Post-Traumatic Ankle Osteoarthritis Alters the Central Organization of Movement

Abstract

Sensorimotor impairments have recently been identified in those with post-traumatic ankle osteoarthritis (PTAO), a condition characterized by pain and disability. The underlying cause of these impairments remains unknown, but evidence suggests that altered supraspinal motor control mechanisms may play a role. Gait initiation (GI) is a functional task modulated by supraspinal pathways, but the effects of PTAO on GI and thus supraspinal motor control mechanisms remain unknown. PURPOSE: To determine if PTAO influences various dynamic postural control measures during GI. METHODS: Five subjects with unilateral PTAO and five age-matched controls were assessed for self-assessed disability and dynamic postural control. Self-assessed disability was assessed with the SF-36, and the ankle osteoarthritis scale while dynamic postural control was assessed bilaterally during GI. Participants completed a total of 20 GI trials (10 per leg) where anteroposterior (AP), mediolateral (ML), and resultant (R) displacement of the center of pressure (COP) during the three phases of GI was captured. RESULTS: Analysis of disability data indicated that those with PTAO had greater levels of pain and disability, consistent with the existing literature. A 2 (group) × 2 (leg) MANOVA revealed significant group effects for AP (p=0.04), ML (p=0.03), and R (p=0.03) COP displacement during the first phase of GI. Specifically, the results demonstrated that in the first phase of GI those with PTAO had decreased COP displacement in the AP (Control: 29.1±7.8mm, PTAO: 18.0±6.5mm), ML (Control: 43.7±8.4mm, PTAO: 25.6±14.3mm), and R directions (Control: 53.2±10.7mm, PTAO: 32.8±15.5mm). Post-hoc analysis further revealed that the observed first phase decreases in COP displacement occurred regardless of the limb that initiated gait in those with PTAO. CONCLUSION: Because the secondary motor areas of the brain control the first phase of GI, it appears that supraspinal motor control mechanisms are altered in patients with PTAO. Further, these data support the need for global coordination/rehabilitation programs for both lower extremities in patients with PTAO so that proper motor control strategies can be restored to improve overall gait function. Supported by a UNC Charlotte Faculty Research Grant and the OrthoCarolina Research Institute