Achilles Tendinopathy in Diabetes Mellitus

Background: Plantar forefoot ulcers in individuals with diabetes often lead to deep infection and lower extremity amputation. Increasing evidence suggests that the process is initiated by increased passive stiffness within the gastrocnemius-soleus musculotendinous unit. The goal of this investigation was to perform ultrasound examination of the Achilles tendon in a consecutive group of asymptomatic diabetic individuals to identify any inherent structural pathology that might be associated with the increased stiffness that appears to be associated with the development of diabetic forefoot ulcers. Materials and Methods: Seventy consecutive diabetic individuals with no past history of diabetic foot morbidity underwent ultrasonography of their Achilles tendons. Each patient was also tested for fasting glucose and glycosylated hemoglobin as a measure of diabetes control. Ten similarly aged non-diabetics with no history of Achilles tendinopathy served as controls. Results: The ultrasonography revealed disorganized tendon fibers in 62 of 70 (89%) patients, and calcification within the Achilles tendon in 53 (76%) patients. The Achilles tendon thickness averaged 5.0 (range, 4 to 8) mm. There was no correlation between patient age and Achilles tendon thickness (r = 0.292, p = 0.014); however, there was a trend for duration of disease and Achilles tendon disorganization (p = 0.073). The oldest patients also appeared to demonstrate a trend for more ultrasound-measured Achilles tendinopathy. There was no correlation between fasting glucose or glycosylated hemoglobin and Achilles tendon alterations. Conclusion: This investigation confirms structural abnormalities within the Achilles tendon of diabetic individuals that might represent biologic changes affecting the inherent stiffness that leads to increased forefoot pressure and the development of plantar forefoot ulcers. This process appears to worsen with advanced age and does not appear to be related to diabetes control.