Page 184 - Reconstructive Techniques in Musculoskeletal Tumor Surgery

Chapter 9
Introduction
Various techniques have been described for management of reconstruction of malignant tumors about the knee in adults, including implantation of osteoarticular allografts1, 2, allograft-prosthetic composites3, 4 and custom-made5, 6 or modular7, 8 endoprotheses. Endoprosthetic reconstruction likely is the most commonly used approach, in part as a result of the ease of use compared with other options and the di culty of obtaining allografts in some centers in addition to the reported risks of nonunion, fracture, and infection5, 6, 9. Potential advantages of endoprostheses include their relative availability, immediate stability, the possibility of rapid recovery, and early weight-bearing6. Compared with custom- made implants, modular endoprostheses provide the ability to adjust the proper length at the time of the reconstruction10.
Nevertheless, revisions of endoprosthetic reconstructions occur frequently. Infection, occurring in 6% to 20% of patients, is the leading cause of failure in the early years after surgery5, 6, 8, 11-14. In the longer term, mechanical complications are the main concern, most notably aseptic loosening, periprosthetic fractures, and wear7, 15, 16. Because the survival of patients with bone sarcomas has improved, and most patients with primary bone tumors are young and active and place high demands on their implants, improving implant designs and reconstructive techniques are essential to reduce the risk of mechanical complications6. The MUTARS system (Modular Universal Tumor And Revision System; implantcast, Buxtehude, Germany; FDA approval pending) was introduced in 1992 and has since been widely used in Europe, Australia, and various Asian countries; results of its use in both orthopaedic oncology and revision surgery have been documented7, 17, 18. To our knowledge, no studies have evaluated the intermediate- to long-term results of the MUTARS knee replacement system in primary tumor reconstructions and revision procedures.
We therefore asked: (1) What proportion of patients experience a mechanical complication with the MUTARS modular endoprosthesis when used for tumor reconstruction around the knee, and what factors may be associated with mechanical failure? (2) What are the non-mechanical complications? (3) What is the cumulative incidence of implant failure at ve, ten, and 15 years? (4) How often is limb salvage achieved using this prosthesis?
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