Background Gout is due to monosodium urate (MSU) crystal deposition after chronic hyperuricemia. Although MSU crystal deposition can occur in every joint and peri-articular structure, spine involvement is scarcely reported. Dual energy computed tomography (DECT) is a performant tool to assess urate deposits, especially in deep structures such as intervertebral discs and apophyseal joints.
Objectives to describe spinal DECT features of urate monosodium deposits compared to peripheral joint DECT.
Methods Patient with gout diagnosis (MSU crystal identification by polarized microscopy or fulfilling “Nijmegen's criteria” (1)) who had undergone DECT were included from November 2012 to June 2016. Images were analyzed by a trained musculoskeletal radiologist. For each DECT, clinical and biochemical characteristics of each patient were collected retrospectively.
Results 22 patients (men 77%), mean age 62.5 years and mean BMI 28.4 kg/m2 were included. Mean gout duration was 108.0±114.4 months, mean of last available serum uric acid level was 520±193 μmol/l, and 15 patients had at least one clinical tophus. Mean estimated glomerular filtration rate (MDRD formula) was 47±27 ml/min/1.73 m2. One patient was on hemodialysis and one had received kidney transplant.
A total of 39 DECT has been performed: 28 of peripheral joints and 11 of the spine (9 lumbar, 1 sacroiliac and 1 cervical). Spinal DECT were done in 10 patients to explore recurrent inflammatory pain (n=3 lumbar, 1 cervical and 1 buttock) or mechanical back pain (n=2 lumbar). 4 spinal DECT were performed in asymptomatic patients with extended peripheral tophi. Spinal MSU crystal deposits were disclosed by DECT in 83% (5/6) and 25% (1/4) of symptomatic and asymptomatic patients, respectively. In all painful patients, MSU crystal deposition was considered as a likely explanation of spinal symptoms. MSU crystal depositions was identified in apophyseal joints (n=5), cervical intervertebral disc (n=1) and yellow or interspinous ligaments (n=4). All involved apophyseal joints were eroded (figure 1). No vertebral bone erosion was observed. Calcification of spinal tophus was observed in 4 patients. DECT identified peripheral deposits in 15/18 (83.3%) patients. In peripheral DECT, bone erosions were observed in 71.4% and joint effusion in 32.1% of DECT positive peripheral joints. MSU crystal depositions were observed in tendons, cartilages or synovial membranes in 82.1% of positive DECT joints and in soft tissues in 64.3% of positive patients. MSU crystal deposits were calcified in 7 cases.
Conclusions MSU crystal depositions at the spine are present in 60% of patients in this retrospective DECT study. DECT can represent a performing imaging procedure for their detection in symptomatic patients. Further studies are needed to assess the clinical utility of DECT of the spine in gout.
Janssens HJ, Fransen J, van de Lisdonk EH, et al. A diagnostic rule for acute gouty arthritis in primary care without joint fluid analysis. Arch Intern Med 2010;170:1120–6.
Disclosure of Interest None declared