Background/Purpose: To compare ankylosing spondylitis (AS) patients and healthy individuals in terms of posture and balance and to identify the factors affecting balance among patients with AS.

Methods: Thirty AS patients (13 women and 17 men) admitted to our outpatient clinic and 33 healthy volunteers (15 women, 18 men) as the control group were included. Both groups were evaluated in terms of balance via Neurocom Balance Master System with weight bearing squat, standing on firm and foam bases when eyes open and closed, walking across, tandem walk, and step and quick turn tests. Postural assessment parameters were tragus-wall distance, Modified Schober test and chest expansion measurements. Pain and disease activity were evaluated with Visual Analog Scale (VAS) for pain level (0-10 cm), and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), respectively.

Results: The mean age of AS and control group were 41.7±7.6 and 41.3±7 years, respectively. There was no significant difference in terms of age, height and body mass index between AS and control groups. Mean disease duration in the AS group was 8.6±8.4 years with a mean BASDAI of 4.7±2.6. Mean VAS for pain, tragus-wall distance, and Modified Schober test were 5.9±2.1 cm, 17.7±5.6 cm and 18.6±2.8 cm in the patient group. Parametric tests were analyzed with independent t-test. AS patients had significantly greater step width (p=0.024). Step length (p=0.011), walking speed at walk across test (p=0.002), and tandem walk test (p=0.015) were significantly decreased among AS patients when compared to healthy volunteers.

In AS group, duration of disease was only correlated to step width at tandem walk test (r=0.443, p=0.014). Modified Schober was negatively correlated to tandem walk step width (r=-0.418, p=0.022), sway velocity on foam base when eyes open (r=-0,473, p=0.008), and closed (r=-0.558, p=0.001). Tragus wall distance was positively correlated to tandem walk step width (r=0.433, p=0.017). Neither BASDAI nor VAS was correlated to sway velocity on foam base when eyes open and closed, walk across speed, step width, step length, and tandem walk step width.

Conclusion: Walking speed and step length were significantly impaired in AS patients. As Modified Schober test measurement decreases, sway velocity on foam base and step width at tandem walk increase. Tragus wall distance lengthening results in increased step width at tandem walk. To sum up, forward head posture and limited spine flexibility are suggested to be the main causes of balance disorders in AS. Postural changes have more effect on balance than disease activity. Poor posture leads to impaired balance and AS patients adopt compensatory strategies, such as increasing their step width and decreasing their speed, to maintain their balance.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/what-impairs-balance-in-ankylosing-spondylitis-posture-or-disease-activity/