Remodelling of bone around intramedullary stems in growing patients

The remodelling of bone around intramedullary cemented stems, used for the fixation of massive distal femoral replacements in young patients, has been studied. Several types of remodelling have been identified, and this is common to all of the retrieved specimens that have been in situ for periods of 6 to 18 months. Transection of cortical bone and the insertion of a massive prosthesis leads to (a) the formation of a pedicle of bone or bony bridge that grows from the transection site over the shaft of the prosthesis, (b) bone resorption at the transection site, (c) the development of an inner porotic cortex surrounding the intramedullary stem and subperiosteal bone formation, and (d) a shell of bone around the acrylic cement. The tibial component that allows continued growth of the proximal tibial physis consists of a press fit metallic plateau with a stem that slides into an ultra-high-molecular-weight polyethylene sleeve inserted below the growth plate. A sclerotic layer of bone forms adjacent to a soft-tissue interface around both the sleeve and the metallic component. Remodelling of bone around intramedullary stems is attributed either to a redeveloping blood supply or to load adaptive changes.