title: Histological Evaluation of Regenerated Semitendinosus Tendon a Minimum of 6 Years After Harvest for Anterior Cruciate Ligament Reconstruction.
abstract: BACKGROUND
  Semitendinosus (ST) and/or gracilis (G) autografts are the most used grafts for anterior cruciate ligament (ACL) surgery. The tendons have been shown to be able to regenerate but with focal areas of scar tissue in the short term. There are no long-term histological studies of the regenerated tendons.
  
  
  OBJECTIVE
  In the long term, the regenerated ST tendon normalizes and has a similar histology as the contralateral nonharvested tendon.
  
  
  METHODS
  Case-control study; Level of evidence, 3.
  
  
  METHODS
  Eighteen patients (8 female, 10 male) who underwent ACL surgery using ipsilateral ST/G tendon autografts were included in this study. Percutaneous specimens were obtained from the regenerated ST tendon and the contralateral nonharvested ST tendon under ultrasonographic guidance at a median of 8.4 years (100.5 months; range, 77-129 months) after the harvest procedure. Specimens from the nonoperated side served as controls. The histology and presence of glycosaminoglycans (GAGs) were assessed using a light microscope and a semiquantitative grading system.
  
  
  RESULTS
  Thirty-six biopsies were obtained (2 biopsies from each patient). In 5 biopsies, the amount of tissue was too small to analyze in the light microscope, and 1 patient had been operated on bilaterally and was therefore excluded. In total, 24 biopsies were included in the histological analysis. In overall terms, there were no significant differences between the regenerated and nonharvested ST tendon in terms of fiber structure, cellularity, vascularity, and level of GAGs a minimum 6 years after harvest of the ST tendon. However, 3 of the regenerated tendons displayed a loss of fiber structure.
  
  
  CONCLUSIONS
  The ST tendon regenerates and may regain a histological appearance similar to that of the nonharvested contralateral tendon, as seen in this study a median of 8.4 years after harvesting. However, in some tendons, loss of fiber structure was found.
authors.affiliation: Department of Orthopedics, NU-Hospital Organization, Trollhättan/Uddevalla, Sweden. ; University of Gothenburg, Gothenburg, Sweden.
authors.forename: Martina
authors.initials: M
authors.lastname: Åhlén
authors.affiliation: Department of Plastic Surgery, Sahlgrenska University Hospital, Sahlgrenska, Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Lidén
authors.affiliation: Department of Clinical Science, Intervention and Technology, Division of Orthopedics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Movin
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Nikos
authors.initials: N
authors.lastname: Papadogiannakis
authors.affiliation: Department of Radiology, SkaS, Lidköping, Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Rostgård-Christensen
authors.affiliation: Department of Research and Development NU-Hospital Organization, Trollhättan/Uddevalla, Sweden.
authors.forename: Jüri
authors.initials: J
authors.lastname: Kartus
keywords: ACL; biopsy; histology; semitendinosus; tendon regeneration