title: The effect of time after shear injury on the subsynovial connective tissue and median nerve within the rabbit carpal tunnel.
abstract: BACKGROUND
  The most prominent nonneurological finding in the common compression neuropathy carpal tunnel syndrome (CTS) is fibrosis of the subsynovial connective tissue (SSCT). Recently, a rabbit model of CTS has been developed, based on the hypothesis that SSCT injury and subsequent fibrosis cause nerve compression. The purpose of this study was to evaluate the effects in this model at earlier and later time points than have heretofore been reported.
  
  
  METHODS
  Sixty rabbits were operated on and observed at two different time periods: 6 and 24 weeks. Nerve electrophysiology (EP), SSCT histology, and SSCT mechanical properties were assessed.
  
  
  RESULTS
  There was no significant difference in median motor nerve amplitude or latency at either time point. The total cell density in the SSCT was significantly higher at 6 and 24 weeks compared to controls. The mean size of the collagen fibrils in the SSCT was higher 6 and 24 weeks after surgery compared to controls. Both the ultimate load and the total energy absorption of the SSCT were significantly higher at 6 and 24 weeks compared to controls.
  
  
  CONCLUSIONS
  In this model, there were signs of SSCT fibrosis and histology changes at 6 weeks, which persist after 24 weeks. Thus, this model leads to sustained SSCT fibrosis, which is one characteristic of human CTS. However, no significant EP changes were found at these two time points, which is in contrast to the findings reported previously for this model at 12 weeks. The significance of the differences in EP findings will be the subject of future studies.
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Matthias
authors.initials: M
authors.lastname: Vanhees
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Takako
authors.initials: T
authors.lastname: Chikenji
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Thoreson
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Zhao
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN USA.
authors.forename: James D
authors.initials: JD
authors.lastname: Schmelzer
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN USA.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Low
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Kai-Nan
authors.initials: KN
authors.lastname: An
authors.affiliation: Biomechanics Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 1st St. SW, Rochester, MN 55905 USA.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Amadio
keywords: Carpal tunnel syndrome; Rabbit animal model; Shear injury; Subsynovial connective tissue