101 - Femoral Revision: Uncemented Implants With Bioactive Coatings

Abstract

The choice of cementless versus cemented implants for mild and moderate bone stock loss is still a topic of controversy. Cementless femoral revision surgery for cases of severe deficiency has increasingly gained acceptance over the past decade because it can provide firm distal fixation and thereby overcome defects of damaged proximal bone. Revision following major femoral component loosening can be difficult both in terms of finding a means of stable fixation of the revision implant and finding viable bone stock. Adequate primary stability must be attained to allow restoration of badly damaged bone around the new implant and to ensure the sound and lasting osteointegration of the new device. Stability will be dependent on the preoperative condition of the femur (e.g., granuloma, osteolysis, fracture, implant breakage) and on what happens at the revision surgery (e.g., inadvertent perforation, fracture, cortical window, extensive femoral osteotomy). Hydroxyapatite (HA) is a naturally occurring mineral form of calcium with the chemical composition Ca5(PO4)3(OH). The crystal form of the material is composed of 2 crystals, thus yielding the composition Ca10(PO8)6(OH)2. Its osteoconductive properties have made it an attractive material for coating both primary and revision total hip arthroplasty (THA) components. This has led to successful fixation of HA-coated implants in the presence of well-vascularized native bone. All of these considerations mean that specially designed devices will be required to attain the necessary primary stability and to find a solution to the individual patient's needs. A whole system adapted to the different situations encountered in revision surgery is required. Nevertheless, on the femoral side, to accomplish the objective of stable implant fixation, we follow a step-by-step strategy that, with appropriate planning and adequate instrumentation and implants, can be summarized as replacing the initial stem by another with fixation as proximal as possible and as distal as necessary. Although numerous techniques have been described to successfully achieve adequate fixation of the femoral stem in revision THA (these techniques are covered elsewhere in this book), our preferred techniques use HA-coated implants. The purpose of this chapter is to discuss the use of such implants in revision of the femoral component in revision THA.