Ossification of the Achilles tendon--a case report.

Ossification of the Achilles tendon is a very unusual condition. We report a case with bilateral Achilles tendon ossification followed up for twelve years, treated twice surgically on the left side and conservatively on the right side. At the age of 51, the patient's plain radiogram showed bilateral ossifications of the Achilles tendon (right 55 mm, left 15 mm in length). The left side small mass was removed. The right side mass was decided to be followed up because of its large size. At the age of 61, ossification recurred on the left side. Conservative treatment with etidronate disodium for two years failed to prevent ossification from progressing. At the age of 63, the mass on the right and left sides increased to 70 mm and 45 mm in length, respectively. The mass of the left side was excised again, and dull pain disappeared postoperatively on the left side.