AB0099 IN VIVO BONE MICROARCHITECTURE ANALYSIS IN A PSORIATIC ARTHRITIC PATIENT BEFORE AND AFTER ANTI-TNFΑ TREATMENT
Authors: E. Soldati, L. Escoffier, S. Gabrie, J.P. Mattei, S. Camilleri, D. Bendahan, S. Guis
Journal: Annals of the Rheumatic Diseases (2021)

<h3>Background:</h3> In psoriatic arthritis (PA), a systemic inflammatory phenomenon, mainly mediated by TNFα, is characterized by a bone loss due to osteoclastic stimulation. Anti-TNFα treatment should inhibit this phenomenon having a role on systemic bone loss. Ultra-high field MRI (UHF MRI) may be a tool of choice for the quantification of bone microarchitecture (BM) <i>in vivo</i>. <h3>Objectives:</h3> The purpose of the present study was to quantify BM using UHF MRI in a PA patient and to follow up changes related to anti-TNFα treatment. <h3>Methods:</h3> An 18 years-old untreated PA patient with knee arthritis and 7 gender-matched healthy controls [21.6±0.8 years] were scanned using a gradient echo sequence at UHF MRI (TR/TE = 15/4.36ms). After a year of Adalimumab treatment, the patient underwent a second UHF MRI. BM analysis was performed on sagittal planes in regions corresponding to tendon insertion: proximal and distal patellar, and posterior tibial. A PET-FNa imaging was also performed before and after treatment. BM was characterized using the bone volume fraction (BVF), the trabecular thickness (TbTh) and the spacing (TbSp) and number of trabeculae (TbN). Student T-test was used for the statistical analysis and a p-value &lt; 0.01 was considered as significative. <h3>Results:</h3> PET-FNa recorded before the treatment illustrated hypermetabolic areas which resumed after the treatment while the patient was in remission. The BM parameters are shown in figure 1. The BM parameters quantified before the treatment were very different as compared to controls. BVF was significatively lower (-33±23%), TbSp and TbN were significatively distinct (-27±3% and +27±9%) for all ROIs but proximal patellar, while TbTh was in the normal range (-2±2%). After 1 year of treatment, BM parameters were significantly improved. BVF was no longer different than controls (-8±6%). Similarly, TbSp and TbN were in the normal range (+13±12% and -15±10%) for all ROIs but posterior tibial. TbTh (-5±3%) was only significantly decreased for the distal patella. Table 1. Data are presented as mean ± SD. "P." refers as patient. BVF: Bone volume fraction, TbTh: Trabecular Thickness, TbSp: Trabecular Space, TbN: Trabecular number. * indicates a statistically significant difference (p &lt; 0.01) with the Healthy reference values. <h3>Conclusion:</h3> Our results illustrated knee microstructure alterations in a PA patient and a normalization after a year of treatment. The abnormalities initially observed were not only localized in the hypermetabolic regions identified by PET-FNa, suggesting that the bone loss was global and not related to inflammatory sites. Using UHF MRI, we highlighted and quantified <i>in vivo</i> BM anomalies in a patient with an inflammatory rheumatism together with the reversibility after one year of treatment. <h3>Acknowledgements:</h3> All the authors declare no conflict of interest. ES has received funding from the European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant agreement No713750. Also, it has been carried out with the financial support of the Regional Council of Provence- Alpes-Côte d'Azur and with the financial support of the A*MIDEX (n° ANR- 11-IDEX-0001-02), funded by the "Investissements d'Avenir" project funded by the French Government, managed by the French National Research Agency (ANR). edgements to declare. <h3>Disclosure of Interests:</h3> None declared