POS0510 A TWO-YEAR COMPARISON OF SPINAL AND HIP MOBILITY BETWEEN AXIAL SPONDYLOARTHRITIS AND CHRONIC BACK PAIN PATIENTS IN THE SPONDYLOARTHRITIS CAUGHT EARLY (SPACE) COHORT
Authors: A. Bento Da Silva, S. Ramiro, M. Van Lunteren, M. L. Marques, C. Fongen, M. G. H. Van de Sande, R. Ramonda, S. Exarchou, D. Van der Heijde, F. A. Van Gaalen
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Axial spondyloarthritis (axSpA) frequently leads to reduced spinal and hip mobility, though evidence pertains mostly to patients with longstanding disease and radiographic damage. More recently, restricted mobility has also been reported in early axSpA. However, little is known about how spinal and hip mobility change in the first years of the disease, especially in comparison to patients with non-axSpA chronic back pain (CBP). <h3>Objectives:</h3> To compare spinal and hip mobility at baseline and after 2 years (2y) in early axSpA and non-axSpA CBP patients. <h3>Methods:</h3> The population consisted of adults (≥16 years) with CBP lasting ≥3 months and ≤2y and starting &lt;45 years of age, included in the SPondyloArthritis Caught Early (SPACE) cohort. Patients had a diagnosis of axSpA or non-axSpA given by the treating rheumatologist at 2y, with a high level of confidence. [1] At baseline and 2y, the following spinal mobility measures (SMM) were assessed: occiput-to-wall distance (OWD), cervical rotation (CR), chest expansion (CE), lateral spinal flexion (LSF) and modified Schober test (mSchober); for hip mobility, maximal intermalleolar distance (IMD) was recorded. The Bath Ankylosing Spondylitis Metrology Index (BASMI) was also calculated. The proportion of patients with an impaired measure (&lt;2.5<sup>th</sup> percentile curves derived from healthy individuals [2]; &gt;0cm for OWD; &gt;97.5<sup>th</sup> percentile for BASMI) was also reported. For the assessment of each outcome, only patients with data available at both timepoints were included. Paired t-test (or Wilcoxon signed rank test, as appropriate) was used to compare baseline and 2y results within groups. For the comparison between groups (axSpA <i>vs</i> non-axSpA), linear or zero-inflated negative binomial regression models with 2y outcome were built, as appropriate, adjusting for the baseline value of the respective outcome (modelling a 2y change in the outcome), age, gender and use of nonsteroidal anti-inflammatory drugs. <h3>Results:</h3> A total of 434 patients (303 axSpA; 131 non-axSpA) had undergone a baseline and 2y visits. Data was available at both timepoints on ≥1 of the assessed outcomes in 286 axSpA and 117 non-axSpA patients. AxSpA (<i>vs</i> non-axSpA) patients were more frequently male (52% <i>vs</i> 25%) and had more SpA features (mean [SD]: 5 [2] <i>vs</i> 3 [1]). Age (mean [SD]: 30 [8] <i>vs</i> 31 [8] years) and symptom duration (mean [SD]: 13 [7] <i>vs</i> 14 [7] months) were similar between groups. At baseline, impairments in ≥1 SMM were present in 51% axSpA and 53% non-axSpA patients (Table 1). Overall, poorer mobility was seen in non-axSpA (<i>vs</i> axSpA) patients for most SMM, except OWD (mean [SD]: 0.5 [1.2] axSpA <i>vs</i> 0.1 [0.7] non-axSpA). After 2y, significant improvements were seen in both groups for CR (mean [SD] improvement: 2.4 [11.9] axSpA <i>vs</i> 2.8 [12.1] non-axSpA) and only in axSpA for LSF (1.1 [4.5]) and mSchober (0.3 [1.2]). In both groups, IMD remained stable between both timepoints. BASMI significantly improved in axSpA and non-axSpA patients (mean [SD] improvement: 0.2 [0.8] axSpA <i>vs</i> 0.2 [0.7] non-axSpA). In adjusted multivariable analysis (Figure 1), at 2y, axSpA (<i>vs</i> non-axSpA) was associated with larger improvements in mSchober (β [95% CI]: 0.26 [0.03; 0.50]), IMD (4.86 [1.93; 7.80]), and BASMI (-0.24 [-0.41; -0.08]), and with higher odds of an impaired OWD (OR [95% CI]: 0.09 [0.01; 0.83]). No differences between groups were observed for CR, CE or LSF. <h3>Conclusion:</h3> Impairments in spinal and hip mobility are common in early axSpA and, most notably, non-axSpA patients and most mobility measures remain relatively unchanged after 2y. However, at 2y, axSpA (<i>vs</i> non-axSpA) is associated with larger improvements in both spinal and hip mobility for mSchober, IMD and BASMI, but also with higher odds of OWD impairment. <h3>REFERENCES:</h3> [1] Marques ML <i>et al</i>. <i>Ann Rheum Dis</i> 2024 (epub ahead of print); 2. Ramiro S <i>et al</i>. <i>Ann Rheum Dis</i> 2015;74(6):1218-1224. <h3>Acknowledgements:</h3> The authors would like to acknowledge the Assessment of Spondyloarthritis International Society (ASAS) for having supported Ana Bento da Silva research fellowship. <h3>Disclosure of Interests:</h3> Ana Bento da Silva: None declared, Sofia Ramiro AbbVie, Eli Lilly, Janssen, MSD, Novartis, Pfizer, UCB, Sanofi, AbbVie, Galapagos, MSD, Novartis, Pfizer, UCB, Miranda van Lunteren: None declared, Mary Lucy Marques: None declared, Camilla Fongen: None declared, Marleen G.H. van de Sande Janssen, Novartis, UCB, Beneke, Janssen, Novartis, Abbvie, UCB, Janssen, Novartis, UCB, Roberta Ramonda: None declared, Sofia Exarchou Amgen, Janssen, Novartis, UCB Pharma, Désirée van der Heijde Abbvie, ArgenX, BMS, Galapagos, GSK, Jansen, Lilly, Novartis, Pfizer, Takeda, UCB Pharma. Director Imaging Rheumatology bv., F. A. van Gaalen Novartis, BMS, AbbVie, Galapagos, Janssen, Lily, UCB, Pfizer, Stichting ASAS, Novartis, UCB.