Attentional demands of postural control during single leg stance in patients with anterior cruciate ligament reconstruction.

The aim of this study was to investigate the amount of attention demands of postural control in patients with anterior cruciate ligament-reconstruction (ACL-R), by comparing the pattern of posture-cognition interaction between two groups of ACL-R patients (n=25) and healthy matched controls (n=25). All participants were examined during single-leg stance on a balance board under both single- and dual-task conditions in 4 dynamic balance tests. These tests were standing on the injured and uninjured legs with straight or flexed knees. The corresponding dominant and non-dominant legs of healthy group were considered as controls. Contact frequency and contact time were acquired as a measure of postural performance. Cognitive performance was assessed by counting the number of errors in a silent backward digit span task. The results of analysis of variance showed a significant higher contact frequency and longer contact time in patients with ACL-R compared to healthy matched controls (p<0.02). Moreover, the ACL-R patients showed a significantly higher contact frequency and longer contact time during dual-task compared to single-task conditions (p<0.01). This pattern of posture-cognition interference was not observed in the healthy control group. In conclusion, patients who had undergone ACL-R surgery demonstrated poorer balance stability during single-leg stance than healthy controls. Also, simultaneous execution of the cognitive task during standing caused a significant deterioration in postural stability which indicates decreased automaticity (increased attention demanding) of postural control in patients with ACL-R compared to healthy controls.