Abstract: A apinal implant has an elongate body which is divided into two portions with mutually opposed contact surfaces and is for insertion into the joint space between two adjacent vertebrae. A cam device or cam devices are movable between the contact surfaces to expand or increase the spacing between the body portions so as to increase the spacing between the adjacent vertebrae.The implant has a porous external surface to facilitate bore and cartilage tissue growth therein. Alternatively, the external surface is smooth and coated with a bioactive material such as a hydroxyapatite, for example, tricalcium phospahte. In both instances bone, cartilage tissue and external surfaces of the implant are fused together to prevent migration of the implant. Advantageously, insertion of the implant requires a minimum incision in skin and cartilage tissue.