Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction.

Although the best method for managing large bone defects has not been established, the variables to consider are: (1) implant constraint (posterior-stabilized, varus-valgus-constrained, rotating hinge); (2) stem configuration (straight versus tapered, standard, or long-stemmed); (3) stem fixation (cement versus press-fit); and (4) method of bone-defect repair (cement, augments, bone graft). In principle, an implant with the least constraint required for satisfactory knee stability is selected to reduce stress on the implant-fixation interface with compromised bone. The severity of bone loss largely influences stem length. Canal-filling stems and cementless stem fixation are indicated when major structural allografts are used. Bone defects can be successfully and reliably repaired with metal augments, allograft bone, or cement, as long as long-stemmed components without excessive constraint are selected. Because structural allografts do not revascularize, the major advantage of the allograft, as compared to cement fill or augments, is the ability to unite to damaged host bone that has a poor cancellous structure.