Chondral metaplasia in calcific insertional tendinopathy of the Achilles tendon.

OBJECTIVE: To ascertain whether tendon samples harvested from patients with calcific insertional Achilles tendinopathy showed features of failed healing response, and whether abnormal quantities of type II collagen had been produced in that area by these tenocytes. DESIGN: Comparative laboratory study. DESIGN: University teaching hospitals. PATIENTS: Tendon samples were harvested from eight otherwise healthy male individuals (average age 47.5+/-8.4 years, range 38 to 60) who were operated for calcific insertional Achilles tendinopathy and from nine male patients who died of cardiovascular events (mean age 63.1+/-10.9 years) while in hospital. INTERVENTIONS: Open surgery for calcific insertional Achilles tendinopathy. MAIN OUTCOME MEASURE: Semi-quantitative histochemical, immunohistochemical, and immunocytochemical methods to ascertain whether tendinopathic tendons were morphologically different from control tendons, and whether abnormal types of collagen were produced. RESULTS: Tenocytes from tendons from patients with calcific insertional Achilles tendinopathy exhibit chondral metaplasia, and produce abnormally high quantities of collagen type II and III. CONCLUSIONS: The altered production of collagen may be one reason for the histopathological alterations described in the present study. Areas of calcific insertional Achilles tendinopathy have been subjected to abnormal loads. These tendons may be less resistant to tensile forces. Further studies should investigate why some tendons undergo these changes.