title: Fine structural alterations in chronic Achilles paratenonitis in athletes.
abstract: The fine structural alterations in chronic Achilles paratenonitis were studied in tissue samples obtained from 14 athletes, who were operated on for this complaint and from 3 patients without any history of this disease. In the chronically inflamed paratendineal tissue mainly two types of cells were identified: classic fibroblasts with a smooth and rough endoplasmic reticulum and only a few mitochondria and lysosomes and myofibroblast-like cells with cytoplasmic microfilaments 5-6 nm in diameter, a rough endoplasmic reticulum, some mitochondrias and free ribosomes. These cells represented 19% of 471 studied non-inflammatory cells. In the extracellular space there was an increased amount of fibrils regarded as either type I or type III collagen as sign of tissue repair. Especially around the myofibroblastic cells a fine granular ground substance was found. The amount of ground substance was as a rule increased in pericellular space. Due to the capacity of contraction in healing tissue the myofibroblasts apparently have a role in the clinical symptoms of chronic Achilles paratenonitis.
mesh_terms: D000125:Achilles Tendon / Q000166:cytology / Q000473:pathology / Q000648:ultrastructure*; D000328:Adult; D001265:Athletic Injuries / Q000473:pathology*; D002908:Chronic Disease; D006801:Humans; D007249:Inflammation; D008854:Microscopy, Electron; D012420:Running