STRATEGIES OF STEM FIXATION AND THE ROLE OF SUPPLEMENTAL BONE GRAFT IN REVISION TOTAL KNEE ARTHROPLASTY

Bone loss is commonly encountered at the time of revision total knee arthroplasty because of loosening of the implant, osteolysis, infection, or difficulty with removal of the original implant. Regardless of the etiology of the bone loss, its location and magnitude may compromise adequate fixation, alignment, and ligamentous stability of the revision prosthesis. In the setting of bone stock deficiency, or when an implant with a constrained articulation is used, it is prudent to use a longer stem to effect stress transition that protects weak or newly grafted proximal bone1. Successful stabilization of the implant construct can be achieved with a variety of fixation strategies: cementing the condylar surfaces of the implant while using a cementless press-fit stem2,3, fixation of the entire construct without cement4, or fixation of the entire construct with cement. All have been used with success5-7. Because patterns of bone loss can vary so extensively, a classification of the bone loss that is encountered during revision total knee arthroplasty is useful when selecting patients for bone graft procedures. The classification system of the Anderson Orthopaedic Research Institute (AORI) provides guidelines for bone defect management at the time of revision total knee arthroplasty8( Table I). Type-1 defects can be restored either with local autologous bone grafts that are obtained during the revision or with particulate allograft. Type-2 defects are associated with damaged metaphyseal bone that requires either cement, metal augments, or a bone graft to restore the joint line. Type-2 defects may be subdivided into Type-2A defects (involving only one condyle) or Type-2B defects (involving both condyles). Structural and particulate bone graft may be used for Type-2 defects depending on the need for structural support of the prosthesis. Type-3 defects are characterized by deficient …