Clinical Relevance of Pelvic and Heel Enthesophytes in Psoriatic Arthritis

Abstract

Objectives Enthesitis is a hallmark feature of psoriatic arthritis (PsA), but its clinical assessment can be confounded by subjective assessment and overlapping fibromyalgia. We aimed to investigate the clinical and functional associations of radiographic enthesophytes in a large longitudinal PsA cohort. Methods Data from 1,602 prospectively enrolled PsA patients with available radiographs were analyzed. Clinical assessments are conducted every 6 months for recording disease activity, patient-reported outcomes (Health Assessment Questionnaire [HAQ] and Short Form 36 physical function [SF-36 PF]), and treatment details, with radiographs obtained biennially. Radiographic pelvic enthesophytes and calcaneal spurs (Achilles/plantar) are systematically recorded. Associations of enthesophytes (all, pelvic, and heel) with demographic, clinical, and functional measures were evaluated using generalized estimating equations. Results 1,176 patients of 1,602 (73%) had enthesophytes over the follow-up period; 763 (48%) had pelvic enthesophytes and 1,017 (63%) had calcaneal spurs. Pelvic enthesophytes were associated with older age (OR 1.04, 95% CI 1.03-1.05), male sex (2.08, 1.74-2.49), and lower tender joint counts (0.99, 0.97-1.00). Calcaneal spurs were associated with lower swollen joint counts (0.98, 0.96-1.00). Both pelvic and calcaneal enthesophytes were associated with higher body mass index (BMI), osteoarthritis, concomitant presence of diffuse idiopathic skeletal hyperostosis (DISH), diabetes mellitus, psoriasis area and severity index (PASI) scores, axial disease, and higher modified Steinbrocker scores. No association was observed with clinical enthesitis. Functionally, calcaneal spurs were linked to worse HAQ (OR 1.24, 95% CI 1.04-1.47) and worse SF36 physical function scores (0.99, 0.99-1.00), whereas pelvic enthesophytes had minimal impact on function. There was no association observed with patient global assessment (Figure 1). Figure 1: Univariable associations with enthesophytes (all), pelvic and calcaneal enthesophytes Conclusion Pelvic and calcaneal radiographic enthesophytes are common in PsA and associate with PsA-related (PASI, axial involvement, greater peripheral damage) and comorbid factors (higher BMI, diabetes, OA/DISH, and for pelvic subtype, male sex and older age). Calcaneal spurs adversely affect functional indices, unlike pelvic enthesophytes. These findings emphasize the relevance of radiographic enthesophytes beyond clinical enthesitis assessment.