A reinforcement device (10) suitable for use with a prosthesis, such as a unicompartmental tibial component prosthesis. The reinforcement device is positionable between said component prosthesis and a surgically resected area of bone, for example, the tibia of a patient. The reinforcement device (10) includes a plate-like main body (12) extending from an anterior end (13) to a posterior end (14) and having an upper surface (16) and a lower surface (17). The lower surface (17) is engageable with a fixing means, such as a bone cement (25), to fix the tibial component to a surgically resected area of tibia. The main body (12) also has a plurality of perforations (15) therethrough.