Altered Balance in those with Back Pain

Purpose: Numerous studies have attempted to find an association between back pain (BP) and altered standing balance. These quiet standing (QS) studies measure a subject's center of pressure (COP) via a force plate system. From the COP data, variables such as COP area and COP velocity are calculated to measure the amount of sway a subject had while attempting to stand still during the QS trial. In reviewing previous research, most studies had relatively small sample sizes, and while some were able to achieve statistically significant differences in sway variables between subjects with BP and healthy controls, most were too underpowered to achieve clinical statistical significance. Also, what is concerning is that some studies with shared variables had inconsistent results of whether BP or healthy control participants had greater values. Our study sought to test potential associations with a much larger sample size (greater than 10-fold larger than many other studies) to find clinically meaningful relationships. Methods: This research is built from the results of previous QS studies and an ongoing QS project at UNTHSC. A Bertec force plate (Bertec, Columbus, Ohio) was used to collect data from participants standing quietly on it for a period of 30 seconds with their eyes open (EO), and then 30 seconds with their eyes closed (EC). Each 30 second period was collected as three 10 second trials for each condition. This study's data was collected from people suffering from BP and healthy controls. Results: COP area was statistically significantly greater for BP subjects, however, only during EC trials. In contrast, during EO trials, the COP area was not statistically different between the two groups. Furthermore, in distinction from previous studies, velocity was statistically significantly greater for healthy controls regardless of the trial's eye condition. Conclusions: These results led us to hypothesize that during the EC trials, BP subjects cover a greater COP area than the controls due to decreased proprioception, in which they sway further from their balance point before being able to detect they are moving. However, in EO trials, this area is not statistically different, likely because BP subjects have learned to compensate for their decreased proprioception by relying more on their vision for positional sense. Furthermore, since the healthy controls exhibited a greater velocity than the BP subjects, this could mean that the BP subjects are taking longer to regain their balance due to decreased reflexes. In conclusion, we suggest that future QS studies screen subjects for delays in reflexes, a lesser sense of proprioception, and whether lighting conditions create altered sway outcomes. This study contributes precautionary information to help prevent falls in those with BP.