title: Non-uniform displacement within the Achilles tendon during passive ankle joint motion.
abstract: OBJECTIVE
  An initial step in the understanding of Achilles tendon dynamics is to investigate the effects of passive motion, thereby minimising muscle activation and reducing internal joint forces. Internal tendon dynamics during passive ankle joint motion have direct implications for clinical rehabilitation protocols after Achilles tendon surgery. The aim of this study was to test the hypothesis that tendon tissue displacement is different in different layers of the Achilles tendon during controlled passive ankle joint movements.
  
  
  METHODS
  Ultrasound imaging was conducted on the right Achilles tendon of nine healthy recreationally active males. Standardised isokinetic passive dorsi-plantar-flexion movements were performed with a total range of motion of 35°. The tendon was divided into superficial, central and deep layers in the resulting B-mode ultrasound images viewed in the sagittal plane. A block-matching speckle tracking algorithm was applied post-process, with kernels for the measurement of displacement placed in each of the layers.
  
  
  RESULTS
  The mean (SD) displacement of the Achilles tendon during passive dorsiflexion was 8.4 (1.9) mm in the superficial layer, 9.4 (1.9) mm in the central portion and 10.4 (2.1) mm in the deep layer, respectively. In all cases, the movement of the deep layer of the tendon was greater than that of the superficial one (P < 0.01).
  
  
  CONCLUSIONS
  These results, achieved in vivo with ultrasonographic speckle tracking, indicated complex dynamic differences in different layers of the Achilles tendon, which could have implications for the understanding of healing processes of tendon pathologies and also of normal tendon function.
authors: Division of Orthopaedic Surgery, Clintec, Karolinska Institute, Karolinska University Hospital, K54, 141 86 Stockholm, Sweden. toni.arndt@ki.se
authors: Anton
authors: A
authors: Arndt
authors: Ann-Sophie
authors: AS
authors: Bengtsson
authors: Michael
authors: M
authors: Peolsson
authors: Alf
authors: A
authors: Thorstensson
authors: Tomas
authors: T
authors: Movin
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging* / Q000502:physiology; D000328:Adult; D000465:Algorithms; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D014463:Ultrasonography