Achilles tendinosis does not always precede Achilles tendon rupture

Purpose: Degenerative change is a typical histologic finding of Achilles tendinosis and is thought to be a factor associated with Achilles tendon rupture; however, this relationship remains controversial. Therefore, the aim of this study was to review the histological findings of ruptured Achilles tendons and analyze demographics and injury patterns. Methods: Retrospective analysis was performed for all patients who underwent Achilles tendon repair for acute Achilles tendon rupture at our institution between 2008 and 2015. The presence of Achilles tendinosis was determined by light microscopic histology of ruptured Achilles tendons. Patients were grouped according to the presence of Achilles tendinosis and patient demographics, sports activities, and clinical outcomes were compared. Ankle activity score was used to evaluate the level of sports activity and Achilles tendon total rupture score (ATRS) was used to evaluate clinical outcomes. Results: A total of 152 Achilles tendon ruptures were included: 112 (77%) showed Achilles tendinosis at a ruptured Achilles tendon on histology and 40 (23%) did not. Patients who had no Achilles tendinosis prior to rupture had a lower ankle activity score (P < 0.05) and higher incidence of non-sports related injury (P < 0.05). ATRS was not significantly different between the groups at final follow-up (P = n.s.). Conclusion: In contrast to previous reports, Achilles tendon rupture can occur without prior Achilles tendinosis, especially in non-sports-related injuries and in patients with low sports activity. Although the direct clinical applications of these results are limited, the findings of this study can improve our understanding of the etiology of Achilles tendon rupture. Level of evidence: Prognostic, Level III.