Effect of body shape on tragus-to-wall distance in the normal population.

Ankylosing spondylitis (AS) may result in a loss of spinal mobility. Therefore, evaluation of spinal mobility is an essential part of follow-up of patients with AS. The tragus-to-wall distance (TWD) is one of the four spinal mobility assessment parameters of the Bath Ankylosing Spondylitis Metrology Index, an index used in the follow-up of patients with AS.