Macroscopic and microvascular blood supply of the canine common calcaneal tendon

Abstract

Chronic tendinopathy injuries to the canine common calcaneal tendon are relatively common in large breed dogs and typically affect the distal portion of the tendon. In humans, poor blood supply, biomechanical faults, poor training methods and fluoroquinolone administration have all been linked with the development of Achilles tendinopathy. The most common sites for Achilles tendinopathy in humans seem to correspond with areas of poor blood supply within the tendon. The aim of this study was to evaluate the blood supply of the canine common calcaneal (Achilles) tendon to determine if variations occur along the tendon. The null hypothesis was that there would be no difference in the microvascular blood supply at varying points along the tendon. Paired pelvic limbs were collected from 12 large breed dog cadavers. A 50% barium sulphate and 50% saline solution was infused into the femoral artery of one limb from each dog and radiographs were taken to outline the blood supply to the common calcaneal tendon. Indian ink was infused into the contralateral limb. The common calcaneal tendon was removed, fixed and sectioned at 1 cm intervals, from calcaneal insertion to musculotendinous junction. The ink-filled arteries and arterioles in each section were counted. Radiographs revealed fine branches from the caudal saphenous artery entering the mid-body of the tendon along its cranial border. The musculotendinous junction had additional branches from the gastrocnemius muscles. Distally, vessels radiated proximally from the calcaneus 2 to 3 cm into the tendon. Mean total vessel counts at the insertion (138.54 +/- SD 31.06) were significantly higher than all other sections (p <0.001). The mid-body had significantly lower total vessel counts. When the cross sectional area of the tendon was taken into account, only the insertion had a significantly higher mean vessel count/cm2 than the mid-body of the tendon. There were no other significant differences in mean vessel count/cm2. Areas of poorer blood supply did not correspond with the most commonly reported site for chronic common calcanean tendinopathies, suggesting that inherent poor blood supply at the site of injury may not play a role in the pathogenesis. Atraumatic handling and minimal manipulation should be used during the surgical approach and debridement to preserve the remaining blood supply in ruptured tendons.