The optimal technique for a transtibial amputation in a young, active, and healthy patient is controversial. Proponents of the Ertl procedure (in which the cut ends of the tibia and fibula are joined with a bone bridge synostosis) argue that the residual limb is more stable which confers better prosthetic fit and improved function especially among high-performing individuals. At the same time, the Ertl procedure is associated with longer operative and healing time and may be associated with a higher complication rate compared with the standard Burgess procedure. The TAOS is a prospective, multicenter randomized trial comparing 18-month outcomes after transtibial amputation using the Ertl versus Burgess approach among adults aged 18 to 60. The primary outcomes include surgical treatment for a complication and patient-reported function. Secondary outcomes include physical impairment, pain, and treatment cost.