Interposition and augmentation devices for tendon and ligament repair, including rotator cuff repair, have been developed as well as methods for their delivery using arthroscopic methods. The devices are preferably derived from biocompatible polyhydroxyalkanoates, and preferably from copolymers or homopolymers of 4-hydroxybutyrate. The devices may be delivered arthroscipiclly, and offer additional benefits such as support for the surgical repair, high initial strength, prolonged strength retention in vivo, flexibility, anti-adhesion properties, improved biocompatibility, an ability to remodel in vivo to healthy tissue, minimal risk for disease transmission or to potentiate infection, options for fixation including sufficiently high strength to prevent suture pull out or other detachment of the implanted device, eventual absorption eliminating future risk of foreign body reactions or interference with subsequent procedures, competitive cost, and long-term mechanical stability. The device are also particularly suitable for use in pediatric populations where their eventual absorption should not hinder growth.