Ruptures of the Achilles tendon: relationship to inequality in length of legs and to patterns in the foot and ankle.

We studied 101 patients who were operated on at Oulu University Hospital for ruptured Achilles tendon from 1987 to 1992 (inclusive), and 87 healthy control patients from among Army conscripts. The mean inequality in length of legs (ILL) was 5 +/- 4 mm. Among the 48 patients with ILL > or = 5 mm, the side affected with ruptured tendon was longer in 48% of cases and shorter in 52%. An underpronating alignment of the ankle and foot (based on beta45 measurement of the angle < or = 4 degrees) was found in 21% of patients and 5% of controls (P < 0.001). A combination of high longitudinal arch and underpronating alignment of the ankle was seen in 10% of patients and 1% of controls (P < 0.001). About 37% of the patients' feet and 29% of feet in controls were classified as having a high arch (P = 0.001). ILL or hyperpronation of the ankle seem to not be predisposing factors for ruptures of the Achilles tendon. High longitudinal arches were somewhat overrepresented, being associated with less pronation of the ankle and less varus in the forefoot than was seen in controls.