RESUMO
BACKGROUND: Concussion, or mild traumatic brain injury, is a major public health concern affecting 42 million individuals globally each year. However, little is known regarding concussion risk factors across all concussion settings as most concussion research has focused on only sport-related or military-related concussive injuries. METHODS: The current study is part of the Concussion, Assessment, Research, and Education (CARE) Consortium, a multi-site investigation on the natural history of concussion. Cadets at three participating service academies completed annual baseline assessments, which included demographics, medical history, and concussion history, along with the Sport Concussion Assessment Tool (SCAT) symptom checklist and Brief Symptom Inventory (BSI-18). Clinical and research staff recorded the date and injury setting at time of concussion. Generalized mixed models estimated concussion risk with service academy as a random effect. Since concussion was a rare event, the odds ratios were assumed to approximate relative risk. RESULTS: Beginning in 2014, 10,604 (n = 2421, 22.83% female) cadets enrolled over 3 years. A total of 738 (6.96%) cadets experienced a concussion, 301 (2.84%) concussed cadets were female. Female sex and previous concussion were the most consistent estimators of concussion risk across all concussion settings. Compared to males, females had 2.02 (95% CI: 1.70-2.40) times the risk of a concussion regardless of injury setting, and greater relative risk when the concussion occurred during sport (Odds Ratio (OR): 1.38 95% CI: 1.07-1.78). Previous concussion was associated with 1.98 (95% CI: 1.65-2.37) times increased risk for any incident concussion, and the magnitude was relatively stable across all concussion settings (OR: 1.73 to 2.01). Freshman status was also associated with increased overall concussion risk, but was driven by increased risk for academy training-related concussions (OR: 8.17 95% CI: 5.87-11.37). Medical history of headaches in the past 3 months, diagnosed ADD/ADHD, and BSI-18 Somatization symptoms increased overall concussion risk. CONCLUSIONS: Various demographic and medical history factors are associated with increased concussion risk. While certain factors (e.g. sex and previous concussion) are consistently associated with increased concussion risk, regardless of concussion injury setting, other factors significantly influence concussion risk within specific injury settings. Further research is required to determine whether these risk factors may aid in concussion risk reduction or prevention.
RESUMO
BACKGROUND: The effect of posterior cruciate ligament (PCL) deficiency on 6 degrees of freedom in vivo knee-joint kinematics is unclear. HYPOTHESIS: In addition to constraining anterior-posterior translation, the PCL also functions to constrain the medial-lateral translation and rotation of the knee during weightbearing flexion of the knee. STUDY DESIGN: Controlled laboratory study. METHODS: Eight patients with a PCL injury in 1 knee and the other intact were scanned with magnetic resonance imaging, and 3-dimensional models of the femur and tibia were created for both knees. Each knee was imaged during quasistatic weight-bearing flexion (from 0 degrees to 105 degrees ) using a dual-orthogonal fluoroscopic system. The translation and rotation of the PCL-deficient knee were compared with the intact contralateral control. RESULTS: Posterior cruciate ligament deficiency caused an increase in posterior tibial translation beyond 30 degrees of flexion compared with the intact contralateral knees. At 90 degrees of flexion, PCL deficiency increased posterior tibial translation by 3.5 mm (P < .05). In the medial-lateral direction, PCL deficiency resulted in a 1.1 mm increase in lateral tibial translation at 90 degrees of flexion (P < .05). With regard to rotation, PCL deficiency caused a significantly lower varus rotation (on average, 0.6 degrees lower) at 90 degrees of flexion. Posterior cruciate ligament deficiency caused a decreased internal tibial rotation throughout the range of flexion, but no significant difference was detected. CONCLUSIONS: This study quantitatively describes the effect of PCL injury on 6 degrees of freedom kinematics of the knee during quasistatic weightbearing flexion. Using the intact contralateral side as a control, we found that PCL injuries not only affect anterior-posterior tibial translation but also medial-lateral translation and rotation of the knee. CLINICAL RELEVANCE: These data provide baseline knowledge of the in vivo kinematics of the knee after PCL injury. Surgical reconstruction of the injured PCL, either using single-bundle or double-bundle technique, should not only focus on restoration of posterior stability of the knee but also the medial-lateral stability as well as the rotational stability. These findings may help to explain the long-term degenerative changes seen in PCL-deficient knees.
