title: Validation of color Doppler sonography for evaluating relative displacement between the flexor tendon and subsynovial connective tissue.
abstract: OBJECTIVE
  A common pathologic finding in carpal tunnel syndrome is fibrosis and thickening of the subsynovial connective tissue. This finding suggests an etiology of excessive shear forces, with relative longitudinal displacement between the flexor tendon and adjacent subsynovial connective tissue. The purpose of this study was to validate color Doppler sonography for measurement of tendon displacement over time.
  
  
  METHODS
  Eight unmatched fresh frozen cadaver arms were used to evaluate color Doppler sonography for measurement of tendon displacement. The middle flexor digitorum superficialis tendon was moved through a physiologic excursion of 20 mm at 3 different tendon velocities (50, 100, and 150 mm/s).
  
  
  RESULTS
  We found that color Doppler sonography provided accurate measurement of tendon displacement, with absolute errors of -0.05 mm (50 mm/s), -1.24 mm (100 mm/s), and -2.36 mm (150 mm/s) on average throughout the tendon excursion range. Evaluating relative displacement between the tendon and subsynovial connective tissue during finger flexion-extension movements also offered insight into the gliding mechanism of the subsynovial connective tissue. During flexion, we observed a curvilinear increase in relative displacement, with greater differential motion at the end range of displacement, likely due to the sequential stretch of the fibrils between successive layers of the subsynovial connective tissue. In extension, there was a linear return in relative displacement, suggesting a different unloading mechanism characterized by uniform relaxation of fibrils.
  
  
  CONCLUSIONS
  We demonstrated the validity of color Doppler displacement for use in the evaluation of relative motion. Color Doppler sonography is useful in our understanding of the behavior of the subsynovial connective tissue during tendon excursion, which may elucidate the role of finger motion in the etiology of shear injury.
authors: Occupational Biomechanics Laboratory, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
authors: Jimmy
authors: J
authors: Tat
authors: Occupational Biomechanics Laboratory, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
authors: Aaron M
authors: AM
authors: Kociolek
authors: Occupational Biomechanics Laboratory, Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada. pjkeir@mcmaster.ca.
authors: Peter J
authors: PJ
authors: Keir
mesh_terms: D002102:Cadaver; D003238:Connective Tissue / Q000000981:diagnostic imaging*; D005384:Finger Joint / Q000000981:diagnostic imaging* / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D013583:Synovial Membrane; D013710:Tendons / Q000000981:diagnostic imaging*; D018615:Ultrasonography, Doppler, Color
keywords: color Doppler sonography; musculoskeletal ultrasound; shear; sonography; subsynovial connective tissue; tendon; viscoelastic