Impaired postural control is a cardinal symptom of concussion and the Balance Error Scoring System (BESS) suggests recovery within 3-5 days. However, instrumented measures of postural control have suggested persistent deficits.
PURPOSE: To evaluate differences in linear (95% area, mean velocity) and non-linear (approximate entropy) measurements in concussed individuals throughout the recovery process compared to healthy controls
METHODS: 18 collegiate athletes with concussion (age: 19.0±1.4 years, height: 175.9±11.4 cm, mass: 82.5±23.8 kg) and 10 healthy individuals (age: 22.4±2.7 years, height: 175.7±11.9 cm, mass: 81.1±21.3 kg) were tested. Post-concussion participants were tested on three occasions 1) acutely (24-48 hours following injury), 2) RTP day (full practice/game), and 3) 30 days following injury. Participants completed three trials of a quiet stance (eyes open, firm surface) on their dominant leg for 20 seconds. Performance at each time point was compared to healthy values using a 2x3 ANOVA for each dependent variable.
RESULTS: There was a significant main effect for group in both 95% area (p<0.01) and mean velocity (p<0.05). Approximate entropy (ApEn) displayed a significant main effect for group in the M/L direction (p<0.05), but not the A/P direction. Acutely, the linear measures displayed significantly higher values compared to controls (95% area: 1251.9±442.6 vs. 789.0±196.9 mm2, p<0.01, mean velocity: 137.3±46.2 vs. 98.1±19.3 mm/s, p<0.05). At RTP M/L ApEn (0.89±0.091 vs. 0.96±0.040, p<0.05) was significantly lower than controls as well as both linear variables remained elevated (area: 1113.0±316.4 vs. 789.0±196.9 mm2, p<0.01; velocity: 127.6±37.1 vs. 98.1±19.3 mm/s, p<0.05). On day 30, M/L ApEn (0.88±0.101vs. 0.96±0.040, p<0.05) remained reduced and mean velocity (126.1±37.4 vs. 98.1±19.3 mm/s, p<0.05) remained elevated.
CONCLUSION: Linear CoP measurements, especially 95% area, may be strong indicators of postural control deficits acutely post-concussion. However, at RTP non-linear measures may better at identifying lingering impairments. Lingering deficits up to 30 days following injury may become apparent when using these measurements.