Quantitative assessment of intravascular volume of the human Achilles tendon.

The pathogenesis of Achilles tendon rupture remains unclear, but vascular patterns may play an important role. We determined the intravascular volume of the Achilles tendon using a new method with injection of radioisotopes. A solution of Tc-99m and gelatin-ink was injected into the lower limbs of body donors. The intravascular volume of each 1 cm section of the Achilles tendon was measured using a gamma well counter. We found that the distal part of the Achilles tendon (0-2 cm above the calcaneus) had an intravascular volume of 59-98 microL/g tendon tissue. In the middle part of the tendon (3-6 cm above the calcaneal insertion), the intravascular volume was much less: 2743 microL/g tissue. The proximal part of the tendon (7-9 cm) had an intravascular volume between 51-100 microL/g tendon tissue. The reduced vascularization in the middle part of the human Achilles tendon may play a role in degeneration and spontaneous rupture of the tendon.