The variability of the Achilles tendon insertion: a cadaveric examination

Pathology associated with the Achilles tendon is a common problem, particularly at the site of insertion. A better understanding of the anatomy in this area would assist in developing and fine-tuning treatment options. A cadaveric examination was conducted using 60 human lower extremities (40 cadavers) to determine the location for the terminal insertion site of the Achilles tendon on the posterior aspect of the calcaneus. The average age of the specimens was 67.8 years (range, 43-98 years). Three different investigators examined each specimen, and a consensus as to the site of termination of the Achilles tendon was made. Upon inspection, 55% (22/40) of the limbs had the Achilles tendon inserting on the superior 1/3 aspect of the calcaneus, 40% (16/40) of the limbs inserted on the middle 1/3, and 5% (2/40) of the limbs inserted on the inferior 1/3. The distribution of the insertion was statistically different from random (P = .000371). Further, 8% (3/40) of the specimens revealed a partially contiguous relationship between the Achilles tendon and the plantar fascia. This correlated with the younger specimens (P < .0001). This study provides a better understanding of the anatomical relationship between the Achilles tendon, the calcaneus, and the plantar fascia.