AB0242 RADIOLOGICAL EVALUATION OF FOREFOOT INVOLVEMENT IN RHEUMATOID ARTHRITIS
Authors: Rym Fakhfakh, Saoussen Zrour, Abir Dghaies, Hibatallah Mosbeh, Olfa Jmaa, Grassa Rim, Jguirim Mahbouba, Ismail Bejia, Mongi Touzi, Naceur Bergaoui
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Severe and often debilitating involvement of the forefoot is seen frequently in patients with rheumatoid arthritis (RA) <h3>Objectives</h3> We aim to determine the prevalence and the characteristics of radiological forefoot involvement <h3>Methods</h3> Monocentric retrospective study of 52 consecutive patients with RA, hospitalized in the Rheumatology Department between 2012 and 2018. Radiological measurements included the modified Sharp/van der Heijde method (SHS) for the feet and forefoot angles: The angle between the longitudinal bisection of the first metatarsal and the first phalanx of the first finger (Hallux valgus: H1M1≥20°), the intermetatarsal angle between the 1st and 2nd metatarsals (Metatarsus primus varus: M1M2≥ 10°) and the intermetatarsal angle between the 1st and 5th metatarsals (splaying foot: M1M5≥ 35°) measured on antéroposterior radiographs. <h3>Results</h3> The average age was 53 ± 15 years and the sex-ratio was 0.21. The average disease duration was 8 ± 10 years and the average disease activity index DAS28 was 5.65±1.12. The prevalence of forefoot erosion and joint space narrowing were 35% and 58%, respectively. In 85% of patients, both ≥1 forefoot erosion score and ≥1 forefoot joint space narrowing score were present. Erosions were the most frequent in the 5<sup>th</sup> metatarsophalangeal joints (MTP) and 1<sup>st</sup> interphalangeal joint (50% and 47% of eroded joints, respectively) and the least frequent in 4<sup>th</sup>MTP (27%). The forefoot erosion score was significantly correlated with age, disease duration and hand erosion score and weakly but statistically significantly with titer of ACPA (p≤0.05). Obesity was an independent protective factor (OR = 0.25; p &lt;0.05) of forefoot erosions. Foot deformities were observed in 71% of the patients; Metatarsus primus varus(MV) (56%), hallux valgus(HV) (38.5%) and splaying foot(SF) (13.5%). The HV was significantly correlated with forefoot damage (erosion score r=0.67, joint space narrowing r=0.7; p&lt;0.01), extra-articular manifestations of RA, disease duration and rheumatoid factor titer. Multivariate analysis showed that the extra-articular manifestations was an independent risk factor for HV (OR = 9.39, p &lt;0.05). There was significant correlation between the MV and forefoot damage (erosion score: r=0.4, joint space narrowing: r=0.5, p&lt;0.05). There was no correlation between the splaying foot and the forefoot damage. The splaying foot was associated with the hallux valgus (OR = 5.7, p = 0.05). <h3>Conclusion</h3> In our study, forefoot involvement is common in patients with RA and it isn't associated with disease severity. Deformities (HV, MV) are associated with forefoot joint damage and splaying foot is associated with hallux valgus. <h3>References</h3> [1] Baan H, &amp; Drossaers-Bakker w, et al. We should not forget the foot: relations between signs and symptoms, damage, and function in rheumatoid arthritis. Clin Rheumatol (2011) 30:1475–1479 [2] Matsumoto, et al. Radiologic Patterning of Joint Damage to the Foot in Rheumatoid Arthritis. Arthritis Care &amp; Research.2014;66 (4):499–507. <h3>Disclosure of Interests</h3> None declared