affected aircrew members. Factors influencing the occurrence of a fracture as well as the impact of a spinal injury on military flight certification have not been addressed sufficiently to date. METHODS: The authors conducted a retrospective evaluation of ejection seat evacuations in German Armed Forces combat aircraft accidents between 1975 and 2021. The total number of aviation accidents with ejection seat initiations and the survived ejections were collected. Accident-specific data and pilot-specific data were collected. In addition, it was evaluated whether aircrew members were recertified for military flight after the accident. The type of spinal injury and the location of the injury were evaluated. In addition to the descriptive statistics, two logistic regression models were developed to assess prediction values of accident- and pilot-specific factors for spine injuries. RESULTS: A total of 103 aircrew members were included in this retrospective analysis. The overall prevalence of spine injuries was 56.3%, and the overall prevalence of spine fractures was 33.0%. In the first regression model analysis, there was no association with pilot flight experience, age, height, weight, BMI, and being diagnosed with a spine fracture. Similarly, aircraft type, altitude, and airspeed were not associated with the occurrence of spine fractures. In the regression model analysis for predictors of rejection in military flight recertification after ejection seat evacuation, lumbar spine fractures were associated with higher odds of being rejected for recertification. CONCLUSIONS: Military aircraft crew members have a high risk of suffering from a spine injury after emergency evacuation using an ejection seat. In the subsequent medical workup, special attention should be paid to the spine, and ideally a consultation with a spine surgeon should be performed. Lumbar spine fractures may have major consequences for military flight certification, and therefore special attention should be paid to successful rehabilitation.

Local Muscle Fatigue and 3D Kinematics of the Cervical Spine in Healthy Subjects.

The authors aimed to further explore the effects of local muscle fatigue on cervical 3D kinematics and the interrelationship between these kinematic characteristics and local muscle endurance capacity in the unimpaired cervical spine. Twenty healthy subjects (38 ± 10 years; 5 women) performed 2 × 10 maximal cervical flexion-extension movements. Isometric muscle endurance tests (prone/supine lying) were applied between sets to induce local muscle fatigue quantified by Borg scale rates of perceived exertion (RPE) and slope in mean power frequency (MPF; surface electromyography; m. sternocleidomastoideus, m. splenius capitis). Cervical motion characteristics (maximal range of motion [ROM], coefficient of variation of the 10 repetitive movements, mean angular velocity, conjunct movements in transversal and frontal plane) were calculated from raw 3D ultrasonic movement data. Average isometric strength testing duration for flexion and extension correlated to the cervical ROM (r = .49/r = .48; p < .05). However, Student's t test demonstrated no significant alterations in any kinematic parameter following local muscle fatigue (p > .05). Although subjects' cervical muscle endurance capacity and motor output seems to be conjugated, no impact of local cervical muscle fatigue on motor function was shown. These findings underline the importance of complementary measures to address muscular performance and kinematic characteristics in outcome assessment and functional rehabilitation of the cervical spine.