Risk Factors for Contralateral Tendon Rupture in Patients With Acute Achilles Tendon Rupture.

The present study was performed to determine the incidence and risk factors of contralateral Achilles tendon rupture after an initial tendon rupture, and to identify the associated patient characteristics. Medical records of 181 adult patients with acute Achilles tendon rupture were reviewed. We investigated the risk factors for contralateral Achilles tendon rupture and calculated the incidence density (per 100 person-years), survival rate, hazard ratios, and 95% confidence intervals. The risk factors were extracted, including blood type, age, body mass index (BMI), occupation, underlying comorbidities, history of alcohol intake or smoking, injury mechanism, and fluoroquinolone antibiotic or steroid use. Military personnel and manual laborers, including farmers and firefighters were considered to have an occupation involving physical activity. Ten patients (5.5%) were identified as having nonsimultaneous, contralateral Achilles tendon rupture a mean of 3.3 years (range 1.0-8.3 years) after the initial tendon rupture. The incidence density of contralateral tendon rupture was 0.89 per 100 person-years. The 8-year survival rate of contralateral tendon rupture was 92.2%. Unadjusted and adjusted hazard ratios (with 95% confidence intervals, p value) of blood type O were 3.71 (1.07-12.82, p = .038) and 2.90 (0.81-10.32, p = .101), respectively, and those of occupations involving physical activity were 5.87 (1.64-20.98, p = .006) and 4.69 (1.27-17.28, p = .02), respectively. Based on the present data, blood type O and occupations involving physical activity are significantly associated with an increased risk of contralateral tendon rupture in adult patients who have sustained Achilles tendon rupture.