Implant selection in revision total knee arthroplasty.

Abstract

Revision total knee arthroplasty implants have evolved from fully constrained (fixed-hinge) to semiconstrained to contemporary constrained designs. The latter category includes nonlinked constrained (total condylar-III) designs ( Fig. 1) and rotating-hinge designs ( Figs. 2-A and 2-B). Fig. 1: Postoperative anteroposterior radiograph illustrating a nonlinked constrained knee design that was used to revise a failed primary total knee arthroplasty in a patient with rheumatoid arthritis. Figs. 2-A and 2-B: Preoperative (Fig. 2-A) and postoperative (Fig. 2-B) radiographs of the knee of a low-demand seventy-nine-year-old woman who was managed with a rotating-hinge knee prosthesis because of a comminuted periprosthetic supracondylar fracture of the femur. Additionally, the advent of limb-salvage procedures following tumor resection and other instances in which there is massive segmental bone loss, such as that seen after multiple failed arthroplasties (particularly following failed reimplantation for infection), has stimulated the development of modular or custom segmental replacement and the use of allograft-prosthesis composites. Segmental modular megaprostheses are rotating-hinge components with modular stems of varying lengths that are used to replace segmental femoral or tibial diaphyseal bone loss ( Fig. 3). Fig. 3: Lateral radiograph illustrating reconstruction of segmental bone defects of the distal part of the femur and proximal part of the tibia. On the femoral side a custom segmental distal femoral rotating-hinge prosthesis was used, and on the tibial side an allograft-prosthesis composite was used. Use of the proximal tibial allograft facilitated reattachment of the extensor mechanism. An allograft-prosthesis composite consists of a structural allograft, usually the distal part of a donor femur or the proximal part of a donor tibia, into which a stemmed prosthesis is cemented. The composite structure is attached to the remaining host bone with use of matching step-cuts at the junction of the allograft and the host bone. The construct is stabilized with an intramedullary stem ( Figs. 4-A …