title: Ruptured Achilles tendons are significantly more degenerated than tendinopathic tendons.
abstract: OBJECTIVE
  To ascertain whether there is an association between tendinopathic and ruptured Achilles tendons, hypothesizing that the histopathological aspects of tendinosis in tendinopathic tendons are less advanced than those found in ruptured Achilles tendons.
  
  
  METHODS
  This was a comparative cohort study at a university teaching hospital. Histological examination was performed using hematoxylin and eosin and alcian blue/periodic acid-Schiff stained slides. The slides were interpreted using a semiquantitative grading scale assessing fiber structure, fiber arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, hyalinization, and glycosaminoglycan. We calculated a pathology score giving up to three marks for each of the above variables, with 0 being normal and 3 being maximally abnormal. All the histology slides were assessed twice in a blinded manner, the agreement between two readings ranging from 0.170 to 0.750 (kappa statistics).
  
  
  RESULTS
  We studied biopsy samples from the Achilles tendon of patients undergoing open repair for a subcutaneous rupture of their Achilles tendon (N = 35; average age (+/- SD), 48.4 +/- 16.9 yr; range, 26-80), biopsy specimens from the Achilles tendon of patients undergoing exploration for Achilles tendinopathy (N = 13; average age, 35.7 +/- 12.9 yr; range, 18-67) and specimens of Achilles tendons from individuals with no known tendon pathology (N = 16; average age, 65 +/- 19.1 yr; range, 46-82). The highest mean score of ruptured tendons was significantly greater than that of tendinopathic tendons (17.4 +/- 4.9 vs 10.5 +/- 6.1, P < 0.001), and highest mean score of tendinopathic tendons was greater that that of control tendons (10.5 +/- 6.1 vs 5.9 +/- 7.3) (P < 0.001).
  
  
  CONCLUSIONS
  Ruptured and tendinopathic tendons are histologically significantly more degenerated than control tendons. The general pattern of degeneration was common to the ruptured and tendinopathic tendons, but there was a statistically significant greater degree of degeneration in the ruptured tendons. It is therefore possible that there is a common, as yet unidentified, pathological mechanism that has acted on both of these tendon populations.
authors.affiliation: Department of Orthopaedic Surgery, University of Aberdeen Medical School, Aberdeen, Scotland, UK.
authors.forename: C
authors.initials: C
authors.lastname: Tallon
authors.forename: N
authors.initials: N
authors.lastname: Maffulli
authors.forename: S W
authors.initials: SW
authors.lastname: Ewen
mesh_terms: D000125:Achilles Tendon / Q000033:anatomy & histology / Q000737:chemistry / Q000293:injuries* / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D016009:Chi-Square Distribution; D024022:Fibrillar Collagens / Q000032:analysis; D006025:Glycosaminoglycans / Q000032:analysis; D006801:Humans; D006818:Hyalin; D008875:Middle Aged; D012016:Reference Values; D012421:Rupture; D018709:Statistics, Nonparametric; D052256:Tendinopathy / Q000473:pathology*; D013708:Tendon Injuries / Q000473:pathology*
chemical_list: D024022:Fibrillar Collagens; D006025:Glycosaminoglycans