There may be a specific reason your surgeon had in mind when offering this advice. You would have to ask him or her that question directly. In general, there has been much debate over the best treatment approach to use with Achilles’ tendon ruptures.
Studies have been done to compare the results in patients treated with and without surgery. Patients who have surgery tend to get their motion back sooner. This seems to make a differrence with better results.
Recently, researchers in New Zealand compared two groups of patients with acute Achilles’ tendon rupture. All were treated within 10 days of their injury. One group was put in a plaster cast for 10 days. When the cast was taken off, movement and weight-bearing were gradually started.
In the second group, surgery was done to suture the torn tendon back together. A special cast was applied right after surgery and kept on for 10 days. This cast allowed the ankle to move from a neutral position down toward a toes-pointed position.
When patients in both groups were taken out of the casts, motion was started. Each patient completed a set of range of motion exercises once every hour. At the end of six weeks, the patients were allowed to put some weight on the injured foot.
They found that both groups had equal return of ankle motion. It didn’t matter if they had surgery or not. The real difference was the use of early, carefully controlled motion after the injury. With the increased risk of infection and complications from any surgery, a nonoperative approach is always preferred whenever possible.