Comparison between the intermalleolar distance measured on the couch and on the floor in axial spondyloarthritis

The aim of this study was to assess whether axial spondyloarthritis (axial SpA) patients' supine position on the couch (OC) or on the floor (OF) affects intermalleolar distance (IMD) measurement and its Bath Ankylosing Spondylitis Metrology Index (BASMI) scoring, using all three versions of BASMI index. OC- and OF-IMDs were obtained for 43 axial SpA patients (M:F = 19:24). Age, gender, height, weight, body mass index (BMI), disease type and disease duration were also collected. Statistical analyses and correlations were performed as appropriate. Mean IMD measurements obtained with individuals in the two distinct measuring positions were not significantly different in the patients studied. Furthermore, there was a significant correlation between OC-IMD and OF-IMD values. There was no significant relationship between IMD and patient age, gender, height, weight, BMI, or disease duration. However, looking at disease type, IMDs of patients with ankylosing spondylitis (AS) were ~30 % greater than those with psoriatic arthritis (PsA) in our study population (p < 0.05). There were no significant differences between the measured patient characteristics that accounted for the greater IMDs of those diagnosed with AS. IMD measurements and resultant BASMI scores were the same whether the patient was positioned OC or OF in our axial SpA cohort. Unexpectedly, IMD measurements were significantly greater (~30 %) in AS patients than in axial PsA patients.