Deficits in Postural Stability Following Concussion Persist Beyond BESS Recovery

Abstract

Assessment of postural stability is a cornerstone of concussion management and the most common assessment tool is the Balance Error Scoring System (BESS). However, BESS has been criticized for the static nature of the assessment. Gait initiation (GI) is a dynamic task which has been effectively identified impairments in postural stability within diverse populations. PURPOSE: The purpose of this study was to investigation impairments in dynamic postural stability following concussion. METHODS: 15 subjects (19.7 + 1.5 years old; 183.7 + 13.1cm; 84.8 + 29.6kg) performed three trials of GI daily from the day after their concussion (Cantu Revised Scale: Grade I - 1, Grade II - 12, Grade III - 2) till their return to play day (mean 10.2 + 3.7 days). Kinetic data was collected by two forceplates (AMTI, Watertown, MA) at 1000hz. All subjects underwent pre-season testing of the BESS. Dependent variables included the posterior and lateral displacement of the center of pressure (COP) during the anticipatory postural phase (S1) of GI as well as step length and velocity. Within subjects comparisons were made between first day after the concussion (Day1), the day the BESS score returned to baseline (BESS), and the return to play (RTP) day using a one-way repeated measures ANOVA. RESULTS: Mean time for BESS to return to baseline was 3 days (range: 1 - 9 days) post concussion. Significant differences were present between BESS day and RTP day for posterior movement of the COP during S1 (3.08 + 2.3cm and 6.3 + 2.0cm, p=0.001), step length (63.0 + 11.9cm and 72.9 + 10.7cm, p=0.025), and a trend for step velocity (0.63 + 0.21m/s and 0.78 + 0.17m/s, p=0.116). There were no differences between Day 1 and BESS day for posterior or lateral movement of COP during S1 (p=0.139 and 0.916 respectively), step length (p=0.481), or step velocity (p=0.989). CONCLUSION: The results of this study support recent findings suggesting that impairments in postural stability persist despite the BESS returning to baseline values. Additionally, the lack of improvement during the dynamic task between day 1 and the time the BESS returned to baseline value raises further concern of the sensitivity of the BESS to identify impairments in postural stability. In light of this and other recent findings, clinicians should exercise caution in interpreting BESS results.