Bone graft retention devices, systems, and methods for retaining bone graft material at a desired site are described. The devices may attach to existing bone fusion systems or components thereof, such as rods or cross connectors, or may be integrated directly into a cross connector. The devices include a fin, and optionally one or more attachment elements. The bone graft material is attached to the fin, such as via an adhesive or by friction fit inside a cavity. Optionally, during insertion in a patient, the fin is flipped upwards so that it does not hinder the insertion. Following insertion of the rod or cross-connector in the desired location and tightening of the screws into their final positions, the fin of the bone graft retention device is flipped into place such that it aligns with the spine, pressing the bone graft material against the spine.
