A multi-layered membrane may include a first layer made by polytetrafluoroethylene polymer (PTFE), a second layer made by fluorinated ethylene propylene polymer (FEP), a third layer made by a reinforcing unit, and a fourth layer made by PTFE. The second and third layers are sandwiched between the first and the fourth layers, and the reinforcing unit is configured to span a bone cavity and used for fixation to bone surrounding the bone cavity. The reinforcing unit is configured to form a desired shape prior to placement on the bone defect and maintain the formed shape upon placement. In one embodiment, the reinforcing unit has multiple elongated members forming a junction or junctions, and the elongated members have a free distal end that extends away from the junction and at least one elongated member has an enlarged appendage formed in the free distal end spaced apart from the junction.
