THU0489 HIP INVOLVEMENT IN DIFFUSE IDIOPATHIC SKELETAL HYPEROSTOSIS (DISH): CROSS-SECTIONAL STUDY

Background: In DISH or Forestier-Rotes disease, hip involvement is often misdiagnosed as hip osteoarthritis, especially when it is the initial manifestation of the disease or in patients with scarce vertebral signs. At present, a correct identification of this entity may suppose considerable therapeutic implications1. Objectives: The purpose of this study was to assess the prevalence and characteristics of hip involvement in our cohort of patients with DISH and evaluate the association of this extra-spinal manifestation with the variables studied. Methods: We carried out a cross-sectional study in DISH patients who met Resnick and / or Utsinger classification criteria. We collected demographic, anthropometric, clinical and imaging data. Hip involvement was defined as the characteristic irregular bony excrescences above acetabulum. The cohort was divided between patients with and without hip involvement. A univariate descriptive analysis was performed with means and standard deviations, absolute frequencies and percentages. The normality of the data was checked using the Shapiro-Willis test. The bivariate analysis, for the qualitative variables, the χ2 test or Fisher’s exact test were identified. For the quantitative variables, the Student’s t-test was used if the data followed a normal distribution, and otherwise using the Mann-Whitney U test. Results: Of the 58 patients included, 67.2% were male. The median age was 69.4 years (44-89). The average time of disease evolution was 14.8 (+9.3) years. Although the most frequent initial symptom was thoraco-lumbar pain (39.7%), hip complaints were initially present in 13.8%. 22,6% of patients did not fulfil Resnick classification criteria. Hip involvement was identified in 53.4% and a 61,3% the cartilage space were preserved. In the bivariate analysis, hip involvement was associated with female sex, a reduction in the intermaleolar distance (IM) and the presence of certain enthesopathies (greater trochanter, superior iliac spines and distal patellar entheses). The acetabular ossifications were significantly related to the mixed pattern compared to the other possible phenotypes of the disease. Conclusion: Hip involvement has been described in more than 50% of our patients. We found out that it was associated with female sex and a more broad ossification phenotype (mixed pattern). The measurement of IM distance could be useful for the clinical evaluation of this condition. Ossifications of other pelvic ring entheses were more observed in association with acetabular hyperostosis than other peripheral insertions. References: [1]Jung-Mo Hwang, Deuk-Soo Hwang, Chan Kang, Woo-Yong Lee, et al. Arthroscopic Treatment for Femoroacetabular Impingement with Extraspinal Diffuse Idiopathic Skeletal Hyperostosis. Clin Orthop Surg 2019; 11: 275–281. Disclosure of Interests: : Teresa Clavaguera Speakers bureau: novartis, BMS, Faes, Eulalia Armengol Speakers bureau: Novartis, Maria Buxo: None declared, Marta Valls: None declared, Eulalia DE CENDRA: None declared, Patricia Reyner Speakers bureau: Faes, Sanofi