Abstract: An arthroplasty shim configured to be inserted into a gap between a bone and a prosthetic joint component. The shim strengthens the prosthetic joint component. The shim can reduce the side-effects of an erroneous bone cut, loss of bone mass or bone failure which may result during revision surgery. The shim can help to balance flexion/extension gaps between bones in the joint and can help balance the joint's varus/valgus alignment. Generally, the shim has a thickness between about 0.5 mm and about 6 mm. The shim may include a spike or lip to anchor or the surface may be cavitated. The shim can be used as a trial to allow for proper fitting of the shim's shape, size and position between the bone and the prosthesis. More than one shim may be used to fill the same gap. Other embodiments are described.