An implantable device intended to be used 1) to create a tunnel through which a discontinuous peripheral nerve can regenerate to bridge the proximal and distal nerve ends, 2) to encase a nerve for protection to aid in repair [e.g., to prevent ingrowth of scar tissue], or 3) for capping the end of an amputated nerve to prevent the formation of a neuroma. It is made of bioabsorbable synthetic polymer(s) in the form of a solid tube or a gel which polymerises in situ, and is designed to be chemically degraded and absorbed via natural body processes. It is also known as a nerve sheath, nerve cuff, nerve protector, nerve conduit, nerve wrap, or nerve cap.