Ruptured Achilles tendons are significantly more degenerated than tendinopathic tendons

Objective. To ascertain whether there is an association between tendinopath ic 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 perf ormed using hematoxylin and eosin and alcian blue/periodic acid-Schiff stai ned slides. The slides were interpreted using a semiquantitative grading sc ale assessing fiber structure, fiber arrangement, rounding of the nuclei, r egional variations in cellularity, increased vascularity, decreased collage n stainability, hyalinization, and glycosaminoglycan. We calculated a patho logy 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 ran ging from 0.170 to 0.750 (kappa statistics). Results: We studied biopsy sam ples from the Achilles tendon of patients undergoing open repair for a subc utaneous 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 fro m individuals with no known tendon pathology (N = 16; average age, 65 +/- 1 9.1 yr; range, 46-82). The highest mean score of ruptured tendons was signi ficantly 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 gre ater that that of control tendons (10.5 +/- 6.1 vs 5.9 +/- 7.3) (P < 0.001) . Conclusion: Ruptured and tendinopathic tendons are histologically signifi cantly more degenerated than control tendons. The general pattern of degene ration 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 unidentifi ed, pathological mechanism that has acted on both of these tendon populatio ns.