title: Achilles enthesis ultrasound: the importance of the bursa in spondyloarthritis.
abstract: OBJECTIVE
  This paper aims to assess the prevalence and relevance of the bursa-synovial lesion in spondyloarthritis (SpA).
  
  
  METHODS
  A transversal blind and controlled two-dimensional (2D) and three-dimensional (3D) ultrasound (US) study of Achilles enthesis bursa in early SpA was undertaken. Clinical outcome measures were collected.
  
  
  RESULTS
  Bilateral Achilles enthesis of 66 early SpA patients (34 women) and 46 control patients (23 asymptomatic healthy subjects and 23 rheumatoid arthritis [RA] patients) were analysed. Mean BASDAI, BASFI and BASRI-spine were 4.55±2.08, 2.16±1.95 and 0.65±0.77, respectively. Mean erythrocyte sedimentation rate (ESR) was 10.93±12.35 mm/h and C-reactive protein (CRP) was 6.46±10.09 mg/l. The κ-values for intra-reader agreement for 2D and 3D images and bursa measurement were 0.82 and 0.98, respectively. Bursas were visualised in 89/132 SpA enthesis (67.4%) vs. 27/46 enthesis (58.7%) of healthy controls (p<0.01), and 10/46 enthesis (21.7%) of RA controls (p<0.01). When the thicknesses of the bursas were analysed, the SpA group had a mean of 1.52±1.47 mm versus 0.76±0.76 mm in the healthy control group (p<0.0001), and 0.38±0.62 mm in the RA control group (p<0.0001). A positive likelihood ratio of 4.6 with a cut-off point of bursa >2 was found. No Doppler signal was detected in controls, but 6.6% of SpA Achilles enthesis had Doppler bursitis. Heel pain was more frequent when bursa was present (p<0.05). When Doppler was present, male predominance, HLA B27 positive, heel pain, and higher number of swollen joints, CRP levels, disease activity by the patient and BASDAI questions 2 and 3 achieved statistical significance (p<0.01).
  
  
  CONCLUSIONS
  The presence of bursa and Doppler signal at retrocalcaneal bursa level could have a relevant contribution to differentiate SpA patients, and were correlated with clinical outcomes of SpA disease activity.
authors: Rheumatology Department, Faculdade de Ciências Médicas da Universidade Nova de Lisboa, Lisbon, Portugal. sfalcao76@gmail.com
authors: Sandra
authors: S
authors: Falcao
authors: Eugenio
authors: E
authors: de Miguel
authors: Concepción
authors: C
authors: Castillo-Gallego
authors: Diana
authors: D
authors: Peiteado
authors: Jaime
authors: J
authors: Branco
authors: Emilio
authors: E
authors: Martín Mola
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging*; D000293:Adolescent; D000328:Adult; D015535:Arthritis, Psoriatic / Q000150:complications / Q000000981:diagnostic imaging*; D002061:Bursa, Synovial / Q000000981:diagnostic imaging*; D002062:Bursitis / Q000150:complications / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D016037:Single-Blind Method; D013167:Spondylitis, Ankylosing / Q000150:complications / Q000000981:diagnostic imaging*; D014463:Ultrasonography; D055815:Young Adult