title: The relationship between in vivo limb and in vitro tendon mechanics after injury: a potential novel clinical tool for monitoring tendon repair.
abstract: BACKGROUND
  Highly prevalent superficial digital flexor tendon (SDFT) injury results in compromised tendon function through fibrosis and high frequency of re-injury due to altered biomechanical function. This study investigated the consequences of SDF tendinopathy on limb mechanics in relation to the mechanical properties of injured tendon.
  
  
  OBJECTIVE
  To develop and validate a noninvasive in vivo assessment of tendon mechanics to investigate the effect of recent SDFT injury on limb stiffness index, providing an objective method to assess quality of healing.
  
  
  OBJECTIVE
  Limb stiffness index would reduce as a consequence of SDFT injury and progressively increase during tendon healing and correlate with in vitro mechanical properties of the respective SDFTs.
  
  
  METHODS
  Kinematic analysis was performed at walk in 10 horses that had sustained career-ending SDFT injury. Stiffness index was derived from limb force recorded via a series of force plates and measurement of change in metacarpophalangeal joint angle using 3D motion analysis software. Horses were subjected to euthanasia 7 months after injury, the SDFTs removed and subjected to nondestructive in vitro mechanical testing.
  
  
  RESULTS
  Limb stiffness index was reduced following SDFT injury in comparison with the contralateral limb and increased during the convalescent period, approximating that of the contralateral limb by 7 months post injury. There was a significant positive correlation between in vivo limb stiffness index and in vitro SDFT stiffness.
  
  
  CONCLUSIONS
  The ability to assess and monitor SDFT mechanical competence through limb stiffness measurement techniques in horses recovering from SDFT injury and the possibility of corroborating this with functional tendon healing may permit a more objective and accurate assessment of optimal tendon repair in the horse. This technique may be a useful method for assessing the efficacy of treatment regimens for tendinopathy and could be utilised to predict time to safe return to performance or re-injury.
authors.affiliation: Department of Veterinary Clinical Sciences, The Royal Veterinary College, Hertfordshire, UK. sdakin@rvc.ac.uk
authors.forename: S G
authors.initials: SG
authors.lastname: Dakin
authors.forename: K
authors.initials: K
authors.lastname: Jespers
authors.forename: S
authors.initials: S
authors.lastname: Warner
authors.forename: L K
authors.initials: LK
authors.lastname: O'Hara
authors.forename: J
authors.initials: J
authors.lastname: Dudhia
authors.forename: A E
authors.initials: AE
authors.lastname: Goodship
authors.forename: A M
authors.initials: AM
authors.lastname: Wilson
authors.forename: R K W
authors.initials: RK
authors.lastname: Smith
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000502:physiology; D005552:Forelimb / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology; D006614:Hindlimb / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology; D006734:Horse Diseases / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006736:Horses; D007794:Lameness, Animal / Q000000981:diagnostic imaging; D008297:Male; D013708:Tendon Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000662:veterinary*; D014463:Ultrasonography