Objective To evaluate ES for quantification of spinal mobility in patients with axSpA. Methods A total of 153 individuals, 39 females and 114 males, were examined:134 axSpA patients, 40 non-(nr-) and 94 radiographic (r)-axSpA, and 19 healthy controls (HC), respectively. The results were compared using mean ES scores and modeling was performed using multivariable logistic regression models resulting in good validity and high discriminative power. Results ES measurements showed meaningful differences between axSpA patients and HC (all p<0.001) as well as between r- and nr-axSpA (p<0.01). In axSpA patients a negative correlation between ES and BASMI values was found: -0.76≤r≤-0.52 (p<0.05). BASFI scores showed a similar trend (r > -0.39). Patients with r-axSpA had a more limited and slower spinal mobility than those with nr-axSpA. Other patient reported outcomes did almost not correlate. Conclusion This study shows that the ES is an objective performance measure and a valid tool to assess spinal mobility in axSpA, also based on OMERACT criteria. RoK and RoM scores provide additional information on physical function of axSpA patients.

ObjectiveAxial spondyloarthritis (axSpA) is associated with decreased function and mobility of patients due to inflammation and radiographic damage. The Epionics SPINE device (ES), an electronic device that objectively measures spinal mobility, including range of motion (RoM) and speed (RoK) of movement, has been clinically validated in axSpA. We investigated the performance of the ES relative to radiographic damage in the axial skeleton of patients with axSpA.MethodsA total of 103 patients with axSpA (31 non- [nr-] and 72 radiographic [r]- axSpA) were consecutively examined. Conventional radiographs of the spine (including presence, number and location of syndesmophytes) and the sacroiliac joints (SIJs, rated by mNY criteria) were analyzed with the ES and assessments of function and mobility using analyses of covariance and Spearman correlation.ResultsThe number of syndesmophytes correlated positively with BASMI scores (r=0.38;P=0.016) and negatively with chest expansion (r=-0.39;P=0.015) and ES measurements (-0.53 ≤r≤ -0.34,P<0.03) except for RoM and RoK regarding rotation and RoK for extension of the lumbar and thoracic spine. In the radiographic evaluation of SIJs, the extent of damage correlated negatively with ES scores and metric measurements (-0.49 ≤r≤ -0.33;P<0.001). Patients with r-axSpA showed significantly worse ES scores for RoM, RoK and chest expansion than those with nr-axSpA.ConclusionThe ES scores, in accordance with mobility measurements, correlated well with the presence and extent of radiographic damage in the spine and SIJs. As expected, patients with r-axSpA had more severe impairments than those with nr-axSpA.