title: The extensor carpi ulnaris pseudolesion: evaluation with microCT, histology, and MRI.
abstract: OBJECTIVE
  To determine if magic angle plays a role in apparent central increased signal intensity of the distal extensor carpi ulnaris tendon (ECU) on MRI, to see if histologic findings of tendon degeneration are associated with increased T1 or T2 tendon signal on MR imaging, and to determine the prevalence of the ECU "pseudolesion".
  
  
  METHODS
  A standard 3 Tesla protocol was utilized to scan ten cadaveric wrists. A 40 mm length of 10 ECU and four extensor carpi radialis brevis (ECRB) tendons were immersion fixed before microCT scanning. Staining with Alcian blue, Masson's trichrome and Safranin O was performed before light microscopy. Fifty clinical wrist MRIs were also reviewed for the presence of increased T1 and/or T2 signal.
  
  
  RESULTS
  Central increased T1 and/or T2 signal was observed in 9 of 10 cadaveric ECU tendons, but not in ECRB tendons. MicroCT and histology showed inter-tendinous matrix between the two distal heads of the ECU. Increased mucoid degeneration correlated with increased MRI signal intensity. The tendon fibers were at a maximum of 8.39° to the longitudinal axis on microCT. Clinical MRIs showed increased T1 signal in 6%, increased T2 signal in 8%, increased T1 and T2 signal in 80%, and 6% showing no increased signal.
  
  
  CONCLUSIONS
  Central increased T1 and/or T2 signal in the ECU tendon indicates the presence of normal inter-tendinous ground substance, with increased proteoglycan content (mucoid degeneration) responsible for increased signal intensity. None of the fibers were shown on microCT to approach the magic angle.
authors.affiliation: Department of Radiology, Temple University Hospital, 3401 North Broad Street, Philadelphia, PA, 19140, USA. alisayan@tuhs.temple.edu.
authors.forename: Sayed
authors.initials: S
authors.lastname: Ali
authors.affiliation: Department of Radiology, Temple University Hospital, 3401 North Broad Street, Philadelphia, PA, 19140, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Cunningham
authors.affiliation: Department of Anatomy, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA, 19140, USA.
authors.forename: Mamta
authors.initials: M
authors.lastname: Amin
authors.affiliation: Department of Anatomy, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA, 19140, USA.
authors.forename: Steven N
authors.initials: SN
authors.lastname: Popoff
authors.affiliation: Department of Radiology, Temple University Hospital, 3401 North Broad Street, Philadelphia, PA, 19140, USA.
authors.forename: Feroze
authors.initials: F
authors.lastname: Mohamed
authors.affiliation: Department of Anatomy, Temple University School of Medicine, 3500 North Broad Street, Philadelphia, PA, 19140, USA.
authors.forename: Mary F
authors.initials: MF
authors.lastname: Barbe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D052256:Tendinopathy / Q000000981:diagnostic imaging* / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014955:Wrist Joint / Q000000981:diagnostic imaging* / Q000473:pathology*
keywords: Ground substance; Magic angle; Mucoid; Tendon