Growing evidence suggests that concussion increases the risk of lower extremity (LE) musculoskeletal injury. However, it is unclear to how the effect of concussion on LE injury risk may be influenced by previous injuries. This study sought to examine the association between concussion, previous LE injuries, and the risk LE injury to the same previously injured limb (ipsilateral) or the opposite limb (contralateral).
This retrospective study examined medical records from 110 concussed athletes and 110 matched controls for LE injuries in the 365 days before and after the concussion event. The effect of concussion on time to injury was assessed with a Cox proportional hazard model after adjusting for injury history. Fine and Gray subdistribution models assessed the cumulative risk of ipsilateral and contralateral injury by group.
Concussion was associated with an increased instantaneous relative risk of LE injury when adjusting for LE injury history [hazard ratio (HR) = 1.67, 95% confidence interval (CI) = 1.11–2.53], agreeing with previous results. Among individuals who had a history of LE injuries before the concussion event, a nonsignificant yet moderate effect of concussion on the instantaneous relative risk of ipsilateral injuries was found after adjusting for the competing risk of contralateral injuries and censored values (HR = 1.85, 95% CI = 0.76–4.46).
This study provides independent confirmation of previous studies, reporting an association between concussion and LE injury risk. Furthermore, this study suggests that future large-scale studies should consider the competing risk of ipsilateral, contralateral, and new injuries in populations with an injury history.
*Department of Neurology, Oregon Health & Science University, Portland, OR;
†Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA;
‡Edward Via College of Osteopathic Medicine, Blacksburg, VA;
§Biostatistics and Design Program, Oregon Health & Science University, Portland, OR; and
¶Department of Sports Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA.
Corresponding Author: Peter C. Fino, PhD, Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd, OP-32, Portland, OR 97239-3098 (email@example.com).
This material is based on work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 0822220.
The authors report no conflicts of interest.
Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
Received November 15, 2016
Accepted June 16, 2017