Assessing the Reliability and Validity of an Objective Method of Measuring Postural Stability

PURPOSE: Postural stability is frequently used in the evaluation of mild traumatic brain injury (mTBI) and can be measured in a variety of different ways. Although Balance Error Scoring System (BESS) is a supported tool for assessing postural stability assessment after mTBI, other clinical tools are available, such as body sensors such as APDM Opal body sensor). The purpose of this investigation was to assess the validity and relationship of the APDM Opal body sensor compared to the modified BESS (mBESS) in individuals after an mTBI. METHODS: Injured subjects were defined as those diagnosed by an appropriate health care professional with an mTBI and compared to healthy controls. Postural Stability was examined using both the mBESS and APDM Opal sensor during the same testing session with the three traditional stances. mBESS was scored according to the conventional grading system. APDM was used in conjunction with a tablet and mobility lab software to collect postural stability data. Root mean square values were calculated for anterior-posterior (AP) and medial-lateral (ML) acceleration. Pearson product-moment correlations were calculated to assess the relationship between average mBESS score and average RMS value, between average mBESS score and diagnosis with a concussion, and between average RMS value and diagnosis with a concussion. RESULTS: The overall mean RMS value was 1.92±1.20 m(s2)-1 while subjects (n=43) committed a mean of 1.20±0.88 balance errors during BESS testing on a firm surface. The coefficient of determination between calculated means of RMS and total mBESS score for the subject pool was modest, however trended towards significant (R2=0.08, p>.05). The coefficient of determination between mean total BESS score and a positive concussion diagnosis was insignificant (R2=0.002, p>.05). A weak and inverse relationship was found between calculated mean RMS and positive diagnosis with a concussion compared to healthy controls (R2=0.009, p>.05). CONCLUSION: While our results did not show a strong correlation between mBESS score and the Opal’s measurement of postural stability, there was a trend toward statistical significance that may be influence by sample size. This is promising given previously established validity and reliability values of the APDM, especially when using only a single sensor.