INTRODUCTION: The entheses are a primary target organ in psoriatic arthritis (PsA) . Differential presentation at the Achilles tendon (AT) in PsA is associated with function . The main aim of this study was to compare rotational movements across the ankle and subtalar joints and ankle joint moments and powers in PsA patients with and without AT enthesitis.
METHODS: Twenty nine PsA patients fulfilling the CASPAR diagnostic criteria (mean (SD) age- 47.6 (12.3) yrs, BMI- 24.7 (3.4), and disease duration- 11.3 (9.7) yrs), and 10 healthy adults (mean (SD) age- 44.7 (10.6) yrs, and BMI- 24.2 (2.5)) were
studied. Standard clinical metrics including pain, impairment and disability were measured. AT enthesitis was detected using high-resolution ultrasound (Esaote MyLab 25 Gold, Esaote Genoa, Italy) and the GUESS scoring system . Video-based 3D gait analysis was undertaken using an 8-camera MOCAP system (Oqus, Qualysis, Gothenburg, Sweden) and force plate (Kistler, Winterthur, Switzerland). Intersegment kinematics and kinetics were analysed using a multi-segment foot model in
Visual3D software (C-Motion Inc., MD, USA). A core set of spatio-temporal, kinematic and kinetic variables was selected a priori and between group differences analysed using one-way ANOVA with post-hoc Tukeys test.
RESULTS: The GUESS score positively identified 20 PsA patients and 6 control subjects with AT enthesitis. A summary of the inter-segment kinematics and kinetics are presented in Table 1. A statistically significant between-group difference was detected for ankle power only. Tukeys post-hoc test indicated a significant difference between PsA enthesitis positive and control subjects only (p=0.008). There was a trend towards slower walking, poor global health and higher global and foot pain in the PsA enthesitis positive group.
DISCUSSION: Complex multi-planar movements have been associated with the differential presentation of enthesitis in PsA, with the AT regarded as a prime site [1,2]. The findings from this cohort of patients do not support this hypothesis. Moreover, enthesitis can be detected in otherwise healthy adults with equivalent function. These findings require confirmation.