Spontaneous rupture of the Achilles tendon is preceded by widespread and bilateral tendon damage and ipsilateral inflammation: a clinical and histopathologic study of 60 patients.

60 consecutive patients with spontaneous rupture of the Achilles tendon (AT) underwent surgery. Biopsies were taken at the operations from the site of the rupture, the proximal part, the calcaneal insertion, and the peritendium of the injured tendon. A percutaneous needle biopsy was taken from the contralateral (uninjured) AT. On histological examination, collagen degeneration, tenocyte necrosis, and acute inflammation were found at the rupture site in all cases. In the proximal part and at the insertion, degeneration was present in 56/56 and 51/55 of the cases, necrosis in 55/56 and 50/55, and acute inflammation in 49/56 and 35/55, respectively. The severity of the histological changes decreased from the rupture site to the proximal part to the site of insertion, and showed no relation to the age of the patients or the time from the rupture to the operation. Peritendineal vascular changes were minor. In the contralateral AT, degeneration and necrosis were present in 47/50 and 42/50 of the cases, respectively, but the severity of the changes was less than in the injured tendon. Acute inflammation was present in only 1 case. Spontaneous rupture of AT seems to be preceded by widespread, bilateral damage of the tendon and widespread ipsilateral acute inflammation.