Various methods and devices are described for retaining a medical implant within a body cavity. According to one aspect, an external reinforcement device is adapted to encircle the exterior of the oesophagus at the gastro-oesophageal junction and comprises: a collar (172) configured to facilitate distribution of forces around the exterior of the oesophagus at the gastro-oesophageal junction wherein the collar is introducable in an elongate configuration, wherein the collar includes free ends, the free ends of the collar being attachable to each other and wherein the collar is formed of telescopic components (174a, 174b).
