title: MRI findings of treated bacterial septic arthritis.
abstract: BACKGROUND
  The purpose of this study was to report the MRI findings that can be encountered in successfully treated bacterial septic arthritis.
  
  
  METHODS
  The study included 12 patients (8 male and 4 female; mean age 38 years, range 9-85) with 13 proven cases of bacterial septic arthritis. The joints involved were hip (n = 3), knee (n = 3), shoulder (n = 2), sacroiliac (n = 2), ankle (n = 1), wrist (n = 1), and elbow (n = 1). MRI examinations following surgical debridement and at initiation of antibiotic therapy and after successful treatment were compared for changes in effusion, synovium, bone, and periarticular soft tissues. Imaging findings were correlated with microbiological and clinical findings.
  
  
  RESULTS
  Joint effusions were present in all joints at baseline and regressed significantly at follow-up MRI (p = 0.001). Abscesses were present in 5 cases (38 %), and their sizes decreased significantly at follow-up (p = 0.001). Synovial enhancement and thickening were observed in all joints at both baseline and follow-up MRI. Myositis/cellulitis was present in 10 cases (77 %) at baseline and in 8 cases (62 %) at follow-up MRI. Bone marrow edema was present in 10 joints (77 %) at baseline and persisted in 8 joints (62 %). Bone erosions were found in 8 joints (62 %) and persisted at follow-up MRI in all cases.
  
  
  CONCLUSIONS
  The sizes of joint effusions and abscesses appear to be the factors with the most potential for monitoring therapy for septic arthritis, since both decreased significantly following successful treatment. Synovial thickening and enhancement, periarticular myositis/cellulitis, and bone marrow edema can persist even after resolution of the infection.
authors.affiliation: Musculoskeletal Imaging and Intervention, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Yawkey 6E, 55 Fruit Street, Boston, MA 02114, USA.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bierry
authors.forename: Ambrose J
authors.initials: AJ
authors.lastname: Huang
authors.forename: Connie Y
authors.initials: CY
authors.lastname: Chang
authors.forename: Martin
authors.initials: M
authors.lastname: Torriani
authors.forename: Miriam A
authors.initials: MA
authors.lastname: Bredella
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001170:Arthritis, Infectious / Q000188:drug therapy* / Q000473:pathology*; D001424:Bacterial Infections / Q000188:drug therapy* / Q000473:pathology*; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents