Biomedical Engineering Reference
In-Depth Information
FIGURE 10.11
Radiographic appearance (montage) of a modular endoprosthetic replacement. Entire femur, hip
joint, and knee joint of the bone tumor patient were replaced with prostheses for limb salvage.
(Figure 10.11). Therefore, material and fixation method for limb salvage endoprostheses are exactly the
same for total joint replacements. Femur, tibia, humerus, pelvis, and scapular are often resected and
replaced endoprostheses. Similar to total joint replacements, disadvantages of the endoprosthetic recon-
struction are prosthesis loosening due to polyethylene wear and cement failure, and mechanical failure
of the prostheses.
Most of the endoprostheses for the limb salvage are expandable type (Ward et al. 1996). Expandable
endoprostheses are required for children who have a potential of skeletal growth. Several expandable
prostheses require an open surgical procedure to be lengthened, whereas others have been developed
that can be lengthened by servomechanisms within the endoprosthesis. Modular segmental system
is a new option for expandable endoprosthesis. They can easily be revised to longer modular compo-
nents to gain length over time. Modular segmental system has several advantages over the mechani-
cally expandable one. The use of the modular system allows for intraoperative customization of the
endoprosthesis during the surgery. It minimizes discrepancy between the custom implant and actual
skeletal defect due to the radiographic magnification and uncertainty of margin of tumor resection. It
allows the surgeon to assemble the prosthesis intraoperatively. The cost of the modular system is less
than the cost of an expandable custom endoprosthesis. The modular system allows for simpler and
