title: The structural and mechanical properties of the Achilles tendon 2 years after surgical repair.
abstract: BACKGROUND
  Acute ruptures of the Achilles tendon affect the tendon's structural and mechanical properties. The long-term effects of surgical repair on these properties remain unclear.
  
  
  OBJECTIVE
  To evaluate effects of early mobilization versus traditional immobilization rehabilitation programs 2 years after surgical Achilles tendon repair, by comparing force-elongation and stress-strain relationships of the injured tendon to those of the uninjured tendon.
  
  
  METHODS
  A group of males with previous Achilles tendon rupture (n=18) and a group of healthy male controls (n=9) participated. Achilles tendon rupture group consisted of patients that had received early mobilization (n=9) and patients that had received traditional immobilization with a plaster cast (n=9). Comparisons of tendon structural and mechanical properties were made between Achilles tendon rupture and healthy control groups, and between the uninjured and injured sides of the two rehabilitation groups in Achilles tendon rupture group. Ultrasound was used to determine bilaterally tendon cross-sectional area, tendon resting length, and tendon elongation as a function of torque during maximal voluntary plantar flexion. From these data, Achilles tendon force-elongation and stress-strain relationships were determined.
  
  
  RESULTS
  The Achilles tendon rupture group uninjured side was not different from healthy control group. Structural and mechanical parameters of the injured side were not different between the Achilles tendon rupture early mobilization and the immobilization groups. Compared to the uninjured side, the injured side showed a reduction in stress at maximal voluntary force, in Young's modulus and in stiffness.
  
  
  CONCLUSIONS
  Two years post-surgical repair, the Achilles tendon mechanical properties had not returned to the uninjured contralateral tendon values.
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; Faculty of Physical Education Sogipa, Porto Alegre, Brazil. Electronic address: jeam_geremia@hotmail.com.
authors.forename: Jeam Marcel
authors.initials: JM
authors.lastname: Geremia
authors.affiliation: Faculty of Human Movement Sciences, Move Research Institute Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: Maarten Frank
authors.initials: MF
authors.lastname: Bobbert
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Mayra
authors.initials: M
authors.lastname: Casa Nova
authors.affiliation: São Lucas Hospital, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Rafael Duvelius
authors.initials: RD
authors.lastname: Ott
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Fernando de Aguiar
authors.initials: Fde A
authors.lastname: Lemos
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Raquel de Oliveira
authors.initials: Rde O
authors.lastname: Lupion
authors.affiliation: Physique Physiotherapy Center, Porto Alegre, Brazil.
authors.forename: Viviane Bortoluzzi
authors.initials: VB
authors.lastname: Frasson
authors.affiliation: Exercise Research Laboratory, School of Physical Education, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Vaz
mesh_terms: D000125:Achilles Tendon / Q000000981:diagnostic imaging / Q000293:injuries* / Q000503:physiopathology* / Q000601:surgery; D000328:Adult; D001696:Biomechanical Phenomena; D002370:Casts, Surgical; D004434:Early Ambulation; D006801:Humans; D008297:Male; D008875:Middle Aged; D012421:Rupture / Q000503:physiopathology; D019415:Torque; D016896:Treatment Outcome; D014463:Ultrasonography
keywords: Achilles tendon rupture; Immobilization; Stress–strain relation; Tendon healing; Ultrasound