A 58-year-old golfer fell stepping into a sand trap and ruptured his Achilles tendon one year ago. He initially chose non-operative treatment, but became unsatisfied with a tender fullness behind his ankle and ankle weakness noticeable during his tee shots. At the time of surgery, a large disorganized fibrous mass is found at the site of rupture. Following extensive debridement there is a 5 cm gap between viable tissue ends. Which of the following surgical techniques provides the greatest likelihood of a successful clinical outcome?